#21  
Old 04-26-2022, 11:43 AM
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Lets take a few steps back here and let me ask something that may have been answered in this string already.

Was the car ok before whatever happened to the fuel pump made you have to replace it?

I think you have something else going on that's not fuel supply related because if the motor at part throttle was not getting enough fuel to go up a slight grade it would be popping back thru the Carb, which is something you have not reported.

Keep in mind that in testing your ignition system voltage that meters only take very very small amount of current to make a reading.
It's quite possible to read good voltage where you should, but a poor connection may not be providing enough current to run the HEI system as needed.

If it where me I would be at the point of testing for proper spark output as described in post number 18.

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  #22  
Old 04-26-2022, 01:09 PM
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Well,
1. Got the correct gasket on, no vacuum leak now. still noticed power loss tho.
2. Remove hei coil ohmed it seemed ok, I had another new coil and went ahead and used it instead. When screwing new coil down the ground screw stripped or was stripped, so my thought is that it was stripped, hei ground strap was the problem the whole time. Thanks for all input.

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  #23  
Old 04-26-2022, 02:10 PM
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So your all back to being good?

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Old 04-26-2022, 02:49 PM
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Yes sir

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Old 04-26-2022, 03:08 PM
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Great to hear, enjoy!

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Old 05-07-2022, 03:01 PM
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I was gonna start a new thread but thought all the help I have received so far and the things i have done would help others know where im at on this.
Well I thought all was well, not. I did get it to stop stalling (COIL or coil ground) and vaccum leak fixed (correct gasket), but I still had a problem about 1500-2000 rpm and up of bad hesitation/ no power. So I said if the coil was bad for the stalling problem must now be the hei control module (chinese crap). I had one and put it on it didnt like it run worse, so i put the other back in. My son and I had already agreed that if the module did not fix it we would take the demon 1900 carb off my 60 c10 and put on the gto, we did and other than a vaccum leak it ran great no hesitation, we put the gasket that was on the afb and now no vacuum leak starts, idols and runs real good. I would rather run the afb. With afb it starts good idols good just the super bad hesitation. Son kept saying carb I said electrical, he won, lol. I rebuilt carb while doing engine bay detailing, I have rebuilt a lot of tripowers carbs and a few elderbrocks, and others over the years, not sure how it ran before I just bought the car. any ideas let me know. thanks

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  #27  
Old 05-07-2022, 03:15 PM
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Rebuilding the AFB is no different then the Edelbrock carbs.
To me now that you have narrowed it down to a carb issue would be that one or both of the power pistons is hung up in the downward / idle position, or today’s crappy fuel has gone bad and now there’s jelled up crap that needs to be flushed out from the passages that go from the primary jets to the discharges in the boosters of the primary bores.

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Old 05-07-2022, 05:08 PM
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Steve thanks, carb should be cleaned soaked in carb clean solution and blew out. Will check it out along with power pistons.
A simple question I should know, can the pvc line from the valley pan to the 2 intake nipples in front of the carb cause any problems if they are loose leaking, we made sure all that was tight when we put on the demon carb, just wanted to be sure that didnt fix afb hesitation?
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  #29  
Old 05-09-2022, 09:03 AM
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does anyone have a pic of a afb carb where the distributor vacuum goes to, when i got car it was in the rear of carb, because i thought i saw a manual with it in the front, i moved to front, i also added a brake vacuum booster which is in the rear of carb. went for another drive yesterday with the demon on it, ran great. while afb still off, i went thru it again found some little holes i dont think i blew out and just double checked everything hope it works when i put it back on today and go for a drive. thanks

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  #30  
Old 05-09-2022, 10:09 AM
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https://www.gtoforum.com/threads/vac...65-afb.133407/ Looks like the factory used the hollow stud in rear for full manifold vacuum. You can use the front left port on your carb if you choose to run a ported vacuum signal.

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Old 05-09-2022, 06:58 PM
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thanks 400, thats what i needed.
Put the afb back on went for a drive, its about as far as hesitation goes about 90% better still a little catch up to itself but definately drivable now. I think its good enough till i find a 65 or 66 tri power intake and carb setup. Trying to keep from spending the money, gonna paint it this fall. But if a deal comes around. Thanks for all the help.

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Old 05-12-2022, 08:14 PM
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went for another drive today, seems like its surging just cruising around 2500 rpm or so. did not do that with the street demon. any ideas.

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  #33  
Old 05-12-2022, 09:07 PM
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Quote:
Originally Posted by convgto View Post
went for another drive today, seems like its surging just cruising around 2500 rpm or so. did not do that with the street demon. any ideas.
Surging at cruise?
A. Lean fuel mixture

B. Too much spark advance (generally, but not always too much travel on the vacuum-advance canister.)

C. Excess EGR Probably not applicable in this case.

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Old 05-15-2022, 12:47 PM
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Thanks Schurkey, can you explain A and B and what to check or adjust/ fix to fix surge. Does anyone know what to do with the big middle adjusting screw on my carb? My tempest manual says its a idol adjustment, (my carb has a separate idol adjustment screw on the side) the carbs and more dude on youtube says its to let cool air in for california shut it down?? Thanks
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  #35  
Old 05-15-2022, 01:44 PM
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Your carb should NOT have the idle adjustment screw on the side of carb, it has been added by someone not knowing that idle speed is set with the large air screw between the idle mixture screws.

Remove the side screw and set idle speed to 600 rpm with the air screw (500 in drive for A/T) and start with the mixture screws 2.5 turns out from lightly seated and adjust for best vacuum/rpm, reset the rpm and finally check the mixture screws for the same amount of turns out for both when finished.
All settings on fully warmed up engine, choke off (and in drive A/T).

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  #36  
Old 05-19-2022, 04:33 PM
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Kenth, Did all the items you mentioned, running much better without surging. I am getting a little hesitation tho, seems to have to catch up at changing gears (4 speed). Definately drivable. What should my timing be on a all stock 389 except for HEI dist. I have it at 8. Thanks

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  #37  
Old 05-21-2022, 04:20 PM
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Its at 8 at idle and 24 at 2500 rpm. vacuum plugged.

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Old 05-21-2022, 10:59 PM
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Quote:
Originally Posted by convgto View Post
Its at 8 at idle and 24 at 2500 rpm. vacuum plugged.
Is the advance "all in" at 2500? If so, that's probably too low an RPM.

24 degrees is not enough advance. I'd expect another 10-ish. Low-to-mid-30s is pretty typical; and at or around 3200 rpm.

Plus another 10--15 from the vacuum advance.

Consider increasing from 8 initial to 15 and see what happens.

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Old 05-22-2022, 08:30 PM
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Schurkey my bad, those numbers were not plugged. is it ok then. thanks

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Old 05-22-2022, 09:23 PM
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Quote:
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Schurkey my bad, those numbers were not plugged. is it ok then. thanks
???

You're saying you have only 24 degrees of timing advance WITH the vacuum advance operating? Hose NOT plugged?

Doesn't make sense. The engine would be a complete DOG.

Start from the beginning. Engine fully warmed-up. At curb idle, in gear, wheels chocked and park-brake engaged. Vacuum advance hose removed from the advance canister and plugged.

What is the initial advance? I'd expect 15-ish, but that depends on the centrifugal advance curve.

Put trans in Neutral or Park, rev engine until the timing advance stops increasing. Note the RPM and the amount of advance. I'd expect 35-ish at around 3200 rpm. Don't stand in-line of the engine fan. The hospital bills are quite extensive if the fan explodes.

Return to idle, in Park or Neutral. Note the amount of advance. Connect vacuum pump (hand-held or otherwise) to vacuum advance canister. Add vacuum until the vacuum advance is fully actuated. Note amount of additional advance. Ideally, 10--15 degrees. Then you need to verify that the vacuum advance hose actually gets vacuum when it's supposed to. Manifold vacuum source should have vacuum anytime the engine is running at part-throttle, including at idle. Ported vacuum source should be the same as manifold vacuum source, except it's shut-off (no vacuum) at idle. Use manifold, or ported--whichever works better for your vehicle and driving style.

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