Larger Venturies for my Webers?
 

I have removed the Weber 40IDC 3A carbs for a rebuild.

They currently have 32mm venturies.

Will larger venturies give more top end power?

The engine is 2.7 from a '77 911. Internals (P/Cs, compression ratio, Cams) are unknown. Bursch Headers with megaphones (with removable baffles).

The car is 90% track. Weighs less than 2100lbs.


Thanks

Eddie

What size ports? I think a '77, assuming they are '77 heads, should have 35mm ports.

I'd use 34mm venturis. You'll need to rejet after the change. Slightly larger idles and mains.

For 90% track, I'd go as large as you can stand on the venturies. I found 36mm venturies on my 2.8 to be a good compromise for max high RPM track power but with adequate street drivability. Talk to an expert, like Richard Parr at PMO to get a recommended starting point for your set-up, but you'll need to know the internal details of your engine.

Good luck,

JP

If you are interested in selling the 32mm venturis I'll buy them.

Daryl

Larger venturi's will give you a bit more flow (assuming the jetting and port sizes will accomondate, as Tyson and others mentioned) but will also reduce your low RPM throttle response.