I have a Shadek pump adapted for Type 4 (which I know some people don't like). The first time I installed the pump cover I did not use a gasket, just case-sealant. For the second time around, should I use a gasket under the cover?

Make sure cover is perfectly flat. Use a gasket, but NO sealer! Measure the outer diameter of the pump and compare it to the original. Mine was undersize.

Yes, a very thin paper one. In the .003 range making sure the cover is flat

As above - I’m a believer in gaskets for something that has high pressure oil behind it.

I know there are those in the VW community that say no gasket. My understanding is that tribal knowledge largely came from people having used aftermarket gaskets that were way too thick which caused low oil pressure due to too much bypass due to the thick gaskets.

The correct gasket is about 0.003” thick. If you lap the oil pump case so that you have no end play on the gears - you’ll gain 0.003” of end play and proper bypass with a gasket installed.

If you already have .003” end play of the gears without a gasket, adding a 0.003” gasket will double the end play. Even at 0.006” end play it won’t be terrible for oil pressure but isn’t optimal. The problem occurs with some of the aftermarket (or home made) gaskets that are more like 0.010” thick which leads to way too much oil bypass.

Hope that helps make a educated decision on which is right for you.

Thanks. I did lap the cover, which was not flat but is now. And I will check the end play on the pump gears.

Gene Berg's book How to hot rod vw engines tells you how to blueprint the oil pump.

Let me check my understanding. Optimum gear clearance is .003". I measured my pump gears (relative to the face of the pump) and got mostly .0005 to .001.

The only gasket I have in my stock measures .0045". That would give me clearance of .005 to .006, which might be too much. Are there gaskets only .0025 thick?

I pulled a new Schadek pump off the shelf and measured the paper gasket to be .003. I am unsure if these can be had directly from Schadek?

In my opinion, that is right on the cusp.

Desired end play is < 0.004” per tribal knowledge - Samba, Berg, VW Bentley manual, etc. In the case of the Bentley manual, that end play 0.004” tolerance is without the gasket. Of course, that was back when OEM gaskets would have been readily available. I’m not sure what OEM gasket thickness was on the Bug but I’m certain they were very, very, thin based on the Bug motors I’ve town down over the years.

The gasket will compress slightly - 0.0005” ? so I don’t think you’re far off with your gasket.

Sure would be nice to come up with a gasket more like 0.003”.

Better to see if you can come up with a thinner gasket. This is the sort of stuff that makes engine building a PITA but it is also where patience and parts sorting pays off.

It's either right or not right.

https://aapistons.com/collections/oil-pumps...mp-cover-gasket Not sure of the thickness, but is sold as a "cover gasket"

I got out my micrometer, and remeasured the gasket I have.

With no pressure, I got .0035". That's .001 less than I got with calipers.

With a moderate amount of pressure, I got a thickness of .0025.

If I have gear clearance in the pump, relative to the pump face of around .001, that give me .0035 total clearance with the gasket installed and compressed. I think that should be right. Right?

That gasket looks pretty sturdy, more like ones I use at the back of the pump.
The cover gaskets I use are thinner than paper.
CB Performance pumps are Schadek pumps. They sell the gaskets.

I would say you are right on the money. get it together and hopefully that was your leakage issue.

I agree on the visual. The old VW gaskets were brown and almost translucent when they had oil on them, they were so thin. From the holes in the gasket, we can tell your gasket is intended for use on the cover side of the pump.

Based on the measurements I think you’ll be fine.

So let’s assume the original VW gaskets were 1/2 as thick - let’s call it 0.002” for argument sake.

Bentley manual allowed 0.004” end play without a gasket. Now combine that with a 0.002” gasket and you have a total of 0.006”.

In your case, the oil pump end play is way smaller than spec at 0.001”. Combine that with a 0.003” gasket and you’re still less than what was spec back in the day without a gasket.

Looking around on the web, it’s the usual BS. No one actually lists how thick their gaskets are . Sometimes I’m really frustrated with the aftermarket and their propensity for marketing hype, claims made without data, and failure to publish specs. That leaves the option of ordering from a few sources and sorting to find the thinnest.

There are plenty of sources for gasket material in any thickness you may need in order to set the clearance to what you desire. They re not hard to make yourself, just a little extra work.

I looked around briefly this morning - didn’t find anything 0.002” thick. I know it’s out there but Google didn’t find it on a quick search.

Got a link to source?

@rudedude

Now that I'm in the shop I measured what I have here. The cover gaskets and most of the rear gaskets are the same thickness, just under .004". I found one rear gasket that was .008" and I have some thick ones which compress quite a bit but I don't use those.
The rear gaskets have a much narrower perimeter and don't have the tiny holes.

aftermarket oil pumps for the 914 are hard to seal

Awesome

Lets hope Bob can get er fixed

Hey, thanks everyone. I also looked for gasket material, and could not find anything thinner than .004".

I feel good about trying the gasket I have. If it does not work, I can always pull the engine again, right?