I had a vacuum leak for (apparently) some time with the 292 in my coupe.  I didn't know for about 3 years.  When I initially bought the car I put on a Holley 650 and was KIND of surprised that I had to jet up a couple o sizes from out of the box.  it would also backfire when I "blipped" the throttle to downshift so I upsized the accelerator pump nozzles.  It ran well enough.  Late season last year I realized it was leaking where one of the runners went into the head. 

I replaced the intake with one I opened up a little and put it all back together.  Now, when I go to pull away from a stop light it bucks.  If I give it a lot more throttle it eventually catches up takes off.  I think it's rich because I can smell gasoline even under soft acceleration.  Not sure where to start or how to know where to start...or if somehow the half hearted port job I did on the intake made a difference and it's somehow lean.  I can't imagine that it's lean because the gasoline smell is so strong.  

Thinking I should jet down a couple sizes before I mess with the accelerator pump nozzle.  Do you think I'm on the right track?

while I'm not an expert on this at all, I would start with looking at the spark plugs before making any changes. They should tell you which way to go with jet size. 

I read what you said about it running rich. I had symptoms very much like you describe back in about 1967. Brand new 1850. I went back to the speed shop and they told me to pull it and bring it in. Opened it up. Brand new Holley with the main jets 10 sizes under what the book listed. Way lean. Changed the jets, problem solved. May not be your problem.

But go look up the factory jet size and see if you’re within 1 or 2 sizes. Check the floats while it’s apart. Set the accelerator pump back. While I’ve never had a carb that didn’t need tuning, I’ve never had one that flat didn’t run new. Not on a mild engine with a single carb.

Reading plugs in the old days worked. Modern fuels, especially ethanol is something I’ve never been very successful with. Soot in the tail pipe, or has it run enough to show?

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Thanks Mike. I kind of had the same thought. Go back to stock.

I bought it brand new and everything checked out. When I had that lien condition with the intake leak, I jetted from 66 to 68. I didn’t realize there was a problem with the intake per se.
When I would blip the throttle, it would backfire, so I now have a 35 accelerator pump nozzle stock would’ve been 31.


It definitely feels better with the 66 jets back in today. I think I’m going to put the stock pump nozzle back tonight and see what it feels like tomorrow.

Just out of curiosity, what’s the manual say the stock jets should be for that model number? The other thought (and this is a little fuzzy) there’s a secondary butterfly adjustment on some Holleys. The screw is under the base plate, so it’s really only accessible with the carb off. There’s some spec for it to be just barely opened. I’ve never dealt with that, just read comment about it. Someone else here should know more.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

"The Holley List" says it should be 66 for the variant of 1850 that I have...and that jives with the fact that my jet assortment kit had 2 pairs of 66s in it.  
The only other thing that has me worried is that I just put a new coil in it.  Same Pertronix Flamethrower that was on it...wondering if that might be my culprit...

On the other hand...I'm guessing the 1850 is probably set up (more or less) to be a good starting point for a 350 with them being so popular...makes sense that without a vacuum leak, I doubt my little 292 should have ever needed 68 jets.  
This is taking off kind of mid-throttle now.  Tonight I could ease into it and it was fine, or I could hammer through the stumble and it felt good.  At about 1800 RPMs, if I have it 1/2 or more throttle to accelerate, it stumbles up to about 2200 or so.  For whatever that means.
The List also says it should have a 31 acc. pump nozzle...so I'll stick one back in tonight or tomorrow.