911SC triple Weber cold start question

[bcoats]

Hello fellow Pelicans - I recently purchased a 911SC with a triple Weber carb conversion, fresh top end on the motor and running Elgin 964 grind cams. This is my first 911 with carbs, starting is a bit tedious, have to really work the gas pedal and eventually hold idle at 1200 or so for at least a minute before the car can idle smoothly. Wondering if this is typical of running carbs? Also, just based on the gas smell it may be running super rich? Any input or similar experiences greatly appreciated. Once at operating temp it's perfect. Thanks, Bryce

[911pcars]

Starting depends on cranking speed and spark strength from the ignition system.

Usually, a couple of stabs of the gas pedal will shoot adequate fuel into the intakes to start the engine. Thereafter, it should take just a few more seconds for the idle to smooth out.

Yes, an overly rich mixture (idle mixture adj., high float level, large or blocked idle jet, etc. can affect the idle. Start from a reference point that the carbs are set up and adjusted correctly and that the engine is in good condition (compression).

Sherwood

[diverdan]

I too have an SC with big weber venturi and no choke. Mine requires the staring procedure you stated. However, it has the grunt of a hot big block Chevy and sucks the gas at about 10-12 mpg. She screams through first gear almost faster than I can react to go to second. Smell the raw gas and see the flames out the exhaust!

Dan

[DanS911]

Yeah two stabs of the gas pedal and hold it open a crack at the start.
If things are right you should only have to work it a time or two to get all six firing.

[Jack Stands]

Up here in the winter, you really have to work the throttle to make up for the lack of chokes. My procedure is as mentioned above, but I often have to keep working the throttle for the first 10 seconds to supply a bit more gas from the accelerator pumps to keep it running.

Once warmed up, runs great and I love the sounds of the Webers. In a perfect world with price not being a problem, I think the individual throttle bodies that PMO offers with electronic injection would be the best of both worlds. You would get the sounds, the drivability, and the mileage all in one setup.

[VFR750]

Completely normal start up. This is the classic " cold blooded" nature of old cars with carbs. Funny how we forget how lucky we are to have modern EFI in our DD. One cold start with the Zeniths is all it takes...

[bcoats]

Thanks guys for all the input and will look into air/fuel mixture as well but sounds like just takes a little getting used to is all, when warmed up and smooths out it's amazing. Thanks again

[marioporsche]

i have the same problem with mi 911sc targa, dose it need the fuel pressure accumulator? or its just for the fuel inj. System?
everything was just fine until i removed it...

[bcoats]

I believe the fuel pressure accumulator is needed for the CIS system not for carbs

[kerthunk]

With the cold weather we have been having up here in the Seattle area, carbs are definitely a bit tougher to get started. Summertime, mine will fire right up. Right now, it takes a couple of pumps of gas and some patience. It sometimes takes a couple of attempts at getting it started.

As for running rich, that is pretty standard with carbs. If you wanted to come across the water, we can hook up a sniffer to your tailpipe and see where it is at. To really get it right, you'll need to get on a dyno to make sure your main jets are correct. Overall, carbs tend to give you a gassy smell and you aren't going to tune that away.

[bcoats]

Hey John, thanks for the offer, I may be in Port Ludlow in a couple weeks, will shoot you a PM if I'm over there and perhaps take you up on that offer and buy you a couple pints at The Public House!

[al lkosmal]

Typical procedure for starting with carbs...............on these cold Seattle mornings.
Two pumps and hold it open a bit to fire it up. I then need to pump it quite a few times to keep it running and get to idle by itself.

regards,
al

After driving with and rebuilding 40+ year old Webers, Zeniths and MFI....I went down the path to develop alternatives. (I like all of the different systems....they all have their pluses and minuses)

Here's some EFI/ITB cold start for you:

Porsche EFI kit - fire up - YouTube

And some before/after dyno results.

D-Zug Tours RSR dyno

[Uncle Enzo]

I'm running webers on my 2.7 and start up is just about the same. It's so rich my wife makes me push it outside before I fire it up. Our house often smells like pit lane.