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Jayru

Reliable/powerful L24?

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Hi guys,

I've been working on cars for almost 10 years now, and have owned/worked on Mustangs, GalantVR4's, 300ZXTT's, but I'm new to the 240Z/ L series engine/carburation, and i have a few questions. I've been doing a lot of searching and haven't found the answers i'm looking for so i thought i'd post my questions.

Can the L24 be a powerful/reliable engine? Every thread i come upon says to use an L28 block, yada, yada. But they don't ever say why. What is the weakness of the L24?

I'm picking up a 72 240Z tomorrow and it has the original L24 in it with double SU's. It runs like crap now and wont barely start (needs a tune up, ect). My original intent was to do a Hybrid-V8, RB motor, ect.

But since the car is original, and swaps wind up costing a lot of money, i'd like to tune the L24 to make some decent reliable power. Is this posible or am i wasting my time?

If i rebuild the SU's and do the Pertrox electronic ignition, can i make some decent reliable power? (200-300 HP range)

Are triple webers a better setup? I have a guy that wants to sell me a triple weber setup (manifold/45mmcarbs) for $300. Is that a good deal?

Sorry for so many questions in one thread. Your help is greatly appreciated. I look forward to posting here and getting to know some of you.

Thanks,

Jay

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you came to the right site, my friend! most of us here hold to the L-series engine (at least that's what i come away with). the l-series engine is one of the best engines (i think i'm on 237K right now and running strong as hell!). the reason that i believe most people get the L28 is for increases displacement. also, if you think about it, nissan has come a long way (as have others) over the years. newer technology usually equals better engineering. anyway, from what i have researched, the l24 is a relatively good motor, especially considering your automotive history :P... anyway, there are tons of other folks that can tell ya more! so here they go:

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Sorry ! You are not going to just bolt on a tripple set , convert the ignition and make 300 HP. on a L-24 or a L-28 . If you have deep pockets and build a stroker . Sorry but this is reality

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Sorry ! You are not going to just bolt on a tripple set , convert the ignition and make 300 HP. on a L-24 or a L-28 . If you have deep pockets and build a stroker . Sorry but this is reality

Well this is why i'm asking these questions. Oviously i'm not an idiot and realize that tripples and and ignition will not make 300HP. That's why i said 200-300. I am trying to find out info on these motors, their best modifications, their weaknesses, what gains are there to be had with tripples, ect.

I found none of that in your reply.

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HI Jared,

If considering keeping your car original.."loaded word" I know you can make 175-200hp with stock head/valves & cam with .o40 overbore, 9.5 compression.

That said, fitting 280 valves in the stock head little larger cam, with standard bore and good quaility rings, should net you similar results.

I like being able to turn 7400 if need be with my 240 engine.

David

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Hi guys,

I've been working on cars for almost 10 years now, and have owned/worked on Mustangs, GalantVR4's, 300ZXTT's, but I'm new to the 240Z/ L series engine/carburation, and i have a few questions. I've been doing a lot of searching and haven't found the answers i'm looking for so i thought i'd post my questions.

Can the L24 be a powerful/reliable engine? Every thread i come upon says to use an L28 block, yada, yada. But they don't ever say why. What is the weakness of the L24?

I'm picking up a 72 240Z tomorrow and it has the original L24 in it with double SU's. It runs like crap now and wont barely start (needs a tune up, ect). My original intent was to do a Hybrid-V8, RB motor, ect.

But since the car is original, and swaps wind up costing a lot of money, i'd like to tune the L24 to make some decent reliable power. Is this posible or am i wasting my time?

If i rebuild the SU's and do the Pertrox electronic ignition, can i make some decent reliable power? (200-300 HP range)

Are triple webers a better setup? I have a guy that wants to sell me a triple weber setup (manifold/45mmcarbs) for $300. Is that a good deal?

Sorry for so many questions in one thread. Your help is greatly appreciated. I look forward to posting here and getting to know some of you.

Thanks,

Jay

I doubt you'd get 200 HP out of rebuilding SU's and adding a Pertronix either.

"Tuning" a L24 to make the kind of power you mention is a pipe dream.

Your best bet for detailed info on what can/should be done to an L24 or L28 achieve HP in the area you mention is to invest $20 on the "How To Modify Your Nissan & Datsun OHC Engine" book.

http://www.zcarparts.com/store/merchant.mvc?Screen=PROD&Product_Code=70-1050

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Jay I believe i can help a little.

Ok so you want to stick with your L24 block? No worries I can understand that however consider going with an L28 with the F54 casting because these blocks have extra webbing between their cylinders and as a result can handle being over bored a bit better.

If you stick with the L24 block you can always use the L26 crankshaft to increase your stroke. Best results from the motor come from port work and a good camshaft profile.

Different people will give you different horse power figures. Since the Z is so light one of the best things you can do is change diff and gearbox ratio's over. This will give you great acceleration.

Don't use the Petronix Ignitor IMO it's garbage compared with the 280zx electronic units. You will want to recurve it to suit your motor this will let you rev it quicker and higher.

These motors are generally quite good and most race parts were actually factory stock parts. As Carl mentioned the book above is a good resource and will give you detailed information.

your motor will come down to your budget if you can spend money on the motor and not worry about the $$$ you'll get a great motor if your on a tighter budget it might be hard to squeeze over 200HP out of the L24.

FWIW the carbs sounds like a good price but they won't do any good without other modifications first.

Gavin,

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Jayru,

Invest in a book by Frank Honsowetz. Titled "How To Modify Your Nissan & Datsun OHC Engine" ISBN 1-55561-237-7.

It will answer most of your questions. I have built all sizes of Datsun engines over the past 30 years. Mostly for racing, but some for street. Powerful & reliable generally don't go together well. There's always compromise. For the street, you need 9.5 or 10.0:1 compression max. With triple carbs, a small cam, a little head work and a header you might see 180 hp out of a 2400.

A similar 2800 might make 200/220 hp. The most radical street motor I ever built made about 260 hp. It had a stroker crank and had a disp. of 3 liters. Consider that a full race SCCA GT2 2800 (+.040) will average around 300 hp, and you will see that building a carb'ed street eng. with the same hp is not reasonable. Unless its Turbo'ed. Thats a whole 'nother ball o' worms. And a another wheelbarrow full of cash. Good luck, and go with what you think is best. Most everybody here has been around the hp block before, and they will tell you like it is. Nobody has an axe to grind, and there's a lot to be gleened from this site. Even for a semi-old guy like me.

Phred

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OK I'll chip in my 2 cents worth.

As you would be aware, changing carbies on a stock motor would have almot no effect on the HP of the engine. It might be able to breathe a little easier through 6 venturi of the triple carb setup, compared to the 2 venturies of the twin SU, but not much gains there unless you cna make the engine breathe better.

Meaning more extreme cams, bigger valves, bigger exhaust. To get decent horsepower you need higer compression, and/or more cubic inches. The V8 guys love telling you, "there is no substitute for cubic inches". but its more accurate to say that the more air/fuel mix you can get in the engine and the more you can compress it is what makes high horsepower.

Thats why people go with the L28, cheaper gains to be had from larger engine displacement. and it has bigger valves.

The L24 is hichly regarded because its a shorter stroke engine, meaning it can rev easier and higher.

The L26 is basically and L24 with increased stroke (same piston diamers as a L24).

and the L28 has the stroke of an L26 but with bigger pistons.

I think is is possible to bore the L24 to L28 size and use L28 pistons and crank (aparenly on of the guys in WA had that setup in his race car). It would still look original apart from the carbies, but would be 2.8 litre engine. The car was basically undrivable on the street.

If you want to keep it original, how about pulling out the motor, laying it up, and stick it in a crate and hang on to it. Then drop in whatever motor you want and do whatever you want to it. That way when the time comes to put it back to original you have the original matching numbers engine to put back in, if you are concerned with resale value.

If you are going for a bigger engine Heres some homework for you:

http://www.geocities.com/inlinestroker/

http://www.geocities.com/zgarage2001/z.html

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Thanks guys for the great responses! This is exactly the type of info i was looking for.

I don't think i want to invest that kind of money for the output of the L24. So i'll probably yank it, put it aside, and save for a L28 or RB swap. No sense investing $ when i know i wont be happy with the end power result. Although i think i'll buy that book anyway, i'm always looking to learn new tricks.

It's funny, I'm just coming off the 2.0L 4G63T motor in my Galant VR4. Although it's turbocharged, that little 2.0 cranked out ~370HP with basic bolt on's. I just can't believe a N/A 6 could make so little HP.

Thanks again, and i'll be posting again i'm sure.

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Jayru, you could also build a respectable 2.4 engine (big valves, minor porting, tuned header, upgade ignition, better cam) and then add a nitrous oxide set up to the tripple carb manifold (a "wet" set up would be best) for that extra 40-80 hp when needed.

I haven't seen any NOS set up in our galleries (possibly concidered too "ricer?), but I'm sure if you contacted some NOS manufactures they could set you up.

Some homework on 5-speed transmissions and rear end ratios (LSD), and final drive ratios, would also be bennefical no matter what powerplant you use.

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The L24 is not a bad engine. Some tuning and maintanance and you will have a good reliable engine. I went to the L28 because it was cheaper to go L28 then to rebuild my broken L24.

If your looking for a little more power and keeping an original appearance then buy a L28 (280ZX motor), 81-83 seems to be the prefered years. You can pick them up pretty reasonable at a junk yard. And they are a direct bolt-in. Buy the book previously mentioned and you can start building. When you get the engine done then do the swap. If your looking for a lot more power than the L24 then go with a L28 turbo. If you want more power than the car can handle then go with a V-8.

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Jayru, I to am coming off a 4g63 with roughly 400hp.

You have to understand these cars are a completly different animal, for one there about 20 years older than our 4g63's.

The main reason your not going to see a large horsepower increase in a 240 compared to your gvr4 is the lack of a turbo. I have always known if you want to make cheap large amounts of power in the import world a factory equipted turbo is really the only way. To me this car is not about straight line power, its more about having fun and simplicity.

For now I will be happy with my l24, but im sure the day will come when I want a turbo again.

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do i smell the topic of L28ET coming up??? anyway, like stated before, volumetric efficiency is what it's all about. and as for the motor not making big HP numbers, the 240 isn't a heavy car. HP isn't always the most important thing when it comes to building an awesome car. the 240 is such a well balanced car that adding too much HP "can" ruin it.

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Jayru,

Welcome!

I feel an L28ET coming on also! I would like to mention something that hasn't been talked about yet... weight! How much did your Galant weigh? That coupled with the fact that the Z is a real sports car. It's not mom's econobox or a AWD family car hopped up on forced air. Not trying to offend by any means, but many cars are a compromise. The Z is just a true affordable sports car.

Good Luck with the gearheads never ending search for more power, and I hope that you stay L-series.

Nate

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Jayru,

Welcome!

I feel an L28ET coming on also! I would like to mention something that hasn't been talked about yet... weight! How much did your Galant weigh? That coupled with the fact that the Z is a real sports car. It's not mom's econobox or a AWD family car hopped up on forced air. Not trying to offend by any means, but many cars are a compromise. The Z is just a true affordable sports car.

Good Luck with the gearheads never ending search for more power, and I hope that you stay L-series.

Nate

most definitely! a torquey 6-cyl in a 2300 lb RWD mass of awesomeness? now THAT'S tasty....

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One of the privious posts mentioned the diff and a gear change. These cars from the factory were vary high geared. They were built as a sports car and not for streight line performance on the 1/4 mile. 356 and higher rear end gearing is common. Put in a 390 and even the stock L 24 will come alive. I to have gone with a 280ZX engine for the same reasons that were already given, the cost and by doing this , the gains are the same as . Boring and strokeing and porting and installing biger valves , plus a stronger block. All this by just switching engines. And everything fits in just like stock. I did change the diff to a 370 , would have gone to a 390 but this one was at hand. With the car at 2600 lbs it should perform at least to my expectations. I will see in a couple of weeks. With the ''street'' cam and 9.5 compression and so on this should do fine . This is a cruser not for the track. If you do decide to keep the inline 6 or to make a change keep in touch , there is a lot of knowledge on tap here . Welcome aboard. Weather on not you realize it , YOU ARE NOW INFECTED AND THERE IS NO CURE . Enjoy the ride. Gary

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Well guys, after this thread and hours of research, i've decided to get the L24 running for now (think a bad fuel pump) and just drive the car until i can save enough for a swap.

It'll be a SR20DET or an RB25/26.

I think i'm going to spend my money first getting the car ready to handle the power. Suspension, rear, and chassis stiffening. So look for my post's in those sections of the board. LOL

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:classic: Before discarding the thoughts of seriously running the existing engine, why not run a compression test? Get a feel for what you have now.

Get the SU video from Ztherapy, study, and then clean/adjust the carbs to function properly, relace the dizzy with a 79-80 280zx part, some headers,"mainly for noise on a stock engine" , get the timing set right, check for timing chain "slop"..most likely due a new one, check hard for vacumn leaks on manifold, carb shafts, brake booster lines....all these items can be used on your 280 transplant if you decide to move in that direction.

175 crank HP is easily attainable...200 possible with semi stock engine, with right setup, and proper tuning

But for the same money spent on the larger blocks "280" + you will always have a more torque and HP.

david

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Hi Mike.....I think it’s great that you bring back these old posts.....always fun to see some of the early members.....keep em coming.

Guy

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