General Category > Quadrajet Carb Talk and Tips

Base setting for throttle angle

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Pav8427:
I am setting up a 17058253 for a friend. I cant seem to find in the book or here any reference to a good base setting for when the secondary throttle plates should start to open. Is there a prefered angle that the primaries should be at when the linkage should contact or start opening the secondaries?

Cliff Ruggles:
The opening point is determined by which linkage is being used.   Some Q-jets used on trucks and larger CID applications have linkage that provides a later opening point.....Cliff

Pav8427:
As it sits now with pri/sec set at 90, I have 62* from  base plate. Its going on a .06 over 67 Pontiac 400 w/4sp. I'm told a 268 comp cam and 67 factory intake. The motor was built quite a few years ago,so I am guessing one of the early 268 cams. # 143 heads.  Not sure of what gears.

Frank400:
   I play mostly with M4MV Qjets, and usually see between 43 and 48 degrees of primary travel before the secondary crack open.  Last year I rebushed a baseplate for a friend's 7042270 (1972 455 HO) and the primary traveled 42.5 degrees before the secondary cracked open.

   hope this helps,

      Frank.

Pav8427:
Thank you. That does help. There doesnt seem to be much discussion on this subject 'out there'. Is there a proper term related to this setting/adjustment? Any search of quadrajet secondary anything most always pertains to air valve adjustment. Kind of like reading Cliffs book. The more you read it, the more you learn. (And retain)

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