4.1 Destroked?

[87chrisss]

ok i found me a 82 regal with a 4.1.. Now im thinking of going for some nice power champion aluminums or iron's on e85 + girdle and forged internals. etcc ..before i go crazy.. i was thinking.. has anyone ever ran a destroked 4.1 and if so please post your pro's and con's, i have had experiences with a destroked 400sbc and it was a mad rever lots of power.. please need some suggestion's

 

[turbo nasty]

Pro for the big bore is the unshrouded valves. With that said I would want as much cylinder fill with a bigger stroke to make use of the better breathing. TJMHO

 

[87chrisss]

the reason i thought of this was since its a bigger bore motor i wont mind taking some torque on low end to gain more rpm power with the shorter stroke.. cylinder fill will be worked by the turbo or no? 25psi+ and with e85 im sure i can run timing as high as 23-28 deg which will bring my torque back up plenty and i'll also gain several hundred rpm to make me a broader powerband instead of such a short rpm range with the longer stroke, good breathing heads matching turbo with a nice cam, i think i'll have me a winner, not sure if someone has tried this before? im sure it has been done?? please some one chime in im by no means a professional engine builder im throwing ideas on the table for something new? should i try this does it make sense? or no?

 

[big reazon]

Call Nick from Arizonagn I think he said he liked his stock stroke better than his stroker motor for some reason but dont quote me.

 

[Nick Micale]

...........not sure if someone has tried this before? im sure it has been done?? please some one chime in im by no means a professional engine builder im throwing ideas on the table for something new? should i try this does it make sense? or no?

Yes, this has been done before with a Buick V-6.

Your post leaves out the reasons or reasons for doing this? Is there a specific race class that requires this, or just a whim to be different?

I have been around race cars before turbos, and a cardinal rule is to increase displacement for increased HP. As far as I know, this works for turbo applications as well.

Also, most drag racers pick increased bore over stroke when given the choice as it can greatly help breathing, and HP in most cases like what was mentioned above.

The de-stroked turbo V-6 I was associated with for years in NHRA class racing was run to 9000 RPM to obtain the needed HP to help compensate for the small displacement.

My personal preference is a 4.1 over a 3.8 for street or strip because of more low end torque. My opinion is that a shorter stroke will hurt, not help, low end performance in your case.

As far as your comment, "cylinder fill will be worked by the turbo", I am confused how that is a factor assuming you have the proper combination including the turbo?

Good luck on whatever you decide, hope it works out for you!

 

[87chrisss]

thanks for your reply i was using turbo nasty's choice of words (the second post) what i understood from his answer was the "cylinder fill" longer stroke will obtain more air/fuel in the CC? dont know maybe i miss understood his comment? anyway's i thought.. if i were to run smaller stroke with the 4.1L bored over then use more forced induction and get the +'s of a higher rpm motor with a larger powerband instead of being limited by the longer stroke lower rev.. i guess im wrong i would like to overbore the 4.1 block and use the smaller stroke i hope im not confusing and no race class reason i whim to be different

 

[big reazon]

Dont overbore the already crack prone 4.1

 

[turbo nasty]

Larger Bore..valves unshrouded...better breathing. Bigger bore with longer stroke.....more volume/cylinder fill (bore and stroke a.k.a. more CID) per intake event .

 

[TurboDave]

The general rule of thumb is: the only time most people destroke an engine is to fit a particular set of class rules, whether it be drag racing or road racing or circle racing. Other than that rule, there's really no good reason to destroke an engine. Too many cons, not enough pros.

 

[Nick Micale]

Dont overbore the already crack prone 4.1

I agree, but I did build a 0.060" over bore on a production 4.1 for a 11 sec. street build and never heard he had a problem?

The low end torque was awesome even with low boost and max ported iron heads, but he was lucky I guess! :biggrin: