Quadrajet adapter plate

[Mertz]

I am going to convert my 350 from an Edelbrock carb to a Quadrajet. I have a performer manifold that is only for a square bore. How much performance will I loose by using an adapter plate? I understand it is best to use a 4 hole plate rather than an open plate.

I am looking for better normal driving gas mileage while having some more power to pull my 5000lb trailer up a 7% grade. It really bogs down now and has to down shift frequently. I am hoping the bigger secondaries and the way they work on the Qjet will make it easier to climb the long hill.

I have a stock cam, MSD ignition, roller tip rockers and ceramic coated headers. I have the time set as far advanced as I can. It did ping a little with the trailer but not under other conditions. I switched to higher octane and the ping went away. It also got better mileage without the trailer going from fishing hole to fishing hole.

[Longhorn Man]

I don't know that a 4 hole one would work with a quadrajet, the huge secondarys may hit. I would just get an open one. Generally, they tend to help torque a tad, and help upper end power too. However, they are so sensitive to design of spacer/adapter and to engien combo... there is absolutly no way of telling what it'll do.
in all reality, you'll probably notice little to no chainge that is spacer/adapter related. If you feel anything, it'll probably be the carb you feel.
Just stay away from the goofy ones that look restrictive.

[Billla]

The purpose of the large secondaries in the Q-jet was to provide better low-speed driveability and fuel economy. You'll see zero difference from the swap. There's probably money well spent for a higher stall torque converter as well. Anything more than 36 degrees mechanical advance won't make more power - and an adjustable vacuum advance is probably a good choice.

IMHO, the problem is tuning, not the carb.

[Longhorn Man]

bill, if he has a stock engine, and is trying to get better MPG, why would he not be better off with the quadrajet?