[Guest]

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.

 

[swearitsstock]

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!

 

[JonnyRedline]

cartest...its an old old dos program and yes it has the 7m in it!!

 

[Guest]

desktop dyno 2000 is what it is called *runs to get engine specs*

 

[JonnyRedline]

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

 

[80sSupraPowa]

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).

 

[Guest]

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

 

[Wade]

To take full advantage of the 5m crank you might as well install some stiffer valve springs and some engine management that will let you raise the rev-limiter.

 

[Guest]

well according to dyno 2k you can gain 1hp in the 5k rpm range and thats it.

 

[ma71supraturbo]

well according to dyno 2k you can gain 1hp in the 5k rpm range and thats it.

What about over 6500rpm?

 

[Guest]

[email protected] peak is at 5500rpm of 250

 

[drjonez]

what about tq?

 

[ma71supraturbo]

[email protected] peak is at 5500rpm of 250

Sweet, it only goes down 3hp over 1000rpm?! Stock drops off pretty strongly over ~5800-6000

 

[Guest]

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).

 

[drjonez]

it's an M crank, so the bolt pattern is the same.

yes, the snout is different.

 

[Guest]

use the 5m balancer and pulley I am doing it now

 

[Guest]

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?

 

[Guest]

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.

 

[Allan"Defiant7M"Sterling]

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

 

[adjuster]

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.