Cam Question for L20b

[07FlyingWagon]

What are your thoughts on this cam?

 

http://www.nissanraceshop.com/product_info.php?products_id=332708

 

Does anyone on here use this cam?

 

Thanks!

~Marty~

[ggzilla]

Nissan comp called it their Slalom Cam. It requires comp springs so makes power over 7000rpm. It does not require a lubricating spray bar. Buy this if you want to run the engine at high revs.

[datzenmike]

Never never never never over cam your motor.

[07FlyingWagon]

Never never never never over cam your motor.

Mike, would you consider this cam to be too much? I've heard of some crazy grinds coming from places like Rebello. What would you definition of overcamming be? I'm still figuring these things out and am used to speaking small block Ford numbers, so this grind does not look out of realm, but again Im not sure and that's why I've asked :D

[datzenmike]

An engine is a large air pump. The amount of power produced is directly related to how much air you can run through it. In a perfect engine with no breathing restrictions, doubling the RPMs will double the amount of air which will double your HP. Simply stated if you make 40hp at 2K you will make 80 at 4K and 120 at 6K and 160 at 8K. At low speeds there is no problem getting the air to flow in by itself and the cam grind reflects this. But as the RPMs go up there is less and less time for this so if you want good breathing and more power from higher RPMs the cam has to start to open the valves sooner and hold them open longer (duration) to get the air in. This works at high RPMs but not at lower.

 

Take a look at the closing of the intake valve on an L20B. Should be at BDC at the beginning of the compression stroke, right? Well actually it's 52 degrees after BDC and the piston is well on it's way up the cylinder. This is because at idle and low RPMs there is enough air speed that it continues to flow into the cylinder under it's own weight or inertia. At extremely high RPMs this inertia is even more pronounced and the intake valve closing can be extended even 20 or 30 degrees more. The problem now becomes that at low RPMs the air can be pushed back out the intake valve by the rising piston This destroys intake vacuum and makes the motor idle very poorly. Too much cam = poor low speed driving. In a race car not driven around town this isn't a problem.

 

A stock cam is an excellent compromise for a street engine with moderate carb and stock exhaust. It's drive-able in all conditions of temp and weather and traffic and at moderate RPMs. A 'larger' cam will move more air or breathe better but at some point the stock carb/exhaust will hold it back. So now you add a larger carb or multiple carbs and manifold. These will improve the breathing at elevated RPMs but at low speeds there isn't enough air passing through them to make them work properly. Too big a carb = poor low speed driving

 

 

 

This is all relative to what you expect and what you want out of it. If strictly racing go as big as you want. If you expect to jump in it in December pump the gas twice bump the key and drive down town then you will be happier with the stock cam. The majority of drivers will fall somewhere in between wanting some improvement in power but willing to give up some drive ability to do so.

 

A stock L20B cam is 248 degrees. Very generally for every 10 degrees of added duration your peak torque moves +-500 RPMs higher. A 290 degree cam is IMHO getting into the low racing end of the spectrum of cam grinds. 40 extra degrees of duration will upset low RPM cylinder filling. Instead of your torque being at 3,200 RPMs it will move upwards about 1.5 to 2K. Things will really start to happen above 4K but will be lacking in all the RPM ranges to drive around town in. Yes you could lower the rear end gears to keep the RPMs up in town and make the motor work for you but then your mileage will suffer. 

 

 

Better to have a smaller cam and wish it were larger than to have a larger cam and wish it were smaller. It's all relative and I know there's going to be someone that says he has a 290 cam and it runs great, what are you talking about? What works for him may not work for you.

[ggzilla]

In Ford small block terms, this cam is probably for 3500-7500 rpm powerband. Is that enough for you?

[Z-train]

And more than likely,the overlap will cause run-on issues.

[EricJB]

Many things to consider. What vehicle are we talking about? Weight/ gearing come into play. What engine and what else have you done to it?

 

On an otherwise stock engine it would be way too much. On a motor built for track only purposes, it wont be enough.

 

I ran the same specs (different brand) in an L20b with bigger valves, stiffer springs, port/polish, dual 40 dcoe's, 2 1/4 exhaust, and drove it on the street for a few years. moved couple times, hauled firewood, commuted. No problem. Ran it down the dragstrip a few times too.

 

If you put it in much less it will be miserable to drive. Stop and go traffic with no power below 3500 will make you regret it. 

[07FlyingWagon]

Thank you all for the great info!

 

Should have clarified a bit - setup is as follows:

 

-Purchased the car in September o this year from some one who had had it for 9-10 years and done quite a bit of "upgrading"

-70 510 four door, Subie R160 LSD, stock 4spd (moving to a 280z 5spd this Christmas)

-L20b with a mild rebuild kit, honed to allow for new rings (according to PO)

-To the best of my knowledge, stock L20 head, valves, and springs

-Hitachi SU's with unknown jetting

-Stock 4-2 ex mani with custom 2-1 down pipe

 

-Will never be a daily driver, only a weekend warrior, so a bit of crappy city driving is fine. Will see some road courses at some point, and enty of Nor-Cal Mountain roads ;)

-I plan to run the vintage mechanics ofte car for the next two years or so, then shift to a SR20det setup, but in the meantime more power on vintage propulsion sounds more better ;)

-Upgrades to the head/springs/valves would coincide with the cam update.

 

Great great info folks! Can't thank you all enough! :D

 

Edited for stupid iPhone errors ;)

[Dime Dave]

I would use a lower duration cam than a 290 for any kind of street use.

 

Try the L4 Spec Race Camshaft  at 278 duration, .580" lift.

 

I personally like higher lift cams. Only issue with lifts this high is you need valve notches or dished pistons so the valves won't hit.

[620Turbo4X4]

I ordered the 278/.580 L4 race spec cam from "Nissanraceshop.com" 8 months ago and it's still on back order....

 

Does anyone know if this cam requires a spray bar, or is it drilled for direct lobe oiling?

 

Nissan race shop said they did not know.

[EricJB]

It depends if the core was drilled or not. I think most, if not all the L4 cams were drilled. If they use a original cam to regrind it most likely wont need a spray bar. If they use a new blank, don't know.

 

Isky and Schnieder both offer a regrind service where you send them a cam core and they grind it and send it back. I had Isky do mine, $125.00 + shipping. Good turn around too.

[620Turbo4X4]

It is supposed to a new cam, not a regrind. I avoid the regrinds as the base circle gets pretty small with the higher lifts that I want, and the oil holes for lubricating the lifters are not in the optimal locations on all lobes with a stock cam.

 

I've done some searching on here for info on whether or not I need a spray bar with no luck.

[07FlyingWagon]

It depends if the core was drilled or not. I think most, if not all the L4 cams were drilled. If they use a original cam to regrind it most likely wont need a spray bar. If they use a new blank, don't know.

 

Isky and Schnieder both offer a regrind service where you send them a cam core and they grind it and send it back. I had Isky do mine, $125.00 + shipping. Good turn around too.

That's interesting - the regrind option could be a good startin point.

 

My car came with an extra L16 head assembly - what are the differences between it and the current L20b head I have on now? I'm guessing the cam specs will be different, and combustion chamber size and valve size??

[datzenmike]

Look behind the #1 plug down where the head would meet the block... should say 210 if a stock north American L16 head. The 210 has very small combustion chambers to keep the L16's small displacement compression up around 8.5. The valves are relatively small as are the ports. A fairly good match for an L16's displacement and gives good port velocity and  throttle response. In other countries there was an L16SSS option with SU carbs and a 219 head with much larger ports and valves. The larger combustion chamber is compensated for by using flat top pistons. The cam for the SSS is very similar to the stock L20B cam's lift and duration.

[EricJB]

It is supposed to a new cam, not a regrind. I avoid the regrinds as the base circle gets pretty small with the higher lifts that I want, and the oil holes for lubricating the lifters are not in the optimal locations on all lobes with a stock cam.

 

I've done some searching on here for info on whether or not I need a spray bar with no luck.

 

I heard the new blanks were not as good as the factory cams. (Softer) And the supply for them is not good. But who knows. For sustained high RPM's I would look into a spray bar. What could it hurt? I haven't had a cam go flat in my application though. 

[Sealik]

http://www.datsport.com/racer-brown.html

 

 

"Pressurised lubrication is delivered to the camshaft bearings by oil holes in each cam tower that line up with oil holes in the cylinder head, which in turn intersect with the main oil gallery in the cylinder head. In L-16/L-18 engines, the camshaft itself forms two additional oil galleries. These are drilled axially and on centre from each end for something less than half the total camshaft length, leaving a wall between the two galleries near the centre. The second and third camshaft bearing journals are grooved and drilled with an oil entry hole in each groove to admit oil into each of the two oil galleries in the cam. Each lobe is drilled to release oil under pressure to lubricate the cam lobe/rocker pad interfaces. Cam lobes for No. 1 cylinder exhaust, No. 2 intake, No. 3 intake, and No. 4 exhaust have oil holes drilled in the centre of the lobe heel. Exhausts 2 and 3 have the oil holes on the lobes opening flanks. For some mysterious and inexplicable (and unexplained reason, intakes 1 and 4 have the oil holes located on the lobes closing flanks, which makes no rhyme, reason or sense at all. Historically, and as one might expect, No. 1 and 4 intake lobes are the ones most frequently damaged or distressed, along with their mating rocker pads - even in completely stock and unabused engines. It hardly seems likely that these two misplaced oil holes represent an oversight. However, it eliminates the need for a fourth indexing station, plus related tooling and machinery for drilling the am lobe oil holes at the factory. In any case, one of two possible fixes can make it right. Pressurised oil is contained within the camshaft by a press-in plug at the back of the camshaft and by the cam sprocket retaining bolt at the front. L-24 cam bearings are lubricated in the same way as in the L-16/L-18 engines, but the cam lobe/rocker pad interfaces are lubricated in a different and much more satisfactory manner. An external steel tubing oil gallery bolts to Nos. 1,3 and 5 cam towers on the rocker. Pivot side. Oil to this gallery is supplied under pressure by drillings in the No. 3 cam tower. Short transverse pipes aim oil streams directly at each of the cam lobe/rocker pad interfaces.

This system works admirably; so well in fact, that it has been more-or-less duplicated on a good number of modified L-16/L18 engines with equal success. When this has been correctly done on the four-cylinder engines, there is no longer any need for interface lubrication from the cam lobe oil holes. Oil sources to the hollow camshaft should be blocked off because they create a relatively large and unnecessary oil leak, which robs oil from the main and connecting rod bearings.

Oil entry holes in the grooves of numbers 2 and 3 camshaft journals must be plugged by drilling and tapping the holes for small socket-head setscrews. Use a bottoming tap to about 3/8-inch depth so the setscrews will bottom out tightly in the oil holes. The heads of the setscrews must not extend beyond the bearing journal surfaces. Loctite the setscrews to secure them. Also, remove the bolt at the front and the plug at the back of the camshaft so all chips can be scrubbed out. Otherwise the chips will inevitably find their way to the cam lobe oil holes with catastrophic results when they become trapped between the cam lobes and the rocker pads. Upon completion, there is no need to replace the rear camshaft plug (which you had to drill out to remove).

Enter SCCA. This August group occasionally comes up with some seemingly odd and misguided rules and regulations - and that's being charitable. According to their 1973 rules, SCCA hath decreed that the L-24 type of external oil gallery is not legal in L-16/L-18 engines. However, some clever lad who shall remain nameless circumvented this ridiculous rule by soldering copper "cooling fins" to his modified L-24 bolt-on external oil gallery. SCCA makes no distinction about the number or location of oil coolers for any on vehicle, so the cam lobe/rocker pad interface lubrication system magically becomes and "oil cooler" - entirely legal and acceptable by SCCA.

If one wishes to retain the stock L-16/L-18 cam lobe oiling system, it is a simple matter to drill intake lobes 1 and 4 with an additional oil hole each, this time locating the new oil holes on the opening flanks of the cam lobes. The cam lobes aren't all that hard, so tungsten-carbide drills are not required. A good, sharp high-speed steel twist drill will do the job. Use a number 47 drill (0.078-inch diameter) or a 2mm drill. Again, thoroughly clean both camshaft galleries before reassembly. This time, replacement of the rear camshaft plug is essential.

With either oiling system. It isn't difficult to imagine the volume of oil being sloshed about under the camshaft cover. Looks like Signal Hill all over again. This condition demands an effective oil drainback system from the cylinder head to the crankcase. In the front, a large hole empties into the crankcase through the timing chain cover. At the back, a 9/16-inch diameter hole empties into a matching hole through the block. This seems small but the top of the head is nicely channelled to direct drainback oil in either direction, effectively preventing an increasing oil level in the head…the wrong place to be of any value...."

 

 

I'd be running a spray bar with that amount of lift (580)

 

Springs would be up to 280 lbs/in + for that app?.....sooooo...that's a 'little' more pressure/wear on the pad and rocker

[tr8er]

I'll add my experience to the collective here.  I put in a 285 degree in with .485.  This engine idles consistently, but not smoothly.  She sounds beast weather at idle or high rpm.  Tuning my weber 38/38 is a bitch because the timing and carb have a tighter acceptability tolerance.   Meaning if it is off a little, the engine will likely stall out.  I love driving this car, but I also loved driving the car when I had an L16 with a Hitiachi  in it.  If I did it again, I would buy a less aggressive cam.  But the troubles with having it only present themselves when I am tuning or changing something.  I drive this car on the street.  Rarely do I go fast, but when I do she gives back.   

[Sealik]

I'll add my experience to the collective here.  I put in a 285 degree in with .485.  This engine idles consistently, but not smoothly.  She sounds beast weather at idle or high rpm.  Tuning my weber 38/38 is a bitch because the timing and carb have a tighter acceptability tolerance.   Meaning if it is off a little, the engine will likely stall out.  I love driving this car, but I also loved driving the car when I had an L16 with a Hitiachi  in it.  If I did it again, I would buy a less aggressive cam.  But the troubles with having it only present themselves when I am tuning or changing something.  I drive this car on the street.  Rarely do I go fast, but when I do she gives back.   

 

Not sure what gears you are running....but.... a 4.11 or 4.38+ diff would help the higher duration engine out of the hole.

One could also advance the cam a tad...if need be

My 510 has a Shadbolt 491/260ish duration with Motorsport valve springs...no lag with the 46mmSUs...excellent as a DD and or.

[datzenmike]

I can definitely agree. Having had a ride in it... this car moves out. It does have the advantage of slightly larger displacement, dual over size carbs and some gears but wow it's a fine combination, something that a cam alone won't give you..

[620Turbo4X4]

I heard the new blanks were not as good as the factory cams. (Softer) And the supply for them is not good. But who knows. For sustained high RPM's I would look into a spray bar. What could it hurt? I haven't had a cam go flat in my application though.

 

I noticed that with the new 270/.475 Isky cam I'm currently running. Had to adjust valves 3 times in the last 1000 miles. Each time I could see more and more wear on the lobes. Hopefully the nissan cam is cast of better quality material. I'm also not to sure about the springs that isky sells with their l series cams... seems to be a bit on the excessive side. The nissan springs for the 278/.580 cam have much less seat pressure and overall spring rate.

 

I'm somewhat hesitant on the spray bar setup. Not really impressed with the through the valve cover method and finding and matching up a set of cam towers machined for a factory spraybar from a l6 would be next to impossible without a good supply of heads.

 

I've read a few horror stories of spraybars cracking or becoming mis aligned instantly destroying the cam. Since this will not be no race truck, I'm sort of favoring the reliability of direct lobe oiling... Was hoping someone on here is running the 278/.580 and could let me know what to expect. I'm not having much luck with searching...

[tr8er]

Not sure what gears you are running....but.... a 4.11 or 4.38+ diff would help the higher duration engine out of the hole.

One could also advance the cam a tad...if need be

My 510 has a Shadbolt 491/260ish duration with Motorsport valve springs...no lag with the 46mmSUs...excellent as a DD and or.

3.88 rear.  I'm going to consider SU's once I get my car back on rubber.  

[Sealik]

I noticed that with the new 270/.475 Isky cam I'm currently running. Had to adjust valves 3 times in the last 1000 miles. Each time I could see more and more wear on the lobes. Hopefully the nissan cam is cast of better quality material. I'm also not to sure about the springs that isky sells with their l series cams... seems to be a bit on the excessive side. The nissan springs for the 278/.580 cam have much less seat pressure and overall spring rate.

 

I'm somewhat hesitant on the spray bar setup. Not really impressed with the through the valve cover method and finding and matching up a set of cam towers machined for a factory spraybar from a l6 would be next to impossible without a good supply of heads.

 

I've read a few horror stories of spraybars cracking or becoming mis aligned instantly destroying the cam. Since this will not be no race truck, I'm sort of favoring the reliability of direct lobe oiling... Was hoping someone on here is running the 278/.580 and could let me know what to expect. I'm not having much luck with searching...

 

Yes...I've also heard the Isky springs are....rather stiff.

There are a couple of guys over on the Realm that can probably help answer your queries 

 

I have an L6 spray bar/cam towers off my 280...probably re-fit that to fit my LZ. Just have to find all the pieces.....lol

 

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