Looking to make a "square" L24 with LD28 crank...

[DavidBoren]

Has anyone done this? And what con-rods will I need? The square bore/stroke is just something I want to do. I know there is no replacement for displacement. I know the L28 strokers are more popular.

I have a numbers matching 1970 240z, and want to use the block/head that it came with. I, personally, like the thought of a "square" engine, and thusly plan on building this one accordingly.

Any insight or advice would be appreciated. My goal is 240rwhp, not sure its it possible, but thats what I am shooting for.

Plans include:

L24 block with stock 83mm bore,

Ported stock head with bigger valves (if possible),

LD28 83mm stroke crankshaft (knife edged),

11:1 compression ratio (91+ octane fuel only),

Lightweight conrods (not sure of length),

Lightweight dished pistons,

New cam (not sure which),

New valvetrain (lightweight, high ratio),

Not sure of intake, 3x2 maybe, or ITB

Might put a mild (75hp) shot of juice to it just for fun.

[madkaw]

Sounds fun, but will only happen with GOBS of money and a professional builder like Rebello and you still won't see 240hp at the wheels. If you do- you will have very prestigious bragging rights. 240rwhp 240 would be a race motor.

Now that I burst the bubble, shoot for 200rwhp and have some fun. I would think that 280 rods would be the trick with custom height pistons- and not dished pistons.

How about introducing yourself and tell us about your engine building experience.

It's obvious that you have some to learn about the L engine, and I'm not trying to be an a$$, just judging by your post.

You might need to take your head to have it evaluated first before you make these plans. The early E-31 was prone to corrosion.

[240260280z]

S2000 motor has 246hp

[DavidBoren]

Ok, hello everyone. As my username may suggest, I am David Boren. I am 28 years old. My daily driver is a 2005 Cadillac V6 CTS. I live in Portland, Oregon.

My fiance's grandpa has a 1970 Fairlady just sitting in his backyard. I want to turn it into a my weekend cruiser. Just something to take out and have some fun in the sun with. I will probably use it in local autocross events just to become a better driver. And a 240z will do A LOT better job zigging and zagging between the cones than my Cadillac luxury sedan.

I have no engine building experience, and am planning on making the Fairlady my first build. I am not trying to break the bank on this, and that is why I want to stick with the stock block and head. I will get everything professionally checked and cleaned. And any porting/machining will be at a shop, not by me.

The 240rwhp goal is simply based on the fact that the car is a 240z. If it isnt feasible, then I will take what I can get from a high-compression "square" L24. The LD28 crank will give the L24 a square bore/stroke (83mm x 83mm). And if the 280 rods will work, they are probably pretty easy to source as well. I want a lightweight/balanced rotating assembly, so the rods and pistons will probably be the largest expense of this build.

Having the block decked or the head shaved to up compression shouldnt be that expensive. And I am not doing anything too radical to the head as far as porting. Mainly just port-matching everything, and having larger valves installed if they will fit.

Any word on whether or not I can fit any larger valves into a E31? As I plan on having the block zero-decked to the top of the pistons, I also need to know if larger valves would hit my pistons, or if high-ratio rockers and a lumpy cam would cause interference between valves and pistons. That is actually why I originally mentioned dished pistons.

Also, speaking of lumpy cams... is there a L-series cam that is more aggressive that would be easier or cheaper to source, or should I just go aftermarket?

Thank you for your replies thus far.

PS. There are LOTS of 240+hp engines out there. I am not interested in an engine swap at this point. I am enjoying the vanity of having a numbers matching car, and just want to play with what I have available. If I was going to swap in anything, it would be an all aluminum 5.7L LS1 stroked to 372" with a 3.9" crankshaft (making it square with the 3.9" bore).

[Zed Head]

I almost replied to this thread yesterday about the "square" concept, but decided to just leave you to your eccentricity. It's hard to tell if you're really trying to be sensible or just want to put an odd collection of parts together.

Sticking with the original engine because it looks original, but modifying it so that it's not original doesn't seem to serve any purpose. The "square" bore-stroke ratio has no technical merits at all, it's just a weird number thing. Porting the stock head and installing bigger valves is what used to be done before the 280Z heads became available. And the most effective way to get more displacement is to get an L28. The money that you're proposing to spend on the LD28 "knife-edged" crank would be more useful elsewhere. Overall, once you do the math on collecting those parts, installing bigger valves, porting the head, buying custom pistons (I don't think that there's a stock set that will work), knife-edging the crank, etc. I think that your bank will be seriously damaged, if not broken. Do the math, then send the engine to Rebello and ask him to give you as much power as possible. You'll be many dollars ahead AND the engine will probably run well and not self-destruct, plus you'll have the Rebello "cool" factor on your numbers-matching engine.

As far as learning goes, you're at about 1980, I think,with the big-valve, high compression stroker engine. No offense, you seem to be learning, probably from various old internet postings, but what you've proposed won't be cheap, probably won't run as designed unless you use expensive race gas, could very well blow up quickly, and won't be tunable by the average mechanic.

Full disclosure - I'm only speaking from what little I've learned over the past few years. Not an engine builder, so I could be way off base.

[HS30-H]

My fiance's grandpa has a 1970 Fairlady just sitting in his backyard. I want to turn it into a my weekend cruiser. Just something to take out and have some fun in the sun with. I will probably use it in local autocross events just to become a better driver. And a 240z will do A LOT better job zigging and zagging between the cones than my Cadillac luxury sedan.

I have no engine building experience, and am planning on making the Fairlady my first build. I am not trying to break the bank on this, and that is why I want to stick with the stock block and head. I will get everything professionally checked and cleaned. And any porting/machining will be at a shop, not by me.

The 240rwhp goal is simply based on the fact that the car is a 240z. If it isnt feasible, then I will take what I can get from a high-compression "square" L24.

Bold emphasis is mine.

1970 Fairladies had either L20A engines or S20 twin cam engines. The L24 wasn't used in the Japanese market Fairladies until late 1971 ( in the Fairlady 240Z, Fairlady 240Z-L and Fairlady 240ZG ), so if it's a 1970 Fairlady it won't have an L24 engine, and it's not a '240Z'.

If the car in question does have an L24, then it's a custom installation and the car doesn't have its "stock block and head" anymore....

[madkaw]

David,

Not trying to cut you down here, just putting your feet down on firma ground. They would cut you up and feed you to the lions over at Hybridz with your nubience. You will find a friendly group here that loves modified L motors. You will be suprised how much fun a well thought out performance L24 can be---- even at 160HP. Do some searching here and you won't see any square bore projects, but some good stuff.

good luck

[DavidBoren]

I will have to take a closer look at the car, but gramps said it was a 1969 240z. I didnt think they came stateside until 1970, so I assumed he was just a year off. To be honest, and to advertise my ignorance, I have just assumed Fairlady was a monicker associated with the 240z. I dont know if its a separate car. And if it is, I stand corrected.

I appreciate the advice and criticism. I do not know much about these cars. It may not have an L24 in it. All I know is that I do not have the money to do an engine swap, so I want to have some fun with the engine that is in there.

As far as making it square, it is just my preference. To each their own. Nobody thinks twice about stroking an engine, and that is all I was proposing with adding an LD28 crank to a L24. It just happens to make the bore and stroke match. And I just happen to like that. The 2jz is a square bore/stroke powerplant, and people do amazing things with that engine.

I will get the VIN this weekend, and get back to you with some better details. Thank you for setting me straight.

[John Coffey]

Race 2.4Ls that ran in GT2 back in the day made over 360 horsepower. Spin fast and you can make power even without a lot of displacement.

[Patcon]

The VIN is a great place to start. If it is a 1969 car it is likely a low number car and would deserve special consideration if its not a rust bucket. A stroker project is not a cheap endeavor, even in the most econo minded setups that I have seen. If you could afford Rebello that would be a sure fire way to end up with good useable power and reliability. Building your own motor takes some attention to detail and what works on a 2jz does not necessarily translate to a 40 year old Nissan motor. 2jz is a dual cam cross breathing engine; a totally different animal than a Nissan L6 type engine. That is why many of the people on Hybrid Z do the swaps they do is because many times it is easier, cheaper or both to just swap or swap and turbo for significant gains. The VIN is the right place to start and some pictures would be good, especially the rust prone areas: battery tray, rocker panels, rear wheel arches, floor boards, dog legs...

Charles

[DavidBoren]

I will check it for rust when I go over there this weekend to check the VIN.

I am pretty sure it has an L24, as that is what the American import 240's had in 1969 and 1970.

This will be my first manual transmission vehicle, so I am mainly just going to play with it at autocross events to become a better driver.

That being I am going to focus largely on upgrading the transmission and differential first, because it is going to take a beating with me pretty much learning how to drive a stick. Suspension and brakes will be a close second because autocross can be hard on these areas.

Once I get the power it already has available firmly and efficiently hitting the ground, I will worry about upgrading the engine. Thank you all for your input, both negative and positive.

[Zed Head]

My fiance's grandpa has a 1970 Fairlady just sitting in his backyard. I want to turn it into a my weekend cruiser.

I probably came across as negative in my post. Just trying to save you some money. The two sentences above shout "thousands of dollars" just to get to the end of the second sentence. Seriously, all of the hydraulics are probably bad, there's probably body/frame rust, the engine may need one or two thousand if you rebuild it along with the carburetors, and on and on. A broken stud or bolt here, a cracked thermostat housing there, the nickels and dimes just start rolling. Wait until you have the car in your possession and know what you have. If it's a very early Z you might decide to just restore it, or pull the numbers-matching motor (if it is) for safe keeping.