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| Vacuum question [message #288278] |
Tue, 06 October 2015 14:02  |
bpimm
Messages: 211
Registered: June 2013
Location: Washougal Washington
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Senior Member |
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This spring I pulled the exhaust manifolds and the intake manifold for a gasket changes. The exhaust manifolds are cracked so headers are in the near future, the cracks are n the flange so the remflex gaskets have taken care of them for the short term, I used the intake gasket from Applied with the stainless exhaust crossover block off plates. It seamed to go together well but I'm wondering if I didn't get a good seal on the intake manifold because I'm only getting 15 inches of vacuum at idle and the right exhaust sounds funny compared to the left.
A little history, Fuel tanks were full of crud, they have been cleaned an reinstalled including all new lines, Carb has been rebuilt by me as I don't have the proper carb numbers to have one of the experts do it. I got the kit form Cliffs high performance who said he knew the GMC carbs and could make this one work.
I added a wideband oxygen sensor to aid in tuning the carb which I haven't started yet because of the low vacuum readings. My fuel mixture on my last trip runs from 9 to 13 spending most of the time in the 9-10 range even cruising, the other problem I see is I can't adjust the idle mixture the screws seem to have little effect and it is bubbling gas out of the primary venturies even at idle. So I'm wondering if the low vacuum is letting the metering rods actuate before they should and could that cause the over rich mixture.
The only vacuum actuated items hooked up are the brake booster (which may be a source of a leak, haven't checked it out yet) and the vacuum modulator. the distributor is hooked to the carb ported vacuum I think.
Any ideas on how to track down the source of the low vacuum would be appreciated, hoping it's not internal engine problems, the coach has 81000 miles on it and has a rebuilt engine, I don't know anything about the rebuild I just found the heat disk that rebuilders use glued to one of the freeze plugs and it wasn't melted.
Brian & RaeDean
1973 26' #383
Washougal WA
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Vacuum question
By: bpimm on Tue, 06 October 2015 14:02 |
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Re: Vacuum question
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Re: Vacuum question
By: bpimm on Tue, 06 October 2015 16:53 |
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Re: [GMCnet] Vacuum question
By: USAussie on Tue, 06 October 2015 16:32 |
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Re: [GMCnet] Vacuum question
By: bpimm on Tue, 06 October 2015 16:58 |
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Re: [GMCnet] Vacuum question
By: USAussie on Tue, 06 October 2015 17:44 |
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Re: Vacuum question
By: bpimm on Tue, 06 October 2015 17:29 |
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Re: Vacuum question
By: bpimm on Tue, 06 October 2015 18:21 |
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Re: [GMCnet] Vacuum question
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Re: [GMCnet] Vacuum question
By: bpimm on Wed, 07 October 2015 08:28 |
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Re: Vacuum question
By: bpimm on Wed, 07 October 2015 13:38 |
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Re: Vacuum question
By: bpimm on Wed, 07 October 2015 19:05 |
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Re: Vacuum question
By: bpimm on Wed, 07 October 2015 15:33 |
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Re: Vacuum question
By: bpimm on Wed, 07 October 2015 19:26 |
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Re: Vacuum question
By: bpimm on Thu, 08 October 2015 22:00 |
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Re: Vacuum question
By: roy1 on Fri, 09 October 2015 00:43 |
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Re: Vacuum question
By: bpimm on Fri, 09 October 2015 10:17 |
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