36 21 stud oil pressure

Brendan

Brendan

Well-known member
I have a friend that has a 36 twodor. he had the original motor rebuilt, it has about 8 lbs on a cold start and will drop to 0 after a few min of running. the guy that rebuilt the motor told him just use thicker oil. so what do we look for?
thanks Brendan
 
That's low pressure for a properly rebuilt engine. I am wondering if he is getting correct readings. Does he have a known good mechanical gauge installed? If so, he needs to find out what is wrong internally rather than just going with heavier/thicker oil.
 
yup, he has a new sunpro gauge, what if the guy left out the oil pressure relief valve, or the plug behind the timing gear?
 
There have been to many problems like this reported over the years. This is why I have posted many times to test the oil pump before installing it in the engine. Lots of new pumps have not worked. Also when the engine is sitting on the floor before the intake manifold is installed, install a mechanical oil pressure gauge, remove the spark plugs, put a little oil in each cylinder, put a rag over the cylinders so the oil don't fly and crank the starter with 12 volts. The pressure you see is what it will be driving down the road. You can adjust the front bypass valve spring with a thin spacer to get the pressure you want if everything else in the engine is OK. It's a lot easier to find and fix a problem at this point then after the engine is installed. G.M.
 
I think your friend should get another engine rebuilder. I see posts like this from time to time, and I wonder what the heck is going on with these guys. I wouldn't take that guys word for anything after his response. I had an O/T 327 rebuilt by a "pro". He put in a high-volume/high pressure oil pump that caused me no end of problems until I replaced it with a standard pump. I think that the fact that the HV/HP pump is almost $40 less than a standard pump had something to do with it. Luckily for me, it seems that whatever else he did was correct.
 
check it with another gauge before you do anything else. I have seen motors torn apart
over a bad gauge new doesn't always mean its good.
 
Was the camshaft reground during this or a previous rebuild? It's not uncommon for cam grinders to grind the journals 0.010 under to provide them with a nice true shaft for grinding the lobes. This is not a bad thing, so long as the rebuilder knows this and installs the appropriate bearings. But 0.010-under journals in standard bearings . . . well, you can see the problem.

Sad to say there's no work-around for this mistake other than replacing the cam bearings with the correct size.

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Is the engine using the original Fuel Pump? If user went electric and did not plug where the fuel pump rod rides the camshaft, you will loose oil pressure.
Just another thought.
 
I always check the easy things first, add a mechanical gauge, and then add another one just to double check, if the oil pressure still reads low on both gauges its time to do some looking, do check to see if the oil plug is installed behind the cam, ask the builder to show you the specs for the bearings installed and how much the crank and cam were turned, its never fun to tear an engine down, but if you have to use plasti gage to check clearances, a quality engine builder would never say add heaver oil to fix that problem, he would have said bring it back and lets find the problem
 
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