911 T to S
 

Looking at upgrading my 911T motor to 'S' spec when I rebuild it if it's economically viable. So what do I need to change out (ignoring the induction system)? I know the crank, pistons, and cams are different but perhaps there is more to it than that...:confused::confused:

Depending on the year of the engine...the heads may have bigger ports and valves.
Bob

Sorry, should have mentioned it's a 1970 2.2 'T'...

Heads have bigger ports (valves are all the same) and the induction system is configured appropriately. MFI stacks & throttles are larger; carbs have larger venturies and jets.

You can bore case to accept 90 mm cylinders for 2515 capacity, with 8.5 rs or 9.5 JEs with E, solex or S cams. even with your 32 mm heads you should get 175 to 185hp. btdt best Henry

Crank (counterweighted), cams (more radical and MFI capable), pistons (higher compression), heads (MFI with larger port sizes), cylinders (I believe were Biral instead of iron). It took a lot to go from the 125Hp 'T' to the 180Hp 'S'.
The more durable and probably less costly route long term is to buy/build a 2.7L engine. Keep the 'T' engine stock and original to the car and build up/source a second engine to tweak.

Might it be better then to acquire a 2.2 'E' core motor to rebuild then? Maybe I would just need to change the pistons and cams if one ignores the induction system....??

I prefer the revvy nature of the earlier short stroke engines rather than going the long stroke 2.7 route. Had a 911 T that had a 911E motor swapped into it. Loved the way it drove and i understand that the 'S' loves to be revved even more which is not a problem round here as it is all fast country roads. If I lived in a built up area the T or E would no doubt be bettter but here I'm not so worried about the rubbish bottom end delivery of the 2.2 S. Plus if i made the upgrades the car would essentialy be S spec. It has the optional S calipers, just needs ARBs other than the motor....

I agree with you about the "revvy" nature of the short stroke motors. They have a slightly different feel about them than all the later stuff, and I like it.

Really all you need to do is the P/C's and cams. The counter-weighted crank of the E and S motors is not a requirement and some might even prefer the non counter-weight crank for its slightly lighter weight. I'm assuming you plan on carbs, so opening up the ports on your heads to the correct size is all that is required. Oh, and the S distributor will have different advance characteristics to match the cams. If your present unit is Bosch I'm sure it can be re-curved. Might be more of a challenge with a Marelli.

I've done all of the above on a 2.0 motor from a 914/6, and it made for a really fun little motor. The very high C/R made it a bit fussy about jetting and fuel quality to avoid detonation, but it was in a car with standard ignition. Yours should have a CD box ignition which will help, and probably the 2.2 combustion chamber will too.

Not mentioned thus far are the necessary mods to the crankcase. That includes head stud thread inserts, bored out crankcase spigots for the 2.7 cylinders and other optional mods e.g., oil bypass mod., shuffle pin, etc. as well as basic machining to bring the crankcase bearing saddles to spec (line bore). FWIW, while the stock T crankcase will work, many recommend using an aluminum or later mag case for added strength and dimensional stability.

Choice of head studs is open (late factory Dilavar, ARP, factory steel, etc.).

The cost adds up. There won't be a single major engine part that won't be touched in some way. Research Wayne's rebuilding book as well as Bruce Anderson's High Performance book.

Sherwood

2.5 case
 

I had comp acces. in CA do a 71 T case into a 2.5 like this 30 years ago. Just took it apart and it has no issues. It would pull to 7k and with 8.5 rs pistons and E/L webers ssi it was a tractable 175 hp. The knock on it was the lower cr. maybe 8.0 but it ran well. Might want to redo it some day with more cr and cams might then have 200hp?

The "upgrade" to S specs pistons/cams is really easy. All bolt on and reversible (except for head porting). This was a fairly common thing to do in the "good old days".

No case mods needed when using 2.2 S P/Cs on your T case. Your steel head studs are perfect for biral cylinders. You can Timesert if needed (or just for your peace of mind), but this is not such a common problem on these cases as the later ones. T cases generally lead pretty mellow lives, and unless badly mistreated, the bore will likely be perfect. The pressure bypass mod won't hurt anything, but not mandatory. You're probably looking at something like 170-180 hp, so shuffle pins would be overkill.

One thing I forgot is that your case probably doesn't have the oil squirters. The boss will be present on the bearing saddle, but I don't think they actually installed them on the 2.2T (my memory could be suspect here). You could have the squirters installed, it is not a major job.

The cams and compression will really wake up a T motor. Not a huge increase in HP, but sure changes the character. A little less tractable, but really sings once up on the cams. Very "racy". Some shorter gearbox ratios would complete the package.

You might want webers too, for ease of jetting. Your Zeniths will potentially work but I don't know how tunable they are to match the S components.

I wonder if it would make more sense to put the original matching numbers 'T' motor to one side and pick up an 'E' motor which only needs pistons/cylinders and cams to get to 'S' spec? 'S' cams are still available from Porsche for about $1500 equivalent in the UK. It is the pistons/cylinders that are the real money. However the 'E' pistons are about 9.1 and the 'S' 9.8 which is only a jump of 0.7. I wonder if I could flycut the heads (and machine the chaincases to suit) to increase the compression to the desired 9.8 and still get the 180bhp that the standard 2.2S gives as the 'S' piston domes are still a different shape to the 'E' ones.
:confused::confused: