901/08 engine advice needed

[maze]

Hi Folks,
I am a long time 356 owner just getting into early 911 cars and enjoying it very much.
A friend has offered a 901/08 motor to me as a rebuild project (chain tensioner failure).
This appears to be a 68 911S from a sportomatic car.
Is this a good motor to build as an upgrade for a T car?
Any opinions on value as is (condition unknown other than its all there and threw the timing chain on one side)?

Thanks for any advice
Maze

[YTNUKLR]

In '68, Porsche made both magnesium and aluminum engine cases (it was a transition year) and what you do really would depend on the case material. The aluminum case is very valuable and will make a VERY strong and fast 911 motor, all the way up to a 2.9L if you want! The magnesium case was of the very first iteration of a magnesium 911 case, with no intermediate shaft bearings (the soft Mg lets the bearing saddles go oblong) and no internal strengthening. It is inherently pretty weak compared to later 911 cases, and requires a LOT of $$$ in machining.

If this case is Al, buy the motor. If it's Mg, either pay very little for it, or don't buy it. The amount of money you can spend fixing a couple hundred dollar magnesium case is astounding. So much, in fact, you'd miles ahead buying a '71+ case (w/ oil squirters, intermediate shaft bearings, more strength) and using that. Not to mention, a jump in bore to 84mm and better cylinder heads do not cost any more than 2.0L engine parts!

Chain tensioner failure may mean that the pistons hit the valves and perhaps broke some rocker arms/bent some valves. If the engine got shut down quickly, you may be in the clear...probably get a few rocker arms, replace the valve guides (manganese bronze is probably a good choice) and get new valves. I hope the valve seats didn't get bunged. You'll pretty much only know if you tear it down.

There are many different possible combinations of 911 engine, from stock to varying degrees of "custom" in every displacement..it depends on what you want to end up with.

[maze]

Scott,
Thanks very much for your response to my inquiry.

I looked in the archieves here and in Bruce Anderson's book to try to find a S/N for the aluminum to mag transition but no luck.

Any ideas where to find the transition S/N? Any definitive way to tell the difference other than S/N? Probably if I saw both side by side i could tell a difference in color. But only one engine on the bench....

Thanks
Dan

[YTNUKLR]

Dan, Aluminum cases are silver vs. grey for Mg. Al cases have fins on the bottom, running longitudinally. Al cases are more "rough" texture, due to the sandcasting, and Mg are very smooth to the touch (if not heavily corroded!). On the bellhousing area, behind the flywheel, Al cases have 2 M8 studs/nuts, while Mg-cased engines have 3 . Mg is much more susceptible to corrosion, so it will likely have a lot more of Magnesium oxide (powdery stuff) than an Alu case would have Al2O3 (Aluminum oxide), which is a white powder. On the sides of the case, near the bottom (sump plate area), a '68 Mag case will have a part number that ends in 1R or 2R.

Let us know what you find!

[YTNUKLR]

Dan, Aluminum cases are silver vs. grey for Mg. Al cases have fins on the bottom, running longitudinally. Al cases are more "rough" texture, due to the sandcasting, and Mg are very smooth to the touch (if not heavily corroded!). On the bellhousing area, behind the flywheel, Al cases have 2 M8 studs/nuts, while Mg-cased engines have 3 . Mg is much more susceptible to corrosion, so it will likely have a lot more of Magnesium oxide (crusty powdery stuff) than an Alu case would have Al2O3 (Aluminum oxide), which is a white powder. On the sides of the case, near the bottom (sump plate area), a '68 Mag case will have a part number that ends in 1R or 2R.

Let us know what you find!