If you l took in the VG engine forum you'll find a post about me wanting to destroke a VG30, that said.

I'd like some information about increasing rod length in a destroked motor. In theory the longer rod will make more torque, and will decrease wear at high RPM operation, which clearly is the goal of destroking a motor.

Assuming that you're already having a custom crank made to destroke a setup, in theory would you not also want to have custom rods made at a considerably longer length, to allow for both high compression ratio, and a R/S ratio given to producing wicked torque?

I understand how all that stuff works in a predefined context, I'm just newly exploring the idea of building a unique, fun motor.

Any guidance is appreciated

Torque is 90% displacement and minscule things like CR and rod length together make up the other 10%.

The theorectical optium for a cylinder displacement is 500cc why the best 6 cylinders are 3 liter.

Still_Good wrote:I'd like some information about increasing rod length in a destroked motor. In theory the longer rod will make more torque, and will decrease wear at high RPM operation, which clearly is the goal of destroking a motor.

A longer rod will not make more torque. The idea behind a longer rod is to reduce peak piston acceleration, allowing higher RPM, and a reduction of piston skirt loading.

Reducing the stroke will reduce torque output since it reduces the displacement of the motor.

Still_Good wrote:Assuming that you're already having a custom crank made to destroke a setup, in theory would you not also want to have custom rods made at a considerably longer length, to allow for both high compression ratio, and a R/S ratio given to producing wicked torque?

There is no theory involved. You shorten the crank stroke, then you must increase the rod by the same amount. Otherwise the piston will travel up X amount less, yielding a 5:1 compression ratio.

If you want to rev to oblivion then you can sneak the wrist pin up on the custom piston and elongate the rod further.

Destroking is for producing high RPM power, period. You will not make "wicked torque", you will simply hold onto the torque the motor produces for longer, provided the rest of the engine is built to supplement that.

Nismo_Freak wrote:A longer rod will not make more torque.

Everything else you said was spot on. But, *IF* things like displacement and compression and other variables are kept constant, a longer rod will increase torque. And earlier explanations actually show why. One benefit is it decreases load on the side walls. Where does this load go then? To the crank to produce power.

Now, that being said, how much more? Not much. Not near as much as an increase in displacement will net you.

So, How would a builder go about building a stroked engine desiring low RPM and torque? I have a lifted D21 truck on 37 inch tires for roclcawling, and it can barely pull its own weight at a 6k foot elevation.
What CR?
What Rod length?
Type of crank?
Headwork?

I am thinking of having Paeco in Alabama build a stroker motor for me.

The only experience I have had with stroker motors is with a bored and stroked Chevy 383 with a 400 crank in it with an 11:1 CR. It was fun....but waaaaay more power than I would ever need for this truck and I want to be familiar with what is best for building a VG30i for my particular needs.