This thread was saved without dates. "Around Jun 2004" is estimated from neighbouring threads.
Go figure ... while looking for bits for a ca18et I came across this for the ca20e instead.
Complete Gasket Set
Copper Performance Head Gasket
ROSS Forged Pistons
*** (84.5, 85, 85.5mm Bore) and
*** (8.5-1, 9.1, 10-1, 11-1 compression)
Performance Rings
Performance Wrist Pins
TOGA HP Main Bearings
TOGA HP Rod Bearings
Timing Belt
$999 US
http://www.importperformanceparts.net/
sounds like the 2nd half to my gasket package. I got the stock pistons and opted out and got the toga perfoamance oil pump, and the toga performance bearings. That copper stuff is expensive.
Oohhh, I wonder if those 10:1 's have the valve cutouts so you could also run a higher lift cam. Forged rods, ross 10:1 pistons, colt cam. :banger: Have it all balanced out, knife edge the crank. Port and polish the head and intake. Sounds sweat, damn, just looked in the pocket book, still broke :frown:
What do the compressions and bore for the piston mean?
The bore is how wide the piston or cylander is, the compression ratio is a ratio of how much air from when the piston is all the way down in its travel verses how much it is sqeezed when its at the top of its travel or stroke. A 10:1 piston will not be a true 10:1 compression ratio as the ratio is aslo dependant on the area of the compression chamber in the head (the volume of air in the part of the head with the valves closed). YOu may get something like 9.5:1, It just means that the air and fuel is compressed, 10 times normal atmosphere (somebody correct me if I am wrong). The ca20 motor is like 8.5:1 stock, and increase would give you an increase in power. How much, I am not sure. But it would make a difference If we were able to up the compression ratio. Problem is with these motors is valve clearance.
I don't think 10:1s would run into valve clearance problems, even with a high lift cam.
Yeah, you're right the ratio is the compressed to atmospheric relationship.
The important thing to know, is that the more you compress a gas, the more violent the explosion. The more violent the explosion, the harder your pistons are driven down. The harder your pistons are driven down, the harder you turn the crank that turns the driveshaft (via the tranny) that drives the ring and pinion, that drives your tires. All that without swallowing a fly.
But the more you compress a gas, the more heat it generates. So higher compression motors require better cooling.
The pistons are offered in different bores, because for the most part, when rebuilding an engine, you need to bring the cylinders back to a true cylindrical shape. Mileage tends to make cylinders barrel shaped. Pistons start to slop around a bit as bearings wear out. After time, the piston is no longer going straight up and down (in relation to the cylinder) so it wears the bore unevenly. You end up losing compression, and can eventually lead to serious engine failure. So you have to overbore the cylinder and run larger diameter pistons to get the proper shape back.
Overboring an engine also increases displacement. This usually results in more torque, but ofthen, going 0.020" larger isn't going to be noticeable. A 0.020 overbore is a standard "clean up" overbore.