Bypass surgery
 

I have a 1974 2.7 with the original oil pump. I have it disassembled and am contemplating on doing the "oil bypass mod". I'm getting conflicting information, and would appreciate a definitive answer. Please don't refer me to other posts.

audiofilius,

What conflicting information are you getting? I had the oil bypass done on my 1975 2.7. I am still using the original oil pump, but you must use the late-style oil pressure pistons.

http://www.pelicanparts.com/cgi-bin/wizards/Parts_Wizard.cgi?command=step5&wizard_root=911_eng ine_rebuild

Rex

Re: Bypass surgery
 

:( :rolleyes:
http://forums.pelicanparts.com/search.php

The conflict is that some people say its a good idea and some dont.

The people that "don't" are kidding themsleves. Why would Porsche include this mod on every car since they instituted it if it isn't vastly superior to the original design, right? This isn't blind faith; the experts will agree and they will be along soon to comment, I am sure. Perhaps the mod you are thinking of is the smaller diameter cam oilers, which increase oil pressure? I have read some controversy on that mod.

I'm certainly not one of those "experts", but I think Kenik nailed it with the oil restrictors being debatable. I don't really like restricting oil to elevate pressure by reducing flow elsewhere.

I'm not referring to the cam oilers. I'm talking about the mod adjacent to the oil pump, which consists of drilling a new hole and plugging the other...

Then you should not worry about it. Any controversy on this mod is ludicrous.

Some people are saying that this mod only applies if changing to the later style oil pump introduced in 1976..I believe this is the cause for the differing opinions. I am keeping the old pump.

Geez, the old pumps are garbage anyway. If your engine is open, replacing it is simple due course. Why are you keeping the old pump?

The only reason I'm keeping the old pump is that the new pump will cost me $806.00..trust me.

That is for new; why would you do that? :D There are nice used pumps of the later style in the $150 - $250 range. Matter of fact, if I get off of my butt, I'll have one for sale next week.

I hear you though.

Here's a nice one that just sold on Ebay:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=8050281274

This Carrera pump is still cheaper than what you were quoting:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=8050448269

Thanks for pointing that out. Tell me more about the one that you're selling...

I believe it is 4 bar pump from a '76 or later from what I can see (it is still in the case). I plan on pulling it next week. PM me for my email address and I can keep you posted.

I don't see why you'd do the mod if you were keeping the old pump. The newer pump has a larger pressure side and a smaller scavenge side. The bypass mod is to make the job of the new smaller scavenge pump easier so the case doesn't fill up with oil. If you keep the old pump the scavenge side is bigger so you don't need to "help" it with the mod.

For a new pump-any post 76 pump will work. You don't have to spring for a new pump.

-Andy

This is a no brainer with all the real info on this. I bypassed mine and did the restrictors never been better !! I do a valve adj. every spring (I flog the crap out of this engine ) and the clearance has not been a issue at all, No big changes, the nice thing this is the 1st time in the life of this car that the oil level gauge actually works. And as a side pt it did raise the oil P.

Do the oil pump bypass, install late style pressure valves and add cam feed restrictors.
There is no down side to any of these modifications.
If your budget has room you should also install a 908/ 4 rib oil pump.
If not, the original pump will work fine.
The key to a good pump in the material it is made of more than the type of pump. Aluminum pumps are better than mag pumps.

Henry, are you saying the early 2.0 litre aluminium pumps are better
than the SC 4-rib pump? Assume both have been modified for additional
flow.

andy