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Re: Jowett Oilpumps

From: kc
Category: Technical
Remote Name:
Date: 29 Aug 2003
Time: 21:19:58


Good on you Ed, I did a similar thing when setting up mine. I set it for 70psi. (This was after guessing the set up and ending up with 120 psi. Drove around for months like this but eventually decided not to risk blowing the flexi transfer pipe anymore and set up the gig.) Note that modern oils are much more slippery at low temperature so the volume of oil going down the galleries should be more than with the older oils. Hence pressure will be much lower for same volume of oil. Volume is more important than pressure and the best test would be to see what volume was pumped to the rear bearings for different oils and temperatures. My fluid dynamics is not what it was 35 years ago so not sure how the adjustable blow off would be affected by dynamic rather than static pressure. My guess is there is an increase in temperature as the pressure goes up which then lowers viscosity and hence lubrication. But lower viscosity and higher pressure might deliver more oil to the bearings and cool them where it really matters. So there is probably a most effective or efficient compromise somewhere. An oil cooler obviously helps in most situations keeping the oil cool and preserving the long molecules that keep the grinding surfaces apart. Except having one without a thermostatic bypass will damage the engine more as the cold oil cannot get to where it is supposed to. You do raise an interesting point on aeration. The later pump was submerged, but adding a flexi pipe to the outlet of the blow off would be a good idea. See pg 26 para 8 of the Jav handbook. I would not worry about too much oil on the chain, as it takes quite a lot of punishment and the splash is used for the distributor drive and worm gear. If there is too much it might be dragged through the sump suction pipe and raise oil consumption. But then the racing boys get rid of that breather method anyway.

I also used the reverse power drill method for setting the distributor springs and weights.

Last changed: November 19, 2008