Pre Serp Oil Pump (Aussie John)

[Bluebottle]

The pre serp pressure relief spring was too short and the usual factory bodge was a loose bolt on the end of the sping in the bore to elivate the oil pressure...that looks a "slightly" better "adjustable" bodge to me

Edited by Bluebottle on Thursday 28th October 16:56

[Aussie John]

Have you seen this before Hamish? and was it done as a Dealer mod or a factory mod? cheers, John.

[spend]

It's a bodge someone has done, you should use a fine thread!

Get another end (I've got several) and drill + tap it with a fine thread, then you have adjuster bolt - lock / sealing nut - compression washer - pump fitting.

The dias are important so that you leave enough surface to seal (the pic as well as course thread looks like an extremely large diameter) and use a disk/washer inside to act on the spring.

It is a common kind of mod, and always surprised me that no one has done it on the serp front covers because of their crap pressure due to the springs?

[spend]

As mentioned earlier Andy, it's common to find packing behind the spring on TVR's to raise the pressure a tad over LR std.

An adjustable one just makes it infinitely easier to set if you use different oil, suspect spring is iffy or run at higher revs, using the 10psi per 1000rpm ready reckoning kind of thing.

[rev-erend]

Des Hamill did a great explanation in his book - how to powertune a Rover v8.

In essence - Kenne Bell and other like Wildcat have looked into this area and sold kits for a while but all stopped because of the associated problems.

It was safeish to 60 psi at 5000 rpm up from the standard 45 psi but this figure and higher caused excessive wear on dizzy drive gears and cam drive gear. 60~70 is the limit for hydraulic lifter because of pump up. Accuracy of guage also needs to be checked.

Also with the hot oil at 60 psi the cold pressure will be 100~120 psi - high rpm with oil not fully warned up will again cause excessive wear. The racers get around this by heating the oil in the sump with a hot air gun

[spend]

rev-erend said:

Also with the hot oil at 60 psi the cold pressure will be 100~120 psi

How does a pressure relief valve raise the pressure based on temperature?

[rev-erend]

spend said:

rev-erend said:

Also with the hot oil at 60 psi the cold pressure will be 100~120 psi

How does a pressure relief valve raise the pressure based on temperature?

Oil is thicker when cold and more pressure builds up when in a confimed space when pumped.

Have you not noticed high oil pressure when the engine first starts ?

[rev-erend]

Quinny said:

I have a very simplistic view when it comes to this sort of thing. ( most things actually)

It's along the lines of, fit the correct spring, and cap, and be done with it..... The trouble with stuff being adjustable, is that people will fiddle with it.... Oh just a little tweak to get a bit more pressure, oh too much now, crank seal is leaking, just back it off a bit, oh st not enough...etc etc until the thread is worn out

Racing cars, and cars that are tuned, and have other mods, may require these so called improvements, but is it really necessary on a standard road car, that's otherwise well serviced, and driven with mechanical sympathy???

Quinney - I think you are spot on.

The MGB shorter oil spring was used to raise the pressure a bit but as you say more is really not needed on a road car as we really do not get to drive them like you would on the track .. or if you can it's not for long.

[spend]

rev-erend said:

spend said:

rev-erend said:

Also with the hot oil at 60 psi the cold pressure will be 100~120 psi

How does a pressure relief valve raise the pressure based on temperature?

Oil is thicker when cold and more pressure builds up when in a confimed space when pumped.

Have you not noticed high oil pressure when the engine first starts ?

Didn't see any relevance in the answer to the question at all? Cold pressure at pump body if above PRV setting will simply trigger the PRV.. thats what it does hot / cold / in space / upside down... whatever AFIK.

PRV is simply a limiting valve, it wont make oil pressure better, increasing spring pressure will just allow more pumping to take place before its says 'ok the engine has enough - no point making the pump work harder' (and of course the converse is true).