So, i’ve followed “71Drmon572”’s post on the 580” engine recently. A comment he made brought up a a question I have had for a long while, and it may just be the answer. I didn’t want to convolute his post wth my question, so i made this new post. You guys can give your opinions.

About 2 years ago, I put together a lowdeck stroker motor with Indy-1 325 heads. Ran on the dyno and made nice power. However, i noticed the oil pressure was hovering around 60 for the entire pulls. Engine made peak hp at 7500 and pull to 7900. Vacuum was at 13-14”. This was a dual ext line with Milodon billet pump and super stock milodon pan (hole for centerlink). I always questioned why the pressure never climbedup to 70-80s. Added data** Dyno run from 4900-7900 rpm. Vacuum was 11.6” at 4900 climbed to 13.4 at 7900. Oil pressure was 62 lb at 4900 and tapered to 58 lb by 7900 rpm.

We even had a discussion in the dyno control room about the theory of whether crankcase vacuum can reduce oil pressure in the engine. Both sides of the argument were supported by different guys in the room. The engine was only run with vacuum, so I don’t have o p readings without vacuum.

So, does vacuum in crankcase reduce oil prssure that the engine sees, or readings,or it is totally unaffected by crankcase vacuum.