i own 69 vette conv 350 cu in/350 hp, 4 spd. I just had the engine completely blueprinted, bored .010 over all new pistons, rings, roller cam, rockers, bearings, oil pump, the works. Pink rods and crank are still original. (LT engine)
Problem is I notice that my oil pressure is 35psi at idle when the engine first starts up and drop to about 20 when warmed up. The mechanic has break in oil in the engine which he says this is why the pressure is low. Is this true?? He said, it will go up considerably when he changes to regular oil. BTW, he wants me to use synthetic changing it every 3000 miles...good idea or bad?

 

What are your oil pressures at higher engine rpm?

 

Unless you have a high volume oil pump, those numbers sound about right to me. My 454bb rebuild has about 36 on start up. I like reg oil and 3000 mile change, but syn and 3000 certainly can't hurt after break in. Did the rebuilder say he "Blueprinted" the engine? Just curious because you hear this term thrown around by rebuilders, and it really doesn't mean a thing for a 1 off engine rebuild. Bringing an engine back to the factory specs is one thing...blueprinting is another.

 

when the engine is warmed up, it idles at about 20psi..when I give it gas, it goes up to about 35 psi...could this be caused by the break in oil?

 

I don't understand why after getting the engine blueprinted, shouldn't it be at 60psi when the car was new? and that's without any high pressure oil pump..

 

I never had a car run 60 psi with a stock oil pump. I think stock pumps have the pressure relief at about 35-40 psi. (not positive on that though)

 

Did the builder run it and break it in? Sounds like he didn't.

He should have run it 20 - 30 minutes to break in the cam at about 2000 - 2500 rpm. Then dumped his "break in" oil, changed the filter, cut it open to be sure all was well, installed a new filter, and filled with new oil.

It sounds like he has lightweight oil in there if you have only 20 psi at idle OR you have far too much bearing clearance. Ask him what he set the bearing clearance at. .0025" ? .003" ? .004" ? Most old builders use too much, when you ran heavy weight oils, and high volume pumps. All of that wastes power today.

The only engine I ran .004" on was my 302 and that was because we were running 9500 rpm with it, and floating the crank with 80 psi of 20W50.

YOU, on the other hand, are not doing that nor will you do that on the street. .0025" is all you need but I bet he has .0035 to .004" clearance and/or is running 10W30 or lower to get the engine along on its first 1000 miles.

If it were me, I'd find out the bearing clearances and what oil he used specifically, not simply "break in".

If it is like I said, you have two options, you can try to prove you are the engine expert and have him redo the bottom end with more reasonable clearance. Or live with it and run heavier oil. 20 is the minimum I'd live with at idle, as with age, the clearances just become more, so the pressure will become less. 35 at normal driving, and 40 for revving it up to 5000 or so.



If not, then I'd run a break in routine of moderate upshifts and downshifts over the next 1000 miles, dump the oil, and put in a weight higher, i.e., 10W30 if he used 10W20, 10W40 if he used 10W30.

I'd also put in a magnet drain plug in the oil pan and watch religiously for metal. If I began to find chunks, I'd be at his door.

 

Also, using real all synthetic like Mobil 1 or Redline is a waste to change at 3000 miles. Change at 5000 miles. Many say go further, and change the filter only at that time.

I do 5000 mile changes with Mobil 1 and have 196,xxx on my Camaro.

 

If you have a GM (stock) oil pump, the pressures you are seeing are "normal". Having lots of oil pressure at an idle condition is a waste of effort. The engine isn't loaded and doesn't need it. Stock pumps put out about 10 psi per 1000 rpm above idle speed. At idle, you might see anything from 10 psi to 30 psi on your console gage. Part of that wide variation is the lack of accuracy of the oil pressure gauge. But, if it reads 30 psi at idle, you have absolutely no problem with the oil pump.

 

just a suggestion, but you also might want to read up on ZDDP (search here at the forum).

 

I agree. Normal.

 

Stock oil relief is 49psi

 

If it was indeed "Blueprinted" then all of that information will be written down, along with all of the other specs and clearances. After all isn't that what Blueprinting is?