Anyone running a LD28 crank w/ L20A conrods in their L24?

[DavidBoren]

I have asked a similar question regarding making a totally square bore/stroke (83mm X 83mm) L24, and was directed towards the ozdat engine calculator. Thank you, by the way, that was very helpful.

 

Now that I know what I am looking for, I want to know if anyone has a similar build. Is anyone running anything comparible to this:

L24 block with stock 83mm bore,

LD28 crank with 83mm stroke,

L20A 128mm conrods,

E31 head,

L20A cam.

According to ozdat, I would be looking at 2.7L (2.694) displacement at 9.854:1 compression. Bore/stroke ratio of 1:1, rod/stroke ratio of 1.542:1, with a maximum rod angle of 18.918*.

 

To be perfectly honest, I do not know if those numbers are good or bad. I do want a compression ratio close to 10, as I will be using 91+ octane fuel. And I like the square bore/stroke ratio. But the rod angle seems a little steep, and the rod/stroke ratio seems a little low. Any help, insight, or advice would be greatly appreciated.  Thank you, in advance, for any productive input.

[djz]

I'm pretty sure that calculator has the wrong rod length for L20A rods, they are the same as L24 rods, apart from the odd ball late L20As that have smaller journals etc.

[NewZed]

Seems like you're going through gyrations just to get a magical/mystical "square" bore/stroke ratio.  And that L20A cam is kind of tiny for a 2.7 liter engine, isn't it?  Add in the small E31 valves and it will be kind of choked, I believe.  I'm not an expert, by any means though.

 

Engine specs. for the L20A are in the 1972 FSM Engine Mechanical chapter.

 

http://www.nicoclub.com/FSM/240z/

Edited August 17, 2013 by NewZed

[DavidBoren]

I am a huge fan of the 2jz motor. Which is loved and respected for being a tiny little engine capable of being a reliable 10,000rpm/1,000hp monster. It is an inline six. And it has a square bore/stroke ratio.

 

I do not want to rev up to 10k. I do not want 1,000hp for my 240z. I was just using the basic principle of that engine as a building point for the one in my Fairlady. Seeing that everyone and their brother borrow freely from one L-engine to another, to create hybrid strokers and everything else imagineable with the combination of parts available, I thought maybe someone has done something similar.

 

I honestly do not know which cam to get. Maybe the L20A cam is too small. I would like a more aggressive cam. I would. I can go aftermarket if I have to. And probably will. I had read somewhere that L20A cam was a little more aggressive. I obviously read wrong.

 

As for the valves, I do plan on having the head thoroughly ported and polished, and larger valves installed. Probably the largest ones that I can find that will fit.

 

My goal is to get the engine producing a reliable 10+hp per pound. Curb weight, that means I need 220rwhp. Race weight would be closer to 2450lbs, so I am really wanting closer to 250rwhp. I do not think that I am asking too much. I know The Purist engine build boasts similar power figures. I also know that a respected racing company does that build. I am hoping to do most of this in my garage, as my first real project car... not send my powerplant off to get built for me. 

 

I know it would probably be easier to just drop in a 2jz-gte stand alone crate motor. But I have a numbers matching 1970 FairladyZ, and I thought it would be cool to keep the block and head casting original. Well, the head would be ported and polished, but still the same chunk of metal that was in the car when it left the factory. Just looking for a super fun, quasi-classic car that I can autocross when I feel squirrelly.

[Xnke]

You are about to start working in circles. Do not go down this road, unless you simply want to spend a lot of money to get nothing.

 

Start with an L28, and save yourself thousands of dollars.

 

The "Purist" engine is flywheel horsepower, not RWHP.

 

250HP in a daily driven car is not an easy or cheap thing to get from an L28, and to do so will require a very good cylinder head, and a very well chosen cam, header, and exhaust. The induction could be either fuel injection with a good intake manifold, or carburation with a nicely matched, correct-runner-length set of triple sidedrafts.

 

Do not bother with a stock cam grind if you are looking to achieve that level of power. The L20A cam is the largest L6 cam that Nissan installed in stock engines, however it is still very small. Same goes for the L26 "C" stamp cam. It's not big enough to bother hunting one down...just send your JAPAN core in and get a larger cam profile cut.

 

You have a target. The cheapest way to get there, is a stroked L28 displacing 3,098cc's, with flat-top pistons, a well-ported P90 head, a moderate-to-lumpy cam, a good exhaust header, and a set of large triple sidedrafts. This setup, when tuned properly, can produce 250HP and be liveable on the street, and can be very, very fun at an autocross.

 

Your proposed 2.7L stroked L24 would cost exactly the same amount, if not a little more, and will not return the performance that the larger displacement engine can.

 

I started down this same road, and now I run a 2.9L bored L28, currently being reassembled into a supercharged, fuel injected, custom manifolded, engine. My target goal is 250-270RWHP, and I will likely end up between 230 and 250RWHP. It has not been an inexpensive path.

 

To expand upon why the 2.7L engine won't make the power that a stock L28 bottom end can make; look at the bore diameter. The larger bore diameter REALLY can make a difference in the intake and exhaust breathing...less valve shrouding, bigger valves, more room to work to correct the airflow in and out of the chamber. The smaller 83mm bore will not allow the maximum airflow possible from the larger valves and portwork you would need to produce the 250RWHP you desire.

 

Keep in mind that you will need to make 300 flywheel horsepower to measure 250HP at the rear wheels, and building a 300FWHP L28 is NOT a simple, easy, or even difficult task...it's a MAJOR EFFORT.

 

To distill this post down; Large bore, large displacement, large cam, big airflow (but not necessarily large ports!) large power.

Edited August 18, 2013 by Xnke

[T-Bone028]

I don't see anything wrong with pulling your numbers matching L24, freshen it up and confirming it's in good order, and then storing it very well in your garage for later. Is numbers matching a vanity or value thing? I would imagine if you were a purist, you would not modify your numbers matching block at all. Not trying to make a dig at you or blast you, just trying to understand your purpose.

 

If it's about having a square motor...i would say that the L engine has been around for a long time. There is a reason why there are more strokers and turbocharged 2.8's than square L24's. Nothing wrong in going with the crowd.

 

However, if you must, try searching for Dizeased (or something like that) on classiczcars.com. I can't recall for sure, but he might have done something similar to what you are describing (or at least stayed w the L24 block)

[mrcheeze36]

However, if you must, try searching for Dizeased (or something like that) on classiczcars.com. I can't recall for sure, but he might have done something similar to what you are describing (or at least stayed w the L24 block)

Here's to link to that thread:

http://www.classiczcars.com/forums/engine-drivetrain-s30/42488-new-engine.html

 

Diseazd's engine specs:

L28 N42 block bored .040 (he's using an F54 on his 2nd build)

L24 crank and rods

L28 P79 flat-top pistons 0.040 over (ITM pistons)

P79 head shaved and shimmed .080 inches

About 9.2 to 1 C/R

Isky stage III cam

[Xnke]

Now that's what I'm talkin' about. If you're just stuck on the L24 stroke, at least get the biggest bore you can run, leaving yourself some rebuild room, and make it breath! Forged pistons...so you can enjoy the "high revving" L24 crank. (Not that it actually revs any better, lots of people have turned the L28 cranks to 8000RPM or better...some higher than that!)

[DavidBoren]

Thank you for the feedback and links. Upon realizing how severely I underestimated what it takes to get 250rwhp out of an L-engine, be it the L24 I have, or any L28 I could pick up, I think a swap is more in order. It would be easier, both financially and mechanically, to just drop in a powerplant producing the ponies I need/want.

 

I did want to keep the numbers matching block/head out of vanity. And the same vanity drives me towards an RB-swap, just to keep it all in the Nissan family. I will probably pick up a RB25DET with transmission from JDM for about $1,500. And a McKinney Motorsports 240z-RB-swap kit for $500.

 

I want to find a RB26DETT, but so does everyone else, and so they are hard to find and expensive when you do. However, I really do like how three cylinders feed each turbo.

 

I would love to build an odds-and-evens inline six turbo set up with the odd cylinders exhaust feeding a turbo that feeds the even cylinders intake, and even's exhaust feeding a turbo feeding the odd intakes.

 

Anyways, thanks again for all the input. Looks like I will be moving over to RB engine side of this forum for the rest of my inquires.

[DatsunZman04]

This is a different concept,  DESTROKING a L28 with a l24 crank. Keeping a higher cubic inch/ bore diameter block with a shorter throw crank. Is this like compairing a stock 350 sbc vr a 400 block sbc destroked using a 350 crank to get a 377?? Kind of compairing apples to oranges here sorry.

 

What would be all the benifits of doing this vr using the longer stroke l28 crak or the vo7 diesel crank?? in a 280 block??

[ctc]

Only reason in my opinion to destroke am L series engine is for class rules or you have the parts laying around. Bob Sharp did this back in the day to get 2.5 liters. Again my opinion, but on anything but a race engine limited by class rules these minor "tweaks" like square bores, rod/stoke length, this crank or that piston does not really matter. Like all engines, power is in how the engine breaths (airflow) and compression. For the L series, head work and compression will get you power on whatever bottom end you build.

Edited August 20, 2013 by ctc

[ctc]

Thank you for the feedback and links. Upon realizing how severely I underestimated what it takes to get 250rwhp out of an L-engine, be it the L24 I have, or any L28 I could pick up, I think a swap is more in order. It would be easier, both financially and mechanically, to just drop in a powerplant producing the ponies I need/want.

 

I did want to keep the numbers matching block/head out of vanity. And the same vanity drives me towards an RB-swap, just to keep it all in the Nissan family. I will probably pick up a RB25DET with transmission from JDM for about $1,500. And a McKinney Motorsports 240z-RB-swap kit for $500.

 

I want to find a RB26DETT, but so does everyone else, and so they are hard to find and expensive when you do. However, I really do like how three cylinders feed each turbo.

 

I would love to build an odds-and-evens inline six turbo set up with the odd cylinders exhaust feeding a turbo that feeds the even cylinders intake, and even's exhaust feeding a turbo feeding the odd intakes.

 

Anyways, thanks again for all the input. Looks like I will be moving over to RB engine side of this forum for the rest of my inquires.

.

 

If you are now talking turbo RB swap, the same money in an L28ET swap with head work will get you a lot farther.

[Tony D]

We made 205 at the rear wheels with our L20A.

 

It did not have a square bore.

 

It can exceed 10K.

 

You have an HS30?!?!? Hens tooth for sure Fairlady 240Z...

 

A stock Eurospec 280ZXT makes 200, bump the boost and there you go...no intercooler required, 220HP!

Edited August 23, 2013 by Tony D