I'm getting a split second hesitation off the line with my 383 that I built up a while ago. It's done it since I built it but i've always just lived with it. First I need to figure out if its a lean bog or a rich bog. I'm pretty sure its a rich bog because I pull the choke to see if that helps but it just makes it worse.

Assuming it is a rich bog, what should I change? Accelerator pump, accel. pump cam, or discharge nozzle? Is there a way to tell what you should change or is it mostly trial and error?

im going to guess that your accelerator pump arm has too much slack between it and the throttle lever, the same thing happend to me on my383 I just kept making adjustments on the accelerator pump spring until I cleared up the bog.

What kind of carb?If it is a holley put a bigger squriter on it.

could be power valve opening point I had a bad hesitation with the stock 4.5 in my carb at any speed switched to an 8.5 and its perfect at every speed.

What cam do you have and how much initial timing are you running?
What gear and stall?
Also what intake are you using?

Its a holley 4150. 750 double pumper, manual choke, manual secondaries. The cam is a comp solid roller, 236*, 242* @.050, on 110LSA. I can't remember what the initial timing is off hand. Rear gears are 3.73 with a manual tranny. The initake is a Edelbrock RPM airgap.

Burn this into your memory banks: ALMOST ALL BOGS ARE LEAN BOGS. Repeat as necessary.

A rich bog often lasts a good long time, and slowly climbs out of it as RPMs rise- but doesn't have that feeling like "the motor just shut off." A lean bog is somewhere between a split-second "blip" or a 2 second long "I just stuck my foot through into a bowl of cold oatmeal and the motor turned off" kind of affair followed by near-immediate recovery and a$$-hauling from there up.

Accelerator pump issue, if I had to take a guess. Either it's not working properly (misadjustment, slack in the linkage, check valves gummed up or dirty, etc) or the squirter/pump cam is just too damned small. .031" is about the bare minimum for most street applications on the primary side and the primary pump cam should be at least an Orange, just to give you an idea where I often start from. Primary side has proven to be the most problematic in my experieince- most of the time the secondary side is adequate from the factory. If you aren't sure whether the problem is on the primary or the secondary side it's very easy to disconnect the linkage to the secondary throttles and just run around (temporarily) on the primaries to see if the bog problem goes away or not. A few quick 3-second WOT runs is all it will take to zero you in on which side of the carb you should be tuning.

If you aren't sure whether the problem is on the primary or the secondary side it's very easy to disconnect the linkage to the secondary throttles and just run around (temporarily) .


Be careful I lost a motor like this and got about 30 stitches all In the driveway, I took the link out and was reving on the primary somehow the darn secondary opened and went WOT a belt snapped and knocked me out and when I woke up the motor was gone! And itwas a DP not a VC.

^^^^^^:eek: :eek: :eek: ^^^^^^

The secondaries have their own return spring built into the throttle linkage (they do from the factory), plus the throttle plates are offset so that airflow tends to close them, not open them further. Certainly, some care should be taken to make sure you don't end up killing or injuring yourself, but I can't say I've ever had a "runaway freight train" kind of situation doing this and I've done it many times.