2.0S spec modification, Cylinder heads?

[91167coupe]

Hello all and thans for a great forum!!!
I am collecting parts for a 2.0 aluminium S-spec engine. Will it be possible to use 2.0T heads which have the bigger valves and make the ports bigger as on the S?
is it other differences on the heads which I have to be aware of?
Are the heads mag or aluminium from mag engines?

I have a 2.0L -68 mag engine with S-cams but it needs full overhaul and repair so will try to find an aluminium case and move over useful parts. Also have a pair of IDA Webers.

I appreciate any thougts on this matter!

Thanks, Kjell T, Norway

[304065]

Kjell, I suppose you could port 2,0T heads (42/38, 32/32) to the 2,0S specifications (42/38, 36/35).

That said the combustion chamber and included valve angles of the 2,0 are inferior to that of the 2,2. If you sourced a set of 2,2T heads you would start with larger valves (46/40) and could start your porting from there.

Take note, however, that the cylinder-to-head sealing is a different design between the 2,0 and 2,2 through 2,7 heads and cylinders. This can be resolved through machining, the use of spacers, custom cylinders, or simply using 2,2 cylinders on the 2,0 case, which does not require boring the spigots.

Our friend and engineer Tom Butler compiled this useful guide many years ago, have fun!



Finding an aluminum case these days may prove exceedingly difficult or expensive. While it's stronger than your 1R mag case, you might consider going with a magnesium 7R from a 2,7 with the larger barrels. These tend to need a LOT of machine work so it's probably not the best for a race engine that will be frequently torn down, the cases tend to warp when they are split and require machining to fit back together.

Also, your 68 crank is of a non-counterweighted design, some racers prefer these due to the lighter mass, but they tend to place a greater load on bearings. If you found a 7R case with the 2,7 (70.4mm stroke) crank that would solve that issue also.

Since originality won't be a factor I would go with a larger displacement, other than setting up the carbs this would be hard to beat.

[91167coupe]

Thank You for useful input and the head chart!!
If I find annaffordable and good alu case I will go the 2.0 route, maybe with S-spec if possible. But nothing beats cubic inches for power and torque.

I belive the -68 911L engine has the counter weigh crank, but I have to check condition when case is split.
I guess the 2.0T heads would be better than standard 2.0 heads, even if porting is the same because of the bigger valves?

[66S]

I wouldnt mix 2.2 heads with 2.0 pistons. With your motor I would port the T heads to S spec and get some Wossner or Mahle forged pistons and use the S cams. You wont spend a lot and a 2.0S is a nice motor with adequate power. If your right foot isnt too heavy it can deliver decent mpg. Also, I think the 2.0 sounds better than any of the bigger motors. All heads are aluminum.

[SIMI BOB]

In case you hadn't noticed from the chart, '69 911S heads had 3mm larger intake valves and 1mm larger exhaust. If you use T or E heads, you may want to go a little smaller than the 36/35 ports of the S. As mentioned above, you don't want to mix 2.2/2.4/2.7 heads with 2.0S pistons, unless you are going to have some custom pistons made.
Probably the easiest thing to do is port some 2.2/2.4/2.7 heads (already 1mm bigger valves than a 2.0S) to 36/35 and install some 2.2S Pistons. Also install an aluminum oil pump. This is what I did to my 2.0S motor.
The 2.2S had 10 more HP than the 2.0.
Bob B

[91167coupe]

Thanks Bob and 66S for input!! Yes, the most reasonable would be to go 2.2, but the 2.0S sounds wonderful and has good power and a very nice power curve. I had an original -67 2.0S engine in the 67 coupe I owned earlier and It is a wonderful engine.
Wossner pistons are reasonably priced, but what about cylinders? Aluminium oil pump is a good tip, which model are these from or are they new only?
Thanks again for very useful input on my engine project!!

[SIMI BOB]

My engine builder just put "3.0 aluminum pump" on the invoice, and it was brand new. Cost in Southern California, $600. You should be able to find a good used one. Make sure you have the "oil bypass modification" done to the early case if you buy a late aluminum pump. The pump you want should be the 1976-1983 pump, with four vertical lines on the side.
Wossner should be able to advise you on cylinders.
Bob B

[91167coupe]

Thanks Bob for info!

[304065]

Kjell, here is a OLD thread I started about performance modifications for the 2,0 liter motors:

http://forums.pelicanparts.com/911-e...-901-05-a.html

While I ultimately concluded that boring the Biral cylinders to 81 and using 9,5:1 JE pistons was the right move, there is lots of information in there about what you can expect from various performance modifications.

The best cylinders are Mahle nikasil, although LN Engineering "Nickies" are VERY good. . . and Charles has even made 2,0 cylinders with the 2,2 and later head register, so you can use later heads on the smaller barrels. (You would probably only do this for race purposes where displacement is limited by class rules).



You can go all the way up to 93mm, which with a 66mm crank gets you 2,689 liters. With the 70.4mm crank, 2,869 liters, which ought to be good for 230 horsepower if you can accomplish the same specific output as the early 911S (80 bhp/liter). If this seems crazy it's not, the Carrera RS accomplished 210 Horsepower on 2,687 liters and 8,5:1 compression (with MFI, of course).

Ahh the possibilities once one starts drawing outside the lines. . . .

[91167coupe]

Thanks for good info! And very interesting thread!!! The direction I will settle for depends on what kind of engine or case I will buy. I know of a 901/05 engine which runs but need overhaul and maybe a late 901/06 aluminium case (early -68). I will also rear down the early mag engine to see what parts that are usable here, hope at least the crank and S-cams have survived.
Thanks again for all your help so far, Now I know more what to look out for!