Quadrajet Problem Solving > Quadrajet Parts and Numbers

29204 Throttle Body

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Kenth:
I have found the main difference of 1969 SBC and BBC throttle plates is the throttle lever.
Since CBB uses either M/T or TH400 no provision for a TH350 detent cable needed.
As for idle bypass air i have found CBB Qjets 9200 and 9215 have the same amount as the CSB Qjets 9202, 9203 and 9207, .072" and .080"-.087" idle needle holes.
With a hotter than standard camshaft larger idle bypass air and idle needle holes may be needed.

HTH

Cliff Ruggles:
Correct, intake clearance is a problem with certain combinations in those years.

As far as the height of the APT it can be a BIG issue depending on the jet/rod combination the carb is using. 

When I build early Chevy and Olds Q-jets that use that system I remove the factory plug over the APT screw, the APT screw, and replace it with one we make here in the lathe.  This has proven to be worth the extra effort as it allows us to not only return the power piston to the same height, it gives us full control of part throttle A/F when custom tuning without taking the carb apart.......Cliff

lintmann:
Thanks Guys, So here is a pic of the passages in my primary ports. From what I'm starting to learn is that I probably don't have to worry about them with this main body but I still wanted to see what you think about them. Should they work okay with my big block carb?

All the jetting, rods, hangar, etc in this carb check out as correct/original and it's a bone stock restoration so given that, is it possible to set up the correct APT without some special fixture? Cliff is this covered in your book? I like your adjustable one that you have but this is a correct "numbers" resto so I'll need to have that plug covering the adjuster when it's all set up.

Cliff Ruggles:
If you can get the APT screw to turn then you can set it wherever you want then put a cap over it.

I can't imagine anyone even noticing the external adjustment screw as it's not visible without getting down low enough to look under the main casting......

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