400ex Piston to Valve clearance

[Kentang4]

Can someone please tell me the minimum piston to valve clearance for a 400ex? I'm using an 11:1 piston and stage 2 hotcam. What I am interested in is how much clearance I should have when the valves are closed and piston is tdc since I don't have an easy way to check it with the valve in the open position without totally assembling the head/cam/cover. I have the cam spec for lift but unless the rocker arms are a 1:1 ratio that isn't going to equate to valve movement. Using the play-doh technique and the valves closed I have .227" of clearance between the valve and the piston dome. My concern is that the previous owner shaved the head. The engine is appart because of a loud knock that I suspect was piston/valve interference. Perhaps it was caused by a worn timing chain? Any help is appreciated.

Thanks,

Kent

[86 Quad R]

to do it accurately your going to have to assemble things and rotate the assembly using the puddy technique.

[Kentang4]

That's kinda what I figured I would end up doing but if I knew the rocker ratio I could calculate the valve movement. I don't think the Clymer manual mentions it anywhere. Perhaps I'll email HotCams and see if they have any more info that would be useful.

Thanks,
Kent

[togup]

You can zero deck your jug (piston flush with top) add a gasket and still have plenty of clearance you must have something broke in the valve train if the piston is contacting with valves (youll see the marks on the valves if theyre hitting)or the piston is in backwards the valve recesses are smaller on the front

[Kentang4]

Thanks for the info. The motor is new to me but has been worked on. In fact it had a brand new piston and cam but I didn't know that until I tore it down due to some heavy knocking. I think the cause for contact was a bunch of carbon baked onto the exhaust valve but I'm not certain. The marks are down in the recess of the cutout, not on the edges so I don't think it was a backwards piston that caused it. A friend bought this thing without starting it and took someones word that it worked fine and just had a top end. Well, it had a new top end but sounded like crap. I think the previous owner put in the new parts, started it and immediately shut it off and sold it to my friend. He brought it to me and started it and I immediately had him shut it off. Soooo, I have since put in a new, larger piston, crank, stage 2 cam, etc. I put it all together with the play-doh and ended up with .060 clearance after pulling it through so I'm content that it won't be a problem. Perhaps I'll have it running next week.

Kent