Jaguar Oil Pressure
Discussion
Can someone please let me know what range the oil p[ressure should be on a newly rebuilt 4.2 engine (XK):
On start up(mine is 55lbs/sqin),
at working temperature 2500-3000 rpm(mine is 35lbs/sqin),
at tick over (900 rpm ish) when warm (mine is 12lbs/sqin).
I'm concerned mine is too low, using a 10w40 oil.
On start up(mine is 55lbs/sqin),
at working temperature 2500-3000 rpm(mine is 35lbs/sqin),
at tick over (900 rpm ish) when warm (mine is 12lbs/sqin).
I'm concerned mine is too low, using a 10w40 oil.
A lot of it depends on the tolerances the engine was built to. Mine is the same as yours when cold at 55psi and if I rev it slightly when cold it will go to over 80psi until the relief valve cuts in. When hot it'll drop to 35-40 when racing, after a race on tickover it drops to 10 or so psi but soon pick up to about 20+psi after a few minutes. My road engine that I used to race would keep slightly better pressure when hot as a lot of it depends on how much tolerance there is in the bearings.
I only use Valvoline VRI 20/50 racing oil but any good quality 20/50 mineral would do if it's for road use, I find 10/40 is too thin and never got good pressure. I wouldn't use a semi or fully synthetic in an old Jaguar engine as you need to build up a seal on the rear oil seal and synthetic will just clean everything out and cause it to leak everywhere.
As long as you have pressure when it's ticking over when hot I wouldn't be overly concerned.
I only use Valvoline VRI 20/50 racing oil but any good quality 20/50 mineral would do if it's for road use, I find 10/40 is too thin and never got good pressure. I wouldn't use a semi or fully synthetic in an old Jaguar engine as you need to build up a seal on the rear oil seal and synthetic will just clean everything out and cause it to leak everywhere.
As long as you have pressure when it's ticking over when hot I wouldn't be overly concerned.
Edited by jagracer on Monday 8th June 17:03
Sounds like you have a crap engine ,jag racer. Localised overheating or the tolerances on the bottom end are totally wrong. They should have the same oil film clearance for road or race. My guess is that the rods are not sized or have gone oval with hard use, if your gauge is correct.
I await an irate caller then.I like a good row.
Seriously though, this sounds very odd .Oil Pressure if too high will lift the surface of the main bearings.It is far, far too high cold.The only way this would happen is if the pressure relief valve has been tampered with so it blows off at too high a pressure ,to try and make up for the loss when hot. Oil film clearance should be plasti-gauge measured at approx 2.5 thou maybe 3, race or otherwise.
A good race engine carefully built should maintain steady oil pressure around the figures 25/55lbs.( not dry sumped of course) Graham Bull`s XK150 being a prime example, still the quickest XK and maintaining these figures.
Seriously though, this sounds very odd .Oil Pressure if too high will lift the surface of the main bearings.It is far, far too high cold.The only way this would happen is if the pressure relief valve has been tampered with so it blows off at too high a pressure ,to try and make up for the loss when hot. Oil film clearance should be plasti-gauge measured at approx 2.5 thou maybe 3, race or otherwise.
A good race engine carefully built should maintain steady oil pressure around the figures 25/55lbs.( not dry sumped of course) Graham Bull`s XK150 being a prime example, still the quickest XK and maintaining these figures.
jagracer said:
It is an uprated pressure relief valve but maybe it's sticking, I'll take it out and check it. As for the hot pressure on tickover I am talking 500rpm and it does pick up well so I am not overly worried.
As for Graham Bull's engine, how much did that cost?
Doesn't Graham use a Sigma engine by Peter Lander?As for Graham Bull's engine, how much did that cost?
I know I was offered a broken one for £12K, it would then have needed the bottom end rebuilding. I seem to remember it had a broken crank.
Don't these engines have extra cooling channels machined into the blocks.
Graham competes in the class C, so it's still on SUs.
Totally out of my league and I doubt 12/15K would get you one of them. I'll have to settle for a few less psi when hot.jagracer said:
CavalierAttitude said:
RW774 said:
I await an irate caller then.I like a good row....
Ha Ha!! This has become apparent lately!Surely having a good engine is only part jigsaw for winning, it`s having a feel for the mechanicals to me is the most important, handling etc and a set up that your skill can complete the picture. I think you will agree, many drivers in historics have no feel for the car.One of the best around for me is Whizzo Williams,so I suppose it`s a question of experience.
What series do you compete in Jag racer and what with?
What series do you compete in Jag racer and what with?
RW774 said:
Surely having a good engine is only part jigsaw for winning, it`s having a feel for the mechanicals to me is the most important, handling etc and a set up that your skill can complete the picture. I think you will agree, many drivers in historics have no feel for the car.One of the best around for me is Whizzo Williams,so I suppose it`s a question of experience.
What series do you compete in Jag racer and what with?
Agreed, the man I bought it from knows how to set his car up and he can drive. What series do you compete in Jag racer and what with?
I mainly race in the Thoroughbred Sports Car Championship with my Dtype cough *copy*, I'll get me coat. I quite fancy a Healy 100 or TVR Grantura, would love a V8 Griffith but funds won't allow. The problem is that now's not the time to sell and I haven't got room for any more cars.
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