Posted by Cowboy (IP: 216.161.250.98) on May 22, 2000 at 20:52:17:
In Reply to: 289 rod trick posted by Ryan on May 22, 2000 at 05:37:20:
Changing the lenght of the connecting rod in any particular engine only gives
the piston a more favorable angle on the crankshaft when it is 90deg
from TDC. When the mixture is compressed and the spark plug fires the piston is forced
down resulting in rotation on the crank. Less angle = less power waisted getting
the crank turning. Ford 302s have pittifully short rods compared to other engines.
The 289 rod is marginally longer and Boss 302s had the same length rod as a 289 from the
factory. The piston will still only move 3" up and down the bore, just a little further from
the crankshaft center line. You could have a rod 18" long and would have a GREAT angle on the crank,
almost none.... But the crank will only stroke 3" and the block would have to be about 13" taller
on each bank. cut shock towers ??? :)
: If the 289 rods insrease the compression stroke they increase all other strokes too. So would this increase the cubic inches of the engine? If it does than this is a cheap way to make a small stroker engine.
: But the way I see it the longer rod pushes the piston farther up the cylinder at top dead center. Then you have to shave the piston down so it doesn't stick out of the cylinder. But if you use the longer rod on the 302 crank, wouldn't that make the piston not come back down as far in the cylinder as the shorter rod would. If this is true then maybe the engine revs up quicker because the piston travels less. And if you combine this with a overbore you can get back the cubes you lost by having the shorter rod?
: I'm so confused! I think I'll stick to my 347. If anyone knows how that trick works I would be interested in knowing so I can stop thinking about it.