Oil pump modification ..I'm a little confused
 

In the process of rebuilding a 1976.3.0 row turbo. I have been reading past post and watching videos . according to what I have read and watched this is a simple mod and should be done. all i see and read only mentions one hole to block .. Well my case has two holes see picture.. So what's the correct course of action. I do have the later turbo pump and oil restrictors on the cam housings so oil in the sump should not be an issue . So is this mod usually done on the Early turbos? and if so what do i do with the second hole ?http://forums.pelicanparts.com/uploa...1575817311.jpg

The basic primis of the bypass is to divert the oil flow from that check valve gallery back into a service gallery and not into the crankcase. I am not completely dialed into the nuances of the changes they made, but I think the difference in pressure and scavenge in the pump around 75-76 prompted the change. What ever, you don't want excess oil in the crank case. The cam gallery restrictors just send more oil to the crank and less to the cams, but it all drains back into the case. I am not real clear on your picture. Which holes exactly are we talking about?

See blue arrow for small hole in questionhttp://forums.pelicanparts.com/uploa...1575941697.jpg

1976 was when Porsche made the change. The oil modification as far as I have read is only for earlier 7R cases.

if so that would be great . i thought the change was a 76 mid year thing this is a ealy case. date stamped late 75 if so then why does it still have the large hole directly in the relief spring oil passage?

Regards Ned

The larger hole is the one that gets plugged with the modification. No Idea what the smaller hole is. early style pressure relief pistons had holes in sides. Post mod pistons are solid. What came out of your engine? Good explanation of mod in this video.

https://www.youtube.com/watch?v=lKuceDywEJg


john

John
thanks the pressure relief pistons in the motor are smooth sided no holes.

HI Ned

the oil by-pass mod is in the other crank-case and not the one you have the photo of, have the head studs been replaced, the valve springs, inter-gear, timing chains, valve guides and the chain tensioners, the cylinder tin work also needs a mod for the cooling, the small hole needs drilling in the R/H case for the timing chain oiling, also the distributor drive needs checking both parts are correctly matched

if you need any more, please let me know

I have paperwork on that engine with the mod's needed

Can you see where the smaller hole leads to? Try sticking one of those little red tubes from WD40 / brake cleaner cans in and see where it goes.

the hole is on the same oil passage as the large one

thanks for the info . the head studs will be replace heads are out being rebuilt all the timing gears and chains guids will be new , new carrera tensioners , tin will be cut , new cam tower oil restrictors and all the usual , bearings ,balancing polishing.

also needs a mod for the cooling, the small hole needs drilling in the R/H case for the timing chain oiling please provide info on this as i have never heard of this

the distributor drive needs checking both parts are correctly matched i assume they are matched as they both look perfect please provide info on this also

i would love to see the paperwork on this engine with the mod's needed

thanks for your help Regards Ned