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Slight acceleration hesitation driving me mad

I think it's a accelerator pump issue too. Heavy cars actually need a "longer" shot off idle to make it to transition smoothly.

Try a longer profile pump cam, and or put in a smaller squirter. I fixed a 1966 300 this way got rid of most of it, had to go to bigger idle jets too (qft carb)
 
Here's the Holly chart, I ended up using the orange one, don't remember what hole tho

Holley_pump_Cams4777.jpg
 
So you guys think that the original Holley carb on the original stock motor that ran fine for 50 years, now for some reason, needs to have its accelerator pump shot changed.

If changing the pump shot eliminates the hesitation, it will only be a treatment for the symptom, not the problem.
 
10-12 degrees initial with vacuum disconnected.
When done connect vacuum advance &check
total advance at 2500rpm.
Should be around 35degress.
May have to adjust vacuum advance to attain.
 
Agree. I don't think I got the right quote though lol.

I'm no expert but an off idle hesitation would have me looking at the accelerator pump / cam. Engine off, looking down the barrel and you just start to move the throttle back you should see 2 streams of fuel going into the primaries. If it sputters or doesn't shoot immediately adjust or replace parts. It's a lean stumble because the transition circuit isn't adding in enough fuel once the throttles crack open.
thank you what i kind of said.i think the age of the motor in the long run will knead tuning.
 
This is getting to getting way out of hand.
Sounds like simple problem of fuels
available at the pump vs what it was
in1969.
Bump the timing & see what happens
 
You were clear. Ill try a little differently. It did not hesitate before. You touched a bunch of stuff. Now it hesitates. Despite what you think, you've screwed something up.
So you guys think that the original Holley carb on the original stock motor that ran fine for 50 years, now for some reason, needs to have its accelerator pump shot changed.

If changing the pump shot eliminates the hesitation, it will only be a treatment for the symptom, not the problem.

this is my thinking on the subject and haven't been able to communicate that partially because of my inexperience. I been trying to ask why it would need larger squirters or new cam, the cam I assumed maybe wear over time, but the shooters were fine for the past two years I have owned and driven the car have worked fine until I rebuilt the carb.
 
This is getting to getting way out of hand.
Sounds like simple problem of fuels
available at the pump vs what it was
in1969.
Bump the timing & see what happens
I have put the timing at 7.5 degrees btdc and 10,11,12 degrees btdc and none of it worked so I returned the timing back to the service manual specs.
 
You were clear. Ill try a little differently. It did not hesitate before. You touched a bunch of stuff. Now it hesitates. Despite what you think, you've screwed something up.
You were clear. Ill try a little differently. It did not hesitate before. You touched a bunch of stuff. Now it hesitates. Despite what you think, you've screwed something up.

im not disagreeing with you, but I have already done the things you suggested to adjust and fix and it didn't correct the issue. I actually spent hours adjusting and testing and adjusting and testing and it still hasn't corrected the issue, that's at 10, 11, 12 degrees btdc and adjusting the mixture screws with a vacuum gauge.
 
Why did you rebuild the carb in the first place? Was it hesitating? Are the throttle shafts worn?
 
..........and adjusting the mixture screws with a vacuum gauge.

So you haven't adjusted them as suggested.

Look, if I understand your description, it is lean off idle. If it is a pronounced bog when you give it a lot of throttle from a stop, its the accelerator pump squirter system. If it's a momentary hesitation under light throttle from a stop it's the idle circuit being too lean. Just because you adjusted the idle screws with a vacuum gauge does not mean you have them adjusted correctly. The vacuum gauge is a starting point, not an end point, especially if you adjusted them in neutral. 800 rpm in neutral under no-load is completely different than 650 in gear trying to move the car from a dead stop. I've read a lot of vacuum gauges at idle, it it far from precision science. And it gets worse if there is anything else not perfect in the idle circuit, including float adjustment.

Also, if you have a slight vacuum leak somewhere, it will have the very same symptom as well.

If its the larger bog under heavier throttle, its the accelerator pump system. Pretty simple stuff, just go fix it. You don't need to change anything.

As for timing, by 1969, the timing was already a compromise with developing emission requirements. Even then, it was common to advance the timing from the manual's recommendation. Plus today's gas is different. These things are subtle and may, or may not have an effect on your situation. Also, is your timing actually set correctly (correct rpm, vacuum disconnected and plugged......) and is the vacuum advance in the distributor factory original and is it functioning properly? If you have indeed adjusted the initial timing to 15° and it did not help the hesitation, it is likely not the issue.

You can either choose to try some of the advice folks are giving you, or not. But you're the one with the hesitation, not us.

There is a saying used to describe folks with your attitude, "... the operation was a success, but the patient died....".
 
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And it gets worse if the is anything else not perfect in the idle circuit, including float adjustment.
Totally agree with BSB67, on his comments. OP makes the statement, the carb worked okay 'before' he overhauled it. Okay, and yeah, it's okay to overhaul a carb, make minor mistakes, and so on. Today's gas is a crap shoot, along with some of the parts. Accelerator pump in the carb...needs to be good, and work with the gas, to even work right! Float levels need to be right. Carb overhaul kits usually cover several different carb #s, meaning have to be careful to use the exact same gaskets, as the old ones. It's a learning process.

Yeah, should be info in the manual, for the distributors. Twist that rotor, and see what it does. Pull the rotor, look in the end of the shaft, and you'll see a felt 'wick'. Two drops of 30wt oil on that wick.
 
So you haven't adjusted them as suggested.

Look, if I understand your description, it is lean off idle. If it is a pronounced bog when you give it a lot of throttle from a stop, its the accelerator pump squirter system. If it's a momentary hesitation under light throttle from a stop it's the idle circuit being too lean. Just because you adjusted the idle screws with a vacuum gauge does not mean you have them adjusted correctly. The vacuum gauge is a starting point, not an end point, especially if you adjusted them in neutral. 800 rpm in neutral under no-load is completely different than 650 in gear trying to move the car from a dead stop. I've read a lot of vacuum gauges at idle, it it far from precision science. And it gets worse if there is anything else not perfect in the idle circuit, including float adjustment.

Also, if you have a slight vacuum leak somewhere, it will have the very same symptom as well.

If its the larger bog under heavier throttle, its the accelerator pump system. Pretty simple stuff, just go fix it. You don't need to change anything.

As for timing, by 1969, the timing was already a compromise with developing emission requirements. Even then, it was common to advance the timing from the manual's recommendation. Plus today's gas is different. These things are subtle and may, or may not have an effect on your situation. Also, is your timing actually set correctly (correct rpm, vacuum disconnected and plugged......) and is the vacuum advance in the distributor factory original and is it functioning properly? If you have indeed adjusted the initial timing to 15° and it did not help the hesitation, it is likely not the issue.

You can either choose to try some of the advice folks are giving you, or not. But you're the one with the hesitation, not us.

There is a saying used to describe folks with your attitude, "... the operation was a success, but the patient died....".
Sent you a dm
 
*Update* had a little time to finally mess around on the coronet today. Didn’t get to everything, simple adjustments take me longer cuz the learning curve and I may have done some stuff out of Order, not quite sure but here’s what I have done from your suggestions so far. I took the carb off and double checked things on the accelerator pump I replaced from the rebuild, the pump diaphragm seemed to be reversed so I tried switching it reassembling and put it back on the car, started and warmed up rpms came down with the choke opening(used to have to kick them down). When trying to drive it almost died spitting and sputtering at the last timing I had put on it 7.5 btdc, I got a new timing light and double checked the point gap which was correct, set the timing at 15 degrees btdc as bsb67 suggested. The hesitation is better but still there, tried adjusting mixture screws in Park as well as in drive, I’m thinking it may still need more tuning. Oh! And before all this I took the distributor cap off and turned the rotor and released it and it did NOT return to original location. I didn’t get a chance to service this situation as I’m not sure I’m searching correctly online, I been looking up “servicing mechanical advance” this also may be part of the hesitation? I also have an assorted set of accelerator pump cams but wasn’t sure which one I should upgrade to. It’s slowly getting there just not ironed out completely yet. Thanks everyone for your help. I keep the car in a storage unit with no lights or electricity and probably won’t be able to get to it again till next week. I also have a couple pics of the timing and dwell to see if I’m even using this timing light correctly. Thanks again everyone for the help!

B1558EDD-22DB-46CC-87EC-ABF20F5EBC53.jpeg 1E52DEE2-8CA8-48AE-88E4-489EE9240049.jpeg A4D3CFC1-8D35-48C0-9727-A230708A6D5C.jpeg
 
Oh! And before all this I took the distributor cap off and turned the rotor and released it and it did NOT return to original location.
It only hurts once!
Assuming the distributor is the original, okay. Single point, or dual points, doesn't matter. It's time to operate. Not that hard...those things, like anything else get used time on 'em. Then need a little care. Probably either gummed up, or rusted.

Best to simply pull the distributor, to work on it. You need the practice anyway, right! Once it's on the bench, look at how the points 'plate' is fastened to the housing. Probably a couple screws...pay attention to how the parts are in the housing, so when it goes back together, it's right.
The part of the shaft, that the rotor goes on, is separate from the main shaft. Might have to be removed first. Under the points plate, will be the main shaft, advance weights, and advance springs. Look it over, and note how things are there. The weights 'pivot' on the main shaft, moving outwards via RPM. The springs control how fast. There's also 'slots' that limit how much the weights move. Hmmm, could that be the mechanical advance??

If there's any sign of rust, clean the rusted parts. See if the weights easily swing out. Usually lube the pivot points with hi temp grease. Doesn't hurt to do a thin wipe of that grease on the entire weight, to help hold down rust.
On the two shaft parts, you'll see the upper part rides, and rotates, on the main shaft. Clean that area of the shafts, thin coat of that lube, so it moves easily. The felt 'wick' in the upper shaft, is a way to keep it lubed.

Anyway, yep, advance is hanging. Just needs a look see.
 
Horning in on this post so I can read through this when I get time. I had installed lighter dist springs and have a stumble going on under heady throttle I can't get rid of now. Timing adjustments impact it but trying to find the sweet spot or drop the lighter springs...
 
Timing adjustments impact it but trying to find the sweet spot or drop the lighter springs...
Could be advance is coming in too quick. Maybe...
Matter of playing with numbers, to give the engine what it likes.
 
To the OP...in your service manual, probably a break-down drawing of the distributor, in the electric section. That will give you an idea, what parts your looking at.

Also will have #s for it, such as stock advance, so on and such. Those #s were for those day's gas!
 
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