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Author Topic: Supporting high hp - thin down the pri and sec shafts?  (Read 1554 times)

Offline 70GS455

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Supporting high hp - thin down the pri and sec shafts?
« on: September 20, 2017, 01:59:56 PM »
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
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Offline Frank400

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Re: Supporting high hp - thin down the pri and sec shafts?
« Reply #1 on: September 20, 2017, 10:37:23 PM »
  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.
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Offline Cliff Ruggles

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Re: Supporting high hp - thin down the pri and sec shafts?
« Reply #2 on: September 21, 2017, 04:20:18 AM »
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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