Carburetor flap won’t open
Thread Starter
1st Gear
Joined: Jun 2019
Posts: 1
Likes: 0
Carburetor flap won’t open
My 1981 corvette starts right up but then turns off and does a little hiss, the small flap on top of the carburetor won’t open/close. It is stuck in a position and it barley moves. The previous owner replaced the crossfire with a carburetor, if anyone can help it will be very much appreciated. Here are some pics of what’s wrong (engine is off in pics)
edit- thanks everyone for the responses so there are a lot of hoses and tubes that lead to nowhere and here are some pictures from above, showing the whole engine bay.
Thanks again, Sean
Last edited by Sean15; Aug 9, 2019 at 11:22 AM.
Instructor
Joined: Jun 2015
Posts: 178
Likes: 34
From: Calgary Alberta
Your 81, never came with a crossfire, it came with a computer controlled Rochester Quadrajet carb. That is not the carb you have now. The carb you have is a Holley and it is not computer controlled which suggests that the Engine Control Unit computer may no longer be present in you car.
As for the flap on the carb, that is the choke, if it is not closing when your engine is cold, you will certainly have a hard time keeping the car running until it warms up fully and the choke is no longer required.
As for the flap on the carb, that is the choke, if it is not closing when your engine is cold, you will certainly have a hard time keeping the car running until it warms up fully and the choke is no longer required.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
And will run badly and drink fuel with choke in that position when warm. OK, we are assuming you are not an accomplished wrench...yet. first we need pics of whole top of engine. That square bore Holley won't work on stock spread bore intake manifold. You don't know what has been done with the distributor. Got tools yet? Youtube videos are basic how-to for carb remove-replace, choke adjustment and hookup, etc.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
You have this carb: https://www.holley.com/products/fuel...arts/0-80457SA
Scroll down and read the instructions on how to adjust the choke, set floats and idle mixture. For now, I would try to loosen the three screws holding the choke housing and turn it until the choke is wide open then tighten. You can adjust it closed but you will have to make sure it has power.....with it adjusted closed, turn the key on (no start) and see if it opens on its own.
Derek is correct on the carb not working right on that manifold.....you have to have an adapter and those things have a horrible mismactch on the primary that cause distribution problems. Knowing this.....you still need it to run the best it can so go E-Mail Lars (V8FastCars@msn.com) and ask for his papers on timing. Post a pic of the distributor.....does it have a vacuum can on it? If not.....it is still running on the "computer". If it does then set timing to the papers Lars gives you. Set idle mixture last with a vacuum gauge.....you want the highest vacuum, there are several places to Google that up.......
The idea here is to get the highest vacuum reading possible to counteract the mismatch....it will run ok with that carb as the old classic Holley is pretty versatile but it would run much better with either a Q-Jet or different intake.
Post your findings and good luck.
Jebby
Scroll down and read the instructions on how to adjust the choke, set floats and idle mixture. For now, I would try to loosen the three screws holding the choke housing and turn it until the choke is wide open then tighten. You can adjust it closed but you will have to make sure it has power.....with it adjusted closed, turn the key on (no start) and see if it opens on its own.
Derek is correct on the carb not working right on that manifold.....you have to have an adapter and those things have a horrible mismactch on the primary that cause distribution problems. Knowing this.....you still need it to run the best it can so go E-Mail Lars (V8FastCars@msn.com) and ask for his papers on timing. Post a pic of the distributor.....does it have a vacuum can on it? If not.....it is still running on the "computer". If it does then set timing to the papers Lars gives you. Set idle mixture last with a vacuum gauge.....you want the highest vacuum, there are several places to Google that up.......
The idea here is to get the highest vacuum reading possible to counteract the mismatch....it will run ok with that carb as the old classic Holley is pretty versatile but it would run much better with either a Q-Jet or different intake.
Post your findings and good luck.
Jebby
Last edited by Jebbysan; Aug 9, 2019 at 08:02 AM.
Racer
Joined: Apr 2019
Posts: 300
Likes: 83
se that black housing on the side of the carb, it has 3 screws holding it on, just loosen the 3 screws enough so you can tun the housing when engine is cold. turn the housing carefully till the top flap is about closed start with 1/4 in. tighten up the 3 screws on the choke housing. you may have to push 2 or 3 times on the gas pedal than try to start car. as the engine heats up, this flap will open up more as the engine heats up, to get it perfect you can only adjust when engine is cold
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
Before any of this you need to find out if this carb is on a correct manifold for it and what distributor you have. This would not be the first time i saw a square bore holley on a spread bore intake. And first pic seems to show a distributor with no vacuum advance.
Last edited by derekderek; Aug 9, 2019 at 08:08 AM.
Le Mans Master
Joined: May 2007
Posts: 5,025
Likes: 1,120
From: North tonawanda NY
my 74 had an aluminum adapter plate with a square bore carb mounted on a spreadbore intake when I bought it. Ironically the spreadbore intake was an aftermarker edelbrock performer and not stock.
Last edited by augiedoggy; Aug 9, 2019 at 09:20 AM.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
And this might. Looks like it may be aftermarket intake. And i have seen spread bore bases with dual bolt patterns. But Sean needs to know more about his car than how to get the choke to work. R&R this carb will be a good start, for the price of a base gasket. Then he can look over and learn how the choke works far easier than on the car. And he still needs to figure out the ignition system. Sean. Any job you pay someone to do will cost more than the tools to do it yourself. These cars ain't that hard to work on. But the constant little stuff is a PITA. At 100 bucks an hour, the constant little stuff will have you hating this car like poison in no time... Start doing youtube videos. Carb rebuilds. Ignition timing and distributor install. Don't take carb apart or distrib out. But next time you look at them you will know what that is and what it does and this engine compartment won't seem so daunting.
Last edited by derekderek; Aug 9, 2019 at 10:48 AM.
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Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
The distributor in the engine is the original computer-controlled distributor with no vacuum advance or centrifugal advance. If the computer has been disabled (which it probably has been with the carb change), it means the timing and timing curve on the engine is really messed up... The OP has some serious ignition system work to do to get that car to run right - with a likely inoperative ECM, the distributor needs to be changed in addition to fixing the problems with the carb.
Lars
Lars
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
And since Sean (OP) called the choke plate a flapper, i think he has a bit of homework to do. Unless one of us is close enough to take under our wing. Personally i prefer not to work on a vehicle for free unless i am sleeping with the driver. Or her kids...
Last edited by derekderek; Aug 9, 2019 at 01:31 PM.
Le Mans Master
Joined: May 2007
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From: North tonawanda NY
I really hope you meant to say "or ONE of her kids"... but hey who am I to judge..
Race Director
Joined: Jul 2015
Posts: 13,082
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From: SW Florida.
No. I meant working on her kids cars. Actually was thinking of my current (22 years) life partner. Now her grandson who we are raising is eyeballing my 75 vert and thinking it is his...