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Discussion Starter #1
has anyone done this and if so how much of a power loss did you have
I have rod knock and also have a spare 5m here so thinking of destroking for higher revs.
 

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there is a "digital dyno" program available in which you can punch in all of your engine specifics and it will give you your mathematical potential... i forgot what its called, but search around and you may be able to find it

if anyone else can chime in and find this program it would be nice!
 

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cartest...its an old old dos program and yes it has the 7m in it!! :)
 
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Discussion Starter #4
desktop dyno 2000 is what it is called *runs to get engine specs*
 

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wow i just checked out the car test site...they upgraded..lol...now u gotta pay for it tho... :(
 

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JonnyRedline said:
wow i just checked out the car test site...they upgraded..lol...now u gotta pay for it tho... :(
The dos one is still free, which should be downloadable.

We need to stop talking about destroking and someone needs to try it. I would like to see it done with some large bore pistons (~2.9l).
 
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I am fixin to do it to my 7mgte and just using the 5m crank, rods, and pulleys, I will be using the 7m pistons
 
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well according to dyno 2k you can gain 1hp in the 5k rpm range and thats it.
 
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Correct me if I am wrong, but a shorter stroke would allow a more favorable rod/stroke ratio and also lower wrist pin location which would allow thicker ring lands? Is the flywheel bolt pattern the same? I think the crank snout is different... This is what i am planning on doing with my next engine. Ultimate power is not the goal. Usable power is (wide power band).
 
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vbpowerhost said:
use the 5m balancer and pulley I am doing it now

Is it as simple as that? The belts line up and it fits with the timing cover?
 
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Discussion Starter #18
I dunno yet looks that way its starting to rain here so I had to cover everything up and quit till the rain goes away.
 

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Eric Barnett said:
Correct me if I am wrong, but a shorter stroke would allow a more favorable rod/stroke ratio and also lower wrist pin location which would allow thicker ring lands?
Yes, you would need to use a 5M rod. Or a rod of the same length but stronger.


Allan :cool:
 

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From what I understand, HKS used the 5M crank in a 7M block, and came up with a high rev 2.8L engine used in the HKS drag car from the 80's. (9K rev limit IIRC.)

Peaky power for sure, not what you'd want on the street I'd think.
 
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