1969Porsche911Targa

Hi all,
I have a 1970 2.2 T engine. Both cams are worn and my mechanic suggests that in search of performance, instead of installing new "T" cams, I should try "E" cams.

Would somebody please comment what are the risks, problems, or benefits to this alternative?

Thanks in advance,
Rafael

JV911

could probably even use S cams

someone will clarify

pete?

Jay Gratton

I have a friend who had a T who went and put in the E cam and it made the car run so mcuh better. The all around performance of the car improved. The E cam is a nice way to go.

Peter Zimmermann

When you do an internal parts swap you must look at what Porsche did with your selected components. A 2.2 T has excellent cylinder heads, which are basically the same as E heads of the same year less injector holes. Each has 46 mm intake valves and 40 mm exhaust valves, and each has 32 mm int & ex ports. So the heads are OK. Now, the cams are a direct replacement (a minor modification must be done to the left cam to deal with the MFI pump drive). However, Porsche's "package" for the E engine includes pistons of a higher compression (9.1:1) vs the T pistons (8.6:1). So, the solution here would be to replace the T pistons/cylinders with a set of E units. Now, to maximize what we've done so far, we have to look at the engine's bottom end, and decide if the T crank (non-counterweighted) will be able to cope with the increase in top end performance, or if an E/S (counterweighted) crank should be found. When that decision process is complete we have to move to the fuel delivery system, in this case the 2.2 T uses Zenith 40 TIN carbs. They are great for street 2.2 T use, but virtually no performance parts (venturis, etc.) are available, so they will not be able to maximize our new engine's performance potential. So now we have to switch to Webers, PMOs, or MFI (which would have been decided on before the project began - injector holes would have been machined into the intake ports). So, to maximze the T to E (cam) change involves a lot more than a simple cam transplant. Yes, you might gain a small bit of driveability, but an E engine it will not make.

Now, to install S cams, well, that just would not work. S heads had intake ports opened up 4 mm, and exhaust ports opened 3 mm, over the T and E configuration. Compression was increased to 9.8:1, and all of those changes were done to maximize the radical nature of the S cam, which allows an engine to come to life above 4500 rpm. The fuel system would be incapable of supplying the fuel/air needed, the tiny ports would be unable to flow a satisfactory mixture, the combustion chambers, as a result, would suffer, and all of the mis-matched pieces would fight each other rather than work together.
Pete

John Fusco

OK Peter, if this is not too far off topic could you do the same analysis of a 2.0 L Normal engine with 2.2 E p/c's and solex cams.
I assume the heads are the orig ones - fly cut to fit.


Thanks;
John

Peter Zimmermann

John, I would be glad to. Solex cams, approximately in the middle between E cams and S cams are one of my favorite cams around which to build a smooth, easy to drive on the street, sleeper. A '68 L is already fitted with Webers, but your problem lies with the heads. They are fitted with the smallest valves Porsche ever used in a 911; 7 mm smaller intakes and 5 mm smaller exhausts than 2.2L heads, even so the ports are the same size. If you can find a set of 2.2 heads, either T or E, you would be so much better off with your project. The solex cam loves 3500-6800 revs, and I'm afraid that the 39 In/35 Ex just won't be able to flow enough mixture. Your torque will be great, but you will definitely sacrifice top end power. Your L motor should have, if I remember correctly, a counterweighted crank, so you're good to go regarding that, but your peak revs won't be as high as an S so the other is OK to. To port your heads would be a huge investment, and, because of space in the 2.0 combustion chamber, you could not use 2.2 (46 mm x 40 mm) valves, so you don't want to go down that road. Decisions, decisions!
Pete

John Fusco

Thank you for that Pete.

Yup - that's the thing - which road to go down.
Love the torque but miss that scream at the top.
I am torn between getting 2.2S P/C's or taking the engine back down to 2.0 but S spec.
I have been told it would cost more to buy an S engine than to remake mine. Is that true ?

Thanks again;

John

Peter Zimmermann

Here's what you're facing:
2.0 "L" heads: Valves: 39 int/35 ex Ports: 32 int/32 ex
2.0 "S" heads (backdate to '67): Valves: 42 int/38 ex Ports: 36 int/35 ex

2.2 "S" heads: Valves 46 int/40 ex Ports: 36 int/35 ex

You can see that, in order to make S heads/cams work, Porsche already knew, in '67, what size the ports had to be. They also realized that 9.8:1 compression was ideal for both motors and readily available fuel, but knew that they must increase valve size. The small displacement increase + valve size increase yielded another 20 hp, for the MFI 2.2 S, over the carbureted '67 S. Torque also went up, but not by much. In order to maximize the gain from adding 2.2 S p/cyls you must come up with a pair of S cams (the Solex cams seem to favor E pistons, or larger displacement such as 92mm bore, than the S pistons), and 2.2 T,E or S heads. To do a 2.0 S engine you will also need S cams, you will need to do a very expensive job of opening up your ports and increasing your valve sizes to 2.0 S specs, and somehow find a pair of Weber 40 IDS carbs that have high rpm enrichment (your 2.0 L carbs do not have that feature). Weber IDSs, or something similar from PMO, would also be needed for a 2.2 S configuration.
Pete

Mike Murphy

I know very little about the early 911 engines, but it's too bad there isn't a way to get up to 2.4 or 2.7 so that you could have both the torque and horsepower that you're looking for.

John Fusco

I thought there was a difference in the ports between the 2.2 S, E and T heads. And that because of the dome size S pistons would only fit with S heads.

There was a 2000R rally option ( 901/30) that used 2.0 39/35 - 32/32 heads with 46 IDA's. S cams. 9.8/1 and 150hp so I imagine S pistons.
Could I use the IDA's with bigger jets/venturis for that (?)

Could you estimate how much in gold plating that might cost me if you think it would be doable , or worth doing at all ?
Thanks Pete;

John

John Fusco

I am looking for (fantasizing) more top end, more revs - doesn't have to be bigger . Just nastier.

ebsalem

Well I have some thoughts on this, given that I have E cams in 2.7 with JE 9.5:1 pistons and Weber 40's.

It's wonderful. Makes for a serious AutoX motor.

951kid

ebsalem.. where did you get the higher compression pistons?

Curious for when i iron out the problems in my dads 911

ebsalem

Engine Builders Supply - JE Pistons just under $1000. They also have higher compression pistions, but my car doesn't have anywhere to store that 50 gallon drum of race gas.

Peter Zimmermann

John: Your last post about the 2000R leads you into "not suitable for street use" territory. The compromise, on the bottom end, to achieve the high rev output is extreme, you won't want to get stuck in traffic. Weber 46 mm carbs are much more suitable for use on a larger displacement motor, say a converted 3.0 SC with E or Solex carbs. You also have to face the reality of reduced life expectancy on anything that you build that turns more than 7K revs. Look at the 911R, for example. An 8K + rev motor, and Porsche felt it necessary to use Titanium con-rods and rocker arms in order to reduce the mass. But boy did it go! With E or Solex cams you can use 40 IDAs and achieve a very good balance between low and high revs. I've always believed that, to reach the perfect solution on the early cars, one must do what Porsche did, if possible. Driving a completely original, properly adjusted, '67 S is a wonderful and rewarding experience, as is driving a proper 2.2 S. Each has its own personality, but you can't go wrong with either. To complete each project version, I feel, requires either IDSs, or MFI. Regarding aftermarket pistons, I think that consulting with Steve W would be invaluable.
Pete