Didnt know if this belongs here or in the 928 section
10-23-2016, 12:30 AM
#1
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Didnt know if this belongs here or in the 928 section
So I was just relaxing today watching my daughter sleep when I started thinking about the 16v swap I've been planning an I'm still missing the pistons and finding a set of S pistons isn't too hard but I was thinking I found a numerous amount of 928 100mm pistons for really cheap and I was wondering if there would be any type of difference or problems I would run into if I went with these?
10-23-2016, 04:50 PM
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You need either Euro spec GT or S4 pistons, UK spec SE pistons, German spec S pistons, or US spec GT/S4/CS/85+ S pistons. These are the only cars that had 100mm 4 valve pistons. Not cheap. The cheap 928 pistons you see available are 2 valve pistons, essentially the same as 8v 944 pistons.
10-24-2016, 12:26 PM
#3
Rainman
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You can't directly use 928 pistons.
928 pistons are 2mm taller than 944 pistons...so sticking a 928 piston on a 944 rod/crank would make it stick out from the block 2mm.
You would need to use a shorter rod...which is a lot more expensive than finding the right 944 piston.
928 pistons are 2mm taller than 944 pistons...so sticking a 928 piston on a 944 rod/crank would make it stick out from the block 2mm.
You would need to use a shorter rod...which is a lot more expensive than finding the right 944 piston.
10-24-2016, 12:29 PM
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Rainman
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You need either Euro spec GT or S4 pistons, UK spec SE pistons, German spec S pistons, or US spec GT/S4/CS/85+ S pistons. These are the only cars that had 100mm 4 valve pistons. Not cheap. The cheap 928 pistons you see available are 2 valve pistons, essentially the same as 8v 944 pistons.
All 5.0L 928 pistons are 100mm/4v pistons.
US got the 5.0 in 1985-1986, then the S4/GT had a different piston design from 1987-1991.
1985-1986 pistons have a 7cc dish
1985-1986 HEADS have a 56cc chamber
1987-1991 have a 25cc dish
1987-1991 HEADS have a 42cc chamber
all the 32v 5.0L 928s were "rated" as 10:1 compression but realistically its more like 9.4-9.7:1./
No 928 2v was made in 100mm bore...the largest 2v-928 was a 4.7L with a 97mm bore.
10-24-2016, 08:21 PM
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You can't directly use 928 pistons.
928 pistons are 2mm taller than 944 pistons...so sticking a 928 piston on a 944 rod/crank would make it stick out from the block 2mm.
You would need to use a shorter rod...which is a lot more expensive than finding the right 944 piston.
928 pistons are 2mm taller than 944 pistons...so sticking a 928 piston on a 944 rod/crank would make it stick out from the block 2mm.
You would need to use a shorter rod...which is a lot more expensive than finding the right 944 piston.