I have a 75 Ranchero with a 351m. I swapped to the 400 crank, 10:0 pistons, mild street strip cam, and holley 650cfm, with performer intake, and exhaust manifolds. I then swapped to the 351c 4v quench heads with a bigger cam .535 lift and about 282 in duration. I added roller rockers and modified some 4v headers from a mustang to fit. I also added a 750 Vaccuum secondary Holley Hp street. I have tuned it fully with vacuum, timing and O2 sensor I installed. I have it jetted and a diff power valve on there as well. I read 13psi vacuum at idle in gear. I have been driving it daily or every other day for a month. I started it the other day to drive it to work and it was lacking a cylinder. I could not tell which one it was based off temperature of header primaries. I did compression test and I was surprised to see they were rather low. 130PSI- 145PSI. The motor had no were on cylinder walls in fact hone patterns were still there and it was rebuilt approx 10k miles ago. I just revived the car after a three year sit in the garage about 6 months ago and my motor builder and I performed the build abot five years ago. Any ideas what I should see for compression results? I have quench heads and previous 10:0 pistons with open heads. ShouldntI see 11.8 or so? Why am I getting such low compression test? The came isnt that big is it? Car ran strong when parked. last any ideas?

 

tankfull of weak sauce? what do you run it on?

 

Runs on 92+ all the time, timing set at 36 total 15 initial advance, no starting problems has a full msd ignition, 6al, pro billet dist. and blaster 2 coil. normally runs great has deer hide tan on all plugs. no gas or oil on any of them, but I haven tran it for very long since it started missing, just around the block when I took off the first time. Hows is octane going to affect compression? it shouldnt matter what gas is in there should it as far as compression testing goes?? Anywho any ideas?