74-77 2.7 parts swap.

[drcoastline]

I have a 74S whose origial engine went away many years ago. I currently have a running 77 2.7 for the car. I would like to get a more appropriate 74 case. Is everything in and on the 77 compatible with the 74 case?

[75 911s]

The 74 case wont have the oil bypass mod which was implemented in 76 I believe.
Aside from that I think the 7R case should be nearly identical.

[eastbay]

Originally Posted by 75 911s

The 74 case wont have the oil bypass mod which was implemented in 76 I believe.
Aside from that I think the 7R case should be nearly identical.

And the oil bypass mod is easily accomplished in your home garage.

[drcoastline]

Originally Posted by 75 911s

The 74 case wont have the oil bypass mod which was implemented in 76 I believe.
Aside from that I think the 7R case should be nearly identical.

Thanks Duane

[drcoastline]

Originally Posted by eastbay

And the oil bypass mod is easily accomplished in your home garage.

It is?

[eastbay]

Yes, there is a posting somewhere here showing the steps. Done it myself.

[Walt Fricke]

I can't think of anything other than that part of the oiling system either. You don't have to modify the 74 case, but you do need one oil piston and one oil spring for a '74 if you don't want to do the oiling modification. Porsche thought it a good idea, but it isn't essential.

The oil pressure regulator on the '74 sends oil above max pressure back to the sump. The modification sends that oil back to the pressure side pump inlet. Keeps the level of oil in the sump down. The parts modification included a different shape to the piston, a longer spring, and a guide tube inside the spring. These are in the oiling drilling which is vertical, with its plug on the bottom of the case.

The other oil piston is the emergency relief. It dumps oil into the sump as before, and the only thing Porsche changed on it was the piston. I think that was simply to avoid having two styles of piston, so you probably could leave that as it is.

The modification involves, while the case is all apart, drilling a hole in the side of a passageway, and then tapping and putting a threaded plug into the hole where the main oiling pressure regulator used to dump oil back into the sump. Easy enough to understand if you understand the oiling and pressure systems (plenty of diagrams around on that) and are looking at the inside of the case with everything disassembled.

The only tricky part is to get the hole you are drilling started, as you are trying to get your drill bit to start at a shallow angle a bit inside a passageway. I don't know how a machinist would do this, but I used a suitable die grinder bit to grind a notch in the side of the tubular surface until I could get a fairly small bit to start, and then used progressively larger bits until the hole was big enough for its job.

By and large everyone sees this modification as a benefit, and a cheap one at that, and does it. In terms of originality, the only way someone could figure out this wasn't 100% 1974 short of taking the case apart would be to remove the oil pressure plug and look at the spring and piston.

But I have to ask - what's the point? You aren't going to have a numbers matching car when you are done no matter what. Is anyone going to pay more if you sell? Or is this a smog and motor vehicle division thing?

[drcoastline]

Thanks everybody for the input and WF for the thorough explanation.

My car is far from original, so I don't have a problem with the mod and even if it were I think it is a good upgrade, anything to make it a little more bullet proof. My only interest in the 74 case is that it is in keeping with the year of the car, but at the same time I am keeping my eye out for a 3.0.

Thanks again everybody for the input.