(Another) Oil pressure question

[TRnorm]

A simpler oil pressure question this time, but still, a little strange.

 

When I was priming the oil with a drill through the distributor shaft access it was quite easy to get the pressure to rise to about 70 and then the gauge would flicker and it didn't seem to want to rise any further, so clearly the PRV was kicking in (seemingly at the correct pressure).

 

Now I've got the beast firing up in its own right the pressure rises to about 90(!) until everything seems well and truly warmed up, when it settles to about 50 (at 2000rpm).

I suppose the PRV might have decided to not work, and of course I should try adjusting it. But I thought that before I did that I would just ask if anyone has a logical explanation.

 

Thanks

Norman

 

 

 

[peejay4A]

I suppose when cold and once the prv has opened the only other thing limiting the ability of the prv bypass to do its job is the size of the oil ways.

Edited July 8, 2014 by peejay4A

[Paul Harvey]

Speed of drill.

Just set the OPRV.

[Guest ntc]

Restricted oil gallery's

[AlanT]

Be interesting to know the history of this engine.

 

Did you do anything to purge out the oil ways?

 

I spent two weeks on and off doing this with pressure-jet solvent.

Eventually fine grey particles stopped being flushed out.

[AlanT]

duplicated

Edited July 10, 2014 by AlanT

[TRnorm]

Since you asked Alan.....The engine was rebuilt two and a half years ago by a Ric Wood to a fast road spec. (I vaguely remember someone saying he does work for Racetorations - but I don't know that for fact). I bought it off someone who had a "change of plans" And it had never been run until I ran it a couple of weeks ago.

 

Checking it over first I found cam lube around the rockers and on the cam fuel pump eccentric (viewing through the fuel pump aperture), and things like the sump nuts were Loctited, and viewing the bores through the spark plug holes everything still looked freshly honed and cross hatched. So, overall, my conclusion was it had been done properly and did not need stripping down so long as I primed the oil systems - which I did. My guess is that the electric drill was anywhere between 500 to 1000rpm (any higher and the oil would overflow up the distributor shaft). And as I said, the pressure would get to about 70 and the needle would then flicker - indicating to me that the PRV was doing its job.

It was only at the next stage of running-in the cam at 2000 rpm (under engine power) that it started to display the characteristic of the oil pressure being well over the 70lbs figure and not falling until the oil was well up to temperature. I guess the PRV setting might have changed or possibly the higher revs and therefore flow rate are giving a higher pressure while the oil is cold (although the PRV should look after that?).

Anyway - I'm not too worried by it and inclined to favour Paul Harvey's advice to simply set the PRV (which I did disassemble prior to start-up and all appeared clean and OK).

 

To be honest, we had been working like hell to get to the MOT stage, so am now taking a little rest from the car as i await the New registration from the DVLA. But a turn or so to the PRV will be the next move.

 

Thanks again to everyone's thoughts and suggestions.

 

Will update in a week or so.

 

Norman

Edited July 10, 2014 by TRnorm

[Guest ntc]

On the first point wrong,second you should not have primed the pump,last change the oil asap after first run up.