oil pressure reading?

[ZooKypr]

Just wondering....last year I installed an AutoMeter short sweep electrical oil press gauge and until today it always reads 38 - 40psi at idle or WOT even with me shifting over 5000rpm in 80+ degrees weather and when the weather is below 60 degrees she's a little higher at 43 ... Today during a 20mile cruise @ 3000 rpm (4.10 rear) I noticed my oil pressure was 32. I know the rule of thumb is 10lb for every 1000rpms but why did it start reading correctly now? When I went WOT the pressure went to 40lbs but no higher @ 5500rpms. Shouldn't my gauge read 55 shifting @ 5500rpms? Is my gauge F'ed up? I don't have a mechanic gauge handy to test her just 'fishing' for some insight. Its a 273 commando mild mods, big cam (.515/..525) and I run VR1 20W-50.

ZooKypr

 

[71dustar]

i know on my 408 engine at idle oil pressure is about 40. when i increase to about 3000 its 60. when i first start the motor it is at 80.

 

[ZooKypr]

Well I went out and played around lil' bit and realized that the electrical oil press. is way slower to react then a mechanical gauge....I revved her up to 3000, 4000 & 5000rpm and the gauge slowly reacted and gave the appropiate readings of 30, 40 & 50lbs. I guess I just forgot how quickly my mechanical gauge used to work. For now, issue resolved....

ZooKypr

 

[fishy68]

Another thing to mention is 10 lbs. of oil pressure for every 1k rpm is just a "rule of thumb" meaning it's not written in stone. In fact it may be pretty hard to achieve that exact figure cause the oil pressure may not rise linearly. You'd probably either need to get super lucky to have it read exactly 10 lbs. for every 1000 rpm or have a special pressure relief valve built to make it accomplish that. Sometimes old sayings and rule of thumbs need to be taken with a grain of salt. Meaning you can get close but to be exact is probably nearly impossible.