I have been running my 540 BBC methanol injected engine so long that it has been honed for new sets of rings 3 times since 1998 from the original build. Since then the engine started to feel a resistance to being able to spin above 8000 rpm so I settled from dropping the shift points for a while. Finally I decided to go through the engine and low and behold I all the pistons were slap hitting the heads due to a huge piston to cylinder wall clearance. No damage, but the piston slap was effectively acting like a wagon wheel that wiggles when you spin it really fast. Turns out that I was essentially running a standard piston with almost a .015" over bore! I know, shame on me, but hey it was working well up until now.
Now I have bored the engine .060" to make a 4.56" bore. The new Wiseco pistons are 10 grams (~ .35 ounces) heavier than the 4.50" pistons. I am running a wet sump oil system so there is plenty of windage no matter what I do. Does anyone out there feel that I should take the time to re-balance the engine (already internally balanced with heavy metal slugs) for only 10 grams of overweight on the piston? Or just shave a little off the underside of the piston to drop the mass delta to 5 grams and call that good? Finally, will the engine ever notice 10 gram heavier pistons in a wet sump application?
It has a 4.25" stroke and I plan on shifting around 7800 RPM.
Any advise would be greatly appreciated.
Regards,
Brian