L24 rebuild/bore options

[Patch]

(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.)

 

We must read different books,

Lets compare the 2 in my book by James Morris (Super Profile)

These are standard motors

a UK 240Z motor 9.0 compression at  has 151/6000 hp and 146/4400 for Torque 280z US 8.3 compression has 170/5600rpm and torque 177/4400 so clear winner for 280z

Yet the uk 240 z )-60mph is 8.0 sec 280z is 9.4 sec

0-100 mph 240z is 24.sec 280z is 30.2 sec

1/4 mile 240z is 15.8 280z is 17.3

 

so is it fair to say even though the 280z has fuel injection and 19 more hp it is a pig in the performance  stakes, so clearly if you spend 5k on both motors very likely the 280 will be higher hp, but is it as good performance wise, fun wise and reliability wise, first thing I learn in my 10 years racings was to win first, first you have to finish, I didn't start winning until I stopped making hand grenades.

 

[Riceburner]

it's L24 or L28 in a 240z not 240z vs 280z, that opens a whole world of differences regarding weight, gearing etc. Remember it was equally built. What the hell has an RB26DETT got to do with anything, it's twin turbo ffs.

 

You answered it in there somewhere "clear winner for the 280z(L28)" the rest although fun to read is meaningless.

 

I give up. I'll keep building my hand grenades thanks.

[DreamZproject]

Yeah, I'm out. This has gotten to ridiculous.

I may have written a couple of little errors, but those ones i did put a (?) mark next to because i wasn't

100% sure. I was just wanting to share around some of the work i guess.

[George]

Shame. Was an interesting topic to start with.

[C.A.R.]

Opinions are like arseholes - everyone's got one.

Sadly the majority of responses in this thread come from backyard engineers, who THINK they know when the reality is they probably don't know how to fix their own lawnmower...

 

It's a pity this thread topic has been hijacked, because as George said, it had the potential to be constructive & interesting...

[dat2kman]

I've actually done it!

Ie had a L28 with standard stroke and a standard crank, with a bit of machining, in the correct places, mated to a purpose flywheel and front balancer, it will spin.

 

The stock crank, with it's 120 degree phasing is an inherent unbalanced piece f coat hanger, they break, at certain rpm's.

In normal road type use, you will not get to the "break" rpm's , unless you are stupids.

 

They have as standard inbuilt harmonic imbalance, the first occurs at around 3600 to 3800, it is very minor, the engine as a who

E can handle it, the secong harmonic imbalance is at approx 7400 to 7600 .

That is why the L28 has a set "redline" for rpm, that and the fact the standard induction setup does not allow it to get there.

 

The L24 engines harmonics are at different, higher points, but still there.

 

Once one has actually done it, rather rhan sprout opinions, heresay, he said-she said, and my dick is bigger than your dick, it means very little.

 

To use a strobe, a balancer, and the harmonic reading device, and see how it works, and better yet, how to "move" the harmonic away, so that it is not an sdue is quite interesting.

It bevomes a "whole of assembly" think, not just a crankshaft alone!

What block it all fits into is irrelevant.

After all the bigger the airpump, and that is the " effective" air pump, the more power is produced.

By effective, the duration ( opening, closing and length of time in crankshaft degree rotation) of a camshaft, has great impact.

 

But then again, what the heck would I know, i'm just an ex-racecar driver, and Mechanical Design Engineer, with a Fitting and Machining qualification thrown in,,,, who has actually done all this stuff, over the last 30 odd years.

 

Continue on boys!

[PZG302]

To the OP, Like Jason I have played with few L series motors over the years, both 4's and 6's.

 

Basically, do you want to build the L24 or keep it in case and use an L28.

 

Being a bigger engine to start with the L28 will give you more power and torque for the same dollars spent. However you have to smart in how you spend your dollars.

 

Either motor done right, and that doesn't mean expensive, will be a fun jigger to drive and both will rev to 7000rpm happily all day every day.

 

Either motor done wrong will be a pig and go bang in a bad way quickly.

 

If it was my money, I would put the L24 aside, get a cheap L28 with N42 head and build that for $5k. I would get new pistons, block machined to suit, a little oversized, and get a bit of work done to the head to flow nicely, again built for torque over top end. Run  a 72-74 degree cam and a set of triples and have a glorious noise that will rev to 7000 when I want but is happy being driven all day around 3000 where it is at the top of the torque curve.

 

Sit down and decide what you want out of the motor, talk to a couple of trusted engine builders, who know the L series, about what you want and most importantly your budget and what you will be doing with the motor. Your ideas will probably change after talking to the builder and what you can get with the budget.

 

No good building a peaky screamer that does road duty running around the suburbs, that get very tired very quickly, I know this from a Stanza I had that revved to 7500 and came on cam at 5500, a ball on the track but a pig around town, especially where I was living in the Blue Mountains. There were a few roads I couldn't drive up in wet weather without drying the road with rubber first, also couldn't sneal home at night, my parents heard me down change to come off the highway and could pin point exactly where I was between there and home by the gear changes. I changed cams to a more sensible grind and peak power came at around 6800, but torque from about 3500rpm.

 

My first proper racing only Datsun had a L18 out to 2.2 that sucked through twin 40mm Webers off my 1200 3k powered Psorts 1300 racer, revved a bit for the day but plenty of torque as well, but I wouldn't have lived with that on the road.

 

A good real life example of building the same thing different is Jason and my race motors, different rules different budgets but similar power, and torque at very different leves, end result similar times on similar tyres for a sprint, mine easier to drive over a 10 lap distance, also different brakes and tyres helped here. But the characters of the cars were very different. Jason's motor in comparison was a lot peakier and is revved a lot harder, my motor was less stressed as it revved to less, but was a big fat lazy truck motor that puled better out of corners, and hence I set my gearing up differently able to run a 4.1:1 diff on 18" wheels, the same as a 3.9:1 diff using 15"s. For hill climbs I had access to 4.8:1 diff to climb walls if I wanted, but horses for courses.

 

My motor also had a lot less spent on it than Jason's and the money spent in different areas to give me more torque than outright power.

[Agno]

*text*

 

Once one has actually done it, rather rhan sprout opinions, heresay, he said-she said, and my dick is bigger than your dick, it means very little.

 

*more text*

 

Bravo Sir, bravo!

 

[Zedman240®]

Sorry, but I don't see the point in revving a motor to some stupid RPM thinking all motors make their peak power at the highest absolute rev limit. My L24 starts to fall off just after 7000 and peaks at about 6500 (I have the dyno sheet) and yet I only rev to around 6200. I only know of another L28 that revved to 9200 but it had the suitable cam and internals to do so. You'll actually drop speed off revving past the motors peak....

 

Depending on what you actually want to do with the motor is the most important thing spending thousands just to rev would be a waste rather than spending the cash on brakes or decent rubber. 

[Riceburner]

No dick comparisons here!

 

I was simply correcting some of the misinformation posted. All I did was give a true account of what a basically stock L28 can do, you don't have to be a rocket scientist to look at the figures and come up with the answer 

 

 

 

[peter mc]

The bigger the better , all the girls know that , , forget big revs make max torque at 4000 and power at 6500 and it will flog a engine that makes power at 7500 to 8000 on the road , go to a racetrack and have 4.3 diff and CR box and then the big rev and hp engine will shine ...

2.4 are only good for one thing racing in that class ... that's it

[d3c0y]

(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

 

 

So why do people build 2.8L and 3.0L RBs then if they are so awesome?

Also if it's not about max revs then isn't light weight internals and ancillaries the way to go? Isn't this a bit of a contradiction to what you have been saying?

My 3.4L revs to 8500rpm pretty quick. Its got a way bigger stroke than a stock L28.

So you are saying L28s are less reliable than L24s or RB26s or all of the above?

Why do you think im not happy with my engine? Maybe you are just getting mixed up with the fact that i have built more than one L series.

There is no point building my motor, as according to you as you can make a $5k L26 hybrid go just as hard, so again what i spent is irrelevant. Please post dyno charts of your 360hp run of your L26 hybrid. I'm sure we would all love to see that. Especially Peter MC all this time he has been wasting time and money building strokers!!!

[munters]

That's a L24 1mm overbored

270HP at 6100 till 7100

[luvemfast]

They have as standard inbuilt harmonic imbalance, the first occurs at around 3600 to 3800, it is very minor, the engine as a who

E can handle it, the secong harmonic imbalance is at approx 7400 to 7600 .

 

The L24 engines harmonics are at different, higher points, but still there.

 

To use a strobe, a balancer, and the harmonic reading device, and see how it works, and better yet, how to "move" the harmonic away, so that it is not an sdue is quite interesting.

It bevomes a "whole of assembly" think, not just a crankshaft alone!

 

Regardless of peoples opinions on block girdles, this is why I beleive in Neil Cartledges design. He used it successfully for many years and could tell the difference in performance and reliability. It helps reduce block flexing and shifts the harmonic vibration higher up the RPM range.

The only other item that would come close, would be the Arizona Z Car cast aluminium baffled sump.

As with Jason's experience and knowledge, I'll take Neils advice above any keyboard warrior. FACT!

It also just happens, that I have 2 spare girdles in my garage. If anyone wants one. lol

 

On a side note.

Why do guys want high powered Z's for road cars?

What are you possibly going to do on the road with 150kW's that you cant do with 120kW's?

Build a nice engine and spend the rest of the money on brakes and suspension. You'll get more benefits and driving enjoyment from that!

[Roberto]

On a side note.

Why do guys want high powered Z's for road cars?

 

If you have to ask, you'll never know. . 

 

Honestly though, it's because standard cars are getting quicker and quicker and a stock z feels slow these days.  Who wants to drive a slow car as there special weekender?  You should know that with a name like luvemfast.

[d3c0y]

For when i want to drive FAST and when I take it out to the track. Same reason you have a high powered road car lol.

[Magnet]

Good read here(probably old news)  http://forums.hybridz.org/topic/74718-new-dyno-numbers/

 

Dude's making 230whp(~170kw) with L24 1mm overbore, seems high but pretty serious head/intake/clutch

[d3c0y]

Don't forget to factor in US dyno