balance motor....

[boricua]

i've read that a 416 will out perform a 426 or even a 440 and that they are more efficient because the weight of the piston is closer to the weight of the stock piston thereby allowing the motor remain closer to being balanced. question is, can you remove material from the bigger piston to bring it closer to the weight of a stock piston? if not, why? thanks guys.

[GPracer2500]

Originally posted by boricua
i've read that a 416 will out perform a 426 or even a 440 and that they are more efficient because the weight of the piston is closer to the weight of the stock piston thereby allowing the motor remain closer to being balanced. question is, can you remove material from the bigger piston to bring it closer to the weight of a stock piston? if not, why? thanks guys.

My opinion?

A 416 can outperform larger displacements but it's hardly a rule. Generally, more displacement = more torque/hp. That doesn't necessarily mean faster on a track though. HOW and WHERE an engine makes power is very important too when riding competitively.

As far as piston weights, I would not try and modify a piston to remove weight. There might be one way to do it right but probably 100 ways to do it wrong. Don't risk it unless your a pro at piston design. Changing the wieght of the counterbalancer would be a much better option for balancing a piston. Afterall, the counterbalancer is just a dead weight lacking pinpoint dimentions.

For perspective (these are JE pistons):

397cc 10.5:1 or 12:1 = 263g
406cc 10.6:1 = 294g
416cc 10.8:1 = 294g
416cc 12:1 = 285g
426cc 11:1 = 298g
426cc 13:1 = 318g
435cc 12:1 = 268g (aka "440")

As you can see piston weights very and bigger doesn't always mean heavier. Compression ratios change the piston wieght too.

If you want a balanced engine than what you want to do is "blueprint" the engine. Every spinning or reciprocating component is measured and modified ever-so-slightly (maybe 1 gram here or a 1/4 gram there for most things) so that everything is in perfect balance. That's one way factory race bikes get more power and reliability than everyone else--blueprinting. Everything is smooooooth and in perfect balance. In racing classes where stock components must be used in unmodified form, factory race teams will handpick cranks, rods, etc. to find ones that are the exact weights they need.

[boricua]

thanks, that was good info!!!:macho
i had no idea that the biggest piston weighs the closest to a stock piston.... you said how and where the engine makes power is important....would you say increasing the displacement without changing anything else should equal the same "how and where", power characteristics as a stock engine only with more power? i understand there are many variables and that the question may be a tad vague, but if it can be answered........
im just trying to get an idea of a next step as far as engine mods and why some may choose on size over another.....thanks again!