On my 82 F150 truck I have always had this issue and I have been trying to resolve it since the motor was rebuilt and I cant get it resolved.

What happens is this. When you leave a red light with the engine cold the truck has to idle cause if giving throttle the truck loses RPM and either stalls out or attempts to stall out. Once the engine is warmed up when you leave a red light the truck has a drop in rpm and then the rpm pick back up like the engine dropped out for a second.

The thing that is confusing me is it doesnt do it all the time once warmed up and that if you are already rolling and you step down on the throttle the truck some times has a slight hesitation but 99% of the time there is no hesitation.

So far I recently replaced the brake booster as it had a vacuum leak. I reset the idle mixture on the carb and went from a dropping dead every time to where its just a stumble. I then replaced the vacuum modulator as I was having to add transmission fluid and it wasnt leaking it and I found it was sucking fluid into the engine. Made a slight improvement again. last thing I did today was replace the ground cable as the terminal was split and it didnt fit too tight. Still got a hesitation. My boss at work says that its carburation if it does it under a load. Well we've put six different motorcraft/autolite 2bbl carbs on this truck since we had it and had the engine rebuilt and all of them did this reguardless of the tuning. another thing that has me not condemning the carb is that the thing accelerates too good once you are moving. Another thing is I can put the truck in gear and hold the brake and step on the throttle and there is no drop in the rpm when hitting the throttle.

I am at a loss at what else to check the ignition module has been replaced before, both battery cables are now new, spark plugs and wires with cap and rotor and I believe even the dist was replaced.

I am starting to wonder if it could be the C6 transmission has an issue internally causing this or if it could be cause this truck has a stock 302 with a C6 transmission and a 2.75:1 rear end gear ratio and with 31" tires I have is dropping the gear ratio to 2.56:1 to 2.60:1 and this is causing the issue. I dont believe this as the truck gets up and goes too good even when you hit passing gear. Its just when you are leaving a redlight accelerating.

 

A bog or stumble is generally caused by a lean condition. Have you tried moving the accelerator pump link up or down to give it a bigger shot?

Where is you base timing set? When does mechanical advance start? Check the vacuum advance to ensure it's working properly and not leaking, too.

 

I cant say on the timing, I cant get the hose unplugged from the vacuum advance as it is up against the dealer installed AC bracket. I been meaning to get a 90* vacuum boot with a plastic nipple to plug the hose into to make it easier to remove for this.

Can you really adjust the accelerator pump linkage on the Autolite 2bbl carbs? I never messed with them and I am thinking maybe this is it. I know I had to replace the accelerator pump twice already as they were leaking and I was going to check it tomorrow after work to make sure it was squirting fuel. Might need to move it one spot if possible and go from there.

I do know the degree on the balancer that I marked is the oem timing spec and when I checked timing the other day during lunch it was advanced by about 4 degrees since the vacuum advance was still hooked up.

 

Hmm, accelerator pump check valve functioning correctly ?
Idle air/fuel mixture screws too tight ?
If there are 3 holes on the pump arm and you want to increase pump shot then move the arm inward towards the pivot point, if you want to decrease pump shot move the arm out away from the pivot point.
If the bog is only off-idle the moment you mash the gas then it's pump shot, if the bog continues after you have mashed the gas then you have other issues to diagnose

 

It was only on the initial acceleration. I resolved it by going from the middle hole to the top hole which was one up. It appears that going up was increasing the accelerator pump spray. If thats not correct well then my bog was caused by too much fuel then cause I moved it up and it corrected the issue. There is a slight hesitation once in a blue moon but its not the engine losing rpm its just a split moment where theres no change. I can live with that as it could be caused by any number of driveline issues from the larger tires I am running down to the C6 transmission and having many miles on it.

The only thing is if you try to drive the truck while cold and you step down on it the engine shakes now but doesnt stumble and lose rpm. If going up was decreasing the accelerator pump squirt then I might need to try going up but I am contemplating just keeping it the way it is.

 

Moving the rod up should increase the pump shot, so it sounds like it may indeed have been a lean condition.

Does it still have the hot air stove off the exhaust manifold running to the air cleaner? Carbs generally run like crap when they're cold even when they're dialed in hot. Heated air off the exhaust manifolds helps with that.

Other than that getting the timing and advance dialed in may help clean it up as well.

 

good advice...

 

The stove fell off the manifold many moons ago, I think it was back in 1997 or so. So as of now the aircleaner doesnt have any warm air to help it warm up being directed from around the exhaust. I planned on fixing that when I do a header swap. Weld a bolt or two to the forward most pipe and bend some sheet metal to allow air to be drawn between it and the tube.

I havent checked timing yet but I did get some 90* vacuum elbows and I installed it but its still a pita to get on and off the vacuum advance due to the dealer ac bracket. I did only install the plastic hard line into the elbow only up to the barb so I can unplug it in the am to check base timing.

I did the valve cover gaskets today and they were leaking afterwards so I got some stuff to do with the engine tomorrow and I will check it then. It does run a lot better, and it does pull better too.

 

What is the base timing set at ? If it's too low (retarded) this will contribute to the problem. The accelerator circuit in the carb can be another problem area. As will old wornout carbs (you've mentioned using several 2100's, you might want to upgrade to a Holley 2 bbl. The combination of the C6 (horsepower sucker with a 302) and the tire size and gearing will not cause a hesitation, but will result in poor accelleration

 

We tried a holley 2bbl once before. Thing with that is we were always having to adjust the idle mixture as the engine would want to idle rough.

As of now I have the truck running good, I havent checked base timing yet I need to do that and probably will after this post.

What I planned on doing is tracking down a Autolite 4100 carb and have this engine gone through, it uses oil but doesnt smoke nor foul the plugs out. So I want to get this fixed, I also wanted to have a bigger RV cam put in for more hp/trq, I want to swap the oem heads out for some edelbrock performer aluminum heads (or maybe a set of cast iron performance heads). If I go aluminum on the heads I would probably have the compression bumped up to 9:1 to 9.5:1.

Not seeking a hp monster with this build, just a reliable 302 build that makes a good amount of trq. I will just use the stock 302 the way it is though till I have enough money to have the engine and transmission done as well as atleast $5,000 to have the cab and bed stripped down to be refinished.



~update~

Base timing is at 10* BTDC. Emission decal states 8* BTDC is what it should be. Added a couple degrees when I last messed with it I remember now to try and get some more power out of the truck. Didnt change the operating temp as the truck just barely starts to hit the N in normal like always.

 

Yes but only because the carburetor was not calibrated properly and jetted for that engine, most everybody finds themselves unhappy with an out of the box carburetor with generic one-size-fits-all calibration.
Consider paying a few dollars more for a custom calibrated carburetor a carb shop or similar or you may someone local in your area..
https://www.google.com/search?q=carb..._sm=0&ie=UTF-8

 

The idle problem with the Holley most likely was caused by something other than the carb. Once you set a Holley, it stays set, for years to come. As for a reliable, daily driver 302, you cannot beat one pulled from a 94-97 pickup or van. These had the same roller cam as the Explorer/Mountaineer but topped with E7 heads. That cam works fantastic with a carb. Also doesn't hurt to remove the Thermactor bumps from the exhaust ports of the E7 heads and top em with a set of full roller 1.7 rockers

 

This block is supposed to be a brand new block when the engine was rebuilt back in the 90`s. if it is a brand new block as I was told then I would like to think its a roller block. Just dont know if the old 1982 heads would bolt onto a newer block and work.

I will know more when I get around to pulling the heads. I hate to go with aluminum as the engine runs good but I would like to boost this engine up some in the trq department. I just dont know what is in the motor as of now, it could have a damn good RV cam but the heads and 2bbl induction is killing the engine.

 

Well if it's a brand new block, then it wasn't a rebuild The 82 heads aren't doing you any favors, those are about the worst SBF heads made. Nothing about the 1980-85 5.0's were anything to write home about. Weak cranks, weak blocks, poor heads, etc. A 2bbl will not kill torque production though, not that the 302 had much to start with. About all you can do here is look at the timing and gearing without getting into the engine. Gearing would net you better acceleration in a truck. The combination of the C6, those 2.75 gears and the 31" tires are what's killing it, if you had a 460 it wouldn't be so bad, but you're trying to move it with a motor that was never intended to put out massive amounts of torque to start with.