Carb ??

[mojavered]

950 Proform carb....
Has a hesitation at first throttle.  Thought is was just maybe my setup.  Since I pulled my engine, I let a guy try it out on his engine, same problem.  It pulls great after first stumble, but that initial hesitation is enough to drive anyone crazy.  Is it possible that the power valve is wrong?  How do I know what power valve I should be running?  It has a 4.5 right now.  Maybe I need to be looking into another direction...thanks for reading!

[brads70]

Not enough or too much squirter?

[burdar]

Is it a vacume secondary carb or does it have mechanical secondaries?  Does the car act normal when you're just driving around on the primaries?

[mojavered]

It is mechanical secondary.  It acts normal until you kind of punch it and then it has a hiccup before getting it on.  I thought maybe my floats were too high and it was flooding, but that was not it.

[burdar]

Is there a secondary air door on that carb?  The door could be opening too soon.   I had that problem with a thermoquad.  I had it on a 360 that was in a 76 Charger.  The Charger had 2.71 gears and a convertor with a stock stall.  I adjusted the air door spring so the door would open later but couldn't get the bog to go away.

The engine got put in an 82 Cordoba with a higher stall and 3.23 gears and the problem disappeared.

 

[mojavered]

I had it hooked up in front of an automatic and my buddy had it hooked up in front of a 4 speed.  Same problem, so possibly not related?

[MEK-Dangerfield]

If this is happening when the engine has been warmed up, then I would say it's your pump shot. Those squirters can be changed out to different sizes. You might have 35's in your primaries, but need 33's. or 37's. (This is an educated guess on size). You must be drowning the engine, or starving it of fuel.

[jimynick]

When you say it hesitates, does it cough or backfire through the carb or just bog out. Does it do it when not under load as in just sitting there and hammering it or only when in gear? Ever looked down the carb when wacking it open (wear glasses) to see if the pump shot is full and coming out of both orifices? Power valve won't have anything to do with it unless it's blown and pissing all the time, but it'd be pig rich at idle and you'd smell it. Good diaphram on the accelerator pump, pump cam/linkage optimal? Idle air bleeds to big/open? Lots of questions and damn few answers, but it'll give you a few places to look. 

[mojavered]

It does not backfire, it actually sounds like it takes a breath before it decides to "run"?  I thought it might be a problem with my setup until we threw it on my buddies.
I have never looked down in there while the engine was running and throttled it up.  I have messed with the linkage and saw both sides on the primary squirt.  It seemed like it was fine when cruising and hitting the throttle, but when slowing down for a bit and hitting the throttle or taking off is when it is noticeable. 
I will have to wait until I get my engine back in before I can troubleshoot, but just trying to get some ideas in case there are some possible adjustments or replacements that need/can be done when the time comes.  Thanks!

[Chryco Psycho]

Make sure there is no play in the pump arm so the arms moves as oon as the throttle is moved , if it doesn't stumble with light throttle opening it may be the squirter on the rear pump is too small causing a bog as the seconday opens . To me it sounds like it is going lean as the throttle is opened . if the hesitation is immediate with light throttle the front squirter either has play in the arm or is too small to get enough fuel in fast as the throttle opens
 the PV needs to be at least 1 " lower than the vacuum reading you get at idle in gear  so if you get a reading of 6" which is typical the power valvein there is ok & will nto open until vacuum drops below 4.5 "