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Steve Arndt
Samba Member
Joined: August 01, 2005
Posts: 1780
Location: Boise, Idaho
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 Posted: Thu Nov 20, 2014 3:06 pm Post subject: |
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I ran a 21mm on my super squish 2275 engine for many years. I only replaced it because a bad cam ate the old pump gears. I couldn't find a new 21mm pump so I had to buy the oversize 26mm. Same oil pressures with both pumps according to my dakota digital gauge under similar driving conditions.
Steve |
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kadub
Samba Member
Joined: November 04, 2004
Posts: 444
Location: Auburn, Wa
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| Posted: Thu Nov 20, 2014 4:46 pm Post subject: |
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| advinnie wrote: |
| ...with the extra oil lines (1/2" diameter) and the restriction the oil filter will give wouldn't the 21mm pump lack the flow/ pressure to work the vw oil system correctly? |
No, it doesn't for me, and shouldn't for you either  . But, like Steve mentioned, it's hard to find new 21mm pumps these days. My point is that, if yours is in good shape, it's totally capable of doing the job. Just plug the pump outlet and case inlet and bolt on a full flow cover and your set.
And I don't buy into the "when the engine is old and tired it'll need a bigger pump" theory. Think about it! If your bearings are warn that bad it's time for a rebuild  .
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Karl
aka Turbobaja |
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Glenn 
Mr. 010
Joined: December 25, 2001
Posts: 76898
Location: Sneaking up behind you
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modok
Samba Member
Joined: October 30, 2009
Posts: 26778
Location: Colorado Springs
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| Posted: Thu Nov 20, 2014 5:39 pm Post subject: |
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I seem to recall there was an in-between size, 23 or 24mm?? geared pumps too. .............. there are many pumps, I bet there are 50 different ones all fit the same hole  or actually "almost fit', would be the correct way to say it |
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GTV
Samba Member
Joined: March 27, 2004
Posts: 2084
Location: Si'ahl
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| Posted: Thu Nov 20, 2014 5:56 pm Post subject: |
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| Glenn wrote: |
What case?
Late model dual relief cases used a 26mm pump. |
I believe this is slightly incorrect... Dual relief was introduced in 1970 on 1600 single port "B" cases. 26mm pumps were introduced with the dished cam in 1971/72 (dished cam allowed the extra 5mm of pump to be inside the case rather than outside).
Splitting hairs, I know
Can a 21mm pump handle an external filter/cooler?
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EMPI Power Rules! |
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modok
Samba Member
Joined: October 30, 2009
Posts: 26778
Location: Colorado Springs
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| Posted: Thu Nov 20, 2014 5:59 pm Post subject: |
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yes.
Clearances impact oil pressure and flow, but coolers and filters do not change anything. |
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advinnie
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Joined: November 18, 2011
Posts: 1389
Location: oxfordshire
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| Posted: Fri Nov 21, 2014 1:29 am Post subject: |
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| So does a 26mm pump go deeper into the case or stick out more ? And if coolers and filters don't impact on flow and pressure a 21mm pump should work? I will be going with a 26mm anyway but why did vw increase the pump size? Do the later engines have a higher oil pressure or was it just because they increase the size of the oil galleries? |
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modok
Samba Member
Joined: October 30, 2009
Posts: 26778
Location: Colorado Springs
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| Posted: Fri Nov 21, 2014 1:43 am Post subject: |
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The 26mm pump probably goes along with the crossdrilled crank.
The OE pump sits flush, but 26mm pumps for use with the 3-rivet cam stick out more.
Even OE oil pumps tend to be a little bigger than needed, as they err on the safe side, thinking of keeping the oil light off until death.
If you are able to keep tight clearances on cam bearings and lifters and oil valves, and other silly places that bleed oil pressure, then might be good to use the smaller pump and get a fraction more HP! It does take power to pump oil.
The "average" vw engine these days.........better keep the pump full-size |
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kadub
Samba Member
Joined: November 04, 2004
Posts: 444
Location: Auburn, Wa
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| Posted: Fri Nov 21, 2014 8:28 am Post subject: |
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I forgot to mention, on my turbo engine with the 21mm pressure pump, I've also had the main bearings cut with an internal groove to feed the rods 100% of the time. No crazy tight tolerances on the bearings by any means either.
21mm pump feeding:
Full-flow filter
Lifters slotted between oil grooves (3 slots each)
Grooved main bearings for constant rod bearing flow
Notched rods (poor man's piston squirter attempt)
Journal bearing turbo
Stock oil control plungers and springs (both plungers non-grooved)
Doghouse cooler
Never more than 50psi on cold start rev.
10psi HOT idle (oil over 200F)
35-40psi from 3K up when HOT
Running Mobil 1 0W-40 full synthetic
It is just facts, not opinion or theory.
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Karl
aka Turbobaja |
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Dan Ruddock
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Joined: October 25, 2012
Posts: 3594
Location: Sarasota, in my adopted state of Florida
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| Posted: Fri Nov 21, 2014 8:53 am Post subject: |
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Excess valve clearance will also bleed off pressure. Can any one say chromoly.
Dan |
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kadub
Samba Member
Joined: November 04, 2004
Posts: 444
Location: Auburn, Wa
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| Posted: Fri Nov 21, 2014 12:21 pm Post subject: |
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| Dan Ruddock wrote: |
Excess valve clearance will also bleed off pressure. Can any one say chromoly.
Dan |
Are you referring to oil pressure lost at the PR end of the rocker due to loose lash??
I ran a set of Pauter Billet rollers for a while with my 21mm pump as well. They were the "new" design w/out needle rollers and they used hollow adjusters which just sprayed oil at the valve cover. Strictly splash-oiled rockers, NO pressurized lube circuit to the shafts. Even with these "pressure leaks" I had only a couple psi drop in across the rev range. Still not enough to cause any real problem, other than the rockers wore the bore tolerances quickly and were an overall very disappointing experience to deal with, being the most expensive set of rockers on the market, and poorly designed in my opinion...
This engine was torn down after about 6,000 miles of blow-thru carbureted use and ALL the bearings looked like new, with the exception of the cam thrust being slightly excessive. Folks don't need big pumps or high oil pressure to keep these engines alive and well. It's just one of the MANY misunderstandings out there.
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Karl
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Dan Ruddock
Samba Member
Joined: October 25, 2012
Posts: 3594
Location: Sarasota, in my adopted state of Florida
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| Posted: Fri Nov 21, 2014 1:58 pm Post subject: |
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Nice to know about the Pauter rockers, thought the new ones were pressure feed to the bushings. almost bought some and am glad I did not. Yes the pushrod to lifter leak is not a lot but it all adds up.
Dan |
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