I know most guys never heard of these, but it was already in my 650 Holley vac secondary. The discharge nozzle has two sizes stamped on it: 28 and 40. I think I need a bigger size. Do I order a 31? or do I already have the largest size at 40? This is to cure a launch problem. When I hit the throttle, it sits and does nothing for about 0.2 seconds or so, then goes. Doesn't bog, am told it that its not black smoking on launch. Want to try tuning this one, before switching to a 700 double pumper that will need tuning as well.
This the spreadbore Holley carb?? They have to have the anti-pullover nozzle due to a different accelerator pump passage check ball system. Can't use regular Holley nozzles on a spreadbore carb...but you can use either style on a squarebore Holley carb. I've never seen one with two size numbers stamped on it.....probably the only way you are going to be able to tell actual size is check it with a micro drill set (pin check), or if you've got goo eyes maybe a comparison check to a set of calipers adjusted and locked to .040" to see if hole size appears the same. Inner wall hole is the one you need to measure..the outer face hole is a clearance hole for the shot to come through. Make sure you've got absolutely no slack anywhere in the accelerator pump linkage....some guys take the .015" clearance spec Holley lists as meaning clearance at the idle position...it's not, it is the spec that you should be able to force an .015" feeler gauge between the pump arm and the overide spring at WOT and not bottom out the pump diaphragm.
In lieu of pin drills,etc. , electrical air , mig are , piano wire all comes in various sizes , use youyr dial calipers to measure whatever size wire fits ( or comes close) to the hole in question ..
yes, Holley put these in the primary side of the spreadbore. Did the wire poke, basically eyeballed it after looking at feeler gages. Inside hole appears to be the 28 and the outside hole 40. My guess is the inside hole is what affects the shot and the bigger outside hole is what prevents the pullover. Gonna order a 31 this week, so I'll find out either way. Thanks for the reminder in the accelerator pump linkage.
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