Big Josh

This may sound like a dumb question, I have a gsr and I built the bottom end the same size as stock and was wondering whats the biggest size valves I can go with my stock bottom end. I was told from a few people that .5 mm would be all I need, but can I go 1mm? All feedback appreciated.

camp1320.com

yes you can go with 1mm but that is very dangerous. depending on the cam specs and vavle to piston clearance you will need to check to make sure your vavles wont the pistonsi dont think you want the vavle to beak and bounce around in the sleeves ?. the .5mm should be good enough.. how much power you looking to make..?? is it a FULL DRAG or street..?many people still use stock or stock size vavles. like i said .5mm would be plenty.

Jared

Not just valve to piston clearance, but with oversize valves and big cams, you'll also need to check for valve to valve contact at overlap.

Big Josh

So do you even suggest going with a bigger valve than stock or should I just keep with the stock size? I would like to go a little bigger to get a little more power. Also on the head all I was going to have done was a port job and the valves replaced. I was going to keep the stock valve springs and retainers and cams. This rebuild was mostly bottom end and a little head work. I wanted to go with bigger pistons and stuff but I got a good deal on the je turbo pistons and darton sleeves I couln't pass it up. They were stock bore.