Shall replace high pressure oil pump with low??

[Crusty]

My twin cam has had a high presure oil pump fitted pre my owner ship and have read that they should only have a low presure pump, the head has been wizzed up by QED and power max pistons fitted.
When my car comes out of cover ready for the summer in April it is booked in for MOT an original tacho to be fitted and ignition sorted shall I have a low pressure pump fitted also ?
Looking forward to the summer and a trip with a good friend to Le Mans
Appriciate you comments..
]

[512BB]

Crusty,

You wont be able to remove the existing oil pump in situ, as there is not enough room to withdraw it without moving the engine over by about an inch, as it will foul on the steering column. That said, I suppose that could be removed, but if the HP pump is working okay, leave it. Twin cams dont need one, unless you are using racing RPM.

Regards,

Leslie

[ardee_selby]

This thread adds more info on replacement by jacking the motor up (plus discussion on
the merits of HP & normal pumps. (Note, in particular, Rohan's input)

elan-f14/oil-pump-t19229.html

Cheers - rd

[Crusty]

This thread adds more info on replacement by jacking the motor up (plus discussion on
the merits of HP & normal pumps. (Note, in particular, Rohan's input)

elan-f14/oil-pump-t19229.html

Cheers - rd

GOOD THREAD THANKS..

[stugilmour]

Crusty, I just changed out my HP oil pump today based on the info in the highlighted thread.

Only tested it in the garage so far, but with the engine warm enough to kick in the electric fan (top of the "normal range" graduation on the gauge) the oil pressure was about 45 to 50 psi on the dash gauge.

Previously with the HP pump it was pinning the dash gauge at over 70 psi, which I considered way to high. HP pump pressure was confirmed with a remote service gauge by the engine re-builder this fall.

Engine is fresh, with only ~1000 miles on it, so not surprised pressure may be toward the high side even with the stock pump. Engine appeared to be weeping a lot of oil, hence the change. Hoping the lower operating pressure will remedy this situation.

On my LHD Plus 2 the pump change was easy, with no displacement of the engine required, but a tight fit to the body. Could see this would not work on the two seat Elan.

[Galwaylotus]

Crusty, I just changed out my HP oil pump today based on the info in the highlighted thread.

Only tested it in the garage so far, but with the engine warm enough to kick in the electric fan (top of the "normal range" graduation on the gauge) the oil pressure was about 45 to 50 psi on the dash gauge.

Oil temperature won't come up to running temperature at idle. The oil needs to be worked hard to fully warm up. That said, it won't be stone cold so the pressures seem reasonable. The only way to check for certain is to go on a good hard run and check the gauge when you have it under load at reasonable revs.

[peterako]

I may be totally wrong but I thought that oil pressure with the stock pump was about 40lbs at revs (maybe going a bit higher at high revs?) and roughly 20 at idle.

Regardless, unless you're racing, the stock pump is the way to go....and changing out the high pressure pump that came with my +2 got rid of most of my engine leaks

(Changed the pump with engine in situ by removing the top of the pump housing)

Peter

(Woo Hoo! 4th Gear )

[Famous Frank]

If your existing pump is burying the needle, that is too much pressure. 15 to 20 pounds at idle and 40 to 50 at full song with a stock pump is just fine.

Is there the possibility the pump is fine and maybe someone put the wrong pressure relief spring in the pump?

Famous Frank

[Foxie]

Crusty, I just changed out my HP oil pump today based on the info in the highlighted thread.
Previously with the HP pump it was pinning the dash gauge at over 70 psi, which I considered way to high. HP pump pressure was confirmed with a remote service gauge by the engine re-builder this fall.

I put a HP pump in on a rebuild I did some time ago. The oil pressure on idle was 70psi

It came out again.......

[stugilmour]

Crusty, I just changed out my HP oil pump today based on the info in the highlighted thread.
Previously with the HP pump it was pinning the dash gauge at over 70 psi, which I considered way to high. HP pump pressure was confirmed with a remote service gauge by the engine re-builder this fall.

I put a HP pump in on a rebuild I did some time ago. The oil pressure on idle was 70psi

It came out again.......

Exact same story here Sean. The highlighted thread came after I bought the HP pump. If anyone needs a Burton HP pump, it is 'surplus to my needs' now. If ordering a replacement pump, don't forget to ask for a new gasket; there wasn't one in the box for mine.

To follow up, Galwaylotus is quite correct. More snow coming this weekend here, so a proper test drive is a while away. However, with ~40 psi on the gauge with just the coolant at operating temperature I seem to be OK with the new stock pump and no obvious leaks. Few other jobs on the list, and hopefully a test drive early spring.

[skelteanema]

When I first got my Elan, I wondered why the oil pressure was so high that the needle was at the maximum, and hitting the stop. After browsing this site, I determined that a high pressure pump had been fitted by the previous owner. I decided to replace it with a standard pump. It wasn't to much of a deal, just loosening a couple of engine mount bolts and raising one side of the engine gave enough clearance to swap the pumps. After replacement, the oil pressure was a respectable 15psi at idle and 45psi at full song. As a bonus many (but not all) of the oil leaks vanished.

[elj221c]

I seem to remember that my original engine, (Dave Smith prepared, Cosworth pistons and BRM Phase 4 cams amongst other mods) had a standard pump but with an aluminium spacer behind the relief valve spring. This I assume increased the pressure as it was was always more than healthy.

I rather suspect that 'high pressure' pumps have nothing more than a stronger spring or said spacer.

High capacity pumps are another matter as I believe they have a larger (wider?) rotor.

Perhaps one could downgrade an HP pump by using a standard spring?

Roy
'65 S2

[john.p.clegg]

Roy

You've got it spot on...

John

[rgh0]

There are two types of non standard pumps out there

A "high pressure" pump that either has a stiffer relief valve spring or just a spacer under the spring. Will peg the gauge when cold but normally reverts to around same pressure as a stand pump of around 30 to 40 psi at normal road revs when hot and the relief valve stops opening . No real use for this type of pump as not enough volume to match the higher relief pressure for a properly built race engine and not needed pressure for a road engine. Sold as a cheap go fast goody by speed shops.

A "high pressure / high volume" pump that has a thicker end cover and longer internal rotor to displace about 30% more volume per revolution and a stiffer relief spring to raise the relief pressure to around 60 PSI so the extra volume can be delivered to the bearings and not be dumped by the relief valve. Costs about twice a normal or high pressure pump and a must for a serious race engine but not needed for most road engines.

cheers
Rohan

[GrUmPyBoDgEr]

Hi Rohan,

I think your posting should be considered as the "Definitive Reply".
A great couple of paragraphs that dispel all of the fables IMHO.

John