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Carb question

1

1969D_Floyd

Guest
My '69 coupe has a Rochester carb that my have some problems. Regardless of how hard I jump on the throttle, the back two blades of the carb do not open. Shouldn't I get a secondary "kick" when I floor it? Is this a choke problem? I am worried my 4 barrel is behaving like a 2 barrel.
 
1

1DOWN6TOGO

Guest
several things that i know of can cause this. i'm not sure which one is the most common. if someone knows i'm sure they'll chime in with their advice.
what i know from my own experience with my quadrjet, is that you can have a number of problems, including:
-a problem with the spring and latch that attaches to the blades
-a problem with the condition of the carb, could there be dirt or grim keeping the valves from rotating easily?
-not enough vaccuum being created by ur engine, with enough vaccuum your 3 and 4 barrels should open up despite any other problems

i'm sure there are more possibilities that other people will mention, but these are the ones i know of or had to experience.

my advice is that you replace the carb if it is the original. autozone and o'reiley's offer affordable rochester replacements, both rebuilt and brand new. that's what i ended up doing. now she roars like a lion when you put ur foot down.

sam
 

Tom73

Well-known member
Joined
Aug 21, 2001
Messages
1,427
Location
Round Rock, TX
Corvette
73 LS4 Coupe - 04 CE Conv
How do you know they are not opening? They are vacumn operated so they will not open no matter how hard you jump on the gas unless the vacumn tells them to open. That is one good thing about the q-jet, you cannot be over carburated as it will allow only as much air through as the engine can use. On carbs with mechinical linkage you can dump too much fuel in at once and bog the engine down.

tom...
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
Q-Jet secondaries open progressively, in response to the engine's demand for air, based on airflow velocity; they don't "snap" open.
 

Pegasys

Well-known member
Joined
May 17, 2002
Messages
48
Location
Toronto, Canada
Corvette
1973 Red Coupe
My 73 has some issues with the carb as well. I suspect the previous owner who left it sitting unused for 2 years did not help the carb functioning.

I think my best bet is to have it rebuilt next year. It also has no kick and backfires for the first minute or so of driving.
 

mmvette80

Well-known member
Joined
May 12, 2002
Messages
273
Location
Central NY
I recently installed a GM Goodwrench engine in my 1980. The carb while on the old engine would hardly open (secondaries). Now they open half way. One problem I have is that it is hard to start. I used to pump 5 times and she would start right up. Now with the new engine I pump it 5 times then turn the key and have to keep pumping till she starts. Whats up with that?
 
P

page62

Guest
Your carb is leaking down. Either you don't have a check valve in your fuel filter, or there are a couple of spots on your carb that need to be sealed with epoxy (carb has to be removed, they're on the underside).

I have a new QJet and I only pump once -- she fires right up!
 

mmvette80

Well-known member
Joined
May 12, 2002
Messages
273
Location
Central NY
What are the spots to be sealed? Should I have it rebuilt. The last rebuild was about 6 yrs ago.
 
P

page62

Guest
They are the fuel well plugs. Any decent rebuilder would have epoxied them. The original carb on my car had epoxied plugs. But in my case I decided to replace the entire carb with a new Edelbrock QJet -- that was a plug 'n play install -- works great!
 

Stingray74CC

Well-known member
Joined
Nov 23, 2001
Messages
183
Location
San Diego, CA
Corvette
Black Cherry 1969 Stingray
Cost of Carb rebuild

I was thinking about having my 2x3 rebuilt. Mine leaks down, carbon build up everywhere, idles inconsistently, no choke, runs very rich and probably a lot of other things that I don't know about.

What is the cost for a rebuild? Any ball park figures?
 
M

MLGower

Guest
Anthony,

I just priced the rebuild on my Q-Jet, and if I remove it from the car, it'll run about $250. And it comes back in like new cond. A lot better price than going with the Edelbrock carb if you want to stay original (or if not). IMHO, the Rochester Q-Jet is a very solid carb. I would sooner rebuild it then buy the one from Edelbrock.

Michael :w
 

mmvette80

Well-known member
Joined
May 12, 2002
Messages
273
Location
Central NY
Yeah, im gona have it rebuilt. I would like to have someone good do it this tiime. Does anybody know of someone?
 

Stingray74CC

Well-known member
Joined
Nov 23, 2001
Messages
183
Location
San Diego, CA
Corvette
Black Cherry 1969 Stingray
I'm gonna look into that. It's expensive but worth it if the car runs that much better.
 
7

78SilvAnniv

Guest
Stingray6974...?

...give Mike a holler, he may do this type of work. I've heard of him doing larger projects (rear ends and such) but perhaps he also does carbs.
CACC member, to boot!

I had my Q-jet rebuilt for the cost of the kit ($16) by a mechanic friend. I won't recommend him because he had to make some adjustments after the carb was re-installed, and I would not like something like that to happen to someone who has had to ship their carb!
*The secondaries weren't opening up*
After that, 78 screams! She had a tune up the week before the carb rebuild, but I noticed a HUGE difference after the carb was rebuilt!

I can't stress what a difference there was in performance!
Silver
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
How do you know the secondaries aren't opening all the way? It won't happen in the garage just by yanking on the linkage, as full opening requires the engine to be under load to generate the required airflow volume in order to open the secondary air valve mechanism.

Open the secondaries manually (engine off) and note where the secondary throttle plate shaft linkage lever stop contacts the carb at full open position; put a spot of chassis grease on the lever at that spot, take it out and nail it, and if you then find a spot of grease on both parts, you'll know the secondaries opened all the way.
 

Pegasys

Well-known member
Joined
May 17, 2002
Messages
48
Location
Toronto, Canada
Corvette
1973 Red Coupe
Follow-up question...

I JUST came home from an hour or so drive..(the first part was great). Then, when I got off the freeway, the car wasn't getting enough fuel - it started choking and then stalled. I managed to restart it and then it backfired and stalled again. It drove for 10 minutes kind of ok, then stalled and took me 10 minutes to get it restarted.

Now it's in my garage.

Is it the same old carburator problem (needs rebuilding), or possibly the fuel pump?

Ideas?
 
7

78SilvAnniv

Guest
Yikes!

I don't know about your recent experience.

Back to secondaries...you can hear if they are opening. If they aren't, when you stomp on it, the engine just winds up slowly. When the secondaries are opening, you can hear the engine work harder, wind faster and accelerate quicker.

This may be harder to determine than I am making it out to be...First test drive after the carb rebuild, I noticed an increase in performance. Second test drive (Kenny driving) he noticed right away the secondaries weren't opening. Mechanic friend looked at carb, saw something and fixed it. Secondaries working great now. I drive and can't wait to put my foot into it just to hear them! I didn't know what I'd been missing, I just knew 78 didn't have the 'punch' she used to have. Now she's got it all!

*My carb was so bad for so long, I thought it was behaving normally, I didn't notice the secondaries not opening, I thought that was peak performance.
Could be just a 'girl thing', about not noticing it....:eek:
Heidi
 

Fred's Vettes

Well-known member
Joined
Jun 26, 2002
Messages
141
Location
Rochester,NY USA
Corvette
1969 Blue/Black 1969 Green/Green Project
I just purchased a remanufactured carb from a great company with a 1 year full warranty for $135.00. It is also a matching # carb for my 74. They will also remanufacture your carb if you send it to them. You have to remember that a remanufactured has new throttle shafts and new bushings along with all new choke components ( vacuum and springs) for mine. It is also has the surfaces remachined and calibrated on a dyno before shipping.
A rebuilt just has a kit put in it and sent on its way.
The company has a great web site and 800 number.
www.recarbco.com. 1 800 282 2272. Located in Pittsburg CA.
They also send you the calibration results for additional info and how to install and fine adjust to your motor if needed. Mine was perfect!!! Good Luck Fred
 

mmvette80

Well-known member
Joined
May 12, 2002
Messages
273
Location
Central NY
Thanks for the reference. Did you have to give a core? I would like to keep my original carb. They will remanufactor mine? Thanks again. How long did it take?
 

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