KGC10 Skyline 2000GT Build

[Babalouie]

One thing I decided to do, while mucking around with the centre console last night, was to restore the 2000GT badge that lives on the centre console. The red paint was peeling and cracked.

 

So much so, that all it took was a little prodding with a screwdriver and all the old paint just fell off :D

 

So first step is to mask...the pinstripe masking tape is actually from Tamiya, a relic from my model-making days.

 

First primer...

 

Then red. 3 coats of red in the end.

 

When its dry I remove the masking tape, and start to sand away the paint from the "GT" letters. First start with 400grit emery, then polish the badge all over with 800 and finally 1200 grit paper.

 

The finished product...much better.

 

...been wanting to do this since I got the car :lol:

[DatsunKid]

Looks great man, you sir have my dream car :thumbup:

[ppeters914]

Nice. Yeah, even my wife says I can have one of these....if I get rid of the roadster. <_<

[muck]

Just read the whole thread... WOW Fantastic Car!

I love the detail and pics you take for each small upgrade.

 

*clicks "Watch this topic"*

[Babalouie]

'Got a super-cool new addition to the car :)

 

It's a Nissan Prince Tokyo Sport Corner Service Plate. Now you're probably wondering what that is...well, you'll have to bear with me for a bit :)

 

Back in the early 70s, Nissan Japan offered a range of pretty serious hot-up parts that anyone could buy for your roadcar or racer, and these parts were marketed under the "Sports Option" banner. Here's a page from the Hako and Fairlady Z catalogs.

 

For the Hako GTR, you could get upgraded cams, suspension and brakes, oil cooler kits, exhaust systems and racing wheels, lots and lots of tasty gear. for the Z, the list was even longer and included triple carb kits too.

 

Not all of it is hardcore racing gear, and Sports Option is essentially the early 70s equivalent of Nismo. To support the parts program, certain Nissan dealers were chosen to supply and fit the parts, and these dealers were called "Sports Corner". The main Sports Corner was the Nissan Prince Tokyo dealership in Shinagawa Tokyo, where the magic happened in the basement floor. As you can see, not only did they supply and fit the Sports Option parts, they also provided maintenance services to Sports Option customers, which went all the way up to race preparation and rebuilds.

 

Nissan Prince Tokyo was actually the main sales office for Prince, before the takeover by Nissan in 1968, and so it was the main place to go, for maintenance and modification for the S20 engined 2000GTRs.

 

If you are a serious classic Skyline fanatic, then believe me, this basement is nothing less than holy ground :)

 

Nissan Prince Tokyo is still a major dealership and still does offer a similar service for Nismo today, but back in the day, if you had a 2000GTR, spent a lot of coin on Sports Option parts and had your car looked after at Nissan Prince Tokyo Sport Corner, then you would have this service plate on your car. I've only ever seen a few of these things, and it's basically a log of work done. This one below just says "O/H" next to the engine section, with a date at the top.

 

As to where this plate came from, it's a gift from my friend (and 2000GTR owner) Alan, who's good mates with Matsui-san from Nissan restorers NP35. Matsui-san and some Skyline enthusiasts had these plates made recently, and Alan was kind enough to obtain one for me. At first, I was a little concerned about fitting the plate if it meant that I was misrepresenting the car....but then in the end, it's all just for a bit of fun and I think you can take the originality thing a bit too seriously, and this is such a nice little period piece to add to the car. It goes next to the chassis plate in the engine bay. Most of the Service Plates I've seen go to the right of the chassis plate, like so.

 

We're going to do some research on what exactly you're meant to stamp on these plates, and I'll try to replicate that as best as I can. I think I'll only have one shot at this, so we better do this properly :)

[Babalouie]

One of the other Hako owners on the http://www.japanesenostalgiccar.com forums (which I would say is...relatively speaking...Hako Central outside of Japan :) ) arranged a group buy recently from http://www.victory50.com so it was a good opportunity to get more swag.

 

The first item wasn't available until very recently. You might remember that the plastichrome trim around my gearlever is very cracked and broken, and it's a part that I've been trying to source for a very long time. Even combing through the trade stands at the Tokyo Nostalgic Show a few years ago didn't net any results.

 

Just about a month ago, reproduction ones appeared on the http://www.victory50.com site, and for $80 they were good value.

 

The vinyl gaiter around the lever itself, I managed to get new for a bargain $25 a few years ago, and it clips to the underside of the trim piece.

 

...which just screws onto the console. It never ceases to amaze me, how easy it is to get parts for this car. If it was a classic Celica or rotary, I'd be screwed, but there's Hako specialists in Japan with all this gear just sitting on the shelf....repro stuff appears all the time, but often they're limited-run, so when they come up, you have to act fast.

 

Other thing was the little rubber boots that go around the wiper posts. My old ones were cracked, and they can allow water to get inside the wiper mechanism, and the resulting rust will wear it all out very quickly.

 

New ones were only $10 and just slide on.

 

Last bit for tonight is the handbrake lever. I'd fitted a new rubber tunnel gaiter for the gearshift lever not long ago, and when I was done, I triumphantly declared that the cabin was now sealed from the underside of the car...and that's when I noticed that the handbrake seal was totally gone :) Here it is from underneath, and removing it is easy enough, just undo 4 bolts and remove that er...paperclip that's holding on the clevis pin.

 

The rubber seal is largely non existent...

 

After greasing up the internals of the handbrake, it all slides together with the new seal ($25)...

 

...and into the car it goes.

 

And no paperclip this time :) We're using a proper split pin...well...since I didn't have a split pin of the right diamater, I cut a bigger one down to size, so we have half a split pin :D

[juancho]

bad ass...........thank god for datsuns!!!!!!!!!!

[Babalouie]

'Was driving along the other day, when I looked up, and noticed that the mouldings that run along the inside of the windows were a bit manky looking. In a modern car, these pieces would be plastic, but in the Hako, it's a strip of textured metal, which has started to get a bit of rust and the paint is flaking off.

 

After a bit of experimentation with some sanding on a hidden bit, it seems as if the leathergrain texture is really quite soft, and sands flat quite easily, so wire brushing the surface clean is probably not going to work.

 

So I decided to have a go at removing as much of the rust as possible chemically, with the POR-15 Metal Ready.

 

After 15mins and a good rinse, most of the rust is gone.

 

Other parts of the trim strip had some rust bubbling from under the paint...

 

...so I lightly flatted back the paint with some 400 grit emery, just to expose the rust, so that the Metal Ready can do its thing.

 

Then rinse, dry, wipe down with prepsol, hit with 2 coats of etch primer and 5 coats of VHT roll bar satin black.

 

You can still tell where the rust was the worst, but overall it's not too bad a finish.

 

At first I thought that polished stainless screws would look nice, but the effect was a bit cheesy, so in the end I painted the screws satin black too....and back on the car they go!

[Babalouie]

Update :)

 

When I got the car, the carbs it came with were Weber 40DCOEs with 32mm chokes. At the time, when we thought that the engine was stock, this seemed a good match, so I went a head and spent some money refurbishing them...but (much, much) later, of course we discover that the motor's got a demon 11:1 comp overbore, and a very worked head, so the carbs would be holding the rest of the motor back. But...hey, it went plenty fast enough and so I've been a happy camper for the past year. Having undersized carbs was not a bad thing, the small chokes meant that they got a nice, good suck though them at low rpm, so that meant that they were tractable and easy to tune. I could floor the throttle at walking pace and the car would just pick up and go.

 

But...lately we haven't had any sexy upgrades so I got to thinking about those undersized chokes. Ideally we'd be upgrading the carbs to the bigger 45DCOE ones, but that would be a $2k exercise, so fitting the very biggest chokes possible into the existing 40DCOEs seemed like a fun idea.

 

One day, I stumbled upon http://www.fastroadcars.co.uk who are Weber specialists in the UK, and their prices for DCOE chokes were a third of what they cost locally. So at A$140 for a set of six (delivered!) I couldn't say no. They were great to deal with and the hardware arrived a couple of days later.

 

Ok...so what are chokes exactly....once you get the cabrs onto the bench, and with the air filter base removed, you can see that there is this tubular insert in the front part of the carb. That's the aux venturi, and that little tube in the middle of it is where the main jet sprays its fuel.

 

They just slide out when you grab them with your fingers, and behind them is the choke tube.

 

The choke tube is wedged between the aux venturi and the throttle flap which is right down the back. You can see that the old 32mm choke is a lot smaller than the 40mm carb body.

 

The chokes basically just slide out and you can see the difference between the old 32mm one and the new 36mm one. 32 to 36mm might not sound like a lot, but if you remember how to calculate the area of a circle from school, then you'll discover that it's actually a 25% increase in cross-sectional area. A lot more airflow.

 

I've fitted one of the big ones on the right, you can see there's quite a big difference.

 

Everything just pops back into place, and you just have to make sure that the new chokes are seated fully home, but since the aux venturi has an inbuilt spring clip that clicks into place, it's easy to tell when you got it right. Just to be sure, have a look from the other side of the carb.

 

Now that the airflow capability of the carbs have been upgraded, the fuelling needs to be retuned to suit. So out come the main jet tubes.

 

The rule of thumb as provided by Weber is that the main jets should be 4 times the size of the choke. This worked really well in the past, I used 125mains with the 32mm chokes and they were perfect. So this time I've got 140mains. For the correctors, I've got a couple of options. The rule of thumb is that the corrector should be about 50-60 bigger than the mains (and the 175 correctors I teamed up with the 125 mains previously were spot on). So logic dictates that a 200 corrector might be the go to match the 140 mains, but then again maybe the new chokes will open up the top end power so much that I'll need more fuel? Anyway I've got some 200 correctors and the old 175 correctors to try. You might remember that the mains control the fuelling from the mid range onwards, but the correctors allow a certain amount of air to bleed in at high rpm to lean off the mixture. So the bigger the main, the richer the fuelling will be across the range, but the bigger the corrector, the leaner it will be at the top end.

 

Repeat with the other two carbs and we're ready to go.

 

It's a shame the headers are mostly hidden by the heat shield under the carbs. The POR15 Black Velvet header paint is holding up really well too, no flakes or chips anywhere.

 

You can see the softmount o-ring gaskets that go between the carbs and the manifold...they can go hard with age so shouldn't be re-used unless they are very fresh, but these are still nice and squashy so I'm reusing them. I did replace the rubber grommet washers that go around the carb mounting bolts though (some of them had split).

 

So how does it drive? Well it's certainly very different! It seems to have lost a lot of tractability below 3000rpm. It'll still lug about at low revs, but if you give it more than half throttle, it starts doing an impersonation of a 3 pack a day smoker by coughing and stumbling a lot. But as long as I roll-on the pedal gradually and not get to full throttle until above 3000rpm, it seems to be fine.

 

Power-wise, everything seems to have moved on 1000rpm. Before, the natural changeup point was 6000rpm (and that's where the power peaked on the dyno). But now, the natural changeup point is more like 7000rpm, with a real big surge after 6k. It doesn't idle any differently and as long as you keep the throttle openings small below 3000rpm, it's happy, but the bigger chokes seem to have changed the character of the engine somewhat. It's not so much of a midrange torque motor now, it's more top-endy and I find myself subconciously revving it out to 5k a lot in normal driving and it feels very zingy and free at the upper reaches of the revrange.

 

After playing around with the corrector jets, I settled on the 200s, which would be leaner up top than the original 175s. A proper analysis will have to wait until the dyno session next week, but from looking at the plug colour, I'd say we're in the ballpark. I'd like to tune out as much of the sub 3000rpm stumbles as I can, and I'll do some research on idle jets and correctors, the answer might be there.

 

I wonder what the new power figure will be :D

[Yakuza]

GREAT THREAD....MY DREAM CAR...I WILL HAVE 1, SUM DAY....HOPEFULLY SOON... :D

 

THE RHD BLUEBIRDS will have to do for now...maybe sell them? and buy a HAKO? :D

[Babalouie]

Update: The bigger chokes have definitely improved the top end power, but as I reported before, the driveability at low rpm was reduced somewhat. Give it too much throttle, and it would not only bog, but also cough and spit. So you had to baby the accelerator until it got to 3500rpm before giving it some serious pedal. Now, I was expecting some of this tractability compromise, but there was definitely room for improvement, and the obvious port of call was the idle jets.

 

Now, we've already spent a bit of time looking at how the main jets and correctors work. In a nutshell, the main jets control the fuelling from about 3000rpm onwards and the corrector jets lean off the mixture at the top end..

 

...and that's it really. To influence the fuelling above 3k, you have to change the jetting. Below 3k, you've probably heard me mention that there is a idle mixture screw, which I'm pointing out with the screwdriver here.

 

But the idle mixture screw doesn't really control all of the fuelling below 3k as we will see. Sorry I haven't got a better pic, but check out this pic from the back end of the carb. See that small red circle? That's meant to be a picture of a single little hole, and that is where the fuel from the idle mixture screw comes out of. When the throttle flaps are closed, this single hole is the only source of fuel. You'll also see that I've circled these 3 little holes a little further back too.

 

...those 3 little holes are the progression holes. You can see them from the top of the carb, there's a cover that you can unscrew to inspect them....you can also see the fuel passage for the idle circuit too (that raised tunnel going from the float bowl to the idle jet mixture screw). You can see that the fuel goes to the progression hole chamber, and only after that does it go to the mixture screw. After the mixture screw, the fuel takes a 90 degree turn downwards and sprays fuel into the intake airflow. So the idle mixture screw has no effect on the progression holes.

 

The reason for the existence of the progression holes is because the carb simply cannot react fast enough when you crack open the throttle from idle. It won't be able to deliver fuel fast enough, and you end up with a flat spot. So Weber had the great idea of having these progression holes. At idle, the progression holes are closed, and out of action. You can see in this pic that there are 3 holes, and you can see the top of the throttle flap covering the top hole. So at idle these things do nothin.

 

But when you crack open the throttle, even a hair, the progression holes will start to be exposed to manifold vacuum, and fuel will spray into the intake. This gives a slug of enrichment to cover that initial lean-condition that otherwise would occur. Now in my case, when I was cracking open the throttle at low rpm, it was spitting and coughing, which is a sure sign of lean mixture. You can to a certain extent compensate by enrichening the mixture screw, but as you can see from the blurry pic above, there is only one idle fuel hole and three progression holes. So tweaking the mixture screw can only compensate so much (and at the expense of an over-rich idle and fouled plugs too).

 

And to increase the amount of fuel going thru the progression holes, the only thing you can do is to increase the size of the idle jets, which is what I decided to do. The idle jets live under the round top cover, and are just behind the main jets holders.

 

And unlike the mains (which need a separate corrector jet) the idle jets have the correctors built in. My old ones were 50F9, and the new ones are 2 clicks richer at 60F8.

 

I took the car for a spin around the block after installing these, and it's made a HUGE difference. I wouldn't say that I can now floor it at low rpm without a protest from the carbs, but it's much, much cleaner and I can get heaps more acceleration at low revs before the carbs complain and cough, and it's opened up the 2500-3500rpm range now, where before I really had to baby the throttle thruthat rev range, I can now really nail it and the engine will just pull. Result! :)

 

So overall the Webers aren't reallythat hard to understand. Hardware like the choke size and aux venturi are to size the airflow capacity of the carbs to the engine's power potential, and once those components are chosen, you have to work backwards to figure out the fuelling requirements, as we have in the past week. You first have an idle jet which controls fuelling up to 3000rpm, and the main purpose of the jet sizing is to get a nice crisp response at low rpm from the fuelling that comes thru the progression holes. Idle mixture can be tuned by the mixture screw, so there is a lot of scope for juggling and adjusting. Above 3000rpm, the idle circuit has faded out (although it is still in play to a certain extent for initial tip-in response) and the main jet takes over. However the main jet will end up over-fuelling at high rpm, so the corrector jet adds an air bleed to balance things out near redline. And that's it! Not really all that complicated after all :D

[jun]

Dreamy car! I will own one of these someday- one of my all time favorites. Love the attention to detail!

[Babalouie]

Since the last update, we've been to the dyno, which is my friend Scott's shop at Insight Motorsports :)

 

However...things didn't quite go according to plan. To refresh, I'd had fitted bigger 60F8 idle jets, 140 mains and 200 correctors to match the bigger 36mm chokes. With that setup, it felt pretty damn good...if you asked too much of it at low rpm it would still cough and splutter a bit, but generally it was driveable and pulled cleanly without any flat spots or hesitation and really ripped in the midrange. It revved out at the top end more freely than before too. The sweet spot seemed to be in the midrange, so when I rolled up to the dyno, I was expecting that perhaps we might only have to tune for the top end.

 

Well I was wrong, because this is what the dyno plot looks like:

 

Basically it starts off just fine. The dyno plot begins at 3000rpm or so (so we are no longer on the low rpm idle circuit) but as the power climbs, it started to get really lean in the midrange and Scott pulled the pin on the dyno run and shut it all down before the revs got too high. You can see clearly that the power curve is starting to really climb, and it's simply running out of fuel and the AFR is heading sharply north towards 14:1 just as we aborted the run. I was a little disappointed, but Scott pointed out that it's a good sign that the engine is hungry for more fuel, because that means it's working and wanting to make power....he also thought that the 160rwhp power figure in the midrange was a great result. It didn't make that power until later in the revrange (5000rpm) before, so it's making more power, earlier. So we should easily eclipse the previous power peak of 176rwhp without any trouble at all.

 

So it was good news, but the bad news was that Scott didn't have any main jets in the right size we needed. And since I was expecting to not touch the mains, I hadn't brought any along either. But the recommendation was that the mains would have to be richened maybe as much as 3 steps, so that meant a 155 jet instead of the 140.

 

I'll have to reschedule the dyno run for another time, but in the meantime we can sort out those main jets.

 

And here they are...155 mains, shiny and new.

 

With the 155s installed, the plug colour looks...okay. It's certainly not over rich (and now I'm thinking maybe it's still not big enough and I need to go to 160s).

 

So to experiment, I put in the old 175 correctors, which live on those long tubes that hold the mainjets, but at the opposite end, under a cover. These should richen the top end somewhat.

 

And the result is...maybe a bit too rich.

 

So how does it feel?

 

Well, pretty good actually. All the low rpm stumbles are gone, it pulls cleanly at low revs and you can floor it at low speed and it'll take it without complaint. In terms of response, it's the smoothest it's been. Power feels pretty good too, definitely more grunt than before with the 32mm chokes.

 

But...subjectively, maybe it's my mind playing tricks, but I thought that, from the seat of the pants, the disastrously lean pre-dyno setup felt the fastest and zingiest. Well....let's see what happens at dyno run part deux :D

[Babalouie]

Okee dokee....quite a lot's happened since the last update :)

 

Where we left things was that the DCOEs ran dangerously lean on the dyno, and so we shut things down before even getting a peak power figure. The recommendation was to fit bigger main jets, which would have addressed the lean mixtures that the dyno found in the midrange. I did install bigger jets, and while it was smoother, it felt like it had somehow lost something.

 

One of the guys following the build thread suggested that maybe I was going about it the wrong way. I hadn't upgraded the emulsion tube size when I increased the choke size, and I was compensating for an over-lean emulsion tube with really large jets, which wasn't a very good compromise.

 

Now the emulsion tubes are these long brass things:

 

You'll recall that the main jet and correctors are the little brass mushrooms that go in either end of the tube. But the emulsion tube isn't just a pretty brass holder for the jets, it also acts like a "cache" for the fuel feeding thru the main circuit. So when you apply throttle, or when the main jets kick in and take over from the idle circuit at 3000rpm, that's when the emulsion tube comes into play. What this guy was saying, was that the lean emulsion tube wasn't allowing the mains to kick in fast enough, thus creating this lean spot right in the middle of the rev range. Sure I can compensate by fitting really rich jets, but while that fills the hole, it makes it over-rich everywhere else.

 

Now this made perfect sense, but what was also becoming clear was that there was a lot more to this, than initially met the eye, and what I had at the moment was settings that worked well at parts of the rev range, and horrible at other parts. Scott at Insight Motorsports was kind enough to invite me back for another go at the dyno, but to be honest I felt like that would be wasting his time. So I went and bought one of these:

 

It's a wideband O2 sensor from an aussie company called Tech Edge. Not really that expensive at $256 and for that you get a Bosch-made wideband O2 sensor, like you get in any EFI car, but with a wider sensing range.

 

That lives in the exhaust headers, and fitting it required a threaded bung to be welded in, which was expertly done by the boys at CHE.

 

The wire then runs up the side of the engine bay, where it enters the cabin thru these two big holes in the firewall, which are for the aircon tubes (which my car doesn't have).

 

The little techedge unit just mounts on the kickpanel...

 

And then you wire it up. There's a power and ground wire of course, and lots of other wires for things like boost sensors, TPS, speed sensors etc...which are useful for tuning an efi turbo car, but which the Hako of course does not have! The only input that we can use is the RPM signal, but ironically I could never get that to work. After a few calls to the TechEdge guys, it seems that I did have it wired up properly (to the coil -ve post) but perhaps I just have a dud. They offered to take it back and have a look, but for my purposes I thought it wasn't a dealbreaker for reasons that we'll see later.

 

Then there's another cable that goes into your laptop, and after you load up the free software, you're good to go! Well in my case the wideband output is a serial port, and since my laptop didn't come with one, I had to get a serial port to usb adapter. But after that it worked just fine.

 

Now we have the ability to view and record the air to fuel ratio in real time...like a dyno, and the first run was quite illuminating. What I did was ask a mate to ride shotgun, and start recording a run just as I floored the pedal at 2500rpm. When I hit 7000rpm and backed off, I'd give ayell to stop recording. So what we'd get would be close to an AFR reading across that revrange. For our purposes, not exactly super-accurate, but good enough. The datalogger would save the data to a .txt file, which we then opened in Excel and graphed into a line chart.

 

At this point, we had the F11 emulsion tubes, richer 155 main jets, richer 60F9 idle jets and 200 air correctors. What the power run showed was that we were quite rich, at 11.5 AFRs for most of the rev range, not improving until the very top end to the ideal 12.5.

 

But what was more interesting were the AFRs on cruise. That is to say, when you just have a little throttle open, just enough to maintain 60kmh in 4th gear. The mixtures were really rich, staying at the high 10s and low 11s at 2500~3500rpm. The ideal is a much leaner 14:1.

 

What this initial run told us was that this guy was right: we'd fixed the lean hole in the midrange, but at the expense of making it too rich everywhere else. In order to lean off the cruise mixtures, we'd have to run a leaner idle jet. But that would mean it would be too lean at 3000rpm when the carbs transitioned to the mains. Compensating with a richer main jet again would be counter productive, because the full-power AFRs are already too rich in the midrange anyway. So with this setup, we're essentially backed into a corner, there's no real way to fix it with just jet changes, we'd have to look into changing the emulsion tube too.

 

So I went and ordered a whole bunch of stuff from http://www.fastroadcars.co.uk/ some mains, some correctors, some idle jets and most importantly, some richer F16 emulsion tubes. I've found that ordering from the UK is pretty cost effective right now, basically everything is 1/3 of the price of buying locally. So I might have gone a bit overboard buying bits, but hey, it's all in the name of science :D

 

First try, I started off with 2-steps leaner idle jets: 50F9s. This would make the cruise AFRs a lot leaner.

 

Then on go the richer F16 emulsion tubes (the top ones)...you can see that the fuel holes on the left are noticeably bigger, and the whole tube is fatter in diameter, so would hold more fuel inside. This I teamed up with leaner 145 mains and 200 correctors.

 

This was a bit of a disaster, we went a step too far. The cruise AFRs were very lean at 15~16 and the throttle response was very hesitant, and there were some massive coughs and stumbles as it transitioned to the mains at 3000rpm (that's the huge spike to 20+ you can see). We didn't even bother to do a power run, this was way too lean on the idle jets. Back to the drawing board.

 

Now we swap the 50F9 idle jets for one step richer, 55F9.

 

Straight away, this felt a lot better. Here are the AFRs on cruise, hovering at about 14:

 

And here's a full power run, you can see there's a lean spike at the beginning as it did a bit of a cough and splutter, but once it cleared its throat, the AFRs more or less stayed between 12 and 13 until the top end, where it got a bit richer.

 

I then replaced the 200 correctors with one step leaner, 215. We mucked up the datalogging of this, so we have no graph :D but the AFRs at redline looked to be about the high 12s.

 

How is it to drive?

 

The response is a heck of a lot better than when we started. I still can't seem to eradicate that stumble at low rpm, but maybe it's something I have to live with. But overall this seems to be a much better compromise, and to be honest I reckon I couldn't have done it without the wideband. Damn tricky things, these DCOEs :D

 

I'll drive the car around for a few more days to get more of a subjective impression, but for the moment, I reckon we might be ready for another dyno session :D

[banzai510(hainz)]

great write up.

Unfortunatley the numbering system on Webers are different(weird!!!) than Mikunis. I think Mikunies are EZer. Not that Im a carb expert Im not.

 

But Dave on here, he had his Webers done by a so called proffessional and it got better but hard to get it dialed in quite right.

 

 

My Mikinus I bolted them on not even looking at the jet size and they work perfect so I guess I got lucky.

[Babalouie]

Yes I agree, I think it's one of those things where you make a change, and one thing gets better and another thing gets worse! So you would juggle settings until you got to a place you were happy with, but maybe it's a compromise. I'm sure that back in the day, there would be "carb whisperers" who'd just sprinkle fairy dust on the manifold and everything would be sweet, but that kind of expertise is hard to come by nowadays :D

 

Drove the Hako to work today and hmmm....still not quite there. I think we have the top end nailed but at 2500rpm there's still too much hesitation for my liking. I might try going one step leaner on the idle back down to 50F9, and one step richer on the mains to 150 and see what happens.

[Babalouie]

Well I'll be damned....

 

Was sitting there, staring at the engine bay, then thought...what the hell, let's crank in more ignition timing and see what happens...and almost magically the low rpm stumbles (almost) go away! But at least it now pulls cleanly, and doesn't feel "fluffy" at low rpm anymore.

 

All I did was put in an extra 3 degrees of advance, so it's now 16BTDC base, and about 30degs all-in. Funny thing was, with the smaller chokes, it didn't want to take any more timing. But I figure maybe the bigger chokes have made it less efficient at low rpm, so now it can take more advance without pinging.

 

NOW it's responding to jet changes in a more logical manner, I reckon we're only a few tweaks away from being good :) I guess it goes to show....never assume...

[banzai510(hainz)]

I hear Mikunis are EZer to dial in for everyday street use. has better low mid range circut.

 

Weber DCOEs where more a full on carb(I believe Bryon510 on the 510 realm mentioned this.)

 

For some reason Mikinis are not popular in Austraila even thu you guys are closer to japan. Even the higer output BMW2002 went with Mikunis before the Tii FI version came out.

 

Maybe the WOGS had a hold of importing Italien carbs over there in Aussie land.

 

Toyota twincam Yamaha 18RG built heads should have came into Austraila back in the day if that option was there. Im sure that were the majority of Mikunnis came in from.

[Babalouie]

That's true, Mikunis have a better, more progressive transition circuit from idle to mains. But the downside of Mikunis is that it's harder to track down jets, etc, whereas with Webers it's dead easy with plenty of local availability and eBay stores offering them too.

 

As far as I know Australia never got the twincam 18RG engines officially (although there are plenty of second hand imports here)

[Babalouie]

Update!

 

After the recent findings that the engine ran a whole lot better with the ignition advanced, I decided to look into that part a bit more. When the motor was rebuilt, the distributor was outsourced and was rebuilt and recurved. But the more I played around with it, the more it seemed to be a poor compromise. Advance it enough so that it felt good at the bottom end, and it would ping up top. Back it off so that the pinging stopped, and it would be all doughy down low again.

 

So I bit the bullet, removed the distributor and dropped it off with L-Series guru Stewart Wilkins at http://www.swmotorsport.com/ Straight off, he says that the advance spring feels way too stiff. Now you might recall that when I took apart the dizzy, the insides looked like this:

 

As revs rise, those metal weights (at 3 and 9 o clock) swing outwards, rotate the shaft a few degrees and advance the ignition. The rate of advance is controlled by that spring you see. The stiffer the spring, the slower the timign is to advance with rpm. The total range of advance depends on those slots in the weights that you see in the pic above. Stewart tested the distributor and confirmed that it wasn't offering full advance until 4500rpm, which wasn't suited to the big cam and webers. So he fitted a pair of much softer springs, and now the dizzy gives us 15 degrees of advance all-in by 2700rpm (compared to 4500rpm before). So now we have a much more aggressive ignition curve than before.

 

And it's all to do with these tiny little springs!

 

Stewart gave me some strict instructions to set the base timing at 13 degrees at 800rpm, so that when the dizzy added its 15 degrees, we would have a total ignition advance of 28 degrees at 2700rpm and above. And once refitted, I was surprised at how much cleaner it was at low rpm. There is still a little bit of hesitation if I floor it at low revs, but it's almost unnoticeable compared to before.

 

So on we continue with the wideband testing :) First run was with 140 mains, and maybe is a bit too lean, with portions of the midrange and top end peaking above 13:1 AFR. You can still see a big lean spike at 2500rpm when I floor it...it looks worse than it feels, rather than a hesitation, you just feel a bit of a hiccup in the power delivery and the engine just accelerates through it. But in terms of day to day driveability, it doesn't happen unless I'm really ham fisted with the loud pedal at low rpm.

 

Next combination was to go a step richer on the mains to 145, and you can see that it's richened everything slightly across the board.

 

Cruise AFRs were more or less where I wanted them too, this is a gentle pull from 2000rpm to 4000rpm on 1/4 throttle, and it stays between 13 and 14 AFR all the way.

 

If I could nitpick, it looked like it got too rich right at the top end, so I bumped the air corrector up from 185 to 200, which only made it slightly leaner, but moved the rich point 500rpm further up the scale.

 

So with that...it was...TO THE BAT DYNO!!

 

Back at Insight Motorsports, and the first things you see are their successful entries from the World Time Attack Challenge at Eastern Creek last weekend. Parked in front of their dyno was their turbo S2000, fresh from its setting a blistering 1'40 laptime and winning its class. Pure porn.

 

Onto the dyno we go...

 

...I would have taken video, but all you tend to hear is the dyno fan....

 

And the result of the first power pull, 189rwhp (up from 176rwhp before). It was felt that the top end was too lean, it's just above 13:1 at peak power, so out came my box of jets and...

 

...we swap the 200 correctors for 175 air correctors, which has richened things up at peak power by half a point, as you can see from the new blue and pink lines below. Scott wanted an AFr of between 12 and 12.5 and that's pretty much what we got.

 

All we've done is upgrade the choke tubes in the carbs from 32mm (on the left) to 36mm (on the right), which will increase the airflow potential of the Webers, but at the expense (as we have discovered!) of making it a bit fussy and finicky to tune.

 

But here's the final result, flat-out, the new setup makes more power right across the range, with peak power being 14rwhp more, or about 20hp at the crank.

 

To drive, top end power is definitely stronger, but at low rpm it's lost some of the brutal punch it used to have at 2500rpm with the smaller chokes, so it's definitely a compromise. But the good news is that the wideband sensor has been a very accurate tuning tool for just $250, its readings are bang-on identical to what the dyno says.

 

But it certainly has been an interesting exercise in understanding how these Webers tick :) In theory, the idle circuit handles the low rpm, the mains the midrange and the correctors the top end. However, changing the idle jets will have an effect on part throttle fuelling right up to as high as 4500rpm. And changing the correctors can actually fatten the midrange, as you can see from the last minute jet change on the dyno. Emulsion tubes are a different science again, but I think it's fairest to say that they mainly affect the interplay between the main jet and the corrector, and hence the "shape" of the AFR curve above 3000rpm. So there is a fair bit more to these things than what the books say.

 

It drives great now, but there is still a bit of a rich spot at 4000rpm, which might be able to be tuned out if I try some richer F2 emulsion tubes. But I think we're done for now :lol:

[Babalouie]

The latest addition to the car had been new rear shocks. The KYBs that I'd been using were a bit tired and while they were okay, the back end was a little bit bouncy.

 

So I ordered a pair of 50mm shortened GAB adjustables from http://www.rubber-soul.net When you order them, you have to specify if you want 40mm shorter or 50mm shorter.

 

Interestingly, it's only the shock rod that's shortened. The shock body itself is the normal length.

 

...so the compressed length of the old and new shocks are actually the same.

 

The main benefit of these shortened shocks, as far as I can see, is that there is less droop travel. With the old shocks, there was 5 inches of droop travel :)

 

With the new GABs there is only 3 inches of droop travel, and where the spring wasn't trapped before at full droop, now they are. Also I guess another benefit is that at the static ride height, the piston of the shock will be in the middle of the shock, rather than right down the end, where there is less oil volume in front of it. With the current setup there is 3ins of droop travel and 2.5ins of bump travel at the static ride height, so I think this is where we want it to be.

 

But while I'm at it, I'm going to check the bump travel too. To do this on a Hako is easy, I just raise the suspension arm with the spring removed....

[Babalouie]

...and at the point where the bumpstop comes into play...

 

The shock is actually very close to its travel limits....hmm...not good

 

But with this kind of shock, it's actually very easy to check how much travel you're using up. Just snug a cable tie tightly onto the shock rod, and go for a drive. Later you can see how much travel is used up, by seeing how far up the cable tie goes. This confirms that we're aaaalmost using up all the travel that the shocks have got.

 

So the solution is to make up a thicker spacer to sit under the bumpstop. There was one there before, but I made a new one out of nylon, that's 4mm thicker. That should work out to 8mm travel at the shock.

 

Back into the suspension the bumpstop goes. It sits in the middle of the spring pan, so it's a bit of a faff to remove the shock and the driveshaft, so that you can get the spring out to access the bumpstop.

 

But after a drive, we got the result we wanted, there is about an extra 8mm of unused shock travel. It might go beyond this if we hit a really big bump under power and really compress the bumpstop, but if that happens, at least we have another 10mm of shock travel left.

 

But overall I've pretty happy with it, the GABs are firmer than the KYBs and there is no more bouncing from the back end. The ride's pretty good, firm but not harsh and still comfy and more of a road compromise than a track setup. The firmer back end should help eradicate some of the understeer we're finding at the track though, can't wait for the next trackday.

[Babalouie]

Update!

 

Since the Webers were upgraded to the larger 36mm chokes, I've enjoyed the extra 20hp at the top end, but at the bottom end, where let's face it, you spend most of the time in everyday driving, it was, well...only ok. Sure it pulled decently if you "rolled" onto the throttle below 4000rpm instead of stomping on it, but even so, you could feel the little hiccups and kinks at low rpm. I was starting to get used to it, but I decided to get around the problem by cheating :)

 

One thing that seemed to help a lot with the low rpm running was ignition advance. The more, the better, but anything more than 12deg base/26max and I'd get some pinging at 4000rpm. So I had the idea of fitting an MSD 6A CDI unit. As you can see, it's a big sucker. US$165 (about A$280 delivered) from JEGS.

 

The spot near the coil seemed logical, but it meant moving some things around. To free up space for the radiator overflow bottle, I'd already relocated a few relays around, but it looks like those relays have to move again to make space for the MSA 6A.

 

It may seem like there's a mess of wiring here but it's actually quite easy to wire up. There's just 6 wires to worry about. One wire is the power feed for the MSD unit, and goes directly to battery. Another is a ground (I put it onto the engine block). Two wires go to the dizzy, and two go to power the coil. Basically the coil takes all its juice from (and grounds to..) the MSD unit and is disconnected from the car's loom. The ignition-on power wire from the stock loom gets spliced into the trigger wire for the MSD (which goes to the +ve terminal on the dizzy).

 

How it works is that the MSD unit takes power straight from the battery, and has capacitors which store up current in between the firing cycles: the idea is that the stored juice is released in one big go, giving you a bigger zap. The electronic dizzy's magnetic pickups send a trigger signal to the MSD 6A, which then fires the coil.

 

The capacitive discharge means that you get a considerably bigger spark, but in addition, at lower rpms the MSD 6A will actually fire multiple sparks. So the idea is that not only do you get a bigger spark, but at low revs you will get about 10 rapid-fire sparks over a period of about 20 degrees of crank rotation. You know...just to make sure the job's done :)

 

So I figured that this gadget might help to fill in the driveability holes, now that the Webers were not as efficient at low rpm. If adding more ignition advance helps, then maybe this spark-increasing device would have the same effect? The more I looked into it, the more it seemed to be the sort of overkill that the Hako needs at low revs.

 

Well that was the theory...it didn't take long to install, once I'd made room for it in the engine bay. As you can see, I've moved some of those relays to a new spot under the MSD unit. Wiring was pretty straightforward, and the only deviation I made to the instructions was that I ran the main power feed thru a 15A fuse block (the instructions say the MSD has an internal fuse). The only thing I didn't like about the install in hind sight is that the tacho signal wire has to plug into the side of the MSD (plugging it to the negative post of the coil doesn't work anymore) and I think it's a little ugly to have that straggly orange wire wiggle around to the top like that.

 

But...it seems to work. I've only had the chance to take it for a quick spin around the block, but it seems that I can now floor it at low rpm and it'll just pick up smoothly without any stumbles. And there does seem to be a lttile bit more grunt in the midrange too. The instructions say that I can now open up the spark plug gap to take advantage of the bigger zap, and I'll definitely give that a go, and I reckon it'll be interesting to fire up the wideband sensor to see if the fuel curve is smoother too (it certainly feels like most of the kinks have been ironed out now).

[Babalouie]

Lately I've been noticing something a little weird. When I reverse, I feel a bit of a muffled clunk coming from the back end. And when I'm accelerating and backing off sharply in 1st gear, I feel it again.

 

In the Hako, the front of the diff is hardbolted to the suspension subframe, and the back of the diff is supported by this transverse bar called the Moustache Bar, for obvious reasons. I was thinking that maybe the bushings in the ends of the moustache bar were gone, and so the back of the diff is thudding up and down against those rubber snubbers as it reacts to the torque of accel and decel.

 

A Datsun-owning mate (Technical Editor John Roper from JNC Magazine) reckoned that the end of the moustache bar isn't meant to be sitting on the lower snubber like that, and is meant to be more like in the middle. So it looked like those bushings have to be replaced.

 

Getting the moustache bar off wasn't easy...unbolting it at the bushing end is easy, but it locates to the diff via these two studs, and so the protruding studs prevent you from dropping the bar down vertically. Unbolting the front of the diff to ease it fwd's so that the studs can slide out seemed like the hard way to do it, so I decided to try to unscrew the studs by locking two nuts together, and unscrewing the inner nut. The steel stud was pretty corroded to the alloy diff casing, so this part was a bit of a pain, as it was one of those things where it was really tight to unscrew, bit by bit all the way.

 

But in the end the bar's off...

 

And on closer inspection the bushes do look a bit ruined, the rubber has torn clear of the metal crushtube in the middle.

 

To remove the bushes, first we cut off the rubber lip that mushrooms out on one side.

 

And for the next step, say hello to my little friend :) It's a 6ton hydraulic press! Basically it's just an upside down trolley jack, as you pull this lever, the piston comes down, and there is a beam and some sturdy metal plates below to brace things against. It's not a very hi-quality one, and was inexpensive (some might say...super-cheap, even :D ) but I figure I'm only going to use it a few times a year to press out a few wheel bearings and suspension bushes, so it didn't make sense to buy a really expensive one.

 

Take a closer look, and the bushing (yes I pushed out the centre tube just for fun) has a few concentric metal tubes. The outer one is the bushing's outer metal jacket, and the inner one is the one we will be pushing out.

 

Brace the moustache bar carefully in the press, and then pick a socket that's just the right diameter to push on the metal tube of the inner bush. You'll notice that I've got clamps holding down the metal plates under the 'bar...when you're working, everything's under tremendous pressure, so the clamps are to prevent the plates from slipping out and flying across the workshop, narrowly missing your head (um...appparently).

 

The press makes light work of pushing out the inner bush.

 

What's left is the outer bush jacket, which is in 2 pieces, so it's easy to tap out with a chisel and hammer

 

...the remains of the diff bushes.

 

Then I cleaned up the inside of the tube with a wire brush

 

And the new poly bushes (from SSS Automotive) just press in by hand.

 

The rejuvenated moustache bar in place! You'll also notice that I didn't put the stock diff studs back in place, but I used bolts instead. So the next time, I can just take out the bolts and the moustach bar will just drop down, which will make diff removal easier too.

 

...and that's where we're at...I'll see how she drives tomorrow, but I'm sure it'll be better than it was...

[bonvo]

dang its tight under there