Any one modify carbs? I'd like to compare notes on some of the changes shown below (thinned shafts, button heads, choke horn removal, booster modification). What were your results?

[IMG][/IMG]

[IMG][/IMG]

[IMG][/IMG]

 

Looks like you went to the extreme with the choke horn removal. I normally just remove the horn itself, not mill then entire top of the carb. But it may be an improvement, I don't know....

Ryan

 

I doubt it also. Originally, I hacksawed the horn off then leveled it with a hand grinder. That's how I ran the carbs last year; there are two. This winter I went ahead and threw it up on the mill, only to make it flat and more attractive. I should have used a bigger cutter, would have looked even better.

Anyway, do you have any before and after information (jetting, dyno, or drag strip mph)?

 

Did you change the boosters?

 

Yes, I machined the bars out.

 

I had some information somewhere on a carb I did awhile back.... Can't find it now though, it was from a flow bench, I believe it picked up 30 cfm over stock with just the choke horn removed and another 20 when I blended the top in better. You have to be careful doing that though. You can also ream the boosters out which gives a bit better response. What all did you do to the carb other than milling off the top? Did you precision lap the mating surfaces?

Ryan

 

I thinned the shafts and installed button heads, removed the choke horn, and removed the divider in the boosters.

That'd be great if you could find the flow bench information.

 

As to the boosters, doglegs would be my next move. The carb shop sells a super booster that looks like it would get the job done.

 

What's the claim to fame with the super booster?

 

I looked and I can't seem to find the flow bench info..... Do you have any detail shots of the thinned shafts? I haven't really heard of doing this. Have you thought about blending the top of the venturis?

Ryan

 

Do you know why the bars were there? What was the reasoning for removal?

 

You can look in summit or Jegs, they sell thinned shafts that come with button heads; They are made by Quick Fuel Technologies. I don' thave any better pictures than the one above, sorry. I put the carbs back on the motor. I run a stub stack of sorts that provides a smooth path for airflow into the venturi. Thinned shafts are also purported to increase booster signal.

The bars provide a restriction in airflow which increases the velocity of the air for better atomization of the fuel and increased signal. I removed them for better airflow at the cost of reduced atomization.

 

Did you remember to put extensions on the tubes in the secondary bowl?

 

since you machined the "bars" from the boosters out this will greatly affect the signal to the boosters.

with out those bars on the boosters the signal will decrease greatly and you will have to put in smaller main air bleeds to have the have the main circuit come in at the proper time as well as run more main jet/PVCR area to keep the engine from running lean. Also this will affect atomization of the fuel.

boosters without the bars are specifically positioned in the venturi to make up for this loss in signal.

You will probably have to have the boosters replaced but, try it for the hell of it to see how it works out

 

I'm not real familiar with extension tubes, are they for foreward mounted carbs, these are mounted sideways.

I've already ran these carbs, with tuning, I went from 10.60 to 10.13. I'm confident they work.

I did add a great deal more jet to make them work. As the AFR came into line the car just keep getting faster and faster. Perhaps I have band-aided the potential air bleed problem. I'll have to look into the air bleeds, but you say they provide main circuit timing not necessarily fuel delivery quantity.