Author Topic: Primary rods and jets for 455 Buick  (Read 99 times)

Offline trusty67

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Primary rods and jets for 455 Buick
« on: October 17, 2020, 08:14:51 PM »
I have an early style qjet (73 Buick 7544540) on a 455 engine with a few minor upgrades (headers, aluminum intake, mild cam). It is a 4 speed car and part throttle cruising is hesitating and bucking. So I am assuming it is running lean at part throttle. It idles decent and WOT works fine,  The primary rods are “45B” so they are 0.045” cruise diameter with a .026” power tip. I see on this earlier model you can not adjust the APT from the top. Any suggestions for a good size primary rod for this application? Thanks

Offline Kenth

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Re: Primary rods and jets for 455 Buick
« Reply #1 on: October 18, 2020, 05:59:40 AM »
The application number is stamped on the widest part of carb, between the air valves and throttle blade axles. Not sure about your number.
If it is a 7043240 i would keep the 45B rods and use #75 main jets.
Also i would use .036"-.037" idle tubes and at least .055" idle down channels.
HTH

Offline trusty67

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Re: Primary rods and jets for 455 Buick
« Reply #2 on: October 18, 2020, 04:28:03 PM »
Ok thank you I will look into that

Offline Cliff Ruggles

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Re: Primary rods and jets for 455 Buick
« Reply #3 on: October 19, 2020, 06:29:09 AM »
Even better remove the APT screw in the baseplate and install one of our external APT screws. 

Then you can raise the power piston up/down and have full control of part throttle A/F......Cliff