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09-08-2004, 10:40 PM | #1 |
Junior Member
Join Date: Jan 2004
Location: Stillwater, Oklahoma
Posts: 63
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rough idle has me stumped
Aquired a 1970 GMC 350 auto,quad, automatic. Truck runs great as soon as it comes off idle, but at idle the whole truck just shudders. Thought it was a vacuum leak, but could not find one. replaced all hoses just for good measure. Then I found Champion plugs and off-brand points, so they went away. I then went into my fit to be tied mode and changed the entire ignition system over to HEI,(don't tell shuttermutt where I got the parts).With timing at 8 degrees and idle set at 950 (no load), it becomes almost bearable, but still not right. Exhaust sounds like a steady miss, but when I pull plug wires,none of them fail to drop rpm's about 75 to 100. Compression is a little low at 90, but no more than 5 to 7 lbs difference between cylinders and that was on opposite banks. Any ideas before the rest of my hair comes out?
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72 C10 10 yr.daily driver 68 C10 18 yr.money pit 72 Nova all original 99 H.D. Heritage[sanity check] 71 VW topless bug[summer fun] "When I have the money, I don't have the time ; when I have the time, I don't have the money. |
09-08-2004, 10:42 PM | #2 |
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is this a qjet?
sounds like the idle ckt is not working correct.
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Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card |
09-08-2004, 10:59 PM | #3 |
Registered User
Join Date: Jul 2003
Location: north of Phx AZ about 30 miles
Posts: 698
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Had a similar thing happen to me when I first got my truck. It wouldn't idle well at all. I finally found out that the idle screws had beed turned in too far and the points had broken off and plugged the idle circuit holes. Just back out your mixture screws all the way and look at the ehd for a nice sharp point. I have also had the idle circuit plug up with old gas in another car, I just pulled the mixture screws out and blew compressed air in the holes to clear them.
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Andy,Phx AZ '67 C-10 (Ahhh, done at last. Well there is that disk front end I want to put in and...) "23 C-Cab-sold '48 Ford 8N tractor(still working) '67 Scout(Now on the road) '70 MG B.-sold |
09-08-2004, 11:11 PM | #4 |
get up! stand up!
Join Date: Apr 2004
Location: austin,tx
Posts: 345
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sounds almost certainly like a fuel delivery issue-good luck!
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9FT STEPSIDE CLUB 40 1-1/2 ton stake 67 c30 disassembled & for sale 70 gmc 3500 canadian 9 foot "fenderside" pickup 06 silverado 71 vet enjoyed by my retired father wtb-67 chevy 1 ton 9ft stepside-in perfect condition |
09-09-2004, 04:15 AM | #5 |
Not Mine But A beauty
Join Date: Aug 2004
Location: Southern CaL
Posts: 368
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could also be the carb throws too much fuel in to the engine turn her on and accelerate it while watching how much gas goes in
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09-10-2004, 11:27 AM | #6 |
Don't say "Oops!", Doctor
Join Date: Nov 2003
Location: Houston, TX
Posts: 677
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Yep, my guess is your woes center around that damn Quadrajet. You've got an adapter plate, why not throw the 1406 that was on the Nova over on it and see if that clears it up. If not, I'd start tracing the fuel delivery system, but that's a distant second, IMHO.
By the way, I got that PS bracket put on the truck (thanks again, Mike!) and everything's quiet and smooth enough now to make me want to fix the fooking exhaust leaks. I'm thinking real hard about having the pipes welded up and a crossover installed. That 1406/Performer RPM combo is a pretty fair match to the cam even with my advance curve out of whack, but I think a crossover will help beef up the bottom end. Oh, and what's the going rate to have a diff rebuilt? Anyone? My 3.73 Posi howls when my foot's in the gas (goes away when I lift my foot off the pedal). PS: Normally, I'd send Tony and Vinnie to break your legs for robbing the Nova for parts, but since you've pulled me out of some jambs lately, I'll let it slide.
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'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list |
09-10-2004, 11:45 AM | #7 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Is ther a chance that you have water in the fuel? Maybe the gas cap is leaking, or a wall mart locking gas cap that leaks.
Toss a 99 cent bottle of fuel dry in it and drive a few days untoll almost empty and fill it back up. It probably is the Q-Jet...but water in the fuel does exactly what you describe. When the wife and I got together, we got her an 84 Plymouth Reliant. (It was actually a pretty dam good car). this sucker had what I was calling a 'variable miss'. the miss would travel from cylinder to cylinder. I would unplug one wire, and it'd drop and have a steady miss, but then it would kick and sputter as another one would miss and the engine could barly keep the flywheel spinning. The exact same thing would happen when I would unplug any single wire. (Be carefull, this was also the day I discovered that a car's ignition system is WAY stronger than the brigs and stratton that I was suckered into holding the wire while the other guy pulled on the cord) I was about to have the holley 2 bbl rebuilt and the old man at NAPA refused to sell it to me untill i ran a bottle of dryer in it. I'll be damed if that didn't fix it. How is it the old parts guy always knows whats goin on? How did they get so smart? |
09-10-2004, 12:55 PM | #8 | |
Don't say "Oops!", Doctor
Join Date: Nov 2003
Location: Houston, TX
Posts: 677
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Quote:
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'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list |
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09-10-2004, 12:59 PM | #9 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
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I like trouble shooting with the dirt cheap methods...and the lazy man methods.
I'm the laziest and cheapest guy you'll ever meet. (that's not quite true) |
09-10-2004, 02:45 PM | #10 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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i hope when you changed to HEI ignition that you didn't use the original resistor wire if so you'll be burning up the module in short order
i to think use fuel cleaner will help i prefer OUTLAW brand it's the best i've found ,also change the filter in the carb and you might check the fuel strainer in the tank on the fuel pickup assy
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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 |
09-11-2004, 12:56 AM | #11 |
Junior Member
Join Date: Jan 2004
Location: Stillwater, Oklahoma
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OK, I took the adjuster screws out, looks like nice sharp ends and no crud. I then sprayed carb cleaner up the holes. It's amazing how the cleaner can blow back in your eyes faster than it left the can in the first place. Didn't fix it, but it did change it, truck now surges at idle and has an occasional moment of sounding right. Pretty much locks in the carb as the culprit.Thanks for the help, as soon as I can see again I'll pull carb and continue the battle. By the way shuttermutt, I didn't want to steal parts from the Nova, so remember the 350 horse 350 we pulled from your Chevelle? see-ya
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72 C10 10 yr.daily driver 68 C10 18 yr.money pit 72 Nova all original 99 H.D. Heritage[sanity check] 71 VW topless bug[summer fun] "When I have the money, I don't have the time ; when I have the time, I don't have the money. |
10-08-2004, 08:38 AM | #12 | |
Don't say "Oops!", Doctor
Join Date: Nov 2003
Location: Houston, TX
Posts: 677
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Quote:
I'm tellin' ya, ditch the Quads and move to an Edelbrock. You'd be shocked at how well the 68 is running after I put that spacer under it and tweaked the mixture screws per the Edelbrock manual. I'll never put a Quad on another vehicle as long as I can help it. PS: Vinnie and Tony will pencil you in for a leg breaking next Tuesday for robbing that 350. Word has it that they may be appeased with a rearend for my truck. The howl from my Posi is getting worse and the clutches are grabbing even with fresh oil and a bottle of GM additive.
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'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list |
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10-08-2004, 09:52 AM | #13 |
blood type; Retumbo
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I'll have to disagree with you on the Qjet-Edelbreak issue. bring your truck in the spring & we can run them before we tear mine apart.
Bumpster, send me the Qjet & I can-will set it up for you. Todd
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Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card |
10-08-2004, 09:15 PM | #14 |
Don't say "Oops!", Doctor
Join Date: Nov 2003
Location: Houston, TX
Posts: 677
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Hey, I'm not saying they can't be set up to run and I'm not saying they can't be tuned to perform better than a 'Brock, but I've gotta stick with my own personal experience. I should've sent that Q-jet back with you, Todd. I'm sending it to Bumpster!
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'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list |
10-08-2004, 09:42 PM | #15 |
blood type; Retumbo
Join Date: Jan 2004
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and to think I was looking at it wondering if it was for sale. I tell you what, send it to me & at my spring meet I will feed you brats until you cant eat any more. not to mention I will promise to let you sleep in on the weekends.
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Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card |
10-08-2004, 10:40 PM | #16 |
Still drivin' a Rat Rod
Join Date: Sep 2004
Location: Monett Missouri
Posts: 4,925
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Don't dis a Qjet till you've had a good one.I'm running one on my truck right now and it's a great carb.But whenb they go bad,
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Rusty Member #13872 Instead of saying.....you are a discomfort in the back of my front.....one should be able to say...... you are a pain in the *a$#* 71 GMC LWB 49 Chevy 85 Chevy G20 Check out my website |
10-08-2004, 11:14 PM | #17 |
Don't say "Oops!", Doctor
Join Date: Nov 2003
Location: Houston, TX
Posts: 677
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Well, I'm not gonna jump in the middle of yet another carb brand flame war. All I know is that my 'Brock is working great. To each his own, freedom of choice and so forth.
PS: Those brats would almost be worth it!
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'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list |
10-08-2004, 10:03 PM | #18 |
blood type; Retumbo
Join Date: Jan 2004
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& I can fit about 30 of them on my grill!!!!!
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Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card |
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