Dozerman51 Posted April 5, 2018 Report Share Posted April 5, 2018 Ok guys, don’t flame me, but I’ve got a question about the cam in my truck. It is a longer duration cam ground for a 251 not a 236. Does that change things as far as timing etc. I can take the bad news. LOL. Did a compression test on the 236. #1 90, #2 100, #3 100, #4 100, #5 80, #6 100. Hoping #5 just needs the valves adjusted although I will check them all. Vacuum gauge reads at 17 (the gauge reading area that says “late ignition timing)with the needle flickering very fast but less than 1/2 “ of mercury. Engine idles real smooth with no miss nor does it miss on acceleration or at high speed. I don’t know if I will install the Aluminum Head when I get it back from the machine shop. I want to have the Spitfire head shaved to give me a compression ratio of around 8 or 9:1. What say guys? Quote Link to comment Share on other sites More sharing options...
Dozerman51 Posted April 5, 2018 Author Report Share Posted April 5, 2018 Here are the specs on the cam. Quote Link to comment Share on other sites More sharing options...
Elwood Posted April 5, 2018 Report Share Posted April 5, 2018 Those compression readings seem sort of low, not just No. 5 cylinder. But I'm not hands-on with the big-block flatheads; what does your manual say for minimum compression readings? Quote Link to comment Share on other sites More sharing options...
Dozerman51 Posted April 5, 2018 Author Report Share Posted April 5, 2018 The Industrial engine manual lists 110 - 140 Lbs. and a compression ratio of 6.6:1. To be fair the book lists the starter cranking speed as 125 RPM’s. Don’t know the cracking speed of my starter but I cranked the engine 4 revolutions for each cylinder reading. Quote Link to comment Share on other sites More sharing options...
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