Do I have a burnt/burned valve?

Start with a compression test dry. Then wet with a few squirts of oil in the cylinders. Then move onto a leakdown test.


If if is a problem due to "lack of lead" in the gas there is an easy check to see if your heads/valves have a problem. Remove the rocker covers and then remove the rocker arms. Look at the top of the valve stems and make sure that they are all the same height (a ruler/straight edge may be used).

On my 340 formula s the guy did not put hardened exhaust seats in the heads when he rebuilt the engine. In less than 10 k miles it started running rough. When I removed the rocler arms to repair the problem, the #7 exhaust valve stem was sticking up approx 1/4" higher than the other valves. The valve had beat up the seat so bad that the valve was sunk in approx 1/4" which shows up when you remove the rocker arms and let it seat on the "beat up seat". The rocker arms hold it open.

It is an easy check to remove the valve covers and rocker arms.