can anyone identify this crank ?

[SteveRacer]

I was wondering how to tell what motor this crank came out of and if it was suitable for use in a turbo motor. It looks just like my 87 turbo crank but it doesn't have the same casting numbers. looks like 1257125. are there other numbers to look for? click for big pic

 

[V6gofast]

Crank ID

Bearing book shows that forging number under 181cu.in. and 231 cu.in.
engines. They are listed in groups by common dimenisions. Might want to
stick it in a block with a piston and rod make sure the piston comes to
the top of the deck . If it does then you have a 3.8 turbo crank.

 

[bison]

Looks right to me. But worth a closer look. I wasnt aware that the 3.0 used a rolled radius on the crankpins so i am pretty sure its a 3.8 turbo or 4.1.

 

[turbofish38]

That looks like the correct crank. The FWD 3.0 crank will have a different flange. From what I can tell it's late 70's vintage from the casting number. It was superceded by the 877 casting that most of us are familiar with.

 

[bison]

That looks like the correct crank. The FWD 3.0 crank will have a different flange. From what I can tell it's late 70's vintage from the casting number. It was superceded by the 877 casting that most of us are familiar with.

Yes it is early. I just checked the one in my engine i just assembled and it was the same part#. Mine came out of a 1978 3.8 turbo.

 

[SteveRacer]

thanks for the replies. was thinking about selling it and wanted to make sure it was a turbo crank.

 

[Nick Micale]

You cannot go by part numbers, or just looking at a crank to determine if it is from a turbo motor or not. If you take your fingernail and check both ends of the rod journals and can feel the rolled fillets [actually a depression], you can then feel safe it is a turbo crank.

If the rod journals have been heavily machined, it would next have to be measured to determine diameter before it is used.

The GM part number, and casting number, for 1986-7 turbo and non-turbo cranks are the same.

 

[bison]

You cannot go by part numbers, or just looking at a crank to determine if it is from a turbo motor or not. If you take your fingernail and check both ends of the rod journals and can feel the rolled fillets [actually a depression], you can then feel safe it is a turbo crank.

If the rod journals have been heavily machined, it would next have to be measured to determine diameter before it is used.

The GM part number, and casting number, for 1986-7 turbo and non-turbo cranks are the same.

The one is his pic has the rolled radius on the rod journals. The only question would be how much its been turned too much already, or if its cracked, welded, or bent.

 

[Nick Micale]

Pics can lie........

Just because it "looks" like rolled fillets in the pic, does NOT mean that they are there.

I have a couple of non-turbo cranks that have a dark mark, like the fillet, on the turbo rod journals, and do LOOK like a depression, but of course are not.

 

[SteveRacer]

i see what your saying about it just looking like a depression. the fillets are there and you can feel them. it's also std size too i believe 2.250/2.500 as measured with calipers, though i realize a nice set of mics should be used

 

[750H.P.V6]

The only difference between the early casting # crank and the later 877 and 229 cranks is the bolt for the balancer. On the earlier cranks the bolt is a smaller diameter.

Neal

 

[turbofish38]

You cannot go by part numbers, or just looking at a crank to determine if it is from a turbo motor or not. If you take your fingernail and check both ends of the rod journals and can feel the rolled fillets [actually a depression], you can then feel safe it is a turbo crank.

I see said the blind man. To get an idea of what to look for compare this crank to your old crank or look on page 70 of the Buick Power Source Manual as there is a much better picture showing the rolled fillet. I was aware that both types of cranks share the same casting numbers but never relized the difference in the rolled filets. You know I hear people saying they found turbo spec cranks in NA motors and I bet they are making the same mistake.