[Sirrotica]

I use a straight edge on the sheetmetal to check for bowing, distortion. I use a bench vise opened up wide enough to set both edges of the valve cover on to work the sheetmetal to straighten it. That's how I do it, seems to work for me for many years.

I use RTV to glue the gasket to the valve cover, but you can use whatever you choose to. The heads are milled flat on the sealing surface so that side isn't the problem, the flexible valve cover is the place leaks usually happen.

If you use cast aluminum covers the problems are lessened, but I realize you're not going to use anything other than a stock GM cover on your car.

One other thing, the builder could have done a perfect job, but detonation can break a ring, or a ring land in a second. I have zero idea of what compression ratio you have, but trying to run the stock compression ratio with today's fuels can break parts that would have been fine with the fuels from the 60s.

My first experience was when trying to run a premium leaded fuel engine was in the late 70s. I was trying to run a perfectly running 65 Bonneville 389 on the only fuel available. In a street car I ruined it in less than a week because of the low octane.

Around the same time I also blew a hole in a forged piston, fresh 428 HO stock car engine in one night of racing. Every piston in the engine was ruined but one. I even doctored the fuel with octane booster, what a waste of time and money. I discussed the problem with Nunzi, and went to low compression 71 400 heads, problem solved.

FWIW. Your builder may have addressed that, when he built the engine, and if he did you should have no worries. It was a suggestion for something to look at because I simply don't know all the facts in your particular engine build.

Wishing you luck finding the leak, and correcting it.