hi comp 4age with 4agze pistons

[legend]

i was wondering could u use a gze 8.9-1 comp piston in a 100kw smallport motor and machine the head or block to get a comp ratio over 10.5-1 for use in a N/A motor.

just thinking out loud here as the gze piston is forged/coated and is priced close to a std smallport piston but could take a lot more than a std cast piston.

would the piston to valve clearence be the only concern ?

thanks

[beerhead]

I've never heard of someone doing this, it'll run away with the money, and you'll end up machining half the coating off the piston anyhow.

I'm planning something similar on a 5SGE build and was quoted $240 to have pistons shaved down and the reliefs cut. Then deck the block $100, head shave $100 + the price of the pistons new or old.

With such an adjustment on the deck height of the block you'll need adjustable cam gears to get the valve timing right too, otherwise your power band won't be where you want it.

If you're not boosting the engine and have it tuned by someone who knows what they're doing I'd be surprised if you pushed the limits of the factory 100kw pistons NA. There plenty of factory smallport bottom ends holding low boost and pushing good numbers on cam's NA too.

What have you got planned for the build?

[legend]

thanks beerhead for your info
i wasn't going to machine the pistons just machine the head right down to get the comp up to 10.5-1 or higher it will need to run cam gears as the camshaft timing would be affected
does anybody know the piston to valve clearence on a 4agze with the 8.9-1 pistons maybe another issue will be machining to much off the head will make it a interference motor or effect the quench area of the head
im looking at reving this motor to 9000rpm with a nice set of cams around 270+ deg
thought this might be a cheaper option than spending $900 on a set of aftermarket pistons when the gze ones are better and cheaper

[mic*]

Longer rods less money than somewhat trial and error machine work?

[mic*]

Longer rods less money than somewhat trial and error machine work?

No need for cam gears.

[mic*]

Longer rods less money than somewhat trial and error machine work?

No need for cam gears.

[beerhead]

At the price of custom rods you're better off getting some hasselgren formula atlantic pistons sent over, $800 atm. Quality made pistons, much like cosworth with teflon lined skirts and oil ring glands, but at under half the price.

If my calculations are correct, per mm that you shave the head or the block, you'll advance both the intake and exhaust cam by 0.5 degree. So it isn't much, but the power gains that people get with cam gears on stock motors makes me think it's worthwhile to be able to get your valve timing spot on.