Please Help, 71 running bad!
Thread Starter
6th Gear
Joined: May 2016
Posts: 6
Likes: 0
Please Help, 71 running bad!
First attempt for help so please be patient with me.
Have a 71 Corvette with 350 small block, 270 HP.
Car will start and idle fine but when put in gear it as if it want do die. When you start off it runs okay but if we pay attention, there is a slight missing as you accelerate. After driving the car for about 30 minutes, everything gets worse. The missing is pronounced and when you stop, the car will eventually die. At stop signs or lights, you need to put the car back into park or neutral to keep it from killing.
I have already done the following:
-new carburetor set properly
-new coil and radio capacitor
-new plugs and wires
-new distributor/rotor
-timed
-followed fuel line, no in-line fuel filter
-engine compression is good
-all vacuum ports on carburetor in use or plugged
Please help, I have run out of ideas and cannot find anything on line suggesting checking something else.
I am handy but I am not a mechanic so I might need detailed suggestions.
Thank you in advance for your attention to my request for help.
Paul
Have a 71 Corvette with 350 small block, 270 HP.
Car will start and idle fine but when put in gear it as if it want do die. When you start off it runs okay but if we pay attention, there is a slight missing as you accelerate. After driving the car for about 30 minutes, everything gets worse. The missing is pronounced and when you stop, the car will eventually die. At stop signs or lights, you need to put the car back into park or neutral to keep it from killing.
I have already done the following:
-new carburetor set properly
-new coil and radio capacitor
-new plugs and wires
-new distributor/rotor
-timed
-followed fuel line, no in-line fuel filter
-engine compression is good
-all vacuum ports on carburetor in use or plugged
Please help, I have run out of ideas and cannot find anything on line suggesting checking something else.
I am handy but I am not a mechanic so I might need detailed suggestions.
Thank you in advance for your attention to my request for help.
Paul
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
I had the same symptoms yrs ago. Was losing power by the minute. Got the car home checked everything. Almost everything. Could not figure it out. Then I checked my brand new chrome plated distributor hold-down clamp. Bingo!
Its design made it impossible to hold the dizzy.
Its design made it impossible to hold the dizzy.
Safety Car
Joined: Jun 2013
Posts: 4,399
Likes: 793
First attempt for help so please be patient with me.
Have a 71 Corvette with 350 small block, 270 HP.
Car will start and idle fine but when put in gear it as if it want do die. When you start off it runs okay but if we pay attention, there is a slight missing as you accelerate. After driving the car for about 30 minutes, everything gets worse. The missing is pronounced and when you stop, the car will eventually die. At stop signs or lights, you need to put the car back into park or neutral to keep it from killing.
I have already done the following:
-new carburetor set properly
-new coil and radio capacitor
-new plugs and wires
-new distributor/rotor
-timed
-followed fuel line, no in-line fuel filter
-engine compression is good
-all vacuum ports on carburetor in use or plugged
Please help, I have run out of ideas and cannot find anything on line suggesting checking something else.
I am handy but I am not a mechanic so I might need detailed suggestions.
Thank you in advance for your attention to my request for help.
Paul
Have a 71 Corvette with 350 small block, 270 HP.
Car will start and idle fine but when put in gear it as if it want do die. When you start off it runs okay but if we pay attention, there is a slight missing as you accelerate. After driving the car for about 30 minutes, everything gets worse. The missing is pronounced and when you stop, the car will eventually die. At stop signs or lights, you need to put the car back into park or neutral to keep it from killing.
I have already done the following:
-new carburetor set properly
-new coil and radio capacitor
-new plugs and wires
-new distributor/rotor
-timed
-followed fuel line, no in-line fuel filter
-engine compression is good
-all vacuum ports on carburetor in use or plugged
Please help, I have run out of ideas and cannot find anything on line suggesting checking something else.
I am handy but I am not a mechanic so I might need detailed suggestions.
Thank you in advance for your attention to my request for help.
Paul
Thread Starter
6th Gear
Joined: May 2016
Posts: 6
Likes: 0
I had the same symptoms yrs ago. Was losing power by the minute. Got the car home checked everything. Almost everything. Could not figure it out. Then I checked my brand new chrome plated distributor hold-down clamp. Bingo!
Its design made it impossible to hold the dizzy.
Its design made it impossible to hold the dizzy.
Thread Starter
6th Gear
Joined: May 2016
Posts: 6
Likes: 0
I believe I will actually change out the fuel pump because there is no memory how long it has been on the car. Car has been in the family since 71. Thanks
Thread Starter
6th Gear
Joined: May 2016
Posts: 6
Likes: 0
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Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Paul -
You can't buy a new Q-Jet. Is this a commercially rebuilt carb that you've procured from an auto parts store or through a Corvette parts supplier? If so, the carb has major problems... e-mail me for a paper listing all the problems with that carb...
Lars
V8FastCars@msn.com
You can't buy a new Q-Jet. Is this a commercially rebuilt carb that you've procured from an auto parts store or through a Corvette parts supplier? If so, the carb has major problems... e-mail me for a paper listing all the problems with that carb...
Lars
V8FastCars@msn.com
Safety Car
Joined: Jun 2013
Posts: 4,399
Likes: 793
Paul -
You can't buy a new Q-Jet. Is this a commercially rebuilt carb that you've procured from an auto parts store or through a Corvette parts supplier? If so, the carb has major problems... e-mail me for a paper listing all the problems with that carb...
Lars
V8FastCars@msn.com
You can't buy a new Q-Jet. Is this a commercially rebuilt carb that you've procured from an auto parts store or through a Corvette parts supplier? If so, the carb has major problems... e-mail me for a paper listing all the problems with that carb...
Lars
V8FastCars@msn.com
Burning Brakes
Joined: Sep 2009
Posts: 1,124
Likes: 140
From: Western New York
When you set the timing, did you plug the vacuum line and was the engine fully warmed up? Also, did you replace the points and condenser? Did you set the dwell angle using a dwell meter? After you've done these things correctly, then move on to carb setup and adjustments. Good luck.
Duane
Duane
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
i am leaning to the carb being the issue.
starts cold fine? but low idle?
as car gets to operating temp it runs worse?
electrical would die not just run slower until stalling?
float
idle circuit not setup
power valve opening from transition and at idle
bog at acceleration
new doesn't mean proper
just a quick guess with the info
starts cold fine? but low idle?
as car gets to operating temp it runs worse?
electrical would die not just run slower until stalling?
float
idle circuit not setup
power valve opening from transition and at idle
bog at acceleration
new doesn't mean proper
just a quick guess with the info
Pro
Joined: Oct 2011
Posts: 743
Likes: 71
From: Jarrettsville Maryland
I had the same sort of symptoms in my 72 Buick 455 a few years ago. The engine would run fine when cold, but as it got hotter, it would idle rough, and then die if put in gear.
It turns out, the main bearings were wrecked. A fuel pump had failed when the arm broke off. It gouged the camshaft and sent metal bits throughout the engine and wrecked the bearings. So, as the crank heated up, it would bind against the bearing surface. I hope your issue isn't quite that serious, but I also went through the carb and ignition systems not finding the answer.
It turns out, the main bearings were wrecked. A fuel pump had failed when the arm broke off. It gouged the camshaft and sent metal bits throughout the engine and wrecked the bearings. So, as the crank heated up, it would bind against the bearing surface. I hope your issue isn't quite that serious, but I also went through the carb and ignition systems not finding the answer.
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
I had the same sort of symptoms in my 72 Buick 455 a few years ago. The engine would run fine when cold, but as it got hotter, it would idle rough, and then die if put in gear.
It turns out, the main bearings were wrecked. A fuel pump had failed when the arm broke off. It gouged the camshaft and sent metal bits throughout the engine and wrecked the bearings. So, as the crank heated up, it would bind against the bearing surface. I hope your issue isn't quite that serious, but I also went through the carb and ignition systems not finding the answer.
It turns out, the main bearings were wrecked. A fuel pump had failed when the arm broke off. It gouged the camshaft and sent metal bits throughout the engine and wrecked the bearings. So, as the crank heated up, it would bind against the bearing surface. I hope your issue isn't quite that serious, but I also went through the carb and ignition systems not finding the answer.
