911T with E-pistons and S-cams jetting question

[farleyd]

Hi to all, i have a nice 911T 2.2 engine w/E-pistons and s-cams. Its running fine but has a flat spot at around 5k rpm. It is a nice blend that gives more power and torque than the stock T set-up.

Was wondering what kinda adjustment the Zenith carbs - in terms of venturies, idle & main jets - would need to run that engine more efficiently that as it is now.

Thanks for helping.

[avendlerdp]

You may be in need of a distributor re-curving. The cam profile is soo different. Ignition first, then jets. Does it break up at 5k and never clean up? Or is it just a flat spot at a certain rpm? You may need to change emulsion tubes. The problem is different sizes may not be made. Webers? Yes. Alex.

[farleyd]

I should have mentionned that i have an E dizzy and Zenith carbs. It never picks up after 5k RPM.

[steveW]

On a similar note, what kind of power would you get with 'S' pistons in an otherwise std 2.2 'T' motor.

Would the existing Zeniths and Marelli dizzy from a 'T' work without any mods and would the valves clear the 'S' pistons?

I'm really trying to find the cheapest way of making a 'T' faster and am in the process of removing weight as a first step.

Cheers

[farleyd]

As far as i know, Marelli will work. But once you update to a Bosch, which i did, youll leave the Marelli alone. If you want to take advantage of all the assest of such a mod, youll need an S-distributor of course, as the timing curve isnt the same.

The engine i am referring to, a T with E-pistons and S-cams, when compared to a stock-T (which i presently have in my 914) is not way faster than the T. The big difference is in the cam response. You can really feel them when you pass 4K rpm. In a T, the torque is more uniform in the RPM range.

I think that teh E-T-S pistons are the same, the differences are in the head, and dimensions of the valves.

HTH

[steveW]

There's a big difference between T, E & S pistons. A 'T' has a comp ratio of 8.6:1 while an 'E' is 9.1:1 and an 'S' is 9.8:1.

I know the cams are all very different as well and they give the engine its 'feel' but I'm not sure how much extra grunt I'll get by just changing pistons.