vacuum advance problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jaybyrd66 · 02-26-2010, 10:35 PM

got a problem guys. my 66 has an 86 model 350 in it with hei distributor. she will start right up and idle just fine but when i slowly rev it up it will start to stutter like its got a rev limiter, but when i unplug the vacuum advance she will smooth out and rev just fine and if i plug it back up it will start to stutter again. if i drive it with the advance unplugged it doesnt have any power at all so that aint gonna work lol. ive replaced my advance curve weights and springs and also replaced the diaghram that the vacuum line attaches too and its not fixed it yet. any ideas? i really hope so lol

**Corts60** · 02-26-2010, 10:50 PM

It sounds to me like you have a timing problem, not a distributor problem.

I would double check that your initial timing is set correctly. Also, has any work been accomplished recently on the engine?

jaybyrd66 · 02-26-2010, 10:54 PM

well the reason i dont think its timing is that it was running fine and then about 3 days ago it just started acting up on me, i put a new double roller timing chain in it about a month ago and it has ran perfect until now.

**Corts60** · 02-26-2010, 11:01 PM

I'm just wondering because you said that it had no power with out the vacuum advance. That should not be the case. There is still a mechanical advance and when the centrifugal force is high enough (high RPMs) the engine should still have plenty of power. Vacuum is just for idle and off-idle acceleration/street driving performance.

jaybyrd66 · 02-26-2010, 11:20 PM

a may play with the timing a little bit tommorow then, its worth a shot. thanks for the response

**Captainfab** · 02-27-2010, 02:23 AM

Is your vacuum advance connected to ported or manifold vacuum? Definitely check your inital timing. I would pull the distributor cap and give everything a good look and make sure everything is as it should be in there. When was the last time you replaced the cap, rotor, plugs, plug wires ?

thunder71 · 02-28-2010, 09:02 AM

could the coil be getting weak? i have seen this happen with the HEI...

neto · 02-28-2010, 09:47 AM

Could there be a wire that is grounding out with the mechanical rotation of the distributor? Is the module tight? Do you have a coil on top of distributor or on the side?

jaybyrd66 · 02-28-2010, 03:23 PM

the coil is on top of the distributor and ive thought about the coil getting weak, ive got a friend gonna bring one over tommorow off his truck and im gonna pop it on there and see if that helps. thanks to everyone for the replys

02-26-2010, 10:35 PM	#1
jaybyrd66 Registered User Join Date: Jan 2010 Location: Crossville TN Posts: 39	vacuum advance problem got a problem guys. my 66 has an 86 model 350 in it with hei distributor. she will start right up and idle just fine but when i slowly rev it up it will start to stutter like its got a rev limiter, but when i unplug the vacuum advance she will smooth out and rev just fine and if i plug it back up it will start to stutter again. if i drive it with the advance unplugged it doesnt have any power at all so that aint gonna work lol. ive replaced my advance curve weights and springs and also replaced the diaghram that the vacuum line attaches too and its not fixed it yet. any ideas? i really hope so lol

02-26-2010, 10:50 PM	#2
Corts60 Just here to tinker Join Date: Jun 2008 Location: Holland, MI Posts: 3,697	Re: vacuum advance problem It sounds to me like you have a timing problem, not a distributor problem. I would double check that your initial timing is set correctly. Also, has any work been accomplished recently on the engine? __________________ 78 C10 SWB Diesel #1 (wrecked)http://67-72chevytrucks.com/vboard/s...1978+silverado 78 C10 SWB Diesel #2 (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=650751 60 GMC Suburban (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=445526 60 GMC 1000 (sold)http://67-72chevytrucks.com/vboard/showthread.php?t=298235 67 GMC 1500 (sold) http://67-72chevytrucks.com/vboard/s...d.php?t=803695 73 Chevy C20(Daily)http://67-72chevytrucks.com/vboard/s...d.php?t=852767 86 Suburban(summer unit) http://67-72chevytrucks.com/vboard/s...d.php?t=810697 88 Suburban 4x4(sold) Last edited by Corts60; 02-26-2010 at 10:51 PM.

02-26-2010, 10:54 PM	#3
jaybyrd66 Registered User Join Date: Jan 2010 Location: Crossville TN Posts: 39	Re: vacuum advance problem well the reason i dont think its timing is that it was running fine and then about 3 days ago it just started acting up on me, i put a new double roller timing chain in it about a month ago and it has ran perfect until now.

02-26-2010, 11:01 PM	#4
Corts60 Just here to tinker Join Date: Jun 2008 Location: Holland, MI Posts: 3,697	Re: vacuum advance problem I'm just wondering because you said that it had no power with out the vacuum advance. That should not be the case. There is still a mechanical advance and when the centrifugal force is high enough (high RPMs) the engine should still have plenty of power. Vacuum is just for idle and off-idle acceleration/street driving performance. __________________ 78 C10 SWB Diesel #1 (wrecked)http://67-72chevytrucks.com/vboard/s...1978+silverado 78 C10 SWB Diesel #2 (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=650751 60 GMC Suburban (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=445526 60 GMC 1000 (sold)http://67-72chevytrucks.com/vboard/showthread.php?t=298235 67 GMC 1500 (sold) http://67-72chevytrucks.com/vboard/s...d.php?t=803695 73 Chevy C20(Daily)http://67-72chevytrucks.com/vboard/s...d.php?t=852767 86 Suburban(summer unit) http://67-72chevytrucks.com/vboard/s...d.php?t=810697 88 Suburban 4x4(sold)

02-26-2010, 11:20 PM	#5
jaybyrd66 Registered User Join Date: Jan 2010 Location: Crossville TN Posts: 39	Re: vacuum advance problem a may play with the timing a little bit tommorow then, its worth a shot. thanks for the response

02-27-2010, 02:23 AM	#6
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,252	Re: vacuum advance problem Is your vacuum advance connected to ported or manifold vacuum? Definitely check your inital timing. I would pull the distributor cap and give everything a good look and make sure everything is as it should be in there. When was the last time you replaced the cap, rotor, plugs, plug wires ? __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

02-28-2010, 09:02 AM	#7
thunder71 Registered User Join Date: Dec 2009 Location: Carolina Coast Posts: 582	Re: vacuum advance problem could the coil be getting weak? i have seen this happen with the HEI...

02-28-2010, 09:47 AM	#8
neto Registered User Join Date: Jan 2007 Location: Madera, California Posts: 291	Re: vacuum advance problem Could there be a wire that is grounding out with the mechanical rotation of the distributor? Is the module tight? Do you have a coil on top of distributor or on the side?

02-28-2010, 03:23 PM	#9
jaybyrd66 Registered User Join Date: Jan 2010 Location: Crossville TN Posts: 39	Re: vacuum advance problem the coil is on top of the distributor and ive thought about the coil getting weak, ive got a friend gonna bring one over tommorow off his truck and im gonna pop it on there and see if that helps. thanks to everyone for the replys



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