I bought a 34 Ford Pickup with a 455 Olds engine, big Isky cam (no idea which one), Carter AFB carburetor (competition series 625 cfm) and vacuum advance points style distributor. It ran but it wasn't adjusted in. The vacuum wasn't hooked up on the distributor. The timing was set at 24 degrees. The carburetor wasn't adjusted. It smelled like raw gas coming out the exhaust. The carburetor jets were set at around 4 turns out. I hooked up the vacuum advance to manifold vacuum to the distributor. Turned the carburetor jets to 2 1/2 turns out. Brought the timing down to 12 degrees. Adjusted idle. Vacuum is 14 inches at maximum vacuum. I was told to advance the distributor until I got the maximum vacuum and back it off 1 inch and then adjust the low side carburetor jet to maximum vacuum and then run it up to 1500 on the high speed jet (left side) until I got maximum vacuum.
My problem is that I don't have enough vacuum to adjust the carburetor jets with these settings. When I step down on the throttle the engine wants to bog out. But once the rpms are up it runs fine.
Can you please tell me if there is something I'm not doing or something that I can do to change to make it run better other than just backing the distributor off a little bit to stop the bog. Is there a better type of distributor that will work or a way to adjust the vacuum and carburetor that I have.

 

Timing may be a bit retarded.
Hotter cams require less advance at high speed, but more at low speed, so the motor could need more advance at off-idle speeds.
Why not see how it runs with a bit more advance? If it doesn't ping, advance some more, then find a sweet spot.

- Eric

 

I think that is a reasonable idea and would second that. With an unknown cam it sure wouldn't hurt to play around a little from the stock specs. You might also double check you dwell on the points, I have found that it has an effect on idle quality for the same advance and carb settings. This might bring up the vacuum on the low side a little too.

Oh, welcome to CO.

 

I believe the vacuum advance needs to be on ported vacuum. Before attempting timing adjustments, set your point dwell to 30 with curb idle set somewhere between 650 and 750 rpm. The initial curb idle timing should be somewhere around 9 deg with your overall timing with advance set to 34 deg @ 2500 rpm, for a start. (adjust curb idle timing hi enough to get good throttle response and total timing to get the best acceleration without engine surge or pinging) Depending on the cam and jets installed, you probably will run a little rich, although most run a 750 cfm for that size engine. I adjust my carb with a tach. Set curb idle around 650 -750 rpm first. Adjust each jet individually first turning the scew in to a rough idle and then slowly out to get the highest curb rpm reading on the meter. The 2 1/2 turns is a good starting point.
Hope this helps!

 

Smelling raw gas is never a good thing!
I'd suspect an internal leak in the carb, and/or a slipped balancer.
I've had large cams in a BB Chevy that pulled 12 inches of vacuum!
I'd borrow a carb you know is good and see what happens, [easiest first] and if that didn't help, find TDC in #1 spark plug hole, and see where your balancer is!
If niether of these things help, pull the distributor, and see if the shaft play is way out, = bad bushings!
If you're sure there's NO vacuum leaks, first!