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Thu May 19, 2005 7:50 pm

hey all,

I'm building a 1776 from my tired 1600 dp. I'm full flowing the case, and I would like to install a bigger oil pump. I'm a little confused about which one to get though. What's this flat cam vs dished cam thing. My car si a1972 with (I think) the original engine. my old oil pump has a flat piece coming out the back where it hooks into the crank. Is that the flat cam?

thx

Jos

Fri May 20, 2005 12:17 am

Firstly the oil pump is run off the cam not the crank, a dished cam is a later model & the flat cam is the early model. All the performance cams I have seen (Engle etc.) are flat early type cams. Your motor in standard form should have the later dished cam. As for the pump the 26mm should be ok but I always use a 30mm Shadeck pump, a little insurance never hurts, especialy when things have worn out a bit.

Fri May 20, 2005 11:00 am

26mm. Most engines will run hotter with a 30mm pump.

John
Aircooled.Net Inc.

Fri May 20, 2005 12:51 pm

Why does an engine run hotter with the bigger pump? The added flow doesn't offset the extra work the engine is doing to turn the pump?

I did know the pump is driven by the crank, I just don't see how the type of cam you have affects the choice of oil pump (since it doesn't hook up to it). I'm going to run a Scat c35 cam, so I guess I should get the flat cam style oil pump by RUI's comments.

Damn, I'm getting more confused! Help!

Fri May 20, 2005 12:52 pm

By the way John -- Nice Nuts

:lol:

Fri May 20, 2005 2:13 pm

Ever see a diagram of the Beetle Oiling System? The way it works is when the oil gets hot, it gets thinner and pressure drops, and when it drop below a certain point the temp relief piston routes the oil thru the stock cooler.

The problem with THICK oil and/or big pumps, is pressure can be too high, and the engine thinks the high pressure oil means COLD OIL, so it never goes to the cooler.

If you look at a diagram of the system it will make sense. But running a huge pump and thick oils is a sure fire way to excessive oil temps. Not to mention pumping the oil back to the pressure relief only to get dumped into the sump again is a complete waste of power and mpg.

You do not need more then a 26mm pump, the EXCEPTION is a turbocharge engine where a 30mm is not a bad idea. I have a 26mm pump on an 8k RPM 2332. Many racing guys run 21mm pumps to decrease pumping losses.

John
Aircooled.Net Inc.

Fri May 20, 2005 3:46 pm

That makes sense. I thought perhaps the pressure loss of going through a remote oil filter and extra lines would warrant the increase in size...

Fri May 20, 2005 11:05 pm

26 is a good size oil pump. Save the 30 for twin external oil coolers, turbo oil feed, oil squirters in the case.

Sat May 21, 2005 12:44 pm

The increase in size is going to 26 from the stock 21 or 24mm.

John
Aircooled.Net Inc.

gatorjos wrote: That makes sense. I thought perhaps the pressure loss of going through a remote oil filter and extra lines would warrant the increase in size...

Sat May 21, 2005 2:27 pm

In that case my stock motor had an upgraded oil pump....

aha, it is all clear to me now 8)

Thanks for all your help. I think I still should replace my oil pump after 80k miles.

Sat May 21, 2005 9:44 pm

[email protected] wrote: The increase in size is going to 26 from the stock 21 or 24mm.
A stock 1600 DP engine came with a 26mm pump when new.

Sun May 22, 2005 9:31 am

26mm pumps are all I use. Like John said, run too much pressure, and you'll end up bypassing more oil past the cooler and pressure relief.

I also don't run thick oils. My daily drivers get 5w30 oils year round, and my race motor gets fairly thin oils too. I tried 15w40 last oil change on it, and wasn't happy with the excessive oil pressure. I'm thinking of trying some 5w40 synthetic next time.

Sun May 22, 2005 11:15 am

Eaallred wrote:

My daily drivers get 5w30 oils year round, I tried 15w40 last oil change and wasn't happy with the excessive oil pressure.

What about regular old 10/40?

Sun May 22, 2005 2:20 pm

Bruce wrote:
A stock 1600 DP engine came with a 26mm pump when new.

I dont think so, the German made VW engines had 21 and 24 mm oil pumps. The after market produced the 26 & 30 mm pumps. But now the new VW engines from Scat with the cast cranks probaily have the 26 pumps in them.

Sun May 22, 2005 2:29 pm

Eaallred wrote: 26mm pumps are all I use. Like John said, run too much pressure, and you'll end up bypassing more oil past the cooler and pressure relief.

Eric didn't you at one time say that the size of the pump did not regulate oil pressure?

Sun May 22, 2005 3:07 pm

turbo_bob wrote: the German made VW engines had 21 and 24 mm oil pumps.
21mm pump = 40hp
24mm pump = 1500
26mm pump came out when the passages were increased in '70 for the 1600 SP.

Sun May 22, 2005 3:23 pm

Thanks Bruce for the info, I looked in the Bently book but it did not list the size.