DamBest Carburetor Update
This simple project was to fix an idle issue on the Mustang. The Mustang has a very healthy mechanical roller cam. To get it to idle required the throttle blades to be open past the idle metering circut and on the sage advice of John Satterfield of DamBest he advised that I do this simple modification. This can also apply to most any standard Holley carburetor. The project was to drill 4 small holes in the carbs throttle blades as well as change the primary idle bleeds. The size of the bleeds and throttle holes depend on tuning and I will defer you to the experts tuners for the starting points. This is simply a quick look at where to position the throttle blade bleeds. If you are using a DamBest carb you will get 2 things, one is a fantastic Carburetor and the second is fantastic support from John.
DamBest 358 Open Track Carb
This is the DamBest 358 Open Track Carburetor. They have long since changed the name but it's what I use on the Road Race Mustang, and also on the yet to be installed Sunbeam Tiger motor. On both occations the Dyno operators commented on how amazingly fast the engine response was with these carbs. I can also say much better than ANYTHING Holley has produced.
DamBest Idle Bleeds
First change was to put in a jet for the 3rd Level Idle circuit.The Jets are actually 3/16" 8-32 brass allen set screws. A quick check for a part number from McMaster Carr and I had them the next day. The jetting that was suggested was a 0.052" hole in all four corners of the 3rd Level Idle. I didn't get a picture of the Idle Air Bleeds but they also got the same treatment, a 0.052" Air bleed. Nothing was in the carb as shipped, so this served to fatten up the Idle circuit a bit. I made a little jig threaded for 8-32 screws out of a block of aluminum and put the set screws in, and just drilled them out. Pretty simple, no broken bits either!
DamBest Throttle Blades
With the low vacuum at idle the throttle blades were too far open for good idle mixture control so this fix allowed me to close the throttle blades back to a good position to allow the idle circuits to work properly (and be adjustable). John suggested a 0.125" hole located close to the idle fuel hole (or what ever it's called). You can see each blade has its hole offset to the idle fuel passage.
I used Blue tape to seal up any exposed holes and slots so none of the drilling bits could get in. Then a shop vac did the rest.
DamBest Idle Bleeds
A bit closer shot to see what I'm talking about. I'm guessing that the position of these holes in the throttle blades will promote better mixing of the fuel with the incoming air stream from the hole in the blade.
The Bottom view, back together. The DamBest carb comes with nice reusable gaskets. Another nice thing is the fuel bowls have a sight glass to help with float adjustment (not shown). I think most parts of the carb are made by DamBest except for the fuel bowls. The carb is also much lighter than the Holley 830 Nascar version it replaced, and looks and works a ton better. One interesting thing about blowing the engine, the spark plugs show the last wide open run until it broke. I don't think I have had a car run with as clean of a set of plugs as what came out of the car. I'll post some pics and you can let me know if they are spot on or not!