73 S Cams??

[pcivalero]

Hi-
Question, my mechanic swapped out my T Cams during a rebuild for E Cams and we didn't get the performance improvement we thought we would. He is thinking about swapping them out for S Cams but wasn't sure if that would work.

I have a 73 911 T 2.4 engine with MFI. Please note we also fly cut the heads too.

Thanks,

[YTNUKLR]

The cams only work if you have the capacity for airflow at higher rpm and enough compression. If you didn't add compression (911S pistons) or add airflow (enlarge throttle bodies and ports) then the cams won't do anything. By the way, you will also need to modify the settings on your injection pump, or rebuild it to 2.4S specifications if you expect power like that. And recurve the distributor.

If not willing/able to do all that, I recommend 911T cams and enjoy.

[Flieger]

S cams will hit T pistons if not cut for valve pockets.

[YTNUKLR]

That's true also but the engine will suck anyway with that low compression and the S cams, I don't think you'd ever want that combination

[911st]

I am not an expert but fly-cutting the heads might get you to 8/1 compression which is what the 2.4 E motor ran. This is still less than ideal but should work.

In many cases the 2.4E was a faster set up in town or autoX than the 2.4S with the stock 915 gears.

I am guessing you do not want to put much more money in this thing to bump the compression, capacity, or such so you might just try to get what you have working well. I also assume you are running a stock 2.4 exhaust.

Basically you might try getting the AFR's and ignition advance near there ideals for the fuel you are running. The T MFI pump might make this a little bit of a challenge. It should be fine at WOT it just might be less than ideal for drivability at part throttle.

First, I assume you swapped the T ignition rotor for an E or S rotor for a higher red line. Next I would concider sending the distributor out to be recurved to E specs. However, I would get it on a dyno and verify your AFR's are good. If they are about 13/1 at WOT around TQ and HP peak you then might experiment with total advance till you find the sweet spot for the fuel you are running.

You should be able to get close to 2.4 E specs with what you have built.

[gearheadgreg]

I think more details on the engine and the rebuild details are in order.

It could very well be that the airflow and fueling aren't correct for the rest of the system of parts and holding back on power that way, or simply that compression is too low already and won't support much more in terms of increased camshaft duration, etc etc.

More info would be a great start, though!

[tadd]

Just a suggestion, but you might consider picking up a shorter gear box if the engine is healthy.

3k in a tranny goes a lot farther than 3k in engine parts .

A 912 only has 90 hp on a fresh motor and is pretty lazy with AFMSX, but with AFJOV it is alot punchier. For a 120 hp T it would be even zooomier.

That said, a size larger cam from stock typically is a good upgrade. For example the 906 carrera was a PITA in rallys (street use) but swap the 38 mm ports for the 36 mm 69S and the runs only over 5k car is now kitten enough to run in heavy city traffic. This is also been shown to be true on the bigger end (2.8) as well as the 2.8SS really likes the RSR sprint cams on the street. Examples here on pelican. So from a head standpoint, the upping to an S should be a nice improvement. I would caution that you may want more compression to work with the greater overlap but you have an extra 400 cc over a 2.0 so I would bet you'd be good. You will need (want) to spin it more so make the distributor adjustments.

t