oversized valves

[Werx615]

my buddy is rebuilding his motor on his 400ex and installing a 11.1 87mm wiseco piston and he is getting oversized valves, will the piston need to be machined for the the larger valves?

also he has the stage 2 cam and we were wondering if we need a HD rod?

[TM426]

Correct me if I'm wrong, but the piston won't have to be machined. The only thing to be machined is the head to open the ports to fit the valves.

[Werx615]

he had the head machined but sumone told us the piston wold have to be machined so the larger head on the valve would fit in the recesses on the dome of the piston.

[TM426]

It could be possible, but I dont think it has to be done. I know what your talking about though.

[Barney]

You can have a problem. Want head gasket are you
going to use? Base gasket too. If you think you going to have touble use a little modeling clay when assebling your motar
to check clearance with piston an valves, It's not hard to do
you use the clay on top of the piston in the exhaust valve pocket spin the motar by hand and take it back down to
were you can see the top of piston and then you will see how much room you have around the valve on top of the piston.
You can do intakes at the same time but the exhaust valve will hit first.

[Werx615]

its a cometic head gasket, its pretty thick looks like around an 1/8th of an inch or so, thanx for all your help

[rap686]

don't forget to set valve clearence before checking piston to valve

[frogburner]

Dont use the paper looking cometic gasket, get the 3 piece steel, or you'll regret it later, especially if your on stock studs.. at least beef up the exhaust stud with a longer one..