4.1 Stroker Build

Ken Adams

Dec 31, 2007
I have a couple of Buick V6 items setting on a shelf in my garage and was wondering if I could combine them to build a turbo stroker engine. Items are: standard production 291 4.1 block, 3.625" stroker crank, 5.70" Scat h-beam rods and JE 4.00" pistons with a CH of 1.757". One concern I have is with the CH 1.757" resulting in too high of a compression for turbo application. I would like a final compression ratio of 8.5 to 1, no higher than 9 to 1. Your responses/input please. Thanks in advance
subscribed,i wanting to build one myself,just need to see more discusions regarding the 4.1 stroker.
I don't think it will work. You should get rid of it all and start from scratch. I will PM you my address to ship it to. Just kidding. I am not to savvy on the stroke vs rod length vs piston CH, someone with more knowledge will have to step up and answer that. Worst case scenario if you had to change pistons or rods you should be able to sell the ones you have to recoup the cost of another set, or someone may be looking to trade for what you have. Definitely a thread to watch if you move forward on this build.
based on your data.. it wont work.

1.8125+5.97+1.757= 9.53

average deck height on a 109 = 9.53 +/- .005.

or use an early HA block.

those slugs better have a massive dish in them.

if there flat tops there no good for boost. perfect for a NA carb motor though.

if you had a piston with a dish of around 30cc's and a head gasket thats .065 thick it MIGHT work... but it sounds like a bad choice.

you best bet, sell the slugs for some turbo spec units.

JE pistons I have are for a turbo application, not flat top. Aj, what year HA block are you referring to? I"m wanting to use a 4.1, not a 3.8 block. Instead of using the Scat 5.970" rods, what about using Buick production 4.1 V6 production rods which I think are 5.953" c to c?
My 4.1 block as well as Downtown Earl Brown's 4.1 block had a taller deck than a 109 so you may not be in bad shape. I'm thinking my block was .030 taller than a 109 block.
sorry sorry... i got ahead of myself... your already into a taller deck block.

what we need to know now then:

your blocks deck height. ( I have found there to be alot of variance in early blocks)
piston dish cc
head gasket choice.

and if you have the specs, your Intake Closing Point (degrees)ABDC @ 0.050 lift plus 15 degrees.

i can tell you what your static and dynamic compression will be.

Aj, the block will be going to the machinist early Oct. to determine deck height. The JE piston dish cc is 26.1. No decision yet as to head gaskets and cam selection.
mine is 3.625 BMS crank 6.5 rods with 1.25 CH using a 484 production block. Think it was like 8.2 comp but dont hold me to it