[Cliff R]

The 7029263 carb is not a direct replacement for the factory 455 HO carb. I would correct the lean issue with the HO carb and put it back in place. It is a special carb made just for those engines. Once the lean part throttle condition is corrected nothing out there will work better on that engine.

Also make sure that you plugged the hole in the air cleaner base after the carb swap. The large front vent tube on the HO carb sealed off any unfiltered air that would enter the engine as that hole is after the air filter.

I've seen a boatload of Pontiac engines ruined over the years and the 1971 thru 1979 Q-jets (and 1970 CA emission engines) used a large front vent tube that protrudes up thru the air cleaner base.......

[bruno17]

Thanks for the tip Cliff. I’ll have the original carb back on next week and let you know how it works..

[bruno17]

Originally Posted by Cliff R

The 7029263 carb is not a direct replacement for the factory 455 HO carb. I would correct the lean issue with the HO carb and put it back in place. It is a special carb made just for those engines. Once the lean part throttle condition is corrected nothing out there will work better on that engine.

Also make sure that you plugged the hole in the air cleaner base after the carb swap. The large front vent tube on the HO carb sealed off any unfiltered air that would enter the engine as that hole is after the air filter.

I've seen a boatload of Pontiac engines ruined over the years and the 1971 thru 1979 Q-jets (and 1970 CA emission engines) used a large front vent tube that protrudes up thru the air cleaner base.......

Thanks for the tip Cliff. I didn’t even notice the hole until you prompted me to check.
Just waiting for your parts and I’ll post an update. Added 5 oz of Seafoam in the crankcase and drove a tank of fuel through it.
That and a new PCV has greatly diminished the blue smoke on deceleration.