webber 40s:Is there a mod ification to the venturi's
 

What tricks do you know?

I have one apart now rebuilding it. Venturi (the magnesium cylinder inside the carb with 30 on it). Are those able to be bored out?

Is there a chart with jets, et al.?

Do I take them to the race shop for tuning. Yes ofcourse I will, but I mean right now (in the parts acquisition stage). I will never forget how much faster rejetting carbs made my muscle cars.

I have to tell you, something funny a parts man said to me this weekend, " Carburators are a dying art". I disagreed with him, and as I smiled said bye.

Oh BTW someone, please add input on how any modifications affect the car (69 911) at club (eg PCA, HSR) events.

Once I learn this, maybe my next early car I will get serious with a sweet mfi set up.

Thank You.

You really need a dyno or a wide band 02 sensor to know what your doing to the jetting... certainly wouldn't want to get things too lean and while adjusting for different temperatures and altitudes

Having said that.
usually bigger venturi's will improve the top end while sacrificing the low end. So for a street car, it might be a mistake to put big venturi's in
We run a 2.0 and went HUGE on venturi's but for track only. the Common sizes that I hear about for a 2.0 motor would be 30 or 32's

brant

Call or fax Richard Parr at PMO and tell him the size and configuration (specifically the cam and CR) of your engine. He'll be able to recommend jetting that will be 95% of the way there. I'm sure that Henry Schmidt or Steve Weiner who post on the Engine Rebuilding forum could do the same. You can get the jetting from PMO or Pelican. Also make sure that the bodies are in good shape with no slop in the throttle shafts or butterflies. If there is, send them to Matt at Eurometrix. He can rebush the shafts and refurb the butterflies to ensure proper fit so that the car will have a good idle and respond properly to the jetting. I've seen his tooling and it's not something that you can do at home.

In the case of 911's, there isn't a whole lot of HP to be found in modifying the carbs. '40's are more then adequate for most applications -- especially 2.0s, so as long as they are jetted correctly, they won't be preventing your engine from making HP. If you're going to be tracking your car, you'll want to make the following modifications:

1) Baffling to prevent fuel surge under hard cornering.
2) Extra venting to the fuel bowls to prevent the fuel from overflowing.