Does anyone have a part # or manufacturer that makes a 4 inch bore piston for the 4.1 block?
I just want to comment on pistons for 4.1's. Since there never was a production 4.1 built for a turbo application, the replacement pistons were never available from the factory or aftermarket.
We have done many 4.1 turbo engines, and only use a custom piston with the proper ring lands, dish CC, pin location and other specs.
Having rebuilt some customer's engines, we have found the off-the-shelf pistons do "work", but performance is compromised especially if other machining is not done to compensate.
For a street build, the pistons available probably will do fine. For a performance build, they may not perform to expectation, or may not be as durable.
Most all of our engines have custom pistons, built to our specs by both CP and Ross. Explaining to the customer that when spending thousands of $$$$ on an engine build, getting the extra few $$ to get the best piston available is usually easy.
Just to verify our turbo Buick engine experience, we have 12 builds currently in process [most from out of state] including 2 TA blocks, 2 stage II, 1 stage I and the rest 109 blocks. At this rate, we will reach our grand total of 500 Buick engines built by the end of the year.
Oh, turn around time is usually 6-8 weeks depending on parts and special needs since we do ALL machining in-house. Our best time was 5 days for a GNX re-build!