Quick Revving L28

[Ted.]

Thats awesome, Brian, thanks! I didn't think about using the big valves from the L28, that would certainly free up some power, especially with a a mild port and the casting flash cleaned up. I think I might have more machine work ahead of me then I expected xD

[Ted.]

Mainly because it eliminates the need to bore the block. Less machine work, less money, plus most of the engine comes from two long blocks, which will save me tons of money since they can be had for pretty cheap as opposed to all new bits from Robello. I did look at that option though, this one just won out price wise

[John Coffey]

Build it and prove me wrong. And yes, I'm an admin on HybridZ - your best resource for information on what you're planning to do.

[LeonV]

Everything was fine until you copped an attitude when you got upset that I disagreed with your first post in this thread, and I retaliated as such. I'm not asking anyone to stroke my ego about the engine. There is a difference between giving constructive criticism and being close minded. You did imply that I am a bench racer and that I am an 'internet engineer'

I understood everything you were saying, I even agreed I was wrong in one instance, but you seemed to focus more on the fact that I disagreed in the first place. Your proposal defeats the purpose of the engine I want to build. I know I can make an L28 do the same thing, I'm fully aware. The fact of the matter is, in order for it to do rev as fast as I want it to, I would need lighter internals, which would defeat the purpose of using stock parts and ultimately the build itself.

The fact is that you think by bashing on someone else's concept, then claiming that they are only wanting someone to stroke their ego when they disagree with you shows YOUR maturity.

Where did I "cop an attitude"? This is the insecurity I'm talking about. I did not call you anything (as you did to me). Nor did I imply anything of the sort.

The first statement of mine that you quoted means that there is no reason to call one engine better than another simply because of some minor detail (R/S ratio, rod angle, etc.). The "bench racing" is in reference to those that take minute differences in these details too seriously, and seem to discuss their merits down to an atomic level. My statement foreshadowed the post by Zedyone, to which my other statement you quoted refers to. So it was not even in reference to you.

You agreed you were wrong in one instance? Great! You acknowledged that you're not looking for a close-ratio transmission. Okay, moving on...

I'm sorry if I hurt your feelings with my proposal, it was just the logical progression of your goals. If you had stated your true goal originally, I wouldn't have bothered.

You seem to be going in circles here. You know that you can make an L28 do the same thing, yet you don't want to for some reason? You can easily use stock parts to achieve this. This is why your goals must be clearly defined. You started out by stating that you like the L28 but want it to "rev happy like the L24" and then change that to wanting a "rev happy" engine that "revs as fast as I want it to". Do you still want it to rev like an L24, or have your goals changed? I'll tell you once more that an L28 can be just as rev happy as an L24 with minimal effort. This is your stated goal in your first post. If your goals have changed, then say so. If you came in saying, "hey guys, I want to build this engine because I want to be different" then there wouldn't be a problem.

Am I supposed to be able to read your mind? If you want to build an engine for the hell of it, then just say so. I never "bashed" your concept, I just explained how and why it could be done easier another way. You tell me no it can't. I explain again, how it's possible. You refuse to believe me and then insult me after a comment is made in reference to something else. Nice.

The problem is, you only seem to acknowledge performance in terms of power, which in motorsports, is an incredibly small area in comparison. To get the feeling I want with the L28, it would cost more. (See; "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."). I understand with light weight components I can achieve freer revving, but not to the extent that I want, which you can't seem to grasp. If I just wanted a freer revving L28, this topic wouldn't have even come up.

Nobody is saying performance only means power. You're just grasping at straws at this point.

I perfectly grasp the extent to which you want your engine to rev, because you clearly spell it out in your first post. Here it is again:

"I love the torque out of the L28, but what I really like is the rev happy L24. I figure why not try to mesh the two?".

"Tell me what you think!"

My response was going off of the information that you gave us. You said you wanted something that revs like an L24. I gave it to you and you got upset. You even asked for our opinion! Seriously? There are absolutely no justifications for your immature replies.

Basically what I'm saying in layman's terms is: "Haters gonna hate."

Yep, typical response from this generation...

[Ted.]

I'll make this really simple. Will an L28 rev as fast (not as high, as fast) as what I'm proposing, with factory parts; Yes or no?

[John Coffey]

Yes if you're willing to do some machining on the parts, especially the crank. Again, the issue is reciprocating mass, not stroke length. Knife edge the crank and take 15 lbs out of it and you'll be amazed at how fast a L28 can spin up. Lightening the flywheel and reducing the MOI of the flywheel/clutch also helps significantly.

BTW... there's not much of a different in "rate of spin up" between a stock L24. L26, and L28. The perceived differences have far more to do with the state of tune of the engines being tested then stroke, mass, or MOI.

Edited December 9, 2011 by John Coffey

[Ted.]

And how much does that cost in comparison to a junkyard L24 crank and rods?

Edited December 9, 2011 by Ted.

[John Coffey]

If your primary concern is cost, then this thread is a complete waste of everyone's time. Power is made in these engines through the labor put into the build. Its not about the parts used, its all about the effort put into the build and labor is by far the most expensive part of any engine build no matter who does the work - even if you do it yourself.

Again, how fast your junkyard build will rev has much, much more to do with the quality of the build and the quality of the tune then stroke, mass, or MOI. Orders of magnitude more.

[Ted.]

Cost isn't the primary concern, but it does play a factor. As stated, I'm not looking for a race motor, so spending race motor money on it (IE That much machine work into the crank would cost a lot) is completely pointless. The heads are getting surfaced, ported and the casting flash is getting cleaned on them as well as a 3 angle job and possibly machined for the larger 280 valves (thanks again for the article, Brian). The block is getting the casting flash in the crank area cleaned, its getting honed, and surfaced, then cleaned and pressure tested after all the machine work. The crank is getting checked to see if its still balanced properly and all of the journals polished. The rods are just getting sonic tested after checking the weights.

I know what needs to go into a motor for it to work properly and as efficiently as it needs to, and machining a crank that much and re balancing it on top of the machine work that is already getting done is too much for what this motor is supposed to do. 90% of the cost of this motor is already going to be machine work, so spending as much on the crank as it will cost for a majority of the parts its foolish.

Edited December 10, 2011 by Ted.

[olzed]

Another Approach. Power From Revs.

Most if us will have heard about gobs of power and torque being extracted from a stroker engine.

For those who don't know, a stroker is an engine that has been given the benifit of a longer stroke,that is the crankshaft throw, which gives more leverage to each turn of the crankshaft.

This is usually achieved by fitting an aftermarket crankshaft, having your standard shaft welded and ground, or in the case of the Nissan 280Z, fitting a Nissan Diesel engine crank.

By a happy chance the bearing diameters are the same for the petrol and diesel engines.

This crank, accompanied by extensive head work to improve air/fuel flow through the engine,as well as careful matching of pistons etc. can result in huge power gains.

The Standard L28 engine has a stroke of 79 mm or 3.1 inches, while the diesel crank has a stroke of 83 mm or 3.26 inches.

These engines have become the way to go for your Z racecar.

Another way to approach the subject is to make power from revs, not unlike the formula one race cars, producing in excess of 700 HP from a NA engine reving past 17000 RPM.

The following is an extract from a magazine long out of print.

"Most small capacity European cars make their power from high revs, and I wanted to move in this direction with my 240Z

What most of these engines have in common is a short stroke of 3 inches or less. This keeps mean piston speed at a reasonable level at high RPM, ensuring that the engine will stay together and give a long service life. The high rpm generates power out of proportion to its displacement, because it allows the engine to transform the energy contained in lots of fuel/air mixture into mechanical work in a short period of time. The downside is that the short stroke reduces the engines ability to produce big torque by shortening the lever- arm length that the pistons and conrods act on to turn the crankshaft.

My 240Z engine, with a stroke of 2.9 inches, came in nicely under the 3 inch limit. Not coincidentally, the stroke of the most popular hot rod engine known to man---the early small-block Chevy V8--- was exactly 3inches.The L24 block gives us 2.4 litres. It occured to me to use my L24 crank in a L28 block, which with a rebore of 1mm gave me 87 mm and a displacement of just over 2600cc.

I knew that this would need careful thought about pistons and con rods if the deck height ( the height of the piston tops in relation to the top of the block) was to be right. Since I was to use the 240 crank, why not use my 240 rods? But which pistons could I mate with them?

Using 280Z pistons would have worked, since the piston pin to piston top dimensions are the same in all first series Z engines. But there was a problem. Almost all 280Z and ZX pistons are dished on top, reducing the compression ratio below the 10-1 that I had in mind. However non turbocharged 280ZXs that were sold from 1980 till the end of the ZX run had pistons with flat tops. These fitted my requirments for low cost, since stock Datsun pistons would be far cheaper than forged racing pistons.

I decided to use the E31 head that came off my engine, since this head has large ports and good quench characteristics between the head and piston top. One problem is the E31 combustion chamber is relatively small, giving more than the 10-1 compression that I wanted. Another is that the E31 uses smaller valves than later Z cars.The solution was to have installed the larger 280Z valves, and unshroud them by removing small amounts of metal from the combustion chamber near the valves. This improves breathing and at the same time lowers the compression to the 10-1 I was aiming at.

All of this requires careful planning and execution with expert advice. Best to talk to a machinist who specialises in this type of performance engine rebuilding, preferably someone with experience in Z car engine rebuilding.

Installing the larger valves requires machine work to replace the valve seats- an exacting process. The costs for this can add up. If you do not require the ultimate in engine breathing, settle for the stock 240 valves in the large port E31 head.

It is possible to purchase an L28 block for very little. If you start with an early 240Z engine all you need are parts from your donor engine, an L28 block, pistons from Nissan or an aftermarket source, and a good machine shop. I had a 280Z camshaft reground, with considerable overlap and opening duration. I have run this engine freely up to 7000 rpm hundreds of time over the years and it's bullet proof. With the use of forged pistons and high qualiy rod bolts etc this engine will happily rev way past that and live."

Edited December 10, 2011 by olzed

[LeonV]

I'll make this really simple. Will an L28 rev as fast (not as high, as fast) as what I'm proposing, with factory parts; Yes or no?

Yes. Refer to my first post. Just put a lightweight flywheel on an L28 and it will likely rev-up faster than a stock L24. Stock flywheels are ~25lb. Aftermarket aluminum units can get down to the 8-10lb range. That's 15lb of rotational mass removed from the crank right there.

Yes if you're willing to do some machining on the parts, especially the crank. Again, the issue is reciprocating mass, not stroke length. Knife edge the crank and take 15 lbs out of it and you'll be amazed at how fast a L28 can spin up. Lightening the flywheel and reducing the MOI of the flywheel/clutch also helps significantly.

BTW... there's not much of a different in "rate of spin up" between a stock L24. L26, and L28. The perceived differences have far more to do with the state of tune of the engines being tested then stroke, mass, or MOI.

If your primary concern is cost, then this thread is a complete waste of everyone's time. Power is made in these engines through the labor put into the build. Its not about the parts used, its all about the effort put into the build and labor is by far the most expensive part of any engine build no matter who does the work - even if you do it yourself.

Again, how fast your junkyard build will rev has much, much more to do with the quality of the build and the quality of the tune then stroke, mass, or MOI. Orders of magnitude more.

John makes good points. This is why there is no need to focus on differences in R/S, stroke, rod angle, etc. The differences are insignificant for a project such as this. Do the simple stuff mentioned, and you'll come out far ahead.

[Ted.]

Yes. Refer to my first post. Just put a lightweight flywheel on an L28 and it will likely rev-up faster than a stock L24. Stock flywheels are ~25lb. Aftermarket aluminum units can get down to the 8-10lb range. That's 15lb of rotational mass removed from the crank right there.

As fast as a stock L24, yes, you're absolutely right, but not as fast as what I'm proposing, which is what I asked. The lightweight flywheel and pulley (technically still a factory pulley, just from a car with no a/c or power steering) are already a part of what I want, so just putting them on an L28 and calling it a day will give me slower revs then what I'm looking for, its just that simple

John makes good points. This is why there is no need to focus on differences in R/S, stroke, rod angle, etc. The differences are insignificant for a project such as this. Do the simple stuff mentioned, and you'll come out far ahead.

Yes, he does, for a racing engine. If I was comfortable dropping $700+ on JUST machining the crank, this engine would be irrelevant and you would be 100% right. The reason these things do need focus is because I can't justify those kinds of costs for a street driven car. The reason this engine is proposed is because it costs the same as a traditional rebuild with the addition of careful machining, faster revs, and keeping power as good if not better then a typical n/a L28 using SUs.