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

mwmeador38 · 08-08-2012, 08:44 PM

ok i've got this 66 283 two barrel truck with a carburetor that is apparently not original. it's a holly. the truck has never idled when cold (no choke) and i assumed it was the carb and lack of choke. i have to baby it for like fifteen minutes before i can finally put it in drive. i was fiddling with it tonight and found a vacuum advance problem. the vacuum advance seems fine - holds vacuum and all, but when i try to manually advance the distributor body it's REALLY hard to rotate. the truck has sat a lot but the distributor advance is not frozen or any thing. it's just so hard to rotate that it hurts my fingers to do it. the advance weights open apart just fine. any ideas? is there a spring under there that's way too tight? i've got the idle mixture screw on the holly at max idle and it doesn't help a bit.

Rich 5150 69 · 08-08-2012, 09:04 PM

The center shaft which is supposed to rotate a few degrees is probably gummed up with old grease, you can try to soak it down with WD 40, but I`m going to guess it would be easier to pull the distributor and clean it well with a good degreaser, (Berrymen in aerosol cans ) and re-oil it with 30 weight engine oil, a light coat of WD40 on the top advance weights. and reinstall it.

markeb01 · 08-08-2012, 09:06 PM

This may seem like a silly question, but are you sure the distributor clamp/bolt is loose enough to rotate the distributor body. Some of the older two piece wire types need to be backed off quite a bit before the distributor will rotate freely.

Another way to check the vacuum advance is to remove and plug the present vacuum connection, and with the engine running hook of a line from a full manifold vacuum source. The timing marks on the crankshaft should advance smartly.

mwmeador38 · 08-09-2012, 03:24 PM

i'm not trying to turn the whole distributor. i am trying to turn
the mechanism INSIDE the distributor the same way the little
arm on the vacuum advance should do when vacuum is applied.
it is just super hard to turn. it should rotate counter-clockwise.

Wrenchbender Ret · 08-09-2012, 04:05 PM

The spring for that is built into the vacuum assem. Yes it is hard to turn the advance plate by hand. You need a hand vacuum pump to pull it in to test it or remove the retaining screws.

mwmeador38 · 08-09-2012, 07:43 PM

hey thanks for that reply. that makes perfect sense to me.
i will remove the advance assembly and see what i have.
maybe different assemblies have different spring tensions.
i know when i plug the vacuum line on it the idle speed does
NOT increase.

08-08-2012, 08:44 PM	#1
mwmeador38 Registered User Join Date: Sep 2010 Location: Decatur, Texas Posts: 31	vacuum advance problem ok i've got this 66 283 two barrel truck with a carburetor that is apparently not original. it's a holly. the truck has never idled when cold (no choke) and i assumed it was the carb and lack of choke. i have to baby it for like fifteen minutes before i can finally put it in drive. i was fiddling with it tonight and found a vacuum advance problem. the vacuum advance seems fine - holds vacuum and all, but when i try to manually advance the distributor body it's REALLY hard to rotate. the truck has sat a lot but the distributor advance is not frozen or any thing. it's just so hard to rotate that it hurts my fingers to do it. the advance weights open apart just fine. any ideas? is there a spring under there that's way too tight? i've got the idle mixture screw on the holly at max idle and it doesn't help a bit.

08-08-2012, 09:04 PM	#2
Rich 5150 69 Registered User Join Date: Nov 2009 Location: Galt, Calif Posts: 2,437	Re: vacuum advance problem The center shaft which is supposed to rotate a few degrees is probably gummed up with old grease, you can try to soak it down with WD 40, but I`m going to guess it would be easier to pull the distributor and clean it well with a good degreaser, (Berrymen in aerosol cans ) and re-oil it with 30 weight engine oil, a light coat of WD40 on the top advance weights. and reinstall it. __________________ `64 C10 vortec 350/350/373 posi `69 RS/SS 350/350/308 `37 Ford 406/350/324 traclock `68 Dart 370/904/323 suregrip

08-08-2012, 09:06 PM	#3
markeb01 Senior Enthusiast Join Date: Feb 2007 Location: Spokane Valley, WA Posts: 8,356	Re: vacuum advance problem This may seem like a silly question, but are you sure the distributor clamp/bolt is loose enough to rotate the distributor body. Some of the older two piece wire types need to be backed off quite a bit before the distributor will rotate freely. Another way to check the vacuum advance is to remove and plug the present vacuum connection, and with the engine running hook of a line from a full manifold vacuum source. The timing marks on the crankshaft should advance smartly. __________________ My Build Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=444502

08-09-2012, 03:24 PM	#4
mwmeador38 Registered User Join Date: Sep 2010 Location: Decatur, Texas Posts: 31	Re: vacuum advance problem i'm not trying to turn the whole distributor. i am trying to turn the mechanism INSIDE the distributor the same way the little arm on the vacuum advance should do when vacuum is applied. it is just super hard to turn. it should rotate counter-clockwise.

08-09-2012, 04:05 PM	#5
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,229	Re: vacuum advance problem The spring for that is built into the vacuum assem. Yes it is hard to turn the advance plate by hand. You need a hand vacuum pump to pull it in to test it or remove the retaining screws.

08-09-2012, 07:43 PM	#6
mwmeador38 Registered User Join Date: Sep 2010 Location: Decatur, Texas Posts: 31	Re: vacuum advance problem hey thanks for that reply. that makes perfect sense to me. i will remove the advance assembly and see what i have. maybe different assemblies have different spring tensions. i know when i plug the vacuum line on it the idle speed does NOT increase.



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