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10/22/16 5:24pm - Original Message: 'Rochester Carburetor Question'
pats67copo
Former Member
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Port St Lucie, FL - USA

Vette(s):
1978 Silver Anniversary L 82 4 speed 66,000 miles just starting process of verifying originality so far mufflers aren't original but pipes are.

Joined: 9/21/2016
Posts: 9
Hi,
Has anyone ever heard of the base plate on a Rochester Carburetor of a 1978 Corvette warping causing the engine to lose vacuum and if you spray carb cleaner around base plate it causes the idle to raise up?
And if so any ideas on how to correct the problem?

  


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10/22/16 6:13pm - Reply: 'Re: Rochester Carburetor Question'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 396
Might try a new gasket if you haven't already.  Try gasket sealer on the new gasket.  New throttle plate maybe.

Or if the warp isn't too bad, you could wet sand on a surface plate or other very flat surface.

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1973 L-82 4 spd

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10/22/16 6:29pm - Reply: 'Re: Rochester Carburetor Question'
Vman73
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Gig Harbor, WA - USA

Vette(s):
1973 L82 4 Speed Coupe - Very original, well documented driver/survivor. 2016 Bend Regional NCRS Top Flight.

Joined: 10/2/2014
Posts: 362
Pat, perhaps others will chime in but I haven't heard many instances of the base plate of a Rochester 4bbl warping. Usually it's the air horn (top section) of the carb that warps due to over tightening. One thing that I am aware of, specially with 4 speed cars, is a vacuum leak in the base plate were the primary throttle shaft goes through the plate. There is no bushings of any kind in the base plate and over time the shaft becomes sloppy, causing a vacuum leak. this may or may not be a contributing factor. The sloppy shaft can be repaired with a bushing kit available from several vendors. Check out Quadrajet.com or do a search for a guy named Cliff Ruggles, both will have just about every part you need for a Qjet. Now if indeed your base plate is warped, it will have to be machined flat or replaced with a new or good used one. You might also try replacing the gasket between the carb and manifold along with the gasket between the base plate and the fuel bowl (center section) of the carb. A new set of gaskets may be enough to compensate for minor warpage of the base plate. Good luck, hope this helps and let us know what you find.

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John Sigmund
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10/24/16 11:31am - Reply: 'Re: Rochester Carburetor Question'
pats67copo
Former Member
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Port St Lucie, FL - USA

Vette(s):
1978 Silver Anniversary L 82 4 speed 66,000 miles just starting process of verifying originality so far mufflers aren't original but pipes are.

Joined: 9/21/2016
Posts: 9
Thanks for the reply I've tried new gasket already will have to keep looking thanks again

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10/24/16 11:33am - Reply: 'Re: Rochester Carburetor Question'
pats67copo
Former Member
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Port St Lucie, FL - USA

Vette(s):
1978 Silver Anniversary L 82 4 speed 66,000 miles just starting process of verifying originality so far mufflers aren't original but pipes are.

Joined: 9/21/2016
Posts: 9
Thanks for your reply I will check out the info you sent me and let you know what I find Thanks Again

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10/24/16 12:28pm - Reply: 'Re: Rochester Carburetor Question'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 396
You can check the throttle shaft bores by limiting the spray at where they go through the throttle plate. I successfully redid the bores on my friend's Holley on his '66 big block roadster using a kit that included a reamer, bushings, and instructions. The hardest part was removing the screws for the throttle plates which had been peened over at the factory.

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1973 L-82 4 spd

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10/24/16 1:47pm - Reply: 'Re: Rochester Carburetor Question'
pats67copo
Former Member
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Port St Lucie, FL - USA

Vette(s):
1978 Silver Anniversary L 82 4 speed 66,000 miles just starting process of verifying originality so far mufflers aren't original but pipes are.

Joined: 9/21/2016
Posts: 9
Thanks for that I will look into it and keep you posted

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10/24/16 9:09pm - Reply: 'Re: Rochester Carburetor Question'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19457
Base gaskets are prone to burn-out around the secondary throttle blade area. The section of the gasket is quite thin in that area, and the heat from the EGR crossover will burn them. Check the gasket first, and go from there. Thumbs Up

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Joel Adams
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10/25/16 7:22pm - Reply: 'Re: Rochester Carburetor Question'
pats67copo
Former Member
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Port St Lucie, FL - USA

Vette(s):
1978 Silver Anniversary L 82 4 speed 66,000 miles just starting process of verifying originality so far mufflers aren't original but pipes are.

Joined: 9/21/2016
Posts: 9
Thanks for the reply will update post as I go

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10/28/16 1:03pm - Reply: 'Re: Rochester Carburetor Question'
nosal1 Gold Member
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Dunedin, FL - USA

Vette(s):
1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.

Joined: 3/21/2006
Posts: 238

Hello All, Please follow Joel's suggestion and then go to Quadrajet carb website and get a new base plate which will have all new bushings etc. Over the years I have had to bite the bullet after many attempts to straighten or level the base plates.I could have bought a new carb for what I spent on trying to fix the plate,and time lost.

Good luck in whatever you do...    Sal C             nosal


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10/28/16 9:39pm - Reply: 'Re: Rochester Carburetor Question'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 396
OEM baseplates didn't come w/ bushings which is why they eventually started leaking.

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1973 L-82 4 spd

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10/29/16 7:56am - Reply: 'Re: Rochester Carburetor Question'
9TEEN72
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Brick, NJ - USA

Vette(s):
1969 (2) - 1970 - 1972 - 1975 - 1989 - 1994 - 1996 - 1998 - 2003 - 2009 - 2011 - 2014

Joined: 10/17/2016
Posts: 15
I currently have my Q-Jet at... Quadrajetpower ... for a restore, and they include the base plate bushing with the restore/overhaul (I am getting mine recolored also). You might want to try him for a baseplate as he sells them separately, or just send your carb to him.

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10/29/16 8:03am - Reply: 'Re: Rochester Carburetor Question'
nosal1 Gold Member
Gold Member
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Dunedin, FL - USA

Vette(s):
1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.

Joined: 3/21/2006
Posts: 238

Thank you for the info and good luck..

Sal C          nosal


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10/30/16 2:31pm - Reply: 'Re: Rochester Carburetor Question'
pats67copo
Former Member
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Port St Lucie, FL - USA

Vette(s):
1978 Silver Anniversary L 82 4 speed 66,000 miles just starting process of verifying originality so far mufflers aren't original but pipes are.

Joined: 9/21/2016
Posts: 9
Thanks to every one who has been helping out I haven't had a chance to work o the car again but will keep everyone posted.

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