Motor pull! (Rated PG-928 due to disturbing content)
06-21-2007, 06:22 PM
#61
Under the Lift
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Originally Posted by mark anderson
Yes and no. You are correct that the 86 block would take some modification but they are much easier to come by and cheaper so you may want to go that route. We seldom get good 87 up short blocks so they do command a bit of a premium. I have several with thrust bearing damage if someone knows how to repair that.
I see this other thread on the subject:
https://rennlist.com/forums/928-forum/313612-short-blocks.html
- It looks like the piston crowns are not compatible with S4 valves.
And this comment from Greg seems less than encouraging.
The starter motor mount is different for an '85/'86 engine. The '87-on starter mount will not fit. The '85/'86 starter mount will not clear the flywheel from the '87 engine. The '85/'86 flywheels don't have the tooth sprocket needed to tell the fuel injection what is happening. This pretty much "paints you into the corner". There is a way around it....but it does get pretty complex. I think the averge guy would be happier using a '87-on engine in an '87-on vehicle.
The combustion chamber is about 20cc bigger in an '85/'86 engine, so the piston has a different design to make up the difference. I took apart a stroker engine recently (from another place) that only ran 50 miles before the pistons galled the bores and ruined the block. The builder needed to go back to basic autoshop 101 and forget about building engines. He used a piston design for the '87-on heads with the '85/'86 heads.....not much compression. Combine what with an early (narrow) thrust bearing and rod bearing that were not champhered for the radius on the crankshaft and you begin to get the idea.
The combustion chamber is about 20cc bigger in an '85/'86 engine, so the piston has a different design to make up the difference. I took apart a stroker engine recently (from another place) that only ran 50 miles before the pistons galled the bores and ruined the block. The builder needed to go back to basic autoshop 101 and forget about building engines. He used a piston design for the '87-on heads with the '85/'86 heads.....not much compression. Combine what with an early (narrow) thrust bearing and rod bearing that were not champhered for the radius on the crankshaft and you begin to get the idea.
06-21-2007, 06:25 PM
#62
The starter on the 928 has had two different mount places, which is the large metal bracket, and early on, it was just bolted to the lower bell housing. While determining the back spacing will be required, you can just put an 87 flywheel on the 86 block, and use the 78 lower bell housing, which, IIRC, Kibort Gladiator man did.
06-21-2007, 06:33 PM
#63
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Originally Posted by BrendanC
The starter on the 928 has had two different mount places, which is the large metal bracket, and early on, it was just bolted to the lower bell housing. While determining the back spacing will be required, you can just put an 87 flywheel on the 86 block, and use the 78 lower bell housing, which, IIRC, Kibort Gladiator man did.
06-21-2007, 09:20 PM
#64
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Originally Posted by Bill Ball
The starter motor mount is different for an '85/'86 engine. The '87-on starter mount will not fit. The '85/'86 starter mount will not clear the flywheel from the '87 engine. The '85/'86 flywheels don't have the tooth sprocket needed to tell the fuel injection what is happening. This pretty much "paints you into the corner". There is a way around it....but it does get pretty complex. I think the averge guy would be happier using a '87-on engine in an '87-on vehicle.
Originally Posted by Bill Ball
The combustion chamber is about 20cc bigger in an '85/'86 engine, so the piston has a different design to make up the difference.
HC = high compression
LC = low compressions
S2 = 84-86 Euro/ROW S
S3 = 85-86 US
S4 = S4/GT
2cc = adding 84-86 Euro/ROW S sized valve cuts to S3 pistons
8cc = adding 80-83 Euro/ROW S sized valve cuts to S3 pistons
