Cam Question

[Dozerman51]

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? 

[Dozerman51]

Here are the specs on the cam.

[Elwood]

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?

[Dozerman51]

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.