Carburetor help needed
03-12-2003, 05:33 PM
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Carburetor help needed
I have a 1970 LT-1 with the stock Holley carburetor. The carb has a couple of problems:
1. It leaks fuel where the butterfly rod passes thru the carb housing.
2. The engine stumbles just off idle when accelerating.
3. The idle speed can vary about 300 rpm.
Can anyone recommend a good place to have the carburetor worked on - preferably one that has the ability to flow check it? Thanks for any help.
Dave C.
1. It leaks fuel where the butterfly rod passes thru the carb housing.
2. The engine stumbles just off idle when accelerating.
3. The idle speed can vary about 300 rpm.
Can anyone recommend a good place to have the carburetor worked on - preferably one that has the ability to flow check it? Thanks for any help.
Dave C.
03-12-2003, 08:29 PM
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Melting Slicks
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Re: Carburetor help needed (DaveC-70LT1)
Welcome. I am not going to be of much help other than to say, contact Lars (a search will find him or contact me).
Enjoy the car and if not done so, please register it.
http://forums.corvetteforum.com/zerothread?id=510897
[Modified by Robert N, 6:30 PM 3/12/2003]
Enjoy the car and if not done so, please register it.
http://forums.corvetteforum.com/zerothread?id=510897
[Modified by Robert N, 6:30 PM 3/12/2003]
03-12-2003, 08:44 PM
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Re: Carburetor help needed (DaveC-70LT1)
Dave -
Glad to have you with us on the Forum - great place to meet people and play with cars..!
Improperly set up and leaky Holleys are a common problem. If the carb leaks fuel out the throttle shafts, this is not a problem with the shafts. It means that fuel is dripping out of the main discharge nozzles or out of the accel pump discharge nozzles after engine shutdown. This drip will hit the throttle blades, and the fuel will then leak out of the throttle shafts. It means you have some internal leakage or an excessively high float level.
These internal problems can also cause your off-idle stumble and an inconsistent idle speed. Further, if the primary and secondary idle speed screws (yes, there is a secondary idle speed screw that needs to be correctly adjusted...) are not correctly adjusted and balanced, it can cause the same problems.
Start by verifying and adjusting your float levels. If this does not cure your problems, it's time for a rebuild and precision setup. I can do this for you if there is not anyone qualified in your area to take care of you at a reasonable price. You can also do it yourself - it's not real hard - just takes a little time.
Glad to have you with us on the Forum - great place to meet people and play with cars..!
Improperly set up and leaky Holleys are a common problem. If the carb leaks fuel out the throttle shafts, this is not a problem with the shafts. It means that fuel is dripping out of the main discharge nozzles or out of the accel pump discharge nozzles after engine shutdown. This drip will hit the throttle blades, and the fuel will then leak out of the throttle shafts. It means you have some internal leakage or an excessively high float level.
These internal problems can also cause your off-idle stumble and an inconsistent idle speed. Further, if the primary and secondary idle speed screws (yes, there is a secondary idle speed screw that needs to be correctly adjusted...) are not correctly adjusted and balanced, it can cause the same problems.
Start by verifying and adjusting your float levels. If this does not cure your problems, it's time for a rebuild and precision setup. I can do this for you if there is not anyone qualified in your area to take care of you at a reasonable price. You can also do it yourself - it's not real hard - just takes a little time.
03-12-2003, 09:26 PM
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Re: Carburetor help needed (DaveC-70LT1)
Dave, in addition to what Lars has already said, sounds like the little plastic bushings on the throttle shafts are worn, letting the fuel leak out. But this also causes another problem, when the car is running these you actually have a vacuum leak from air being sucked in past these bushings causing a lean situation which could be the cause of your off idle stumble. At any rate sounds like the carb is in need of a rebuild which is pretty simple on a holley. Make sure you take the throttle shaft out and replace those bushings. Alot of people fail to do this and they still have carb problems. Good luck biggjimm
03-13-2003, 06:31 PM
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Re: Carburetor help needed (DaveC-70LT1)
Robert, Lars and Biggjimm,
Thanks for your help guys.
Robert - I will certainly be registering my car in the registry. I have been meaning for quite some time to check out the various C3 forums but really haven't had the time. Hopefully that will change!
Lars - I probably should have added that the carb is the original one. I had to have it rebuilt once before due to a bad tankful of Sunocco gas. I had it done locally and mentioned to the guy about the stumble and the variation in idle speed. When I put the carb back on the car ran fine except for those problems. I could probably due the rebuild myself but I would like to have someone do it that REALLY knows these carburetors, can flow test it or actually run it and if it's not right - make it right. Do you have this ability? How much would you charge? You can e-mail me @ gnhhydro@aol.com if you would like.
Biggjimm - Thanks for your input also!
Thanks for your help guys.
Robert - I will certainly be registering my car in the registry. I have been meaning for quite some time to check out the various C3 forums but really haven't had the time. Hopefully that will change!
Lars - I probably should have added that the carb is the original one. I had to have it rebuilt once before due to a bad tankful of Sunocco gas. I had it done locally and mentioned to the guy about the stumble and the variation in idle speed. When I put the carb back on the car ran fine except for those problems. I could probably due the rebuild myself but I would like to have someone do it that REALLY knows these carburetors, can flow test it or actually run it and if it's not right - make it right. Do you have this ability? How much would you charge? You can e-mail me @ gnhhydro@aol.com if you would like.
Biggjimm - Thanks for your input also!