924Board.org

Robert Hooper · Joined: 15 Mar 2004 Posts: 70 Location: Christchurch NZ

Team,

I would like to increse the CR, this is normally done by skimming the top of the block,

1 - has anyone done this and what differance in hp were gained?
2 - How much do you skim off?

Cheers

Rob

ps - i understand this will be an interferance engine, but as its a race car im not worried.......
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1982 924 Race Car
1981 931 Road Car

Lizard · Posted: Mon Mar 21, 2005 6:04 am Post subject:

you can do a search on the board as this has been covered many times, iirc .50 is about the max you can do and it wont raise it that much, why not find a set of used 931 pistons (they are not expensive) and install those, with an NA head it will yeild about 10:1 with 80 pistons
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3 928s,

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

I shaved .050" off mine. Can't tell you what difference it made as I received the car not running with most of the engine laying in back seat. This raises the compression a full point as in I went from 8.5 to 1 up to 9.5 to 1. I believe you could shave more. The block is plenty thick in the deck area but you will start having some timing problems with the cam without an adjustable sprocket.

Todd
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'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....