308 30mm choke

I don't have any experience with that, but on the surface, it doesn't seem to make sense. You're asking the carbs to pull more air/fuel mixture into the combustion chamber with smaller venturies and smaller jets. That just doesn't add up in my opinion.

Bob Wassam

 

Russ?

 

I can see the higher velocity due to the smaller choke size to maybe, improve mixing of the emuslified fuel and air and why the car may run better/smoother at lower RPM's (not necessarily with more power), but a smaller choke is what it is, a smaller restriction. You will lose out at higher RPM and I don't see this point of going to a smaller size. Does this guy have hard facts/Dyno data to prove the claimed benefit?

It would be a waste of time and money to change IMO. Stock set-up is more than satisfactory for all driving conditions.

 

Sounds interesting!
Not sure he is actually feeling more 'low-end power'; unless he has dynos to prove otherwise, I think what he is actually feeling is improved lower end throttle response due to the increased air velocity from the smaller venturi. It really can be felt quite noticibly as more kick in the pants when you floor it: not more power, but what you have becomes available for that throttle setting all in at once.
With the smaller venturi - for equivalent steady state throttle openings -the resistance is higher, thus lower flow and lower hp at roughly equivalent throttle settings. But, with the higher velocities, when the throttle is opened, you get the power increase 'right now', **feeling** as if it has more 'mid-range' punch.
Just an idea
best
rt

 

I'd have to agree here. The smaller throats would give a better throttle response, but no more hp. The only way I can see it producing more hp, is if the original throats were grossly oversized. Just my $.02

 

Many years ago I experimented with 40 DCZs and later the DFIs and DCNs. I had a 275 two cam with 28mm chokes. Went to 27mm and slighlty smaller jets. Low end was better but mid range and top end suffered a little.

Then I went with 32mm on a 330 GT 2+2. Standard was 27mm. I used the same jetting as on the 365 GT 2+2 DFIs. Made a big difference on the top end with a very slight sacrifice on the low end. Mid range was great. I couldn't readily find 32mm venturis so I went to the local Weber dealer at the time and found something very close and then I had the outside machined to slide in. A small dimple was machined for the set screw. I had a Euro Daytona for a while. I played around with the DCNs and did the same thing. Had excellent results. I will have to go through all of my records to find the jet sizes I used for both. It may not help much but my experiences. I am sure some of the older members who have done a lot of work on their cars have worthwile experiences.

I completely agree with other writer- smaller will not improve high end (or mid-range for that matter).