Crank and Rods

[lazaris]

Wanted to get opinions on a 4.1 build up.
I have a raw forged crank. I was thinking of having it turned for a 3.625 stroke. I was wondering if I can have the crank turned to use a Small block chevy rod journal size (2.125)I think? Arent the Buick crank rod dia's 2.25? This way I could use a more common chevy type rod thats easier to get. Would there be a problem with clearance in the block (off center)? If so what about dropping the stroke to 3.590 for added clearance? Opinions?

 

[KendallF]

The Chevy SB standard size is 2.100"..our motors are normally 2.200". You can do this and probably get some increased clearance, depending on the rod design used. The downside is that you lose some strength at the split between the rod journals (the smaller diameter leaves less material there).

 

[Jay Wicks]

Some of the Busch engine builders(Harper, etc.) had run cranks with SBC 2.100" crank pins in some of the qualifier motors. The Stage II even fire cranks were turned down from the normal 2.250". This was done to reduce bearing speed, oil requirement, and heat on the journal for extra RPM when needed. This practice was not used for the endurance of the race. Although this should be fine in a street Stage II, I would not recommend doing this if horsepower levels over 700 were anticipated, as this would weaken the journal. Also, common small block Chevrolet rods are 5.7", 6.0", or 6.125". The common rod in the Stage II is 6.250". 6.350", or 6.500" depending on the compression distance of the piston, and stroke of the crank. Odd fire motors are 2.100 journals, but got away with it okay because of the common crank pin. Althoug those rods are pretty common. Hope this helps. Anything is possible.

 

[lazaris]

Well I guess 700 hp in a 4.1 stroked motor wouldnt be too hard to achieve. I just thought it would be another option to get a more common rod at a cheaper cost. As well as being able to get fast replacement if one failed. Thanks for the feedback.

 

[geno]

I dont think id waste that forging on it. Id find a hurt crank

 

[TurboCrazy]

Good call Geno! I totally agree. Save that forging to turn it into a good stroker
crank. JMHO