Destroking - Facts or fiction

[Mr.Spool]

which is why I think I am on the hunt for one of the short stroke fancy crank to go in a 291 block with a couple middle billet caps and see what kind of power I can make on a budget with a 4" bore

to save you from the suspense the blocks are the limiting factor.want to play with a 4 bore a stage block would be the worth it.

 

[TexasT]

stage block not in my budget and I have a 291 that a machine shop hot tanked and gave a good bill of health to. Would like to get an estimate on one of the cranks. Even the worst one. Could have it offset ground and use a smaller size big end on the rod I choose, and some custom pistons to get the zero deck and decent compression.

 

[gunzandgearz]

Ok I'll check with my buddy

 

[Mike T]

If there’s no limitation on turbo I’ll take the larger bore engine every time regardless of stroke. Big bores have more potential to be filled. I’ll make everything work around it. Filling the cylinder is more important than anything. Everything can be adjusted around cylinder fill.


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Anyone that has taken a close look at the way the valves are shrouded on the typical 3.8 should be able to come to the same conclusion.

 

[gunzandgearz]

Agree with that 100%

 

[TexasT]

I believe the shroud in the GS400 is why Buick didn't go to larger valves in that engine until 1970 when the 455 bore got big enough bore to take better advantage, though as I learn more I'm not sure the regular size valves of a 455 don't flow just as much in the lower rpm range. Along with my dreaming of a short stoke 291 this new Betts Racing block to do a bbb and a turbo has me intrigued. I have been studying up on stand alone ecu and think a twin turbo where one feeds a second and then through the ic into the engine is where I want to head. But that is a whole 'nother dream.

I think with a 4" bore in the Siamesed block the piston and ring availability is opened up along with the valves. And if I can hunt up a rod with the right size on the ends and length I can make plenty of power on a budget.

 

[gunzandgearz]

actually they will flow more at the low to midrange lifts

 

[Mr.Spool]

Lots of info and you can see a trend where he destrokes and spins it faster

10,500rpm

 

[Mr.Spool]

Anyone that has taken a close look at the way the valves are shrouded on the typical 3.8 should be able to come to the same conclusion.

yes but you dont have to unshroud the valves to kill a 109 block

 

[gunzandgearz]

Who says the figure skater has to be a woman?

I used to figure skate.

Bahahaha just kidding

 

[gunzandgearz]

View attachment 329323

That's some funny shit right there now

 

[Jerryl]

Principles apply.