Carbs for 3 liter

[zztot]

Guys or Ladies:
Now that I bought them I am trying to decide if it is the RIGHT thing to do....
Have 914-6 conversion with an SC 3 liter... stock engine.

Have a set of 40 webers to install. IS this a good upgrade ...better yet is it an upgrade at all. Will I gain HP ........will I gain anything?

Thanks ,
Terry

[Dave at Pelican Parts]

You should gain something on the order of 10 HP from going to carbs. Fuel economy will suffer, possibly very significantly. The car will be much more "cold blooded", and not be very happy for the first ~5-10 minutes of running.

It'll sound unbelievably awesome, too....

--DD

[sww914]

You can also add higher performance cams than the CIS could tolerate if you ever want to.

[jhora]

P&Cs and Cams to get any real benefit
CIS is a pretty good system as is...if you have all the parts with the engine

[Dave at Pelican Parts]

Carbs and headers together on a 3.0 are worth 20+ HP according to Anderson. The CIS is relatively restrictive, evidently. The 914-6 should have headers already (even the Six heat exchangers are closer to headers than the not-so-great 911SC exhaust) and adding the carbs should get it the rest of the way there.

--DD

[John Rogers]

Most of the vintage racers I race with use PMO carbs, usually the 50mm setup. Not cheap but they are tuned easier, have sight windows in the float bowl and make the HP.

[rfuerst911sc]

For what it's worth I'm useing a 3.0 in my 914/6 conversion and I'm going to use 40mm Webers. I'm also currently useing 46mm PMO's on my 3.0 911 and love them. I don't expect the Webers to be as smooth as the PMO's but I bought them for much less than the PMO's and my mechanic can tune carbs well. You can always go back to the CIS if you wanted to but I see no reason to do that. The carbs are better looking,clean up the engine bay and are fairly easy to tune. Down side is fuel economy but some of that is the user meaning it's too much fun flooring them and hearing that roar !!!

[Rich76_911s]

Throttle response will also be improved, giving your butt dyno some posotive results.

What year 3.0L engine? I do beleive that if you are running an 1980 or later engine you will have to use an earlier SC distributor (must be a 78 or 79 SC distributor). I know I have read about this over on the 911 board so do a search to find out exactly what years, and the reason.

It is worth the trouble.

Rich

[rfuerst911sc]

Originally Posted by Rich76_911s

Throttle response will also be improved, giving your butt dyno some posotive results.

What year 3.0L engine? I do beleive that if you are running an 1980 or later engine you will have to use an earlier SC distributor (must be a 78 or 79 SC distributor). I know I have read about this over on the 911 board so do a search to find out exactly what years, and the reason.

It is worth the trouble.

Rich

My 83SC distributor is being used and works fine, however I did have to have it sent out to be recurved/setup to work with carbs.

[justinp71]

I talked to a guy with a stock 78 3.0 motor, SSI's and 46mm webbers, he dynoed his motor @ 240hp at the flywheel...

[racer]

My experience (a 3.0L 911sc) was that yes, SSIs and a sport muffler improved HP, but that a switch to CARBS and NOT changing cams doesn't do much. The CIS cams are not ideal with a Carb set-up. Now. Throw on some GE60/80 cams and you have a real nice motor. I also found the car had much smoother throttle/throttle response with CIS than with Carbs.

[Joe Bob]

964 cams and free flow exhaust did the most for my 3.0.....I kept the CIS. Nice being able to simply hit the key and have it start.

[jess p]

40mm is an minimum size carb for a 3.0 sc engine. If you want serious HP put
some ge 40 cams with non cis pistons and a header exhaust.