oil pump sizes

GABA Learner Dubber

3 posts · joined Sep 2006 · 1 Oct 2006, 7:23 pm

#539892

Hi a question that will probably have lot of you smiling at my lack of knowledge but can anyone tell me about the sizing of oil pumps. I have a 1970 bug (H series engine ) that I just bought and wanted to change the oil pump as pressure a bit low...but the pump I've bought seems to have too deep a body compared to the one I have now just pulled out..any ideas. Im unsure if the 26 mm gears that are often quoted mean 26 mm diameter or the length of the gear tooth section...my old one was about 21 mm long..the replacement if about 30mm..any advice on this and possibly the best place to find the correct size pump much appreciated!:beer:beer Thanks !

PurpleT3 Fahrvergnugen

880 posts · joined Apr 2003 · 2 Oct 2006, 9:51 am

#540053

Oil pump sizes are according to the depth of the gears, not the diameter. There are certain combinations of pumps and cam shafts that will not go together. If your original pump was a 21mm, then you need a 21mm replacement. It sounds like you got a 30mm, which is an aftermarket pump generally used on high po and race engines. If you need a 30mm pump to maintain oil pressure, you have major problems somewhere else. What did you use to measure the oil pressue and what was the reading?

Either your pump is worn, in which case blueprinting it may help, or your bearings are shot. Installing a bigger pump to overcome low pressure is a pretty short term fix.

Ain't nothin' like the wind in your hair.

GABA Learner Dubber

3 posts · joined Sep 2006 · 2 Oct 2006, 7:26 pm

#540208

Much appreciate the reply!! Did a bit of research and yup agree need a 21 mm pump...alas the pump I was sold wasnt described as a 30mm pump (actually sold as 26mm) ...I just asked for a 1970 beetle pump...was listed as suitable by the seller (listed as 68-79 so foolishly assumed was suitable!) . Measured pressure with a pressure gauge..was definitely low at idle (5 psi) and the red light flickered on from time to time so it seemed like a worn pump problem. hmmm looks like I need to hunt around a bit! Thanks again, :beer:beer:beer

dangerous 23 Windows of Awesome

5,901 posts · joined Jan 2005 · 4 Oct 2006, 7:48 pm

#540977

There are two types of oil pumps to match the two types of cam.
Early ones are most common for non standard camshafts, and 26mm long gears were the longest std gears that VW ever used.

By all means try a new pump, but there are many places in a worn engine(or case) where pressure can bleed down.

I have used 30mm pumps in engines that specifically had large oil clearances built in,
but 26mm is what I am currently using and is the most you should ever need.

Bigger pumps just empty the sump faster than it can drain back.

Which ever pump you choose, make sure:

That the "in" and "out" hole are aligned with the case holes,

And the cam bolts (or rivets) dont interfere with the pump body.

westi wrote:That's mad Alan.

GABA Learner Dubber

3 posts · joined Sep 2006 · 4 Oct 2006, 9:11 pm

#541026

Thanks again for the info, much apppreciated!