Help building a 4.1

[DAVID C]

I'm considering building a 4.1 to replace my 3.8 I read the info on the GN.org site. I'd like some more recent info from others that have gone that route. I picked up a 60k '83 4.1 for next to nothing. I'm going to have the block checked for cracks, if good, I'll probably bore to 4". Who do I go to for forged pistons? Direct to J&E, or through a distributor. It sounds complicated to get the proper dimensions. Why can't I just give them one of the old cast 4.1 slugs, and say " give me 6 just like them, only forged and for a 4 inch bore"? I think I'm looking for the same compression ratio. Also... Will my 3.8 intake, cam & crank sensors work with the 4.1 timing cover and heads? I know about the turbo oil return line. Any other unexpected modifications or cost? I'm trying to keep the $$ low. Any info for saving money on this project would be appreciated. I'm looking to push it to high to mid 10 sec range. Dave C.

 

[cool 84]

I'm going through 4.1 piston hell right now. It was a piece of cake since all the 3.8L stuff bolts up- until I ordered pistons. I've been jerked around and lied to for 6 months now. I wouldn't even bother trying to go through anyone but JE for pistons. My machine shop said they could get me a deal on 3 different brands of forged pistons and it always took over a month to tell me they couldn't do it after all. If you want a set like mine I'm sure there's a # that comes with them. They're 8.5 comp, 1/16, 1/16, 3/16 (for total seal rings) and use the stock wrist pin but they're full floating.

 

[DAVID C]

Cool 84, I'd be real interested in those part numbers. What size bore and how much are they costing you? Please keep me posted after the install. Thanks. Dave C.