General Category > Quadrajet Carb Talk and Tips

Supporting high hp - thin down the pri and sec shafts?

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70GS455:
Is it advisable when supporting high hp (say 600) to thin down the primary and secondary throttle shafts or choke flap shaft (street/strip)?  I've seen this done on throttle body shafts to get a few more cfm by reducing shaft cross section.  The downside is if you get a backfire strong enough to break the shaft, you get instant WOT

Frank400:
  I really don't think it's needed.  Cliff's own carb (on a 600 HP Pontiac motor) is physically 100% untouched except for correct calibration.

  Also, many Stock and Super Stock racers are deep into the 9 sec. range without any physical mods.

  I wouldn't do it if it was me.

Cliff Ruggles:
Complete waste of time on a Q-jet, IMHO. 

We have Q-jets on high HP and Super Stock applications well into the 9's w/o touching the shafts, and many of them are the smaller "750" cfm castings!......Cliff

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