how much to have a crank turned

[mbartell]

I've been digging thru the back pile of a machine shop, and found a coupple of buick 3.8cranks that I can use for my new motor. The first one is plain, and needs to be turned .010 .010
The other is a turbo or 4.1L crank that needs to be turned .020 on most of the rod journals, and at least .030 to .040 on one.
How much is safe?
I'd like to use the turbo crank, but is that too much to turn it?

 

[b4black]

I think this could be best answered in the General Tech forum so I will move it there.

We talking about a NA 4.1 engine right? The non-turbo crank has proven to be durable, so I don't think you can go wrong with either.

 

[gnx7]

my machine shop charged me $75 to turn mine

Some say tighter than factory clearances and others say stick with stock. I went tighter. Target was .0018" on mains/rods.

Some have run .020/.020 GN cranks into the low 10's... most prefer .010/.010 or standard. Tuning without detonation when pushing the envelope with these motors is crucial.

-Mark

 

[fc227]

I was running a .030 /.030 for many years. at that time I was running mid to low 14's. The only problem a had /have is about every 4 years of consistant racing (Bracket) & street use. I would lose a thrust bearing.