'Busa pistons

when you start going in to milling head only way to do it right is to measure.
ps.stay away from to much lift on cams.

[yorkie_chris]

Cheers zadar.

So would I be right in thinking to build it and check piston-valve clearance with clay, then mill and build again?

I've heard various figures chucked around about the required clearance, roughly 1.5mm seems common, is this about right or what?

Ta.


p.s will check lift on JHS cams by lobe-vs base circle method, just out of interest. Not sure how to check the duration though.

Also, busa gudgeon pin or the SV one?

not fan of clay.there are better ways to measure.but yea,you need to measure.
1.5mm is not enough.also different for intake and exhaust.
degree wheel on crank to check duration.
wrist pin has to be busa,they are not interchangeable with sv.

[yorkie_chris]

I don't think checking the duration would make much difference to me, after all I don't have facility or inclination to mess with that. Figure JHS know better than me.

How do you check clearance? Solder? Or could you set it up with some light valve springs and try to open the valve a little further than the cam does in overlap period... no problem setting up degree wheel and feeler gauges, check every 5 degrees or so.

What would you allow for clearance?

I like dial gauges.
I also like safe clearance

I think Zadar ment it will be lift duration/timing that will effect clearance more than valve lift so its the duration that will need to be checked?

I take it you are going for peak power not the mid range?

timing can make valves hit each other.

[yorkie_chris]

Safe clearance to me sounds like "a lot"

I'm yet to test a stock engine for clearance, but I'm guessing there's a fair bit, the question I have is what is a safe minimum?

2mm

Originally Posted by zadar

2mm

Bloody hell, and whats standard?