Author Topic: vaccum advance  (Read 5546 times)

Offline mikewb

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vaccum advance
« on: December 28, 2007, 08:11:04 pm »
How can i figure out if my advance is working ?

Offline VileZambonie

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Re: vaccum advance
« Reply #1 on: December 28, 2007, 09:32:55 pm »
with a timing light. Idle the engine and apply vacuum and remove vacuum.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline mikewb

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Re: vaccum advance
« Reply #2 on: January 03, 2008, 01:41:56 pm »
ifi pull the line off and put my finger against it shouldnt it be pulling pressure

Offline ccz145a

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Re: vaccum advance
« Reply #3 on: January 03, 2008, 02:02:08 pm »
on the engine side of the line, yes.
1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)

Offline mikewb

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Re: vaccum advance
« Reply #4 on: January 03, 2008, 03:46:37 pm »
pull which end off? from the vaccum advance or from the carb?

Offline mikewb

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Re: vaccum advance
« Reply #5 on: January 03, 2008, 03:51:24 pm »
tried both and dont feel any vaccum being pulled either end

Offline ccz145a

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Re: vaccum advance
« Reply #6 on: January 03, 2008, 04:08:32 pm »
The engine is the source of the vacuum. Whichever part you disconnect, the side still connected to the engine will have the vacuum. If it does not, then your vacuum source is pluged somewhere or your hose has holes in it and you will have to track it down.
1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)

Offline mikewb

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Re: vaccum advance
« Reply #7 on: January 03, 2008, 04:12:08 pm »
ok thanks. ive pulled it and theres no vaccum being pulled from it. guess ill have to check out my carb

Offline ccz145a

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Re: vaccum advance
« Reply #8 on: January 03, 2008, 04:15:15 pm »
Try varying the throttle a little, some the carb ports are what they call "ported vacuum" and may be a little weak at idle. rev it up a little and see what happens.
1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)

Offline mikewb

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Re: vaccum advance
« Reply #9 on: January 03, 2008, 04:20:31 pm »
done that. still nothing ill check and make sure nothings in the line\

Offline Redneckchevy

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Re: vaccum advance
« Reply #10 on: January 03, 2008, 04:39:46 pm »
What kinda of carb do you have? Holley? q-jet?
1986 Chevrolet K10 Swb "Women love the hood scoop"
1997 Chevrolet K10 Lwb "Dunno what women love"

Offline mikewb

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Re: vaccum advance
« Reply #11 on: January 03, 2008, 04:42:32 pm »
edelbrock 1406

Offline Redneckchevy

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Re: vaccum advance
« Reply #12 on: January 03, 2008, 05:15:39 pm »
Might be time for a rebuild..But u could take a q-tip with the end cut off and push in the port...Dont jam it in and dont force it in ..And see what u find
Also what condition is Ur vacuum line in? ...I no that not the problem..But that could of caused it..Some times that dryrot from the inside
« Last Edit: January 03, 2008, 05:17:59 pm by Redneckchevy »
1986 Chevrolet K10 Swb "Women love the hood scoop"
1997 Chevrolet K10 Lwb "Dunno what women love"

Offline mikewb

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Re: vaccum advance
« Reply #13 on: January 04, 2008, 02:20:32 pm »
i found that under throttle it pulls vaccum. must be another problem