I've got a 350 in my '84. I've got a Edelbrock performer 750 cfm carb. w/ electric choke and mechanical secondaries(#1411). Lately, I've been noticing the car bogs down if I floor it, but if I floor it and back off a bit it seems to not bog at all and actaully accelerates very nicely. Is this a result of getting too much fuel (having too big a carb.)?? I've been told it's too much carb. but I wanted some second opinions.

I have the adjustement kit for it with different size jets, springs, and rods. Would changing to a smaller jet size help or is the change to insignificant to make any real difference?

 

Speaking from experience it's not too much carb. People will most likely tell you that the mechanical secondaries are your problem. Unlike vacuum secondaries, when you floor it with your carb everything open immediately. This is most likely your bog issue but it's not because of the size of the carb, just the way the fuel is getting delivered. This issue can be tuned away. The rest of the carb guru's here can help you with that. I know the problem and the solution, just don't know how to enact it.

 

First off, the problem is too little fuel, not too much. The reason too big a carb causes bog is that there isn't sufficient air flow through the secondaries to properly pull fuel through the secondary booster venturi (at least not as soon as needed).

The Performer carbs don't have "mechanical secondaries". The throttle base butterfly is opened mechanically, but the air flow through the secondaries is controlled by an air valve arrangement. This is specifically to prevent secondary opening "bog".

The standard Performer series does not have an adjustable AV. The Thunder series does. The Performer AV has a weight on it, and to avoid bog, you'd have to add weight - not a simple task.

Check this out if you haven't already http://www.edelbrock.com/automotive_...ers_manual.pdf . Page 4. There is an auxiliary system to prevent secondary opening bog. If the carb is "too big" for your engine, what that really means is the auxiliary system is too small, and/or the AV is opening too quickly.

Going to leaner rods/jets/springs will only make the problem worse. Since this is a secondary opening issue, don't try to solve it with primary tuning.

 

Interesting... I always thought it was mechanical due to the linkage. Now I'm learned

At any rate, what would be your best suggestion to resolve this problem or at least make it better?

 

Make sure the air valve is closing completely. Make sure you don't have any vacuum leaks.

Is this a new or used carb?

 

I bought it new roughly 2 years ago.

 

It started doing this with no other changes to anything else?

 

Other than a tune-up and a few oil changes... yes, nothing has been touched/changed since the engine/tranny swap, which was when the carb. came into the picture. I thought it was due to the major heat wave we're getting this summer, but does temp. really affect a tuned carb. that much?

 

to answer your question, Put a HOLLEY on it!!!


Just my opinion

 

Yeah, I talked to some techs at a local restoration shop that has done some excellent restorations and they said the same thing. I just don't have the money to spend on a Holley at the moment, so I wanted to see if I could figure this Edelbrock out in the meantime.

 

Any ideas here? Or is just "get a Holley" because that's not going to do me any good right now.