2 liter T engine teardown find.

[safe]

A friend of mine are rebuilding a 68 T engine and we found a few surprising things.

First the crank has counter weights:


Second, there were 2 types of pistons (this engine has been apart before).
5 of these pistons:



1 of this:




Was there 2 liter T engines with counter weighted cranks, or has this been replaced?

Are these 2 types of pistons both 2 liter T-pistons?

[tom1394racing]

Your orphan piston is a 2.0T Mahle piston. It should have the marking 80V69 under the dome. The other 5 are Kobelschmidt 2.0T pistons and should have the marking 80160 under the dome. I have never heard of the factory mixing them as the weights should be different enough to set up an imbalance.

I'll bet that the crank was replaced when the other orphan piston was replaced.

[safe]

Thanks Tom!

There is also an issue with the intermediate shaft bearing. Looks like an oiling problem. Is this common?

[tom1394racing]

Looks like an oiling problem led to the bearing failure. This is unusual as the intermediate shaft bearings are lightly loaded and normally do not show much wear.

Your case looks to be one of the early '68 Al cases. If I recall, these were designed from the factory to not use the int shaft thrust bearing. It appears that the case was updated to use the bearing. Given the other unusual finds in this engine, I would have the machine work on the bearing checked to insure proper bore size and alignment

[safe]

The case has now been sent away for machining to accept a bearing.

Finding 2 "new" Kobelschmidt pistons look difficult. Are there different weight or size groups for pistons to take into account?
Actually 6 S-pistons would be the best option, since we have a pair of s-cams on the shelf.
Would a set of custom JEs be a good solution?

We have found some 84mm 2.2/2.4 litre piston and cylinder sets. What needs to be done to the heads to make them fit?

[tom1394racing]

I can provide pistons if you need them. The S pistons are difficult to find. I do have both the Mahle and KS T pistons. A better bet might be a set of 2.0E pistons to go with the S cams or a set of 2.2E pistons and cylinders.

PM me with your email if you are interested in more details on used pistons.

[nabilious]

FYI, I took apart a '68 T motor in an Aluminum case that was never apart before....I also found a counterweighted crank. I suspect that the 70-71 2.2T's were the only non-counterweighted cranks.
My .02 cents.
Nabil

[Walt Fricke]

Per Bruce Anderson's book, the '68 through 71 T cranks were cast and had no counterweights. However, Porsche is notorious for using higher grade components in lower grade cars/motors from back then, if a parts shortage required it. Who would complain about getting a counterweighted crank?

I recall suggestions that these non-counterweighted T cranks from those years were desireable for quick reving motors - maybe autocross engines?

The sand cast aluminum cases did not have intermediate shaft bearings. Don't seem to need them, either. I've had four of these cases, and the bearing surfaces all looked fine. End thrust is taken up on the cast iron cover plate, which is shimed to get a specified end play tolerance. However, either the end loading is scant or oil film strength/pressure is enough, because I have run a magnesium cover with negligible wear. I think the thrust from the IS gears is toward the rear (pulley) end of the engine.

With the mag cases (at least after the first of them) the pulley end bearing got a thrust bearing, double flanged.

This engine got some kind of odd cobbling done - a plain bearing. Maybe with no locating slot/tang?

The early intermediate shaft has at least one bearing surface which is larger than that on the later shafts. So at least one (the middle, I think) of the case bearing bores is too large to use with the later shafts, and can't accept the later stock bearing to make up the difference.

Fixing Magnus' motor will call for some cleverness.

Walt