'73 240z - Project Build

[Stoffregen Motorsports]

I don't think you need to blow the budget with a fancy regulator. Yes, I've heard of issues with Holley regulators, but ours work just fine.

 

As far as all the metric fittings, just get adapter fittings for the carbs and run NPT to AN fittings everywhere else. Or maybe drill the fuel rail to AN o-ring for that special touch. Regular AN is much easier to find than metric and come in all shapes, sizes and colors. -6 AN with push-lok hose/fittings would be more than enough, but I've been using real Aeroquip hose and fittings these days. Yes, it's spendy, but super high quality.

 

I was going to suggest using Oetiker clamps on your fuel lines, instead of all those screw clamps, but sounds like you're changing all that anyway.

[iceman510]

I switched from a Holley red and Holley low pressure adjustable regulator to a Carter pump on my race 510 last fall. I think the Holley was working fine, but I was having real pressure inconsistencies on my gauge.  That said, my set up is also fuel direct to dual sidedraft Webers 45's, then return line to a regulator and back to the tank.  Lots of line.  Gauge is reading off the regulator, but I don't think it is reading right or my understanding of the setup in incomplete/inaccurate.  I get a good 3.5 psi at start of day, but it fluctuates and drops as the track sessions continue.  I actually replaced the regulator too and disassembled it.  Can't find anything wrong.  Really just an FYI for your consideration with the return line setup.

 

This spring I plan to play around with it some more and perhaps try to measure the FP at the carbs directly to see what's happening.  I never had any starvation issues even when on the straight at 100 mph and would see my fuel gauge reading 0.5 psi!😱

[demo243]

1 hour ago, Stoffregen Motorsports said:

I don't think you need to blow the budget with a fancy regulator. Yes, I've heard of issues with Holley regulators, but ours work just fine.

 

As far as all the metric fittings, just get adapter fittings for the carbs and run NPT to AN fittings everywhere else. Or maybe drill the fuel rail to AN o-ring for that special touch. Regular AN is much easier to find than metric and come in all shapes, sizes and colors. -6 AN with push-lok hose/fittings would be more than enough, but I've been using real Aeroquip hose and fittings these days. Yes, it's spendy, but super high quality.

 

I was going to suggest using Oetiker clamps on your fuel lines, instead of all those screw clamps, but sounds like you're changing all that anyway.

 

The thing with the Holley regulator is it seems to be designed for a deadhead system. That was the main reason for looking at the fancier regulators since they are designed to be run on the return side after the carb. I guess I could run the Holley before the carb and then utilize a restrictor on the return line- like the Watcom one I mentioned.

 

The fitting at the carb is pretty specific and utilizes o-rings. The clearance between the “pair” of carbs is pretty tight to so I think I’m stuck using the Mikuni inlet and 5/16 fuel hose there- I thought about those Oetiker clamps, and may use them down the road but for now I picked up some spring band clamps which will make changes or adjustments easier. Agree the screw clamps are hideous.

 

Part of choosing the m14 and m12 fittings was I already have the taps for them. Seems like m14 uses a 12.5mm bit just a hair under 1/2” - and -6 orb seems to be 9/16-18 is just a hair over 1/2” (33/64)- fuel rail I’m looking at has an ID of 1/2”

 

Thinking about just running 5/16 fuel line for the rest of the system- I guess I could step down to 1/4 for the return.

 

Just looked into 6an push lock - I think I can use it for the rest of the system, but again too wide for between the carbs. 
 

1 hour ago, iceman510 said:

I switched from a Holley red and Holley low pressure adjustable regulator to a Carter pump on my race 510 last fall. I think the Holley was working fine, but I was having real pressure inconsistencies on my gauge.  That said, my set up is also fuel direct to dual sidedraft Webers 45's, then return line to a regulator and back to the tank.  Lots of line.  Gauge is reading off the regulator, but I don't think it is reading right or my understanding of the setup in incomplete/inaccurate.  I get a good 3.5 psi at start of day, but it fluctuates and drops as the track sessions continue.  I actually replaced the regulator too and disassembled it.  Can't find anything wrong.  Really just an FYI for your consideration with the return line setup.

 

This spring I plan to play around with it some more and perhaps try to measure the FP at the carbs directly to see what's happening.  I never had any starvation issues even when on the straight at 100 mph and would see my fuel gauge reading 0.5 psi!😱

 

Sounds like the Carter pump is the way to go- works for me. Price is right and I’ve used it before- also the same pump as the 510 so in a pinch I could steal one from the other vehicle if I really needed to. 
 

Which Holley regulator are you running post carbs- the standard 12-804 low pressure one? Might be worth a shot if it’s working for you. 
 

https://www.summitracing.com/parts/hly-12-804?seid=srese1&gclid=CjwKCAiA0PuuBhBsEiwAS7fsNdcNFiDyXwnPDyn5vpB_DeOzFe7JfGr1Sy7h1ldist7VxM0whhr7TBoCsdoQAvD_BwE

[Crashtd420]

I know heat can play games with the fuel gauge..... 

Definitely don't put it near the exhaust....

I had one fail and cause a small fire...

The pressure fluctuation use to drive me crazy.....

So I just set the pressure and then removed the gauge... 

 

I would actually have a fuel issue under full throttle when I used the regularor.. problem went away once I switched to no regulator and just the return....

 

[Crashtd420]

4 minutes ago, demo243 said:

 

The thing with the Holley regulator is it seems to be designed for a deadhead system. That was the main reason for looking at the fancier regulators since they are designed to be run on the return side after the carb. I guess I could run the Holley before the carb and then utilize a restrictor on the return line- like the Watcom one I mentioned.

 

The fitting at the carb is pretty specific and utilizes o-rings. The clearance between the “pair” of carbs is pretty tight to so I think I’m stuck using the Mikuni inlet and 5/16 fuel hose there- I thought about those Oetiker clamps, and may use them down the road but for now I picked up some spring band clamps which will make changes or adjustments easier. Agree the screw clamps are hideous.

 

Part of choosing the m14 and m12 fittings was I already have the taps for them. Seems like m14 uses a 12.5mm bit just a hair under 1/2” - and -6 orb seems to be 9/16-18 is just a hair over 1/2” (33/64)- fuel rail I’m looking at has an ID of 1/2”

 

Thinking about just running 5/16 fuel line for the rest of the system- I guess I could step down to 1/4 for the return.

 

Just looked into 6an push lock - I think I can use it for the rest of the system, but again too wide for between the carbs. 
 

 

Sounds like the Carter pump is the way to go- works for me. Price is right and I’ve used it before- also the same pump as the 510 so in a pinch I could steal one from the other vehicle if I really needed to. 
 

Which Holley regulator are you running post carbs- the standard 12-804 low pressure one? Might be worth a shot if it’s working for you. 
 

https://www.summitracing.com/parts/hly-12-804?seid=srese1&gclid=CjwKCAiA0PuuBhBsEiwAS7fsNdcNFiDyXwnPDyn5vpB_DeOzFe7JfGr1Sy7h1ldist7VxM0whhr7TBoCsdoQAvD_BwE

 

 

You can come grab the regulator off my firewall if you want it..... I even have a Carter pump on the shelf thinking my old one was the issue.... it wasnt....

 

Edited February 28 by Crashtd420

[datsunfreak]

3 hours ago, Crashtd420 said:

The pressure fluctuation use to drive me crazy.....

So I just set the pressure and then removed the gauge... 

 

This.

 

My shop partner puts a pressure gauge on everything he builds. I install one to set the pressure then remove it. 😁

[datsunfreak]

3 hours ago, demo243 said:

 

The thing with the Holley regulator is it seems to be designed for a deadhead system. That was the main reason for looking at the fancier regulators since they are designed to be run on the return side after the carb. I guess I could run the Holley before the carb and then utilize a restrictor on the return line- like the Watcom one I mentioned.

 

Correct. That Holley style is only to be used between pump and carb, not post, and normally with no return line. My gut says a post carb regulator with a return line will be more consistent for this style of carb. 

 

3 hours ago, demo243 said:

Thinking about just running 5/16 fuel line for the rest of the system- I guess I could step down to 1/4 for the return.

 

I always run a bigger return line than the feed. 

 

Reason #1 - I don't like the idea of the fuel returning to the tank under any pressure, which could possibly cause the regulator to be inconsistent.

 

Reason #2 - That's how Nissan did it (I think because of reason #1). 😁

 

If you know how an external wastegate on a turbo works, it's kinda like that. You really don't want any restriction downstream or the regulator could possibly not bleed off pressure quickly enough. 

Edited February 28 by datsunfreak

[demo243]

20 minutes ago, datsunfreak said:

My gut says a post carb regulator with a return line will be more consistent for this style of carb. 

I agree- from what I have read the needle valves can be overpowered fairly easily, even when using the smallest one recommended for fuel pump usage. If that happens then the carbs overflow through the tubes out the bottom- hence my connection and routing of those. If it surpasses those then it will over flow out the side vent. A fear I definitely have.

 

So maybe worth just spending the money on a good regulator.

 

20 minutes ago, datsunfreak said:

 

I always run a bigger return line than the feed. 

 

Reason #1 - I don't like the idea of the fuel returning to the tank under any pressure, which could possibly cause the regulator to be inconsistent.

 

Reason #2 - That's how Nissan did it (I think because of reason #1). 😁

 

If you know how an external wastegate on a turbo works, it's kinda like that. You really don't want any restriction downstream or the regulator could possibly not bleed off pressure quickly enough. 

To reason 2- Did they?  Looks like the feed on my Z is 5/16 and the return is 1/4” (or whatever the metric equivalent is). From what I have read there is a small restriction in the stock fuel rail to keep pressure in the lines.

 

I mentioned swapping to 1/4” on the return since the return hard line is smaller

Edited February 28 by demo243

[demo243]

Edit——

Pretty positive they are ZX which looks to be pretty hard to come by… found a pair on eBay for $100 but the quality is most definitely questionable… Rock auto has the other side for $100 for a single caliper, I guess cheaper since I do actually have a core to send in…

 

Side note-

 

Can anyone identify this caliper by sight? I think they are 280zx- the e-brake brackets aren’t the same as my maxima ones on the 510

 

 

 

I am going to do some digging… but need to figure it out to decide if I replace it or upgrade… With all this fuel rail talk- and suspension work to be done… I’m thinking the cheaper just replace it route may be a good option for now…

Edited February 29 by demo243

[datsunfreak]

14 hours ago, demo243 said:

To reason 2- Did they?  Looks like the feed on my Z is 5/16 and the return is 1/4” (or whatever the metric equivalent is). 

 

If they did, it would be the opposite of everything else. On a 510 the feed is 1/4" and the return is 5/16" (or as you said probably 8mm and 6mm), Same for 620 and all the early EFI cars like the S110 200SX. 

 

As I recall on the 280ZX they changed to 5/16 feed and 3/8 return. 

 

14 hours ago, demo243 said:

From what I have read there is a small restriction in the stock fuel rail to keep pressure in the lines.

 

That would be surprising on a 240Z. In my experience (YMMV), SUs love really low fuel pressures. All of mine have ran best at 2psi or less. 

 

 

Longshot but any chance your lines were swapped at some point? I know it's commonplace on 510s (with deadhead Webers) to swap over to the bigger line for "better flow". 

[demo243]

41 minutes ago, datsunfreak said:

 

Longshot but any chance your lines were swapped at some point? I know it's commonplace on 510s (with deadhead Webers) to swap over to the bigger line for "better flow". 

Anything is possible on this car… but I don’t think so.

 

SUs are fed from the outputs on the larger lower rail- as I have see on every other Z car running the stock rail. This connects to the larger fuel line from the tank.

 

 

[Stoffregen Motorsports]

You guys ever play around with a fuel pressure snubber? I did a few years back., The customer was complaining of fluctuating pressure so I looked into it further and diesel guys use them. I don't remember much else, but I did get one that fit and functioned properly. Though I don't think we gained anything from it other than peace of mind.

[datsunfreak]

2 hours ago, Stoffregen Motorsports said:

You guys ever play around with a fuel pressure snubber? I did a few years back., The customer was complaining of fluctuating pressure so I looked into it further and diesel guys use them. I don't remember much else, but I did get one that fit and functioned properly. Though I don't think we gained anything from it other than peace of mind.

 

If you mean like a pulse damper sort of thing to even out the pressure, yes. Some companies used them on OEM applications. Used to be commonplace to use VW fuel pumps for EFI swaps because they had a built-in surge tank and fuel damper. 

[demo243]

After a quick search last night it seems I may be good up to ~4psi … digging more to confirm this but that does give me some leeway, to maybe just try a deadheaded set up. 
 

Still think a return would be nice though. Maybe just run the Carter pump by itself and run an adjustable in-line restrictor like this -

 

 

https://www.atlanticjetsports.com/products/riva-fuel-line-return-restrictor

 

Driving myself crazy trying to figure this out….

 

As for the rail - I think I’m going to follow @Stoffregen Motorsports ‘s advice and use -6/8 fittings. Thinking -8 rail with an 5/16barb/-8orb inlet; -6orb/5/16 barb for each carb. Then either a plug if I decide to dead head it- or a -8orb/-6an adapter to a -6an 180 bend and an -6an/1/4” barb to a 1/4 fuel line back to the regulator/return. I like metric fittings… but in a pinch if I needed a replacement AN fitting would be easier to find

 

As for brakes- I think I’m gonna roll the dice on some of the 280zx calipers. Then pick up some fresh rotors front and rear and Powerstop z23 pads front and rear (limited options for performance pads on the non vented Toyota calipers I have). This should hold me over for a bit (couple years?) till a decide on an upgrade and have the extra cash.

Edited February 29 by demo243

[demo243]

Big Day Today!

 

@mainer311 dropped by my place with a nice piece of stainless steel - THANKS!!!!! 

 

Couldn't wait to get to work on it so I dragged the carb set up inside and posted up at the kitchen table - 🤫 don't tell the wife I brought car parts inside 🤣 

A couple carbs on and so far so good!

 

And we have connection! Dragged em back to garage before she got home.

 

 

Video - Click to open and play 

Really stoked right now that this actually worked! Impressed that miraculously my measurements were accurate. Did a quick and dirty shop vac flow test and the sync is very close! First round was between 5-9 for all 6. Did a quick 5 minute adjustment just using the play in the slide actuator arm and was able together them all in a 5-6 range. Little more playing and I think I can get them all synced on the bench. Hopefully I don't need any wider adjustments once it on the car and running, 

Of course in my excitement I put that whole thing together... but forgot that I still need to drill and tap the manifold for the heat shield mounts... guess it will all have to come off again.

Thinking I am going to copy something like the T3/Kameari heat shield out of aluminum sheet since I don't need the mounting hardware or holes that either of those come with... 



Just going to use some aluminum bar stock to make and angled mount that bolts to the manifold and supports the shield.

Lots of work to come!

 

 

Edited March 4 by demo243

[demo243]

Snuck out to the garage for a bit this morning. Got the carbs back off (my L brace along the bottom makes this a bit tricky… will likely be hard to do on the car…)- drilled and tapped the manifold and got the carbs back on. Then bent up some simple heat shield mounts and cut some cardboard up. 
 

Here is a mock up of my heat shield. Gonna order a sheet of 24x10” .05 (16g) aluminum ~35 bucks- definitely better then $100+ for a T3 shield I would need to cut up anyway. Thinking I will probably try and bend the left and right edges up a little too to help stiffen up the panel but we’ll see…

 

 

 

 

 

On the topic of taking the carbs of the manifold being tough… has anyone used a copper gasket? MSA obviously says to use their header gasket… but I may need to take the manifold off a few times when I first get these carbs mounted up - mains can be easily changed on the car- but pilots require dropping the float bowl… 

 

Something like this-

https://zociety.org/product/lspec-l-series-copper-gasket/
 

Cost is about 10 times as much… $120 vs $12 so maybe not worth it?

 

Edited March 5 by demo243

[datzenmike]

RE: fuel overflow tubes.

 

You will never know if/when a carburetor suddenly starts to overflow and if directed into a catch can container it will eventually, sooner or later, fill it and over flow it under the hood. The L4 SUs just dangled a hose from each down beside the block... a little concerning with the exhaust manifold so close* but the air would waft it away. I think that could be improved on. Likely you would smell fumes getting in the rear and investigate it.

 

* gasoline ignites at about 530F and I doubt the down pipe and back get quite that hot at low speeds and at high speeds there's the rush of cooling air. Maybe run the hose under the oil pan to the starter side.

 

Slide carburetors FTMFW!!!!

[demo243]

3 minutes ago, datzenmike said:

RE: fuel overflow tubes.

 

You will never know if/when a carburetor suddenly starts to overflow and if directed into a catch can container it will eventually, sooner or later, fill it and over flow it under the hood.

 

Slide carburetors FTMFW!!!!

I had that same thought- I still like the catch can idea… thinking about maybe a clear one? With a second drain tube that runs down to the side of the frame to the ground. Or I may just run the hose all the way.

[mainer311]

Not sure if you bought that aluminum already, but stainless works better as a heat shield, and can usually be had for cheaper.

[demo243]

2 hours ago, mainer311 said:

Not sure if you bought that aluminum already, but stainless works better as a heat shield, and can usually be had for cheaper.

hmmm 

 

I did not

 

saw someone of the church or s30 facebook saying they had the opposite results 

 

I guess maybe aluminum transfers the heat quicker? But cools quicker too?

[mainer311]

Heat transfer is slower. It doesn't want to heat up as quick. I ended up using a stainless sheet on the bottom, with rock wool on top (basalt) and reflective textured aluminum on top of that. It's a product from DEI. It works great.

 

 

https://www.designengineering.com/form-a-shield-12-x-21/

[demo243]

20 minutes ago, mainer311 said:

Heat transfer is slower. It doesn't want to heat up as quick. I ended up using a stainless sheet on the bottom, with rock wool on top (basalt) and reflective textured aluminum on top of that. It's a product from DEI. It works great.

 

 

https://www.designengineering.com/form-a-shield-12-x-21/

I saw that- I was thinking about using something like that on top of it as well.  Then probably pop rivet the shield to the brackets. Do you remember what thickness you went with?

 

Looking on their site- I’m actually using their floor and tunnel shield as a shifter hole cover in the 510

Edited March 5 by demo243

[demo243]

scratch this below—- definitely too fragile based on Amazon reviews
 

Maybe I should just snag a sheet of this stuff?

 

https://www.designengineering.com/form-a-barrier-12-x-24/

 

Probably not stiff enough and likely to get bent/beat up just working on the car

Edited March 5 by demo243

[mainer311]

For the stainless, I used McMaster 8983K56, 0.036" thick 304. Even at that thickness, it's rugged.

[datsunfreak]

On 3/5/2024 at 10:42 AM, demo243 said:

On the topic of taking the carbs of the manifold being tough… has anyone used a copper gasket? MSA obviously says to use their header gasket… but I may need to take the manifold off a few times when I first get these carbs mounted up - mains can be easily changed on the car- but pilots require dropping the float bowl… 

 

Something like this-

https://zociety.org/product/lspec-l-series-copper-gasket/
 

Cost is about 10 times as much… $120 vs $12 so maybe not worth it?

 

 

IMO, not worth it because it is still intended to be a one time use only gasket. 

 

FWIW, I had had good luck with applying a thin film of grease to the gasket. This makes it reusable, at least a few times. Then whenever you decide it's "done", swap it out with a fresh one. 

Edited March 6 by datsunfreak