zerotofifty
Samba Member
Joined: December 27, 2003
Posts: 1581
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 Posted: Sat Mar 23, 2024 4:03 pm Post subject: Re: Oil pumps- Modifications? |
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| BFB wrote: |
| zerotofifty wrote: |
| RickS wrote: |
| zerotofifty wrote: |
never use the flat pump cover, use the ones with the bent up raised edges instead. the raised edges stiffen the cover a lot. even a 1/4 inch steel plate flat cover will bow out when the four cover nuts are torqued down. the stock cover does not bow.
I have proven with with a dial indicator, and watched the flat plate type bow out as the four nuts are torqued to spec. the bow was on the order of several thousandths of an inch, ( I did this many many years ago, I recall it was around 0.004 inch of bow or so) more than the paper gasket thickness!,, the stock cover does NOT bow, not even .001 of an inch. The bent lip on the stock cover is near half an inch high, so it really stiffens the cover to prevent bowing. You need that tall bent lip on the cover, dont be fooled by using a thick steel flat plate cover, they will bow. |
What torque did you use on the cover nuts? |
I used the factory manual torque specification. I set indicator in center of the cover plate. As the nuts first started to tighten the dial indicator went down as expect, but as I approached the factory torque value, the indicator started to raise up, indicating that the plate bowed up as the torque specification was approached. I recall it was on the order of 4 or so thousands of an inch bow up. This value exceeds the thickness of the cover gasket! I repeated this several times on each cover, same results each time. the ONLY covers that did NOT bow that I tested were the factory covers with the large raised edges on all four sides of the cover. This raised edge stiffened the cover and prevented any bowing. The flat steel plates bowed every single time, even though they we near 1/4 inch thick. This surprised me. A cast aluminum plate with ribs cast in also bowed, as the ribs ran in only one direction, they stiffened it in one direction, but not perpendicular to the ribs, this plate deformed in one direction, rather than both directions, but still that is a fail if one wants to maintain minimum gear to cover distance.
Another thing is do not fill the groove around the pump body with sealer, this ring of a groove has a little "return" groove to the low pressure side of the pump. thus any oil that does make it past the gasket will be intercepted by this groove ring, and presumably be sucked back into the low pressure side of the pump. A minor leak past the gasket can be prevented this way. |
You didnt say what you bolted the covers to when you did these measurements but i assume the case? . I find it hard to believe that theres much warping when the cover & pump body are bolted to and backed by the case, seems like a pretty rigid area. even if there is it’s apparently insignificant as ive never had any covers leak and dont recall tearing any down that had been leaking at the cover either. |
My measurements were taken when cover is torqued down on the pump body on the engine case. This is not an external leak issue, rather it is an internal leak issue which will result in reduced oil pressure. The gap between the gears and the cover is supposed to be very little, else the oil leaks past and there is pressure loss. this is why you lap the gears level with the body, and lap the cover flat, then use the very very thin gasket, just 2 or 3 thousands of inch thick. the bowing of the cover is measured in the center of the cover, and it creates excessive gear to cover gap. the bowing is such that it is almost like using two gaskets!
If you have a dial indicator and torque wrench, you too can try it. I have done this test many times, on many different covers. the flat covers bow, the stock covers with the bent edges do NOT bow. VW took extra effort on the stock covers to make sure they did not bow. they had good reason to have raised edges. the raised edges prevent the bowing. it would have been much cheaper and easier to have had a flat cover, but VW knew better, even back on the old 36 HP engines they used raised edges.
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modok
Samba Member
Joined: October 30, 2009
Posts: 26794
Location: Colorado Springs
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| Posted: Sat Mar 23, 2024 5:45 pm Post subject: Re: Oil pumps- Modifications? |
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I've noticed the CB filter pumps seal well, probably becase the cover is extra sturdy on the high pressure side.
Next time I make a cover it will be .600" thick, where the nuts go counterbored .200 deep
Give or take |
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