Carb Swap: Edelbrock 1407 to a 1405

[Orion88]

I just got my 79 Silverado on Friday, and I've been driving it everywhere since then. Over the weekend was strictly highway cruising and she did quite well. Lately has been mostly city cruising and she's not performing very well. She tends to sputter, hesitate, cough, etc in the mornings before the engine is up to temperature. Accelerating is a real chore and I'm constantly fluttering the pedal to keep her from stalling out. Once she's up to temperature she does a lot better, but still stumbles from a dead stop or going up a hill. The truck has 10,000 original miles and had sat for several years before now. Part of me thinks the problem could be parts of the carburetor are sticking, such as the float bowl. It could also be the fuel in the tank. I don't know how old the fuel was when I got it but I have since put fresh gas in it, as well as a can of seafoam. The truck has an edelbrock Performer Intake and the 1407 750cfm carburetor. Aside from that it's all original. I have a 70 GTO that I am restoring that has the 1405 600cfm carburetor on it, and I was thinking about swapping the two out. It doesn't make sense to me to have a 600cfm carb on a Pontiac 400 and a 750cfm on a 350 small block chevy. Personally I'd rather have a well-built Quadrajet on both, but unless someone wants to trade me straight up I really can't afford it right now. The truck is my daily driver so I can't have any downtime. Whatever work I do I need to be able to do in one afternoon/late night. When I was still driving the GTO it was almost impossible to start on cold mornings and restarts on hot days was a chore as well. A choke and an original air cleaner should hopefully fix these issues.

So all that being said, any Edelbrock experts have some knowledge/wisdom they can shed on the subject? I'm much more knowledgeable about Pontiac engines than Chevy, and despite both of them being GM, there is virtually nothing similar between the two. I plan on doing the swap this weekend and it shouldn't take more than a half hour. I just want the truck to perform well in all conditions. A well-tuned carbureted engine should fire up every time, in any temperature. And since this is my daily driver I aim to meet that expectation.

[79Betty]

I'd swap em. They should both mount in the same pattern. Someone will chime in on floats and needle's and etc, which is where i'm dumbfounded. BUT i agree, it makes more sence to have a 600 on there. The plugs real black from too much carbon? I have a 600 on mine that is straight from the box, not perfect but will run when i hit the key

[Orion88]

I will be checking the plugs when i get time and the motor is cool. Both carbs are unmodified from the box. No jetting/metering rod changes.

[rich weyand]

I'll see you tomorrow night and take a look at what you've got. Betcha I can fix most of that right in the Hardee's parking lot.

Even simpler would be if you stopped by here some time. I'm sorta-kinda retired, so it's whenever you're free.

[Orion88]

I'm probably going to swap the carb out tonight, that way any issues I have with the 1405 you can help me figure out tomorrow. Even if the 1407 was working just fine it still doesn't make sense to me to have the bigger carburetor on the smaller engine.