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MG MGB GT V8 Factory Originals Technical - Oil pressure problem...

I've fitted a Rover 3.5 V8 in my mgb and i'm having problems with the oil pressure.

When assembling the oil pump it was packed with vaseline and we first primed the oil pump using a length of bar and drill with the dizzy removed and got an oil pressure of 50 lb's.

I then started the engine got an oil pressure of around 40 lb's from cold and it then dropped to about 20 lb's when cold and it was running and sounding very nice.

However after turning it off and leaving it for about 10 minutes when i came back to it and started it i had no oil pressure on the gauge and i could hear the engine knocking! so i stopped straight away.

If i use the drill to prime the oil pump i get oil pressure again.

What could be causing the oil pump to 'unprime'?

Anything to do with pressure relief valve?

I'm using the remote oil filter set up and the oil pump base i fitted was brand new.

Gavin Jewkes

Oil filters have a check valve to prevent the oil from leaking back and maintains oil in th system to prevent dry starts.
You must beusing a cheap filter with a bad check valve or not valve. Prevent using Fram filters, K&N, Sinclair Etc this filters have weak check valves. This filters combine with remote filters causes a big problem.
Use an AC, Filter, Napa gold or industrial type.

Now, this could be partofthe problem. The other is bad check valve on the oil pump.First try the filter change and location of the new remote filter. Do no install higher than the engine, this position will drain the filter back to the pan.
Bill Guzman

If you can reprime it with the drill, then the relief valve looks ok, sounds more an empty oil filter.
As Bill has stated, check that the filter is not mounted too high, and also check that you haven't reversed the flow and return pipes to the remote oil filter.
J Robinson

Oh, that's not good news...the part about mounting the filter too high, or it'll drain back to the pan. I've seen them mounted high in the engine bay, and wanted to look into installing my remote filter inside the right front wheel well, as I've heard recommended by someone. Are all these folks experiencing bad knocking at startup? An empty filter can't do an engine any good, and sounds awful! Would a filter with a better check valve prevent this happening? Seems to me that mounting it much higher than the top of the pan would give the same situation. Any more thoughts? Joe
Joe Ullman

I have built 2 cars with the filter mounted in the passenger wheel well just behind the head light. I have never had an oil pressure problem with this set up and ran the engines well over 200,000 miles, one a 215 Buck, the other a 4.2 Rover. The factory V8's had the filter mounted high inside the engine compartment & this caused no problems other than being ugly.

I am a firm believer in Wix or NAPA Gold filters(they are the same).
Jim Stuart

That is why you never had any problems Jim, you use good filters with a good check valve that does not allowed the oil to drain back. I never forget your car running the drag strip in Indiana wiht all of your tools in the back of the GT and still running decent times.
Jim, are you going to TN.?

I am living in the morning for Alaska and will return just in time to get the car ready for the 5200 mile plus trip to TN. I am really looking forward to the trip and see all of you again.
Bill Guzman

Including the spare & tools, I had almost 200lbs. in rear balast. That is why it hooked up so good. Too bad the last 1/3 of the track was wet & I spun the wheels for 150' in 4th gear or I mght have had really good times.

Yes, I will be in TN, but don't know which car I will drive, maybe the roadster if I get some miles on the engine - new 4.0 Rover.
Jim Stuart

Hi Joe, I used the lower method for the filter. It's located in the right front wing. Never any prime problems even after a year in storage.
Kelly Combes

In my MGA, I have my WIX oil filter mounted in front of the radiator,just below the hood latch and behind the grille. I've never had any type of oil pressure problems. The gauge shows about 45-50 psi. at speed and about 25 psi at idle when hot. I'm running a Buick 215.

This thread was discussed between 13/05/2006 and 31/05/2006

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