Slight acceleration hesitation driving me mad

[Coronet-383]

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Not sure why this blended in to the original post but this is in reference to the pics above .....Ok so not sure if all the readings made me more confused or not but here’s some pics of the new distributor measurements for mech advance for the new distributor which was .475 which = 15(x2)= 30(36-30=6) so if I’m understanding correctly, when I put this particular distributor on the car my initial timing should be set to 6 degrees btdc so that my total timing advance equals 36 degrees? The original distributor mech advance measurement was .425=11.5 (x2)= 23(36-23=13) which means 13 btdc would be initial timing for that old one, is this correct? Sorry if I sound like an idiot, I’m a Marine and need to break it down Barney style hoping to get this thing on and running again today or tomorrow. Thanks again for everyone’s help.

 

[miller]

The original distributor mech advance measurement was .425=11.5 (x2)= 23(36-23=13) which means 13 btdc would be initial timing for that old one, is this correct?

Correct. And, that's the advance numbers, I'd suggest you try. It's in range to bring your initial timing up where it should be, for the gas.

69/70 was in the year range, when emissions were being included, for engine timing, and so on. And, lower initial timing. Not needed, or wanted, these days.

You can easily stay with the advance springs, with that set. One light, one heavier, that gives a 'two-stage', or curved advance. Usually best for on the street. And, look at what you've learned. Good job!

 

[Coronet-383]

Correct. And, that's the advance numbers, I'd suggest you try. It's in range to bring your initial timing up where it should be, for the gas.

69/70 was in the year range, when emissions were being included, for engine timing, and so on. And, lower initial timing. Not needed, or wanted, these days.

You can easily stay with the advance springs, with that set. One light, one heavier, that gives a 'two-stage', or curved advance. Usually best for on the street. And, look at what you've learned. Good job!

But if I use the numbers from the old distributor wouldn’t that bring my total advance up to 43? (30 mech advance on new distributor + 13 initial timing=43) I thought it was supposed to stay within 34-36. Or am I still confusing that part?

 

[threewood]

But if I use the numbers from the old distributor wouldn’t that bring my total advance up to 43? (30 mech advance on new distributor + 13 initial timing=43) I thought it was supposed to stay within 34-36. Or am I still confusing that part?

You're using the new one, right? Your numbers above are correct for both of those distributors. New one, set at 6 btdc. Or you can swap the mechanical arm from the old one to the new one to get more initial timing.

 

[Coronet-383]

You're using the new one, right? Your numbers above are correct for both of those distributors. New one, set at 6 btdc. Or you can swap the mechanical arm from the old one to the new one to get more initial timing.

Well, the distributor is back in the car, timing set at 6 btdc and still has the hesitation, retuned the carb, dwell is at about 34 degrees, RPMs are about 780-814. It’s getting better but still not completely where it should be. If I slowwly ease into the gas there no hesitation, if I push the throttle relatively quick there is a slight hesitation. Double checked the accel pump cam put it in position 1, spaced the accel pump arm to .015 gap, and in the morning I’m taking the carb off to double check the accel pump diaphragm. If it’s not that I can only assume it needs more initial timing? But if that’s the case my mechanical advance will be over 36 total. Doesn’t seem to be a vacuum leak as the car runs and drives great minus this slight hesitation. Am I missing anything else that you guys can think of? Mixture screws were turned in all the way then backed out about a turn and a half. Thanks again for everyone’s input and patients with my lack of knowledge

 

[miller]

But if I use the numbers from the old distributor wouldn’t that bring my total advance up to 43?

Yeah, it can be confusing. Right now, you have two kinda/sorta the same distributors. But, slightly different. Being the same, for the main parts, the parts can easily be swapped from one to the other! You can easily build the distributor how you want it.

The original distributor mech advance measurement was .425=11.5 (x2)= 23(36-23=13) which means 13 btdc would be initial timing for that old one, is this correct?

The piece with the .425 slots, is the one, I suggested you use. That piece should fit either distributor! That would raise the initial timing to 13 btdc, limit the advance at 23, and give 36 full advance. Choices!
It's all a numbers game. The different parts, give you the choices, of making the distributor do what you want it to.

If you want to keep what you have, at least you now have a working advance.

I'll have to remind myself, what carb your working with.

 

[miller]

To my knowledge everything is all original including the Holley 4160.

Ugh. (I'm a Carter man.)
What kinda shape is that peach in? Clean? Could be a few little things, letting it bog. Start with the basics. Might do a search on that carb, and it bogging, to get clues what to look for. Yeah, hard look at the accelerator pump. Bore, pump itself, and the ports...might even have a check ball in there. Got a handbook?

 

[Coronet-383]

Ugh. (I'm a Carter man.)
What kinda shape is that peach in? Clean? Could be a few little things, letting it bog. Start with the basics. Might do a search on that carb, and it bogging, to get clues what to look for. Yeah, hard look at the accelerator pump. Bore, pump itself, and the ports...might even have a check ball in there. Got a handbook?

Well I fudged it up good boys took the carb off to triple check the accel pump diaphragm, took the front float bowl off, looked for any dirt or sediment in the fuel everything looks pretty clean, sprayed some carb cleaner in the bowl and holes in the metering block, after taking off the gaskets it all looks clean, checked the shooters, hooked everything back up, had a hard time getting it started but finally turned it over and I kicked down the idle too quick and The RPMs started surging slightly, sorta sounded like it had a lopey cam in it (but doesn’t ) here’s some pics I took of the carb, the gasket between the carb and intake has a strange discoloring on it, is this possibly a vacuum leak and maybe the cause of the hesitation? I’m gonna double check all my vacuum connections when I get out of work but not sure why it’s doing this all the sudden. Lemme known if you guys see anything outta place. I’ll try to post a video of it running but it’s hard to hear it. Thanks again guys

 

[RJRENTON]

If everyone is worried about the accelerator pump shot, perhaps a change to Holley's 50cc pump and cover plate maybe the solution. The original accelerator pump diaphragm provides a 30cc shot. This will still allow for experimenting with pump cams to tailor the delivery. Just my opinion of course.

 

[Bee1971]

With the factory four hole intake , why are you running a open plenum carb to manifold gasket ?

I have seen four hole / divided intakes with open spacers and or thicker open gaskets , not respond so well off idle down low

Try a four hole gasket if you can

 

[Coronet-383]

With the factory four hole intake , why are you running a open plenum carb to manifold gasket ?

I have seen four hole / divided intakes with open spacers and or thicker open gaskets , not respond so well off idle down low

Try a four hole gasket if you can

Guess I was going off what came off the carb before the rebuild. It had one originally but it was too worn and compressed the throttle linkage was rubbing and getting stuck on the intake manifold so I replaced it with one that was like I had on it.

 

[miller]

If you still have the Holley down, kill a little time, and re-check the float settings. Yes, get the correct base gasket, and make sure the surfaces on both the intake, and carb base are flat and clean.

Is the accelerator pump diaphragm new, from the kit?

 

[Coronet-383]

If you still have the Holley down, kill a little time, and re-check the float settings. Yes, get the correct base gasket, and make sure the surfaces on both the intake, and carb base are flat and clean.

Is the accelerator pump diaphragm new, from the kit?

The pump is new from the kit, seems like it’s leaking fuel on the base gaskets now, (it’s back in the car). I’m assuming it’s coming from what I took apart yesterday but couldn’t really see much in the storage unit last night. Where would I find the correct base gasket? It needs to be about 1/2” thick or the throttle linkage hits the intake manifold and the throttle sticks

 

[Coronet-383]

The pump is new from the kit, seems like it’s leaking fuel on the base gaskets now, (it’s back in the car). I’m assuming it’s coming from what I took apart yesterday but couldn’t really see much in the storage unit last night. Where would I find the correct base gasket? It needs to be about 1/2” thick or the throttle linkage hits the intake manifold and the throttle sticks

 

[Coronet-383]

Guess I was going off what came off the carb before the rebuild. It had one originally but it was too worn and compressed the throttle linkage was rubbing and getting stuck on the intake manifold so I replaced it with one that was like I had on it.

With the factory four hole intake , why are you running a open plenum carb to manifold gasket ?

I have seen four hole / divided intakes with open spacers and or thicker open gaskets , not respond so well off idle down low

Try a four hole gasket if you can

Any idea where I can find the proper carb to intake manifold gasket that is about 1/2” thick so the throttle linkage doesn’t rub against the intake manifold? Should it even need a spacer in it like that in the first place? Thanks in advance

 

[Bee1971]

I thought the factory 68-69 Intakes used a thin carb base mounting gasket while the 70-71 Intakes used the thicker 5/16” gasket in relation to the choke thermostat ?

Anyways this might work but it’s .250 1/4” thick

https://www.jegs.com/i/Mr-Gasket/720/758/10002/-1

 

[Bee1971]

One more thing

Looking at that carb list number on the air horn

Pretty sure that is not a factory Holley carb

Would explain the carb linkage issue and hitting the factory intake manifold with a thin four hole gasket

 

[Coronet-383]

One more thing

Looking at that carb list number on the air horn

Pretty sure that is not a factory Holley carb

Would explain the carb linkage issue and hitting the factory intake manifold with a thin four hole gasket

I was wondering that, the build sheet says it’s a factory Holley car, maybe it’s not the correct Holley, I’ll double check the numbers. Does the factory thin gasket have any issues with vapor lock or anything? Thanks for the tips.

 

[Bee1971]

If you want to continue running that same carb

And must have at least a 1/2” gasket because of throttle linkage issues

Run one of these

It comes with the 4 hole wood laminate spacer and two 4 hole gaskets and proper length studs

https://www.summitracing.com/parts/edl-8723/overview/

https://www.edelbrock.com/carbureto...2-4-hole-spacer-wood-fiber-laminate-8723.html

Wood laminate is your best heat insulator

I just wanted you to try a 4 hole gasket or 4 hole spacer to match your 4 hole intake manifold for a better carb response signal off idle to see if that would help with your hesitation issue , that’s all

I run a 1/2” wood laminate spacer with my Edelbrock 800 AVS 2 on my 383/432 Stroker

 

[miller]

The pump is new from the kit, seems like it’s leaking fuel on the base gaskets now, (it’s back in the car).

I've dealt with a few of those Holley carbs. So, the pump housing is leaking. Needs to be pulled, and check the sealing surface. Probably not flat! It takes lapping the surface, until it is flat, so it will seal.
Same thing on the base surface of the carb...if not flat, lap it in, until it's flat. Bore sizes change (on any carb) depending on the cfm size. And, it needs to work with the manifold, your mounting it on. No gasket, set the carb on the manifold, work the throttle arm all the way to WOT (wide open throttle), to see if there's any binding. Shouldn't be. If there is, wrong carb or wrong manifold. A spacer can be used, made to fit, so all four throttle blades move freely.
One other note...any time you re-adjust idle speed, you have to re-adjust the pump arm gap.
This stuff ain't rocket science, but Holleys tend to be a little harder to dial in, unless everything is perfect.

Initial timing...assuming you already know. If you have a vacuum advance, before you set initial timing, you pull that vacuum advance hose off the carb base. Cap off that port, then adjust initial timing.

Still don't know, why your having problems with understanding distributor mechanical advance, and working with the numbers. Anyway...another day.

Bee1971 is giving you some good advice! But, basics have to be dealt with, too.