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#1
12-19-2016, 07:58 PM
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Quadrajet Base Plates
I picked up a 7029268(1969 400 Auto) quadrajet core which is the correct carburetor for my 69 GP 400. The base plate has a crack on the outer part of the throttle shaft bore. I have a 7028262(1968 400 Auto) quadrajet core as well and was planning to use the base plate from it since it is in better condition. The only difference I can tell is that the idle bypass air ports are about 0.040" diameter on the 7029268 and about 0.094" on the 7028262. Is this difference significant? Is there anything else I should be looking at?
Mark |
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#2
12-19-2016, 08:06 PM
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A bit of patience and Mr Cliff Ruggles should be able to answer your question in fine detail.
Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#3
12-19-2016, 09:17 PM
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It will be fine, but more bypass air does change the idle calibration slightly.
A crack on the outer portion of the correct throttle body usually isn't an issue. When the bronze bushings are installed you can set the new bushing deeper into the bore or use a full length bushing, either way will be a good repair, and it should get bushings anyhow. I haven't seen any of those early TB's that didn't need bushings installed, so basically you'd be killing two birds with one stone.......Cliff
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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#4
12-19-2016, 10:05 PM
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CLIFF's Baseplate bushing kit and ya got a great baseplate & Q-Jet again.
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#5
12-20-2016, 01:11 AM
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Thank you Cliff.
The throttle shaft is bent enough that I cannot rotate it, which is what appears to have caused the crack. I will see if I can get it apart with out further damage. If I have to use the other base plate is it just a matter of adding fuel with the idle mixture screws? Mark |
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#6
12-20-2016, 06:17 AM
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Correct, it was probably dropped which caused the crack.
About all the additional bypass air is going to do is lower throttle angle slightly. Depending on where the timing is at, engine condition, etc, it may not even be noticed.....Cliff
__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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