correct oil-rebuilt engine
Thread Starter
Intermediate
Joined: Jan 2017
Posts: 25
Likes: 5
From: South East Florida
correct oil-rebuilt engine
My 66 vette, 327-300 engine, A/C, auto trans (700r4) has been completely rebuilt. My question is what is the best oil to use? Some say use a synthetic such as Mobile 1, and others say use a 20W-50w oil. My oil gauge reads 30-40 psi when I start it up but goes down to 0 psi after warm up. Clearly the gauge is wrong, as I have driven local and highway speeds for long periods of time and I have no problems with the engine. I have not burned any oil since the engine rebuild. I am replacing the original oil pressure gauge and tube. Any thoughts out there from you pros?
Melting Slicks
Joined: Jan 2010
Posts: 2,079
Likes: 541
From: Woodland Hills CA
Oil
This topic has been covered 100 times. Use what your rebuilder recommends, since we dont know what internals are now in it.
If its an original rebuild, with orig spec parts, you need an oil with alot of zddp in it. A diesel oil like CJ-4, or the newer equivalent or a designer oil specifically designed for flat tappet cams like Brad Penn.
If its an original rebuild, with orig spec parts, you need an oil with alot of zddp in it. A diesel oil like CJ-4, or the newer equivalent or a designer oil specifically designed for flat tappet cams like Brad Penn.
Race Director
Joined: Apr 2015
Posts: 17,571
Likes: 3,460
From: Fresno California
This^^^^. All the protection you need. 20/50 oil is too thick unless your engine is worn out or has large clearances. Racing oils do NOT have the additive package that is necessary for a street driven car. Race oil is meant to be run hard and changed after the event. No corrosion protection. I've been using Rotella in everything flat tappet for years and tons of miles without incident. Cheap, too.
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
I wouldn't bet the gauge is wrong and even if it isn't, changing oil won't fix that problem.
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
Racing oils do NOT have the additive package that is necessary for a street driven car. Race oil is meant to be run hard and changed after the event. No corrosion protection. I've been using Rotella in everything flat tappet for years and tons of miles without incident. Cheap, too.
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Safety Car
Joined: May 2014
Posts: 3,783
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For a street driven engine a C rated 10w30 oil is fine. If your oil pressure gauge reads zero when the engine is hot I would not even drive the car until someone verified the pressure. Are you saying driving down the road at speed the gauge reading is zero or just at hot idle speeds.
Drifting
Joined: May 2006
Posts: 1,469
Likes: 329
From: Southold New York
Choice of oil is not your priority. Repair/replace your oil pressure monitoring system immediately before you are forced to buy another engine. Not speaking for others. but I am very concerned that you have a decent (not ideal) reading at cold start up and "0" at warm idle. How many miles since the rebuild? What oil is presently in the engine? Are you still running a very thin "break-in" oil as filled by the engine rebuilder? Have you even spoken to the rebuilder about your concerns?
Team Owner
Joined: Apr 2008
Posts: 31,785
Likes: 2,395
From: Middle TN by way of KY, OH, VA, IL, CA, FL, NY, SC, HI
Choice of oil is not your priority. Repair/replace your oil pressure monitoring system immediately before you are forced to buy another engine. Not speaking for others. but I am very concerned that you have a decent (not ideal) reading at cold start up and "0" at warm idle. How many miles since the rebuild? What oil is presently in the engine? Are you still running a very thin "break-in" oil as filled by the engine rebuilder? Have you even spoken to the rebuilder about your concerns?
If you have 0 oil pressure at any time the engine is running, you have a more pressing problem that overarches your quest for a correct oil formulation.
First and foremost, I strongly recommend that you confirm that your readings are accurate. If you truly have no oil pressure (0 inches) then you need to not operate that engine until you figure out why.
Do not be lulled into thinking that using a heavy weight oil such as 20W-50 will address a bearing clearance, bad oil pump, or oil gallery issue. Nothing about these engines required heavy weight oils back then, and none should need that now. Find and fix the root problem. No engine should have to require a heavy oil to overcome poor lubricant management and distribution problems.