Today I called Dwayne Porter. THAT guy can talk engines for days!
He was surprised with the cranking compression numbers that I reported. He said that the '509 cam is a long duration cam that should have had cranking compression numbers under 200. I told him that I had 2 guages and used the one that showed the highest numbers.
Dwayne suggested I finish the install of the 1.6 ratio Mancini rocker arms. The higher ratio will make the cam act larger. The effects on lift will be the most dramatic, but there will be some slight gains in duration too. like other smart engine guys have said, to reduce cylinder pressure, I'll need a later intake closing event. I asked about retarding the cam. He thought it was worth a try but made a few suggestions.
First) I'll install the 1.6 rocker arms and do a cranking compression test to determine what difference they make.
Second) pull the timing cover and retard the cam. Do not reassemble yet. Do another cranking compression test. If the numbers drop further and are below 185-190, button it back up and drive it. If the numbers do not change, return it to the straight up position and reassemble.
Dwayne had no specific recommendation for a replacement cam. I was hoping to get some advice there. He did feel that a later intake closing would help, but was wary of suggesting too big of a cam for fear of losing low end power. Instead he said that I could benefit from some distributor tuning, primarily slowing the advance curve.
So I installed the rockers on the 1357 side and measured the pushrod length. I came up with 9 1/8". Summit racing has some Crane pushrods in Reno, so I'll drive there tomorrow. Hopefully by this time tomorrow I'll have some good news to report.