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#1 |
Registered User
Join Date: Nov 2009
Location: conrad, montana
Posts: 253
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hey guys i got a 72 gmc 1/2 ton 350 4 speed. the motors got 20,000 since a complete rebuild. its got a quadrajet and i put some headers on it (stock headers off something?) anyways its my DD 30 miles a day. i run scrap 75 miles away every weekend and cruse alot. i wrap the engine up often and sometimes run open headers if im tweaking my exhaust. i have purple hornies 18in header mufflers with about 4.5 feet of 3in with turn downs.
now my problems started when i got the pickup last summer. if it was 60 degrees out it would hardly start, i mean it would start but wouldnt like to keep running. and if it got any colder then that it sucked. anyways i finally acted like i knew what i was doing and adjusted the 2 air fuel? screws. i finally got it dialed down and it ran great for awhile. then one night it was -10 outside and i started it up and it ran on like 4 cylinders for about 10 minutes then it got warmed up and started running right. its done that a couple more times when its been about 15 degrees outside and i cold start it. so anyways the pickup was running great and i was in a town about 20 miles away and i bought a magazine and sat in my pickup idling reading the magazine for about 20 minutes then i drove home. i was on the interstate and the pickup kinda jerked twice on the 20 miles drive. almost like the engine stopped running for half a second. that was about 5 days ago and its got to it will hardly run. i thought it might have been running rich cause it was popping out the exhaust when i was just driving normally, and doing that half second stop alot. anyways i pulled a plug and the (i forget what its called but its not the electrode tip, its what it arcs to) anyways that was almost white(the plugs have about 1000 miles on them) so i turned the 2 air fuel screws out but it didnt much better, its drivableish now. and i got a carb kit that my neighbors going to help me put in so mabey tomorrow. the only thing is that i gassed up in the other town so mabey there was something in teh fuel and mabey plugged the filter? ive gassed up since then. anyways im going to the shop and hopefully ill get it fixed. but any input anyone has would be greatly appreciated! thanks |
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#2 | ||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,936
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Re: 350 running rough
If you rebuild that old Q-jet, it will probably need a throtthe shaft rebush. The shafts that the butterflys are on will "egg out" the holes and cause some serious vacuum leaks. A competent carb shop can do it. There are also rebush kits available for the DIY guys.
Gary
__________________
'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
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#3 | |
Registered User
Join Date: Nov 2009
Location: conrad, montana
Posts: 253
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Re: 350 running rough
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#4 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: 350 running rough
have you changed the fuel filter or just thought about it?
ever try throwin a gan of fuel treatment like berrymans in the tank? maybe try a fuel pumping capacity check? has the gas tank ever been cleaned out?? you can throw carbs at a problem allday long but not getting a steady reliable supply of gas it wont run right with any carb you care to use
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71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY |
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#5 |
Chemist under the hood...
Join Date: Apr 2009
Location: Fort Erie,ON, Canada
Posts: 617
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Re: 350 running rough
You haven't mentioned if you did anything with the distributor. HEI or points type, if points, are the points set properly, is timing set right, plug wires in good condition? There are quadrajet tuning manuals on the web but the quickest things to change out to remove doubt are the distributor parts. These points wear and if you're using it as a DD, they need adjustment. A dwell meter is good or you can do it by ear. To adjust timing, you'll need a timing gun. You can rent these from the autoparts stores.
As for the carb, what I've done in the past (no expert for sure), is turn both mixture screws all the way in and then back them out the same number of turns and start there. Is the choke working properly? Lots of things need to be run down first. Good luck-this board has lots of experts! ![]()
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Current fleet: 2013 GMC Sierra, 5.3L, 4x4 1988 GMC Sierra, 305, Auto 1984 Jeep Grand Wagoneer, 360 V8 1997 VW Cabrio, 2.0L 2017 Toyota Rav4, 2.5L Stuff I wish I still had: 2013 Toyota Matrix [RIP] 1967 GMC 910 Fleetside, 283 V8 [1st Love-SOLD] 1987 Jeep Cherokee Laredo 4X4, 4.0 I-6 [SOLD} 1994 Chevrolet Caprice Classic, 5.7LV8 [SOLD] 1995 Chevrolet Astro AWD, 4.3L V6 (RIP) 1998 Chevrolet Suburban 4x4, 5.7L V8 [SOLD] |
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#6 | |
Registered User
Join Date: Nov 2009
Location: conrad, montana
Posts: 253
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Re: 350 running rough
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im thinking tomorrow ill get a new coil, points, condensor, rotor, and cap? also when i was adjusting my carb i could turn it down untill the engine started to slow down then i turned it the other way and i got to 4 full turns out and it still didnt slow down, i was afraid of turning them all the way out so i turned them out 2 turns from slowing down from the bottom. |
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#7 | |
Registered User
Join Date: Nov 2009
Location: conrad, montana
Posts: 253
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Re: 350 running rough
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#8 |
Registered User
Join Date: Nov 2009
Location: conrad, montana
Posts: 253
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Re: 350 running rough
ok so it turns out my points were burnt so i put some new point in it and when i had the air cleaner off my boss came up and said my vaccume lines were all messed up. we fixed teh lines and it has never ran better!
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#9 | ||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,936
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Re: 350 running rough
Sweet...
![]() Gary
__________________
'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
Quote:
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#10 |
Chemist under the hood...
Join Date: Apr 2009
Location: Fort Erie,ON, Canada
Posts: 617
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Re: 350 running rough
Good to hear. That's why a lot of people go to HEI to eliminate the whole points thing. I still have points-it gives you something to tinker with.
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__________________
Current fleet: 2013 GMC Sierra, 5.3L, 4x4 1988 GMC Sierra, 305, Auto 1984 Jeep Grand Wagoneer, 360 V8 1997 VW Cabrio, 2.0L 2017 Toyota Rav4, 2.5L Stuff I wish I still had: 2013 Toyota Matrix [RIP] 1967 GMC 910 Fleetside, 283 V8 [1st Love-SOLD] 1987 Jeep Cherokee Laredo 4X4, 4.0 I-6 [SOLD} 1994 Chevrolet Caprice Classic, 5.7LV8 [SOLD] 1995 Chevrolet Astro AWD, 4.3L V6 (RIP) 1998 Chevrolet Suburban 4x4, 5.7L V8 [SOLD] |
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Tags |
350, chevy, filter, gmc, idle |
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