The V8 Owners Forum -

Posted this on Pistonheads but worth repeating:

Car is a 1986 TVR 420 SEAC

Routine oil change

Went to local Unipart and asked for GFE181 - been superseded by GFE295

Change went OK - oil pressure sat at start where it was before and then as the engine warmed the needle started to fall. It got to 0.5 and I switched off. Checked the filter for leaks and started again revved to 2000 and it would not hold pressure properly - it was all over the place.

Thought that the pressure relief valve might be sticking but it was OK

I don't know why but I decided to order a Fram and tried that: Oil pressure 50% higher at ide and no falling back when warm or variability

As you can see there on the Fram there's an angled shoulder leading to the rubber ring, there are eight larger holes and a much more pronounced plateau leading to the centre hole

Also there is a spring mechanism about an inch inside the central hole of the Unipart not present on the Fram

Had this years ago, went through 3 filters before one worked. Was told it must have been a bad batch? I wouldn't go too much by the design differences as manufacturers have their own way of doing things. Either the filter hasn't been superseded and its the wrong one or its just faulty. Pretty sure Unipart would have checked the design worked before they started selling them. It shouldn't happen but sadly it does.

I had similar problems with 2 Unipart filters, fitted a genuine LR filter and all was fine.

Hello dmsims,

The Unipart filter that you tried and removed has an inbuilt filter bypass valve...the coil spring inside the centre chamber is the pointer to such. The Fram filter has no such inbuilt valve, so this filter is only to be used with an oil pump front cover that incorporates such within.

The oil pump front covers fitted to Rover V8 engines up until circa 1976 all had inbuilt filter bypass valves (not to be confused with the pressure relief valve which is entirely different) and as such the filters did not incorporate filter bypass valves. After 1976 the oil pump front covers changed eliminating the inbuilt filter bypass valve, this now being within the correct filters designed to suit. The diameter of the spigot which accepts the oil filter also changed at this time.

I can only imagine that the sealing ring on the Unipart filter was at fault allowing oil to leak out.

If your oil pump front cover has no inbuilt filter bypass valve, and the filter that you have fitted also has no such valve,. then should the filter medium become blocked or the engine revs exceed a given point when the oil is cold, the filter can bloat and even possibly split, but more likely the seal will rupture and oil will pour out everywhere...

Filters with inbuilt bypass valves must always be used when such has been omitted from the oil pump front cover.

Ron.

Probably not relavant to a 420 Seac but I recently changed the oil and filter on a Chimaera (crank driven pump) and was surprised to find that the oil pressure was slightly lower than before the change. I put it down to a slightly different oil visc.
I then noticed that the take off point for the oil pressure gauge was before the filter which would give a higher gauge reading as the filter cloggs up with use.
That's TVR for you.

Regards Denis

Forget to add that someone else posted a pic of a GFE295 they had - identical to the Fram and different to mine ??