Quick Revving L28

[madkaw]

It sounds like a cool project. There will be the folks who say it's crazy to destroke a l28, but it has been proven that it's not all about displacement. It's more about tuning and building it right. Compression can be maintained if the details of squish are observed. I think it's a harder way to make power as far as a destroked motor, but it makes for interesting read!!!

[Ted.]

I haven't been able to find much, but I did find what seemed to be a Z Car based email group archive that mentioned it. No real info in there, just a hint of recognition. I would LOVE you see that article whenever you get a chance at uploading it. Thanks Brian!

[Ted.]

It sounds like a cool project. There will be the folks who say it's crazy to destroke a l28, but it has been proven that it's not all about displacement. It's more about tuning and building it right. Compression can be maintained if the details of squish are observed. I think it's a harder way to make power as far as a destroked motor, but it makes for interesting read!!!

Well, thats the cool thing about doing it this way. Later on if I want to I still have the option for the 2.8l displacement with an 89mm bore and custom pistons, and that is literally all I would have to do to get back up to a 2.8l (technically 2751cc, but close enough). Granted, afterwards I would probably run a hotter cam and switch to triples, but never the less, the option is always there!

[olzed]

I have it on email. pm me your address.

[Bonzi Lon]

On the induction, it is claimed (internet & bench racers) that the N36 intake manifolds flow a bit better & maybe a few more cc than the other 3 available, also has the water connections.

Bonzi Lon

[Zedyone_kenobi]

I am going to throw some more light on the areas that have already been lit up. First let me commend you on entire engine thinking, and trying to match all the components the way you are. Good show.

Now building a short stroke is a sure fire way to build an engine that is capable of spinning. The smaller diameter spinning around does make it spin easier, but another reason, that is JUST as important if not more is the angle of incidence of the rod to the piston bore. A short stroke long rod combination means the rod is never at that extreme an angle form parallel to the axis of the cylinder bore.

Small block Chevy guys destroked a small block 400 by putting a 350 crank in it thus creating a 383, which would give torque and revs. A potent engine for sure. My greatest engine creation was a small block 400 with a 6" long rod kit and custom pistons with the wrist pin moved way up almost into the last oil ringland. It had the killer torque of the long stroke 400, but with such long rods (stock rod length was 5.565") it could still rev to over 7500 rpm.

L28 to get you displacement is a good start. Displacement is free torque. USE IT.

L24 crank to get you the smaller stroke and thus smaller angles against your cylinder bores. Good, that will make sure it can spin

Rods, not sure what to tell you but get the longest rods you can fit and get custom pistons that are flat tops, the less reliefs or domes on your pistons the better. A featureless flat top aids in fighting detonation.

The aluminum head will help you out as well, but I cannot quantify how much. I would not fixate on compression as much as I would about flow. Get large CC combustion chambers and get them blended and smoothed. Everything up to this point is about building revs. Keep that going with a LOT of smart head work. Does not have to be expensive, but the mods you choose must be smart. Strong valees that are large and properly undercut. Smoothed out intake and exhaust runners. Good set of springs that can handle the rpm you are looking to run. Naturally a good set of bolts and studs to hold it all together is important.

Lastly, a CAM that will enjoy being up top. This usually means more duration and more lift. For a streetable car in a small block chevy, I can pick a cam rather easily, but I have no experience with L series cams. I would usually tell people to pick the smallest cam that will get you the rpm you desire. But I have heard that L series like bigger cams. I cannot speak intelligently on that. But if driveability is a trait you desire, the closer to stock the better.

Lastly induction and ignition. Both must be in tip top shape whatever you choose. For an RPM engine, I would be inclined to go with triples, but I would bet a set of SU's would work darn nearly as well.

I actually plan on building an RPM loving L24 one day in the future.

the lightened flywheel and crank pulley will make it spin crazy fast as well. keep the weight down and your revs will climb quickly.

[LeonV]

Its not just the cam, its also the fact that the L24 crank is a shorter stroke. Shorter stroke means a shorter distance it has to travel for a full rotation, I.E. faster revolution, or 'rev happy' in comparison. The L24 cam has 8 degrees of duration over all of the L28s and the lift is virtually the same, so it doesn't have as much to do with the cam as you would think.

As far as the transmission goes, the entire reason for the gear swap is because I want the gear ratios from the earlier 1st and 2nd because they are taller to help deal with the wheel spin from a rev happy engine. They would be going into the later transmission, because of the earlier 5th/reverse fork issues. This gives me a stronger tranny with gearing I want.

The 3.9 is an open diff, which isn't really what I'm after since I want to have a car that would be effective when I take it to a track or autocross event. I do have a question though; would the 3.9 gear work in the 3.7 lsd? They both have the same pinion, right?

I figured something out now, actually using all L series parts, too! So, it is possible to get 2.8l with the L24 crank, though it requires a set of custom pistons and a bore, which isn't really necessary for my goal, so, I've decided a 2.6 is fine for me. Round 2, start!

Block: L28 F54

Head: L24 E31

Crank: L24 E31

Con Rods: L24 E31

Pistons: L28 P79

If everything is right, and I triple checked this time and the checked again in the engine calculator Zed Head posted, with a Nismo .6mm head gasket it would give me 2569cc (2.6l) and 10.6:1 compression. Run this with the L26 cam (256/256 and same lift) and I think I would be set!

It is the cam! An 8 degree differences does more than you think. To quantify, it's least 500 rpm if not more. There's your difference, plus you have more displacement to work with using an L28. You can theorize about strokes and R/S ratios, but it really doesn't matter. An L28 is just as "rev-happy" as an L24 if you build it so. I'll bet that given multiple engines, some L24 and some L28, you would not feel the difference in the "rev-happiness" if set up properly. What you will feel is a difference in torque.

"Quick revving", "fast-revving", "rev happy" can all be used to perfectly describe an L28 with the work done to it that I described.

I find it somewhat ironic that you spec'd an L26 cam. That's just 8 more degrees than an L24 cam. Your words exactly were, "it doesn't have as much to do with the cam as you would think." Then why use an L26 cam at all? On the contrary, it has everything to do with the cam! The camshaft sets the engine's powerband. If you want higher revving, you get a camshaft designed for it. If you want quick revving, put on a lightweight flywheel and clutch. Boom. Done.

I'm still confused on why you want the earlier 1st and 2nd gears. Early 1st and 2nd gears were shorter, not taller. You will have more wheelspin with early gears. I'll repeat, the late ZX 5-speed is already a close ratio transmission. By putting in the early 1st and 2nd gears, you are essentially recreating an early 5-speed but with a taller overdrive. This will not be a "close ratio" transmission.

Just think for a second. Don't get into all the bore-stroke, rod-stroke, piston speed, rod angle, internet bench racing. You are not building an F1 engine. These things simply do not matter within the confines of our situation.

The L24 stroke is 73.7mm, compared with 79mm for the L28. Either engine will go to 7000rpm just fine, however, the L28 will have more power and torque. I know which option makes more sense to me.

Now, if your whole goal of this is to build your own engine from an assortment of parts, then go for it. This goal seems to match better to what you seem to want to do. More power to you. Just don't go thinking that an L28 can't be made to achieve the same thing.

10.6:1 with 93 octane and proper ignition and fuel should be fine. I'm still researching that aspect of it. If it ends up being an issue, Kameari makes a 1mm head gasket with the stock bore that would put it at almost 10:1 even (its actually like 9.983 technically), so I'm not to worried about it as of yet

It likely won't be fine with the cam you spec'd.

Let the bore-stroke, rod-stroke, piston speed bench racing continue...

[John Coffey]

Another Internet engine build... (yawn) My old racing 3L had a LD28 crank and it ran to 8,000 rpm regularly and would rev faster then the Autometer Tach could keep up. The issue under discussion here is not the stroke or the displacement. The issue is the reciprocating mass.

[LeonV]

Another Internet engine build... (yawn) My old racing 3L had a LD28 crank and it ran to 8,000 rpm regularly and would rev faster then the Autometer Tach could keep up. The issue under discussion here is not the stroke or the displacement. The issue is the reciprocating mass.

I had to resist from quoting your phrase in my post: "this is an exercise in internet engineering masturbation"

[steve91tt]

But unlike other forms of masturbation I enjoy watching other people do it. I always learn something from these sort of threads.

[Ted.]

Well, at least I know who the all knowing, narrow minded assholes are on this board. I'm going to take a shot in the dark and say you both frequent Hybrid Z?

@Leon: I was simply proposing an idea and told you why I disagree with you, and you snapped back calling me a bench racer when you don't know anything about me, or what I've done as far as motors are concerned. I'm not aiming for a 8000 or 9000 rpm monster racing engine. By rev happy, I'm talking about FASTER revving, not higher, hence the point of the short stroke and lighter crank pulley and flywheel.

As far as the displacement is concerned, I already said why I'm using the L28, because I like the torque. I'm going to lose some with the shorter stroke, yes, but I'm going to gain most of that back over an L24 with the larger bore.

Onto the camshaft, yes, the L26 has only 8 degrees more then the L24. Correct me if I'm wrong, but thats what, 16 over the standard L28? And if we use your obviously incredible insight, that equates to 1000 or more revs up top! WOW! Again, its not about high revs, its about faster.

Now onto the transmission, and again you miss the point. In the first post, I said "close ratio" transmission, which I'll admit, was said incorrectly. Yes, I'm recreating the earlier transmission in the later housing because they are STRONGER. The longer first and second gear (I.E. taller), will put me in the lower rpms LONGER, to reduce wheel spin by keeping me out of the power band.

Onto your point about me not building an F1 engine. First of all, duh, I never said I was building a racing engine. Second, yes, all of that DOES matter when you're building an engine, especially when you're changing the characteristics of the engine by messing with the stroke. About the power aspect, yes, I will probably end up with less power then an L28 that had been worked over, but its HOW and WHEN that power is being put down that I'm interested in. If you want power, go get a Supra and do a single turbo, problem solved, and hey, it even has that awesome displacement you're so keen on.

I never said the L28 couldn't be rev happy, but it takes an extensive amount of work to do it, where as I'm using all factory parts. Again, I'm NOT building a race engine. And as far as the last comment about cam and fuel, well, we'll just leave that alone since you don't really seem to be able to comprehend anything thats been said thus far.

However, I'll cut you some slack since you seem like most of the people in the car scene, and don't know **** about how an engine actually works. Congrats on changing the cam, pulley, and flywheel on your car. I'm sure haynes helped you out a bunch. You might want to actually learn something before you try to put someone down.

@John: Yes, your "RACING" engine put out 8000 rpm. Where in ANY of my posts did I mention I wanted a full out race engine? And when you're talking about faster revving, yes, stroke does matter, just as much as reciprocating mass. Also, the L24 crank weighs less then the L28...so what exactly is your point?

@Kenobi: I actually messed around with GM motors a bit, too. Not to the extent of a stroked or destroked engine, though. You understand everything I'm actually going for, which is good. I would love to be able to shell out money for custom pistons, but the L28 flat tops will do just fine. As far as the cam goes, for the range and drivability I want, the L26 cam should be just about right. If not, I'll give a 260/260 a try.

[LeonV]

Wow, okay... a bit insecure are we?

I wasn't trying to be "snippy" and never called you any names. You have to learn to not take things so seriously on the internet. Is that how you'd respond to someone giving you advice in reality as well?

I was simply trying to help you by giving practical, real world advice but your purely ignorant attitude clearly demonstrates that the advice is unheeded and unwanted. I guess being a mechanical engineer and having experience in internal combustion engine design just doesn't cut it anymore. I'm sorry I gave you the wrong advice, according to you at least.

BTW, you're still wrong about the transmission, but I really don't care anymore. Go ahead and swap gears and have fun with your "stronger" transmission.