09-13-2007, 05:10 PM | #1 |
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383 Stumble/miss
Hola fellow Chevy men (and women?),
Hola fellow Chevy men (and women?), I come in need of assistance. I have a 1967 Chevy C-10 with a 383 in her (2 wheel drive auto tranny, no A/C). She has developed a VERY noticeable stumble/hesitation/miss while under load and almost seems to backfire through the exhaust. She seems to idle just fine but as soon as you put a load on her is when the issues begin. I changed the plugs/plug wires/cap and rotor. I have a Crane Fireball digital ignition. After all this I was I got frustrated with it so I decided to take it out to see what it would do. Once I "went through the gears". As I expected it "fluttered" until I let off the throttle... then as I got back down to a cruising speed and pressed the throttle again it wanted to die. I had to feather the throttle for a few seconds before it would get going again. I was thinking maybe a fuel issue but, I just had the carb (Holley 750 vacuum sec.) rebuilt about 8 months ago and then I checked the fuel for water, it's clean. I'm at a lose here. She was running great up till this point. I first noticed it about 7 months ago but went away for 6 months and just got to work on it. It is driving me crazy. Any help would be greatly appreciated. I miss cruising in my ole truck Thank you in advanced Last edited by StrokedOne; 09-14-2007 at 03:26 PM. Reason: missed info |
09-13-2007, 05:44 PM | #2 |
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Re: 383 Stumble/miss
sounds like your carb is advance to far?
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09-13-2007, 05:52 PM | #3 |
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Re: 383 Stumble/miss
Spark plugs or coil, if its not pinging the timing is probably not an issue I would look at the coil first since they usually fail under a load, If both are fine check your valves my 68 did that when a exhaust valve was to tight
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1968 Short Fleet 350/700r4 http://67-72chevytrucks.com/vboard/s...d.php?t=249435 1997 Bagged XtdCab Vortec350/4L60e http://67-72chevytrucks.com/vboard/s...44#post2286144 1993 XtdCab Longbed 4x4 6.5Turbo/NV4500 "Daily Driver" 1985 Toyota XtdCab 4x4 22re/W-56/Dual T-cases, Doug Thorley Header, Homebrew front and rear spring packs, Tons of Mods to suspension and drivetrain, 35" boggers, coming soon ARB's and 5.29's, Possible 4.3/700r4 swap Last edited by Scott68-93-97; 09-13-2007 at 05:54 PM. |
09-13-2007, 05:52 PM | #4 |
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Re: 383 Stumble/miss
you mean the dizzy , and a retarded spark causes backfire throught the exhaust, to far advanced would fire through intake
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1968 Short Fleet 350/700r4 http://67-72chevytrucks.com/vboard/s...d.php?t=249435 1997 Bagged XtdCab Vortec350/4L60e http://67-72chevytrucks.com/vboard/s...44#post2286144 1993 XtdCab Longbed 4x4 6.5Turbo/NV4500 "Daily Driver" 1985 Toyota XtdCab 4x4 22re/W-56/Dual T-cases, Doug Thorley Header, Homebrew front and rear spring packs, Tons of Mods to suspension and drivetrain, 35" boggers, coming soon ARB's and 5.29's, Possible 4.3/700r4 swap Last edited by Scott68-93-97; 09-13-2007 at 05:53 PM. |
09-13-2007, 07:34 PM | #5 |
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Re: 383 Stumble/miss
Thanks for the advice..
I was thinking the same thing about the coil and the valves.. But I figured the coil either worked or not worked.. and I did adjust the valves (hyd flat tappet)..I think I did them right..it's been a while.. still the exact same thing.. I will see about getting a coil (a cheap one to trouble shoot with) I have an after market one and would hate to spend the money too find out it's something else..lol And I'm not sure how to check the carb... nothing was touched for a good 3 or 4 months. All was good and then this.. Thanks again |
09-13-2007, 08:54 PM | #6 |
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Re: 383 Stumble/miss
I,D SAY ITS THE POWER VALVE IN THE CARB. darn caps need to remove the button.......
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09-14-2007, 12:32 PM | #7 | |
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Re: 383 Stumble/miss
Quote:
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1968 Short Fleet 350/700r4 http://67-72chevytrucks.com/vboard/s...d.php?t=249435 1997 Bagged XtdCab Vortec350/4L60e http://67-72chevytrucks.com/vboard/s...44#post2286144 1993 XtdCab Longbed 4x4 6.5Turbo/NV4500 "Daily Driver" 1985 Toyota XtdCab 4x4 22re/W-56/Dual T-cases, Doug Thorley Header, Homebrew front and rear spring packs, Tons of Mods to suspension and drivetrain, 35" boggers, coming soon ARB's and 5.29's, Possible 4.3/700r4 swap |
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09-14-2007, 01:03 PM | #8 |
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Re: 383 Stumble/miss
it sounds like the carb.. i had the same problem until i rebuilt mine.which is an edelbrock and as you stated it also sat for several months and the insides got all gunked up... also it might not be getting enough air.
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09-14-2007, 01:22 PM | #9 |
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Re: 383 Stumble/miss
Thanks for the info.. I was thinking it maybe a fuel issue.. and to answer the question ..the card 8 months ago..was suppose to read... had the carb rebuilt 8 months ago..sorry..got ahead of myself...
As for the coil, I did the power brake trick and as soon as it gets under load it "stumbles". if you hold it at 2000 RPM you have here it "stumble". I got out and held the rpm at 2000 with my hand and you can see the motor have a definite shake to it at the same time you hear the stumble..or what ever you'd want to call it... |
09-14-2007, 02:06 PM | #10 |
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Re: 383 Stumble/miss
Throw a cheapy in it and see what happens
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1968 Short Fleet 350/700r4 http://67-72chevytrucks.com/vboard/s...d.php?t=249435 1997 Bagged XtdCab Vortec350/4L60e http://67-72chevytrucks.com/vboard/s...44#post2286144 1993 XtdCab Longbed 4x4 6.5Turbo/NV4500 "Daily Driver" 1985 Toyota XtdCab 4x4 22re/W-56/Dual T-cases, Doug Thorley Header, Homebrew front and rear spring packs, Tons of Mods to suspension and drivetrain, 35" boggers, coming soon ARB's and 5.29's, Possible 4.3/700r4 swap |
09-14-2007, 03:53 PM | #11 |
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Re: 383 Stumble/miss
When the optical sensor went in my Mallory Dizzy, it would hesitate and then backfire through the exhaust. I repalced the sensor and all is well. Yours sounds more like a fuel problem though.
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09-15-2007, 11:11 PM | #12 |
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Re: 383 Stumble/miss
OK..so I went out and did some more trouble shooting and this is what I found.. the # 1 exhaust valve was hardly moving.. I pulled the valve and found the valve shot as too the cam lobe just about gone.. guess it's to summit I go.lol..wife is loving me.. (pictured it the #1 intake and exhaust lifters)
I hope once this is taken care of my issues will be over... |
09-17-2007, 11:35 AM | #13 |
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Re: 383 Stumble/miss
What cam was in it?
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1968 Short Fleet 350/700r4 http://67-72chevytrucks.com/vboard/s...d.php?t=249435 1997 Bagged XtdCab Vortec350/4L60e http://67-72chevytrucks.com/vboard/s...44#post2286144 1993 XtdCab Longbed 4x4 6.5Turbo/NV4500 "Daily Driver" 1985 Toyota XtdCab 4x4 22re/W-56/Dual T-cases, Doug Thorley Header, Homebrew front and rear spring packs, Tons of Mods to suspension and drivetrain, 35" boggers, coming soon ARB's and 5.29's, Possible 4.3/700r4 swap |
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