This mod was inspired by Stumper's thread on Street Stock Speedway and the carby mods he's done. When i had my 4011 Holley apart the other day, I noticed that the barrels had some pretty rough casting marks and misalignment between the top and bottom halves of the Venturi.
Might not show there but it's like they took the safe approach with their mouldings and made the top half slightly narrower than the bottom (so there's no chance of any ledge jutting out) with a distinct inward ridge all round. I looked at the finish and all i could see was turbulence and restriction, yet on my little 302 it probably wouldn't make any difference, or so i thought. Regardless, i just couldn't help myself...
Anyway about 10 min with my little Dremel and this is the result:
So i slapped it all back together and did notice a smoother transfer to main circuit but was a little doughy up top compared to before. I figured that more air was flowing around the booster instead of through it, so less fuel was being pulled out and needed more jet to compensate... So i thought (again). Chucked in some 70s up from 67s and it went worse!
Yesterday i chucked in some 64s and was slightly better, so today i thought I'd go way down to 61s and blow me down, it's going pretty good! Maybe the extra flow is giving more velocity and more booster signal, so it draws fuel harder. Hard to tell what's the go in this hot humid weather but it's fine for now.
What I'm trying to say is that messing with fiddly things like carbies can be trouble and can give you the opposite result to what you expect, but if you're keen to learn then this is the only way.
And thanks Stumper for showing what can be done with a bit of man-shed engineering
tpak addict reacted to gerg in Budget upgrades for the DIY
tpak addict got a reaction from Stumps in Budget upgrades for the DIY