71monteme Posted September 29, 2011 Share Posted September 29, 2011 Ok. here goes. when the engine 1st start up, oil pressure is at 70-80psi. oil warms up, 20-25psi at idle. drive around the block, oil drops to almost 0psi at idle. bring rpm up to 2000, get 10-15psi. it does it with 5w-30 oil, 10w-40, 15w-45, 20w-50. oil full, 1 quart low, 2 quarts low. any guess on what it might be? engine is coming out, just getting some ideas. thanks thanh Quote Link to comment Share on other sites More sharing options...
robs70monte Posted September 29, 2011 Share Posted September 29, 2011 try a gauge a different gauge like a under hood one with a small lead maybe. Quote Link to comment Share on other sites More sharing options...
TrunkMatt Posted September 29, 2011 Share Posted September 29, 2011 Rule of thumb is 10psi per 1000rpm when warm.... I get maybe 5psi at 750rpm idle when hot. Since your start / cold pressure seems fine etc... and your running pressure seems close - I am going to bet on your guage not reading low pressures correctly, or that it is off by 5psi and the spring doesn't work right, or it needs calibration. Maybe before you get too into the thing, buy an Oil Pressure test kit from Harbor freight that allows you to test on-block: http://www.harborfreight.com/engine-oil-pressure-test-kit-98949.html Quote Link to comment Share on other sites More sharing options...
Mike 57 Posted September 29, 2011 Share Posted September 29, 2011 Yeah, I would try a different gauge. I had the same issue, new sending unit fixed it. but then I had to get another gauge to make sure. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted September 29, 2011 Share Posted September 29, 2011 I conquer verify with another gauge, if still low the next easiest to do would be the oil filter adapter (check the bypass in it) I tap and plug my bypass, no luck with that I think a bearing inspection would be next, along with the oil pump something else to consider would be the distributor housing, if housing is damaged/cracked/ect it could! effect your oil pressure, remember it seals off the oil galleys that parallel the cam which feed the crank Quote Link to comment Share on other sites More sharing options...
dbreese Posted September 29, 2011 Share Posted September 29, 2011 Thanh do you have a mechanical oil pressure gauge or electric? If electric it could be a sending unit going bad. I agree on trying a different gauge. Hope it is nothing serious. Mike Treed me!! David Quote Link to comment Share on other sites More sharing options...
Mr70Monte Posted September 29, 2011 Share Posted September 29, 2011 years ago, I helped a friend start up a 396-375 in a 68 Camaro, I didn't know he reused to old solid lifter cam, fired up 2500 rpms for 30 minutes, great oil pressure during this time, then I found out the cam had already been broken in, dropped the rpms down to an idle.......no oil pressure, called my friend that built the motor, his first question was what oil filter did he use......FRAM....changed it to an AC Delco....not a problem then. just a thought1 Quote Link to comment Share on other sites More sharing options...
LS5 Posted September 29, 2011 Share Posted September 29, 2011 Hey thanh, The Chevelle just got the 454 rebuilt and is 420hp and still had the breakin oil in the car and had the same symptons as you but also had a Fram PH30 oil filter on it with 5psi. phoned Vaughn and asked for help and the engine shop that did the 454 and both said for the love of god shut the car off your filter has folded in and no oil pressure. I was told to go with a WIX filter which has a tinned liner throughout the filter and paper lined too. sure enough the Fram filter came off and it had almost sucked itself inside out looking inside all the paper linning had folded and rolled up and blocked the flow, I dumped the oil and put in 20w50 with a bottle on Zink and a new Wix filter and bingo 80psi all the time and put on 200 miles on Saturday and 90 degrees out and zero problems still holding 80lbs at idle the lowest it ever dropped to was 75-80....just my input and feedback thats all. Darren. Quote Link to comment Share on other sites More sharing options...
71monteme Posted September 30, 2011 Author Share Posted September 30, 2011 thanks guys for the ideas. the engine's coming out anyway. I wanted to freshen up the lower end, so i will post what i find when i have it out. thanh Quote Link to comment Share on other sites More sharing options...
amsterdam84 Posted September 30, 2011 Share Posted September 30, 2011 Yeah Fram filters are the worst. Never will I use them again. All the internals are paper that's just glued together. Quote Link to comment Share on other sites More sharing options...
TrunkMatt Posted September 30, 2011 Share Posted September 30, 2011 Yeah - even this small furry creature knows about the dangers of Fram Filters.... check out the response when I asked "Should I use a Fram Filter?" Quote Link to comment Share on other sites More sharing options...
amsterdam84 Posted September 30, 2011 Share Posted September 30, 2011 LOL that is a odd cat. Quote Link to comment Share on other sites More sharing options...
Andy's Auto Posted October 11, 2011 Share Posted October 11, 2011 Thanh, low hot oil pressure is usually a sign of beat rod bearings and done cam bearings after everything else checks out. Dying to see pics of the bearings when you get it aparts. The 496 I sold out of the 71 Monte a few months ago got a fresh set of bearings. And it had 20 pounds at hot idle. Somebody was playing with the timing a little much.lol. Nothing kills rod bearings like detonation. Quote Link to comment Share on other sites More sharing options...
jim's 70 Posted October 12, 2011 Share Posted October 12, 2011 Thanh...please check the gauge.... I heard nothing "odd" at Atco.... if you want to tear it down for the fun of it...great.... but definitley check your gauge first...at least when you fire up the new build you will know the gauge is right.... Quote Link to comment Share on other sites More sharing options...
71monteme Posted October 12, 2011 Author Share Posted October 12, 2011 Thanh...please check the gauge.... I heard nothing "odd" at Atco.... if you want to tear it down for the fun of it...great.... but definitley check your gauge first...at least when you fire up the new build you will know the gauge is right.... Jim. I'm tearing it down for my piece of mind. I wanted to replace the bearings anyway. it's been a while scince i had the bottom end apart. tranny's going to the shop for a freshen up and trans-brake install. Rear end getting shorten and ford ends put on. and new pressure gage installed. so i need something to do over the winter to keep me sane. might even end up putting the roll- bar in the car to keep it legal. Andy. pictures will post as soon as i get to it. thanh Quote Link to comment Share on other sites More sharing options...
Mom's Car Posted October 12, 2011 Share Posted October 12, 2011 Originally Posted By: jim's 70 Thanh...please check the gauge.... I heard nothing "odd" at Atco.... if you want to tear it down for the fun of it...great.... but definitley check your gauge first...at least when you fire up the new build you will know the gauge is right.... Jim. I'm tearing it down for my piece of mind. I wanted to replace the bearings anyway. it's been a while scince i had the bottom end apart. tranny's going to the shop for a freshen up and trans-brake install. Rear end getting shorten and ford ends put on. and new pressure gage installed. so i need something to do over the winter to keep me sane. might even end up putting the roll- bar in the car to keep it legal. Andy. pictures will post as soon as i get to it. thanh Lot's of luck with the winter project......... Quote Link to comment Share on other sites More sharing options...
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