View Full Version : .030 OVER COMPRESSION
Does a .030 over amc 360 pick up a noticeable compression increase over a stock bore, and if so how much?
tufcj
09-09-2008, 07:38 AM
Overbore has nothing to do with compression. Compression is all in the piston and/or head design. If you use a stock style replacement piston, you will have stock compression. Some replacement pistons actually lose a bit of compression if you don't deck the block or mill the heads because they move the piston about .020" LOWER in the bore to allow for decking. A .030" overbore will gain you about 6 cubic inches of displacement.
Bob
tufcj
ironman_gq
09-09-2008, 10:21 AM
doesnt compression increase slightly because you are pushing more air and fuel into the same amount of volume in the head? provided you deck the block for 0 deck height.
Wrench Man
09-09-2008, 06:58 PM
they move the piston about .020" LOWER in the bore.
You'll probably have LESS than you had before!
tufcj
09-09-2008, 07:13 PM
doesnt compression increase slightly because you are pushing more air and fuel into the same amount of volume in the head? provided you deck the block for 0 deck height.
The volume of the cylinder increases by less than 1 cubic inch, probably negligible in terms of compression increase.
Bob
tufcj
jeepsr4ever
09-10-2008, 08:27 AM
You get a small bump if you are using the same dish the same compression height and the same valve relief but on a larger piston the dish diameter is wider to make up for this.
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