weber set-up*** please help

[haycait911]

I have a 911/51 engine with 2.7 p/c and 40 IDA-3C webers. I currently have 30mm venturis. I was going to go to 34mm as this seems to be what would work best. upon further investigation I found my heads have 30mm intake ports.

question; is there any point to going to 34mm venturis with the small ports. are the ports going to act as a 'bottleneck' , negating the effect of the larger venturis? or will the 34mm venturis allow the engine to draw more air anyway?

any input/advice/help would be greatly appreciated. thanks! Don.

[2.7RACER]

Don,
Not much point in going with 34mm venturi's with 30mm intake ports.
You mention 2.7 P&C's. What comp ratio pistons? Is the cam stock?
Unless you are willing to take things apart and open up the ports to close to 35mm and put in a warmed over cam, something like a Solex cam, I wouldn't change the carbs. And then maybe up to 32mm.
Things all need to work together. Big carbs only work well with cams and ports. The Valve sizes are fine. 9.5:1 pistons are better than 8.5:1's.
An open free flowing exhaust will help too.
It all works together. Good luck,

edit: I like your car. Silver and the wheels work.

[Joeaksa]

You will have more torque and better driveability with the 30's. Larger venturi's are better for WOT (wide open throttle) used in racing applications but not as good for general driving.

Concentrate on getting the gasses out of the engine before worrying on putting more fuel in. Streamline the exhaust and go with some SSI's or other good exhaust and muffler before spending a moment on the carbs. Once you can flow more air through the engine (its really only an airpump) then work on the other issues for performance.

Nice looking car and like the above post, love the color.

[haycait911]

thanks guys! pretty much what I was thinking. car has SSI's and a stock stainless one outlet muffler. the p/c set is #911 103 928 01. I don't know the comp ratio. the engine has perfect compression and leakdown #'s (170 psi and 2-3%) so at this point I'm not ready to get into boring the ports. you're right about the drivability, great torque, I can floor it in 5th at 2000 rpm and it just goes, no stuttering or missing. what would be a good distributor? it has the original mfi one with no vacuum advance. any thoughts on a better muffler? thanks again for everything! Don.

[Joeaksa]

MK911 (Ben) on this forum makes a very good muffler. Believe that Pelican sells it but do a search and you will find a lot of info here.

Now, if you are happy with the engine, spend some money on the suspension. All the power in the world is worthless until and unless you can put each and every last bit of power on the ground going the right direction. Far too many people worry about more power and do the suspension later.

Make sure that the shocks are fairly new or in good condition, then look at sways and torsion bars. Then get the entire mess corner balanced and aligned. After that you might think about upgrading your brakes but truthfully the stock 911 brakes will handle the car in almost every situation unless the engine has been upgraded.

Will make you very happy with the car and no reliability issues.

[haycait911]

good thoughts, actually I'm in the middle of putting together 19/26 torsion bars, weltmeister spring plates and koni shocks from fellow pelicaners. I think I'll leave the stock sway bars for now and see how things shake down in spring. thanks again! Don.

[Joeaksa]

Don,

Good plan and once you get the car totally sorted out and are happy with it, then is the time to start looking at the engine.

Have fun, drive it like you stole it and take lots of photos and post them here!

joe

[Fishcop]

Hi Don

In reference to the distributor question you had... none of our dizzies are 'vacuume advance'. I stand to be corrected, but they're all pretty much mechanical advance (spinning weights). The vacuume unit was/is to retard timing.

You can certainly send the dizzy off to be rebuilt and 're-graphed' to suit your engine specs. This (combined with a Crane XR electronic ignition unit) made a very noticable difference to how my car ran.

Cheers