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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: mikewb on December 28, 2007, 08:11:04 pm

Title: vaccum advance
Post by: mikewb on December 28, 2007, 08:11:04 pm

How can i figure out if my advance is working ?

Title: Re: vaccum advance
Post by: VileZambonie on December 28, 2007, 09:32:55 pm

with a timing light. Idle the engine and apply vacuum and remove vacuum.

Title: Re: vaccum advance
Post by: mikewb on January 03, 2008, 01:41:56 pm

ifi pull the line off and put my finger against it shouldnt it be pulling pressure

Title: Re: vaccum advance
Post by: ccz145a on January 03, 2008, 02:02:08 pm

on the engine side of the line, yes.

Title: Re: vaccum advance
Post by: mikewb on January 03, 2008, 03:46:37 pm

pull which end off? from the vaccum advance or from the carb?

Title: Re: vaccum advance
Post by: mikewb on January 03, 2008, 03:51:24 pm

tried both and dont feel any vaccum being pulled either end

Title: Re: vaccum advance
Post by: ccz145a 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.

Title: Re: vaccum advance
Post by: mikewb 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

Title: Re: vaccum advance
Post by: ccz145a 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.

Title: Re: vaccum advance
Post by: mikewb on January 03, 2008, 04:20:31 pm

done that. still nothing ill check and make sure nothings in the line\

Title: Re: vaccum advance
Post by: Redneckchevy on January 03, 2008, 04:39:46 pm

What kinda of carb do you have? Holley? q-jet?

Title: Re: vaccum advance
Post by: mikewb on January 03, 2008, 04:42:32 pm

edelbrock 1406

Title: Re: vaccum advance
Post by: Redneckchevy 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

Title: Re: vaccum advance
Post by: mikewb on January 04, 2008, 02:20:32 pm

i found that under throttle it pulls vaccum. must be another problem