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L24 rebuild/bore options


Magnet

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Looking to rebuild my matching no. L24, little hard to find reading as most people start with a L28 block(which I may even do if the gains are huge)

 

Currently running L26 with e88 head, mild cam, extractors and 240 carbs.

 

Basically I want to build something that revs hard, 7.5k minimum(mainly for the noise :P). Budget isn't a massive factor, around $2k on the bottom end, maybe $5k all up would be nice? Triples and forgies will soak up a bit though

 

-How big can you get the L24 bore with sleeves?

-What's the highest CR you can run?

-What stroke/bore, cam/CR is gonna rev highest and how high?

 

 

Thanks,

 

Ryan

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No point doing a L24 unless you want it for racing or originality. A L24 will rev to 7.5k easier than a L28, but it's not too

hard to get one there (7k is a touch more realistic?) an unknown L28 will cost you somewhere around $200, and it about

the biggest HP boost you will get for you money before you go turbo. Save the original L24 for when it comes around to

selling it.

 

To get the same sort of power from a L24 to a L28, you are looking at roughly double (please correct me here if i am wrong)

ie. 5k on a L28 will cost you 10k on a L24 for similar power...

 

Stroking any more than .1L is often regarded as real pricey so not much point stroking a L24, may as well have a L26 or L28.

(Unless racing)

 

L's can go up to 9,000rpm roughly before you're in ridiculous territory. But getting an engine to that will cost you the price of

a new car... L24's reach the higher RPM's easier than L26 or L28's, but its a similar to that old saying about having a turbo vs.

NA; "It's better to have turbo lag than to have power lag". :D

 

CR on PULP (98) i BELEIVE is around 10:1 before pinging??? with E85 around 13:1 but for 5k this would be money spent on a

lesser HP gain.

 

I hope this helps, and anyone please correct me if any of this is incorrect.

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As I said, matching number block, so i'd like to try and use it if possible.

 

Some people say you can bore it out to 86mm for L28 pistons with sonic testing, others say 85. I'd like to know how far it would go with sleeves.

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Have you had it sonic tested for bore wall thickness yet?

 

That will tell you just what you can get, at thinnest point, you should be keeping at least 3 mm of bore wall, bear in mind you are cutting a radis from a centrepoint in any machining.

 

With sleeves, use a thickwall CDC type that sits on a bottom of bore step, to stop it punching out the bottom.

Sleeves work well, and due to higher specific graphite content, give more horsepower.

Downside can be water sealing issues, if not done correctly and to tolerances.

 

Could drop a L28 crank into the 24 block, that keeps your matching numbers, run longer stroke, longer rods ex 240, and short height G200 isuzu pustons, with top of piston machined to suit.

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Hi Magnet,

putting a 280 crank will be the same as the 260 pig you have now that can't rev, you sound like you want a fun car with out spending too much $, you will not get that feeling unless you spend huge $ on a 280 motor look at 15-30k if you want a fun high revving car for less $ stay with the 240 crank, if you want a big bore you can put a 240 crank and rods into a 280 block.

there is a good book put out by HP Books (How to modify your Nissan/Datsun OHC Engine), which will tell you what nissan parts fit what. Book says you can go 2mm with out sonic testing.

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Hi Magnet,

 

I have a nice L24 that I think will make 250hp, based on what the engineer has done on prior builds, and in my case. My engine was line bored, and bored 40thou taking swept volume to 2.5L. We run a balance but OEM crank, lighter internals and modified L28 valves, plus a pretty serious bit of head work (that itself took several days to a week). The motor is shown running (very gently) in my video posted on my brown hornet page. Its not even run in yet, so the revving you see does not get it beyond 3000rpm. In the video it needs the carby's re-seated as there is a vacuum leak, and they need a full tune, then dyno time. All in all, its a very quick engine to spin up, and should be very responsive to drive. On the cost side, I'd be budgeting 5-10k for the engine, depending on type of carbs and internals etc.

 

Good luck with your decision.

 

Adam

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Thanks for the info guys

 

I'll have to decide between something similar to acf321's build(maybe look into sleeves/bigger pistons) and stay factory numbers, or build an L28

 

Will update my build thread when the build starts :)

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If resale has any weight on your decision, and by the sounds of it originality is not critical. I reckon I would rebuild a fast L28 with triples etc. for the time you own it, higher hp/$ spent. Then when it comes time to sell it, put the matching number motor back in with su's and sell the complete hot L28 separately.

I reckon that would be the best way to recoup the costs of your build and enjoy a pokey motor whilst you had it.

I guess this theory is most relevant if you plan on keeping an original theme for the car, no flares, cut guards etc.

Mick

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At this point in time I don't really plan on ever selling it, I guess I just like the idea of having the original engine in there, feels a little more right. Again, if I'm only gonna get 2.5L out of it, as opposed to 3.0+ with the L28, and the power difference is significant, id definitely consider the L28.

 

I was pretty set on dropping an RB26 in there, could have that in and running for about $3k(mate has running car), and make a million kw, but had a change of heart as its not really what this car's about for me. I want that notorious z roar bouncing off the rockfaces on the twisties in the middle of the night. The car is being kept original, just repainted original colour, stock body, that's why I'm in two minds about the engine.

 

I'm not going for big numbers, it just needs to rev hard, sound good and be fast. I think anything over 120rwkw will be fast enough in a 1 tonne car

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Dear Magnet,

 

 

An L28 with triple 45s, headers, exhaust and a decent cam will make 120rwkw. It will also rev to 7k every day of the week which is the limit of cast pistons. Forged pistons at this power level are a waste and will eat up heaps of your budget. L motors get all their power from head work, better to spend your money there. The L28 makes more power more easily, that's why everyone puts them in.

 

Hi Magnet,

putting a 280 crank will be the same as the 260 pig you have now that can't rev, you sound like you want a fun car with out spending too much $, you will not get that feeling unless you spend huge $ on a 280 motor look at 15-30k if you want a fun high revving car for less $ stay with the 240 crank, if you want a big bore you can put a 240 crank and rods into a 280 block.

 

 

This is so wrong that it makes baby Jeebus cry. Why do you and DreamZ insist on posting stuff that just isn't right? This is two threads now...

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d3cOy, what part is wrong,

A 280 crank is the same stoke as a 260 crank (fact)

if you put a 280 crank into a 240 motor you will make a 260 motor (fact)

In standard form a 260 or 280 with the same stoke is a pig of a motor that doesn't like to rev (fact)

If you spend lots of $ you can make a 280 stoke motor fun. (fact)

If you put in a 240 crank and rods you can make a 280 block become a 2575cc motor that will rev easy and be fun motor cheap.(fact)

So what parts are so wrong.

Can you confirm how much $ you have spent to make your 280 stoker fun so we can confirm if that part is fact.

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I rebuilt my L24 because it's the original motor for my 240. It was built by Les and is almost a 2.6 liter engine and makes a good 150rwKw. I had a L28 that was almost 2.9 liter and that made 153rwKw but that was on a different dyno. Cost was around the $6k mark and this is with the ITB setup on both cars. Any cammed L series sounds good; you don't need to rev to 7 to get a nice note. Mine never goes above 6200 rpm as I'd like the engine to last for a while ;)

Rebuild the L24, spend some cash on a nice induction setup either ITB's or carbs, and you will not be dissapointed.

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d3cOy, what part is wrong,

 

In standard form a 260 or 280 with the same stoke is a pig of a motor that doesn't like to rev (fact)- He wants to spend money on it so it wont be a standard motor. Despite the fact that a stock L28 is faster than an L24 in the same car (fact)

If you spend lots of $ you can make a 280 stoke motor fun. (fact) - You dont need to though and L28 can be a fun motor for cheap, cam and carbs(fact)

If you put in a 240 crank and rods you can make a 280 block become a 2575cc motor that will rev easy and be fun motor cheap.(fact) - If you arent spending lots of money it, it will rev to 7500rpm like the rest, be limited by cast pistons and make no torque so it will be slow (fact)

 

 

So what parts are so wrong. - the ones above

 

Can you confirm how much $ you have spent to make your 280 stoker fun so we can confirm if that part is fact. - As i said with cam and carbs you can have an L28 that revs and is fun and makes more power for less money than an equivalent L24 (fact) AND i have actually built the engine. My L28 build is hardly relevant here. I assure my dog L28 is pretty fun to drive though, although you would probably find it boring since it's got an even bigger stroke than an L28.

 

 

 

Do you have a stock motor or built a modified L?  :)

 

 

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Whaaa what did I post thats wrong? I was completely telling him that there's very little reason not to go L28...

 

 

I agree with that statement.

 

 

But these ones i dont:

  • L's can go up to 9,000rpm roughly before you're in ridiculous territory. - Maybe a built L24, but any 9000rpm in an L is serious money. Please tell me what i need to build one of these motors
  • To get the same sort of power from a L24 to a L28, you are looking at roughly double (please correct me here if i am wrong)ie. 5k on a L28 will cost you 10k on a L24 for similar power... - Why the parts for either motor are either the same or nearly identical? If the motors can attain the same volumetric efficiency (both Ls why couldnt they?) why would such similar capacities have such a massive difference?
  • CR on PULP (98) i BELEIVE is around 10:1 before pinging??? -Mine runs 11:1 on pump 98
  • with E85 around 13:1 but for 5k this would be money spent on a lesser HP gain - Can you link me to this E85 L motor you are referring to?
  • and it about the biggest HP boost you will get for you money before you go turbo - What about cam and triples?

I'm not trying to be a dick, but there is no need to post stuff you don't seem to know about. Last week you didnt know how and ITB system worked and now you're  posting about building L motors for more power?

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I think d3coy has got it right  :-\

 

This is my old L28.

 

It was a stock, not rebuilt, original engine. Stock P90 head not ported, stock bottom end with dished pistons giving a comp ratio of 8.5:1. Ran great, good power, revved fine. It did have bike carbs, but no different to throwing a set of triples on. Also had a mild 72 deg cam. Otherwise it was an old, tired, stock motor.

 

Unless you're limited and have to run an L24 or you want to run one for the sake of purity the L28 wins hands down everytime.

 

How many times will you see 7k on a street driven Z? With no head work there's not much point.

 

If you're on a budget, rebuild an L28 yourself, get a 72 deg cam, headers, triples and electronic dizzy. It'll be a blast to drive.

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It will see high revs, I do a lot of driving. It will make it a faster car if it revs higher, and again, sounds sweet.

 

Maybe I'll buy the gear; triples, ignition, decent extractors and run it on a cheap L28 and see how I feel about it, if I'm happy with the power/rev range(obviously big cam is going to change it a lot too), and go from there.

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It will see high revs, I do a lot of driving. It will make it a faster car if it revs higher, and again, sounds sweet.

::)

 

It'll make you think you are going faster, meanwhile the other guy with the L28 will be pulling away ;D

 

Either way it's your ride so do what makes you happy, but an L28 will always be faster than an equally built L24!

 

 

 

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(If you put in a 240 crank and rods you can make a 280 block become a 2575cc motor that will rev easy and be fun motor cheap.(fact) - If you arent spending lots of money it, it will rev to 7500rpm like the rest, be limited by cast pistons and make no torque so it will be slow (fact))

 

Really, tell me what is the bore and stoke of the king of the Nissan motor, RB26Dett has a bore of 86mm and a stoke of 73.7mm  L28 bore standard is 86mm L24 crank is 73.7mm, it is not about max revs it is how quick it gets there, shorter stoke gets there quicker with less repercussion forces placed on the motor, Less of a hand grenade.

(Can you confirm how much $ you have spent to make your 280 stoker fun so we can confirm if that part is fact. - As i said with cam and carbs you can have an L28 that revs and is fun and makes more power for less money than an equivalent L24 (fact) AND i have actually built the engine. My L28 build is hardly relevant here. I assure my dog L28 is pretty fun to drive though, although you would probably find it boring since it's got an even bigger stroke than an L28.)

 

Clearly you have built a 280 motor spent all that money and yet not happy, can you tell us how much you have to spend on a stoker as you have just done to make you happy now. I believe this is important and needs an answer. so if others go the same road as you, they will need to know what price is happiness, using my idea gets you there for 5k easy

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