Stoopid noob question

[just plain john]

I've read several engine build articles and have seen the term 'balanced at xx%' (38 and 50 are the two I remember off hand). Is that number relative to the bob weights used to balance a rotating mass?

 

[87GN_70GS]

To figure how much bobweight to add to the crank to do the balancing, you will add the rotating weight (big end of the rod, bearing) plus a percentage of the reciprocating weight (piston, pin, rings, small end of the rod, etc). It's this percentage of reciprocating weight they are referring to.

 

[thadeal4real]

% ?

90' and 60' ('=degree) engines use differnt %s or formulas the V6 buick is a 90' engine:biggrin: good luck
ps there are lots of forms of bal engines for differnt reasons ie under and over bal.

 

[charlief1]

Buick power source has 2 different ways to balance and for different reasons.

"To optimize main bearing loads and reduce engine vibration, the crankshaft should be underbalanced to the production formula (36.6 percent) and isolated from the chasis during mounting. Or you can avoid various amounts of verticle imbalance and monitor main bearing loads and vibrations on a rigidly mounted engine to determine if sutable compromises exist."

This is for the even fire engines but for the odd fire it is sugested that you balance to the 50% formula.

Hoe this helps.

 

[just plain john]

That certainly clears things up for me. Thanks for the info.