Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Adjusting carb for higher altitude?

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leeklm:
My 72 qjet is currently running great with #71 jets on a low compression pontiac 400 where I live at 900ft altitude.  I am selling the car to a buyer that lives at approximately 4,000ft.  I assume the carb will run a little rich for him.  Should l lean the Jets a little, or possibly increase the size of my adjustable upper air bleeds?  Or, will the altitude not be a major change in air/fuel mixture?  Thanks!

Cliff Ruggles:
I wouldn't worry about it.  Even at your altitude you'll have days with higher DA than 4000' and I'll bet it works just fine.

BTW, what is the carburetor part number, and application?......Cliff

leeklm:
Thanks for the note Cliff.  Carb is a 7042264 installed on a 400 4x heads, manual trans car.  Basic rebuild with a Comp 268H cam ( I didn't do it :)).  Carb has 72 jets, .039 rods, .036 idle tubes, .055 IDC, and about .09 bypass air.  I sized the mab down to about .070.  all seems to work pretty well, but I do not have an A/F connected.  I am a little short on secondary rods, and only had a .040 or a stockish .052, so installed the .052.

Cliff Ruggles:
For sure not the best cam choice for a Pontiac 400 with low compression and it will like the .072/.039" combination in that carb number.  I certainly wouldn't start leaning it up anyplace even for a little higher elevation......Cliff

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