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I have a 911 2.4E with a 2.4T engine with S cams. The carburetor venturis are 28.5 mm, as original.
The S cams lift the valves 0.072" higher than the T cams. Does this imply that S cams provide correspondingly greater air flow? Or does the port size limit the flow anyway?
I am thinking about installing venturis with larger diameter.
Einar
Only one way to know,,,,try it and see.
I think you'll find it really needs to match to be efficient, meaning they match up larger head ports, intake valves, and stacks, all to take advantage of the longer duration of the S cam. with restrictive T ports and all else you'll probably see little to no gain top end all while giving away some of the T's nice low torque... so worst of both worlds would be my guess
Back in the day Stoddard sold a sport kit for 2.0 and 2.2 T which I bought. Air cleaners, sport muffler, 34 mm ventures and appropriate jets. Made a big difference in throttle response and power farther up the scale. For a 2.2 T I would pick E cams or the early solex cam before S but the heads and intake are the chocking point with T stuff.
I have now replaced the 28.5 mm venturis with 31 mm. No noticable difference. I am not very cleaver with these kind of modifications, and I asked the question because if there is no potential for output increase, I would rather spend my time doing something else.Quote:
Originally Posted by edmayo
You may also need to increase main jet size a little. Do back to back comparison times with a stopwatch starting from a roll in second gear(always same speed) and accelerate to a consistant speed and compare average times.
I did a full rebuild of my zenith carbs with bigger venturi and a rejet. Plus Motorsport style aircleaners with rain hats and a Stock style sport muffler. Did it turn my 2.2 into a race car? No. Does it pull harder when passing or going up hills? Yes. Plus it doesn’t seem to run out of steam as early in the rev range.
An 'S' ENGINE in a 'T' car would increase flow over 4000 RPM...
Besides the higher lift and long duration of the 'S' camshaft, the bigger ports, valves, sodium filled exhaust valve stems, induction size and mixture, higher compression ratio and distributor curve all work in harmony to boost an 'S' engine's output.
Harmony being the watch-word. Schoenberg!
Interestingly the PET catalog shows only one stock 'silencer' (muffler) for all the engine permutations.
That shows the importance of streamlining the low-pressure side on the INTAKE compared to the mired of aftermarket exhaust systems that are ready to lighten the wallet of owners.
The stock air cleaner on my '69 S flows better than the K&N open air filters I had and loved the sound of.
The car is faster but the sound one can modulate with the accelerator is gone.
I bet it is the closeness of the K&N's lids to the tops of the velocity stacks- That's awful close and a tight turn.
Would it run faster W-O-T with shorter or no stacks? It seems the throttle bodies are pretty tall themselves-
Worth a try with K&Ns and at the cost of already weak low end torque. But then a 'S' wasn't made to jump traffic lights.
Understand that and the weakness of the low end that can be frustrating against a Plymouth Neon (or a 911E) disappears...
The original air cleaner has bulges designed in to increase the distance over the stacks and its shape also ushers the incoming air as well.
The very best hook-up would be open velocity stacks.
Would one answer be a free-flow filter to fit under the intake grill to increase flow compared to the stock "can" and allow the glorious sounds out?
It would also be filtering the huge volume of cooling air to the engine as well so maintenance of the filter would be tedious-
And well worth it for a hobby car!
After all- the oil temperture gauge would indicate a need to clean the filter!