Hey guys, I was told that an old hot rodder's trick was to reverse the 302 piston on the rod, making the arrow point to the back of the engine instead of the front, by taking it off the wrist pin and turning it around backwards would make about 40 more HP? Is this true or what? I was told that with a stock piston, this would yield around 40 to 50 HP.
true, never was and won't make even 2 hp more...if any at all. Pin offset (in the piston design as it's not 100% centered on the rod) is to reduce/eliminate piston slap at start-up. Wish it were true!
This message has been edited by machoneman from IP address 67.176.173.151 on Jun 29, 2009 7:59 AM This message has been edited by machoneman from IP address 67.176.173.151 on Jun 28, 2009 11:46 PM
We used to do that on 392 blown chrysler in AA/FD for more piston dwell. It does work but like bob said, noisy. Only really good for wide open throttle applications where the air mass is moving really fast for better filling. An engine masters kind of thing on a budget.
PME (Pro Motor Engineering) a top flight engine shop I used to run out of in the 70's, did back to back dyno tests long ago on a BBC with std. pistons and centered pistons. Results? Less than a 2hp gain on a near 600+ hp engine and even then, since it took a day to switch 'em, the 2 hp was well within the margin of error and was likely due to the change in air temp/humidity!
Btw, PME moved from the Chicago area years ago and has been mainly doing NASCAR engines for the Nationwide and Truck series. They really knew their stuff even way back then.
This message has been edited by machoneman from IP address 67.176.173.151 on Jun 29, 2009 7:53 AM
I didnt think it sounded right, but was curious? what about changin to higher mompression pistons? Ford had a nasty habbit of neutering the compression ratio's for a long time.
full point of c/r increase should roughly (and this is a very rough estimate btw!) increase hp by 3%. Not that much unless one has the right combo and the right fuel to accommodate the higher c/r. As is often stated, a 10 to 10.5 to 1 ratio is about all modern pump gasolines can handle although some combos could go a tad higher. Race engines on race gas are, or course, a whole different, story.
It does pay to check the actual or true c/r on even a street engine as often the real c/r is far less than then one may think. Why leave hp on the table if the calculated c/r say 10 to 1 when the measured c/r may only be 9.2 to 1?