no compression on revalved head?

bountyhunter wrote:

richrand wrote:

Motor Head wrote: You say you put some valves in. Please expend on that a bit, did you use new valves, or grind the old ones you had? Did you check the guides, and cut the valve seat angles? Did you check for install height? Check the valve clearance to camshaft? Etc.

All new valves (but spec for a 1976 not a 1977). I did not check the guides or cut the valve seat angle. I also did not check for install height as I believed these would be OEM spec. I did not check for clearance. Just put them in and put it back together. Being honest here. I need advice. Thanks.

I'd start there.

x2

Definitely check valve clearances. But I would lap the valves regardless of what compression you get after getting proper clearances. Poor contact between valves and valve seats can easily burn the valves, and then you must buy new ones again. Lapping them is pretty easy and cheap; stick with a suction cup and paste. Grind lightly and take your time. When you have a uniform ring og contact between valve and seat, you're done. Unless you're going racing, it doesn't matter much whether the seat is 1 or 3 mm wide as the difference in flow will hardly be felt by your arse dyno. But if you are set on doing it the perfect way, you must cut your valve seats to at least 3 angles before lapping in the valves.

Once valves have been lapped, you must clean everything with petrol or similar. Make sure you get everything off, or the grinding paste will continue to do just that after you start the engine. Now fit everything back again and measure stem height to calculate correct shim sizes. Or buy the thinnes shim and fit to each lobe and measure clearances and then calculate how much thicker you must go to get the correct clearance.

Thank you all so much. This is very helpful.

What youre dealing with is basically the same result as putting new piston rings in a motor with egg shaped bores,the parts dont seal against each other.
Pull head back off and flip it on its back so intake ports are laying on the bench then fill exhuast ports with solvent then blow compressed air around edge of exhuast valve faces where they meet valve seat and watch for bubbles in ports,flip head the other way and repeat on intake ports.