GMCforum: GMCnet » Carb / Vacuum issue

Home » Public Forums » GMCnet » Carb / Vacuum issue

Show: Today's Messages :: Polls :: Message Navigator

Carb / Vacuum issue [message #288553]

Mon, 12 October 2015 10:33

bpimm

Messages: 211
Registered: June 2013
Location: Washougal Washington

Karma:

Senior Member

I'm starting a new thread to continue this discussion, was vacuum question. I was loaned a known good carb from a local GMC'er to test mine against. At idle mine was developing 16" of vacuum, dribbling fuel out of the primaries and running mostly in the 10-12 AFM area. After switching carbs idle now developing 19" of vacuum, not dribbling out of the primaries and operating in the 11-15 AFM area plus it runs a great deal better. the replacement carb is a little lean coming off idle and into the primaries under load it can bog a bit if you don't feather the throttle so it's not perfect but it is much better. it is idling at 14 to 1 and doesn't load up if it idles for an extended period.

So now we know that the carb is the problem. what should I be looking for on the tear down. History is carb was rebuilt by me 2 years ago but I had fuel problems, gunk in the tanks plugging the filter, this has been resolved by cleaning the tanks and replacing all the fuel lines, including hard lines. I had the top off of the carb a few weeks ago to check the float level and everything looked clean inside but I didn't tear it down any further.

Problems are low vacuum, fuel dribbling out of the primaries and little or no effect from the idle screws, which is probably from the excess fuel being pulled from the primaries.

I'm not a carb expert although I have rebuilt and tuned a few through the years, mainly Weber side drafts.

any and all help is appreciated.

Brian & RaeDean 1973 26' #383 Washougal WA

Report message to a moderator

[Message index]

		Carb / Vacuum issue By: bpimm on Mon, 12 October 2015 10:33
		Re: Carb / Vacuum issue By: Bullitthead on Mon, 12 October 2015 11:03
		Re: Carb / Vacuum issue By: bpimm on Mon, 12 October 2015 11:23
		Re: Carb / Vacuum issue By: Bullitthead on Mon, 12 October 2015 11:27
		Re: Carb / Vacuum issue By: Bullitthead on Mon, 12 October 2015 11:29
		Re: Carb / Vacuum issue By: Bullitthead on Mon, 12 October 2015 11:33
		Re: Carb / Vacuum issue By: bpimm on Mon, 12 October 2015 12:05
		Re: [GMCnet] Carb / Vacuum issue By: USAussie on Mon, 12 October 2015 15:36
		Re: [GMCnet] Carb / Vacuum issue By: bpimm on Mon, 12 October 2015 17:31
		Re: [GMCnet] Carb / Vacuum issue By: bpimm on Tue, 13 October 2015 10:01
		Re: [GMCnet] Carb / Vacuum issue By: Loffen on Tue, 13 October 2015 11:32
		Re: [GMCnet] Carb / Vacuum issue By: USAussie on Tue, 13 October 2015 17:19
		Re: Carb / Vacuum issue By: JohnL455 on Mon, 12 October 2015 16:24
		Re: Carb / Vacuum issue By: bpimm on Mon, 12 October 2015 17:45
		Re: [GMCnet] Carb / Vacuum issue By: k2gkk on Mon, 12 October 2015 18:00
		Re: Carb / Vacuum issue By: JohnL455 on Mon, 12 October 2015 19:09
		Re: Carb / Vacuum issue By: mercdave on Mon, 12 October 2015 19:44
		Re: Carb / Vacuum issue By: bpimm on Mon, 12 October 2015 20:09
		Re: Carb / Vacuum issue By: bpimm on Tue, 13 October 2015 14:07
		Re: Carb / Vacuum issue By: roy1 on Tue, 13 October 2015 14:28
		Re: Carb / Vacuum issue By: bpimm on Tue, 13 October 2015 14:59
		Re: [GMCnet] Carb / Vacuum issue By: Kosier on Tue, 13 October 2015 21:07
		Re: Carb / Vacuum issue By: mercdave on Tue, 13 October 2015 14:45
		Re: Carb / Vacuum issue By: bpimm on Tue, 13 October 2015 15:17
		Re: Carb / Vacuum issue By: Loffen on Tue, 13 October 2015 16:15
		Re: Carb / Vacuum issue By: bpimm on Tue, 13 October 2015 17:38

Previous Topic:	[GMCnet] Black water tank
Next Topic:	[GMCnet] What's the light on the roof, at the front.

Goto Forum:

-=] Back to Top [=-

Current Time: Fri May 17 02:25:41 CDT 2024

Total time taken to generate the page: 0.01353 seconds