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The 6.5 compression ratio I stated was using the L-28 rods not the L-24. And this compression is on my motor with enlarged chambers on my N-42 and my 2mm HKS head gasket. The swith to the L-24 crank and rods on the L-28 motor will only lessen the piston height in comparison to a stock flattop L-28 by -.35mm according to my calculations.
(133.0-130.35)rods minus 1/2(6mm) the difference in stroke between the L-28 and L-24 crank.
 

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> The 6.5 compression ratio I stated was using
> the L-28 rods not the L-24. And this
> compression is on my motor with enlarged
> chambers on my N-42 and my 2mm HKS head
> gasket. The swith to the L-24 crank and rods
> on the L-28 motor will only lessen the
> piston height in comparison to a stock
> flattop L-28 by -.35mm according to my
> calculations.
> (133.0-130.35)rods minus 1/2(6mm) the
> difference in stroke between the L-28 and
> L-24 crank.

Shame on you! heh

Seriously though there was an article in Zcar Magazine about a year or year and a half ago about a guy that did this, (gotta look through the old ones and find it) it was on the last few pages, and he went fairly in depth with what he did. (I was thinking what a great turbo engine it had potential as) So now that I have a 280 turbo engine sitting on a stand in my garage I'm thinking about getting the bottom end out of a 240 and doing the destroke. Seems like a highly oversquare engine that revs quickly would be awesome with a turbo.
 

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In my opinion the only reason they say a 3.2 liter is no good is because the diesel crank is very heavy and doesnt like to rev. But i have seen 280 with stock crank rev up to 8500 in circuit racingwith no reliavility problems , also I remenber that in Japan (10 years ago) they had 280 engines reving to 9500 (doing 9 secs in the 1/4)ofcourse they had to be custom made cranks.
With a biger crank you could use the higher torque to move a bigger turbo and them you could have more power.

Danilo

> The 6.5 compression ratio I stated was using
> the L-28 rods not the L-24. And this
> compression is on my motor with enlarged
> chambers on my N-42 and my 2mm HKS head
> gasket. The swith to the L-24 crank and rods
> on the L-28 motor will only lessen the
> piston height in comparison to a stock
> flattop L-28 by -.35mm according to my
> calculations.
> (133.0-130.35)rods minus 1/2(6mm) the
> difference in stroke between the L-28 and
> L-24 crank.
 

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THE DISEL CRANK IS ONLY 1 LB HEAVIER

DANILLO,I have personally
weighed the diesel crank and it
is only around 1 lb heavier
than a stock 280 crank. What you
are thinking about is the 38 lb
flywheel ,which you do not use
anyway. Later, norm
 

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The 3.2 litter will give more power

I believe the diesel crankshaft will give more power, It was the idea of destroking that I don't believe is good. People like Top End believe that this crank weights too much, Not me. But Im sure that with the proper mods this crank will rev as much as the 240s and give more power at the same time, unless ofcourse you just want to rev more without expending money, even when you get less power.

Danilo

> DANILLO,I have personally
> weighed the diesel crank and it
> is only around 1 lb heavier
> than a stock 280 crank. What you
> are thinking about is the 38 lb
> flywheel ,which you do not use
> anyway. Later, norm
 

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L24 = More bang for the buck!!

A guy named Lawrence Howell owns a Datsun junkyard about 15 miles from me, in Riner, VA. He has been into racing for a long time and dominated the mini-stock series in my area for years. He used a destroked L-series four banger with a few little tricks to make lotsa horsies and quick, high revs. I think this theory would carry over to the in line 6 pretty well. You can just look at the turbo ford pinto 4 banger pieces of crap out there spankin' chevelles, and big bad mopars down the 1320 to realize that Cubes don't necessarily = HP. The reason I came up with this set up in the first place was out of wanting to fill the void in my 240's engine bay, and to make some extra ponies without spending too much extra $$$. However, IF I did have the cash to spend on this engine I'll bet a knife-edged 240 crank, lighter 240 rods, lightened flywheel, some 240sx pistons, and a few other small goodies would probably make for a powerful combo. I'd be interested to see how it would stack up to the infamous 3.1 litre set-up. It's often been said that if you want to do the 3.1 right you can easily spend 3 grand or more, I've already got all my hard parts minus the rebuild kit! I doubt that would cost over $200, much, much cheaper!

Tony Rohn
 

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Whoops, Destroke = More bang for the buck!!

A guy named Lawrence Howell owns a Datsun
junkyard about 15 miles from me, in Riner,
VA. He has been into racing for a long time
and dominated the mini-stock series in my
area for years. He used a destroked L-series
four banger with a few little tricks to make
lotsa horsies and quick, high revs. I think
this theory would carry over to the in line
6 pretty well. You can just look at the
turbo ford pinto 4 banger pieces of crap out
there spankin' chevelles, and big bad mopars
down the 1320 to realize that Cubes don't
necessarily = HP. The reason I came up with
this set up in the first place was out of
wanting to fill the void in my 240's engine
bay, and to make some extra ponies without
spending too much extra $$$. However, IF I
did have the cash to spend on this engine
I'll bet a knife-edged 240 crank, lighter
240 rods, lightened flywheel, some 240sx
pistons, and a few other small goodies would
probably make for a powerful combo. I'd be
interested to see how it would stack up to
the infamous 3.1 litre set-up. It's often
been said that if you want to do the 3.1
right you can easily spend 3 grand or more,
I've already got all my hard parts minus the
rebuild kit! I doubt that would cost over
$200, much, much cheaper!

> Tony Rohn
 

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Re: Whoops, Destroke = More bang for the buck!!

> A guy named Lawrence Howell owns a Datsun
> junkyard about 15 miles from me, in Riner,
> VA. He has been into racing for a long time
> and dominated the mini-stock series in my
> area for years. He used a destroked L-series
> four banger with a few little tricks to make
> lotsa horsies and quick, high revs. I think
> this theory would carry over to the in line
> 6 pretty well. You can just look at the
> turbo ford pinto 4 banger pieces of crap out
> there spankin' chevelles, and big bad mopars
> down the 1320 to realize that Cubes don't
> necessarily = HP. The reason I came up with
> this set up in the first place was out of
> wanting to fill the void in my 240's engine
> bay, and to make some extra ponies without
> spending too much extra $$$. However, IF I
> did have the cash to spend on this engine
> I'll bet a knife-edged 240 crank, lighter
> 240 rods, lightened flywheel, some 240sx
> pistons, and a few other small goodies would
> probably make for a powerful combo. I'd be
> interested to see how it would stack up to
> the infamous 3.1 litre set-up. It's often
> been said that if you want to do the 3.1
> right you can easily spend 3 grand or more,
> I've already got all my hard parts minus the
> rebuild kit! I doubt that would cost over
> $200, much, much cheaper!

My friend has that Z Car Magazine I will try to find out the issue. I believe it has 2 red Z's on the front. He said something about getting the stroke to as close to 3 as possible that is considered the optimum stroke. Ford did this once with a V-8 one time. Most of the Ferrari and other high dollar forien performance cars use short stroke motors. The L-24 I think has about a 2.8 or a little higher stroke. He had a very detailed article about everything he did sounded great. Good luck. It also sounds like a good turbo option if you can get the compression down and also what about turbo lag? Sam 75 280z
 

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Rod ratio affects reving more than LD crank weight

> In my opinion the only reason they say a 3.2
> liter is no good is because the diesel crank
> is very heavy and doesnt like to rev. But i
> have seen 280 with stock crank rev up to
> 8500 in circuit racingwith no reliavility
> problems , also I remenber that in Japan (10
> years ago) they had 280 engines reving to
> 9500 (doing 9 secs in the 1/4)ofcourse they
> had to be custom made cranks.
> With a biger crank you could use the higher
> torque to move a bigger turbo and them you
> could have more power.

> Danilo

Stroker engines are less rev happy than 240's or destroked 280's due more likely to lousy rod ratio. The ratio of rod length to stroke is very important to an engines willingness to rev.

This is one of the reasons that it is so important to use the 240 rod, which is longer than the 280 rod, when you use the diesel crank which has the longest stock stroke. By using the 240 rod and pistons w/ a short compression height helps to maintain the rod ratio.

Rod ratios of 1.8 are desirable. Mid range rod ratios are between 1.65 and 1.79 are mid range and below that are slow. Short rod ratios have more accute rod angles and side load the pistons more (amongst a bunch of other differences between long and short rods....each has its good and bad points depending on desired results.)

I have a reasonable spread sheet that does displacement and CR quickly. I will add rod ratio to it & maybe even rod angle. It is great fun for doing Datsun L-XX engine what-ifs. I will send it to anyone that requests a copy, it is in MS excel 97 format. E-mail me if you want a copy

my $.02

tomh
 
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