So I have a 1969 camaro with a 1972 402 bbc in it with a turbo 400 transmission and a mild cam whose operating range is 1200-4600 rpm. I installed an Edelbrock performer intake manifold and performer carburetor 750 CFM.
When I drive the car from first to second gear the car runs well and has decent throttle response but sometimes will backfire, but when I get up into third gear, the engine bogs soo I think we are over carb'd or something. So do I buy a 650CFM carb or do I install some 3:73 gears because I have a really weird gear situation where I get 1.5 turns of the drive shaft for every one turn of my rear wheel (with posi grip). I will take any advice because I'm very frustrated with this car. If I need to explain something in detail let me know.

 

A 750 is not too much carb for your bb. You might want to double check your distributor timing, and the advance. Is the distributor mechanical or vacuum advance? If vacuum, where is it hooked up to?
Considering the bb makes a grunt load of torque by nature, your cam has a bit of a lower operating range. But that wouldn't be the source of your backfiring, I'm just saying.
And your gearing turns don't work out right. Are you sure you have a posi (both wheels spin in the same direction)? What happens if you have only one wheel off the ground? That's how you give the spin test on an open diff, not having both off the ground. By what you said, I have a feeling you may have 3.08 gears.

 

My timing is on 10 right now and i have a vacuum advance on my distributor running to the constant vacuum port on the carb. It does have posi grip cuz both wheels spun when I jacked it up and spun the tire, I even tried it with one on the ground and it wouldn't spin in that case. I just don't think my rpm's are very high after third gear, so i'm getting too much gas or something at that point.

 

What rpm's are you at when in third gear? Without getting into a whole manifold or ported vacuum debate with anyone, just for fun, try moving the vacuum advance hose to the ported/timed fitting on the carb (passenger side) and see if it acts any differently. Also make sure you don't have any open vacuum lines.
With the gears, try turning the driveshaft instead of the tire and see what you get.

 

Fine tuning a carb and a distributor is a art form. Your not going to learn how to do it from this or any forum. It take years to get to the point you can walk up to any car and make it run at it peak. Sound like you really should take it someone who knows how to set up a street/strip motor. If you can find a good one they will dyno tune it. Once you get a good base line you can play from there. I have never heard anyone say that dyno tune was a waste of money. I normally I hear it was the best $400 upgrade I made to the car. Or OMG why didn't I do that a year ago.

If you don't know of a place just ask around at a car show once you get 4 or 5 hot rodders saying the same guy you got your man.

 

I put an edelbrock 650 on it and the engine was starved for gas. Had to keep the carb at an idle of 1000rpm in order for the thing to not kick off. Didn't think it would drastically screw up so much, but that's just my luck. So i'm going to pop that 750 back on and take it to the speed shop and drop the cash there for them to mess with. I just want the damn thing running, it's not a performance engine by any means, so I don't care about all that dyno noise. I just want this car running.

 

wow did you even read the replies??? did you adjust the air fuel mixture screws at all?? might be set to low for the higher rpms but would run fine at lower??
when you installed the new intake did you use silicone on the ends or those crappy gaskets? did you torque it properly??

 

I've done all the basic stuff. I have great vaccume on the carb, there are no leaks on the manifold, Yes i did use silicon and not those crap gaskets on the china wall. Yes I adjusted the fuel air mixture, but it still didn't work. The engine dies if I put the idle anywhere below 800rpm. At that point if I put it into gear, the engine just cuts off because it doesn't get enough gas or something. I've been taking everyone's advice into consideration here and have double/ triple checked my steps. I appreciate all the input, it's just getting real frustrating.

 

What happened when you moved your vacuum advance over to the ported vacuum on the carb (passenger side) as I suggested you try? Vacuum advance will only have an effect on throttle response from off idle up to around 2000~2200 rpm until the centrifugal weights take over. That's why I also asked about where your rpm's are while in third gear, wondering if the engine is lugging in that rpm range? The size of your carb is just right, it's a tuning issue you have.

 

I tried the other vacuum port and it didn't really help. The 750 works great up until i get into third gear and open the throttle. The 650 was just too small. I'm getting great throttle response with the 750, it's just the top end bogs down. I'm thinking it's a metering/Jet issue that can be tuned. I only did the 650 cuz I had it lying around and figured what the hell? I'm putting the 750 back on tomorrow.