Carburetor questions
Thread Starter
Racer
Joined: Apr 2011
Posts: 471
Likes: 3
The April 2010 edition of 'Corvette Fever' had a tech article called 'Servicing the Rochester Quadrajet Carburetor'. It has lots of pictures. I can scan it, and email it to you if you want.
Also, another thing I found useful the first time I rebuilt my quadrajet, I bought an old quadrajet of the same style to use as a reference. That was a good thing too. When I went to put my carb back together, I couldn't see how the fast idle, and choke linkage went back together. Having a second carb as a reference helped figure that out. Then you can rebuild the old one, and have a spare carb.
Also, another thing I found useful the first time I rebuilt my quadrajet, I bought an old quadrajet of the same style to use as a reference. That was a good thing too. When I went to put my carb back together, I couldn't see how the fast idle, and choke linkage went back together. Having a second carb as a reference helped figure that out. Then you can rebuild the old one, and have a spare carb.
The problem it's hard for me to find an old quadrajet here in Italy! This is for sure a good advise, at first I will try without, I hope I will have no problems!!!
Melting Slicks
Joined: Mar 2006
Posts: 2,465
Likes: 0
From: Orange Park Fl
One of Lars' Q-jet papers has a list of carb numbers and which cars they came on. This will let you know if you have the original carb or another. Then you can find the right kit more easily. I use the Sorenson kits available at Autozone, although I have had issues with some of their substitution kits (X is the right kit but Y will substitute for X). If you do not have Lars e-mail, PM me and I will give it to you.
God bless, Sensei
God bless, Sensei
Thread Starter
Racer
Joined: Apr 2011
Posts: 471
Likes: 3
One of Lars' Q-jet papers has a list of carb numbers and which cars they came on. This will let you know if you have the original carb or another. Then you can find the right kit more easily. I use the Sorenson kits available at Autozone, although I have had issues with some of their substitution kits (X is the right kit but Y will substitute for X). If you do not have Lars e-mail, PM me and I will give it to you.
God bless, Sensei
God bless, Sensei
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
You just need his basic kit, it comes with the good viton accel pump.
But since you are in Italy, I would get the better kit that includes the proper later float etc. Not that much difference in price.
Get some extra gaskets too.
But since you are in Italy, I would get the better kit that includes the proper later float etc. Not that much difference in price.
Get some extra gaskets too.
Le Mans Master
Joined: Aug 2006
Posts: 7,417
Likes: 1,554
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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With pics
Hardest part for me was part #12, removing and installing the choke rod and getting #49 to line up.
You must remove this part to get the top off. If you remove screw #45 then 46-47-48 come off and you can remove 12 but #49 comes out with it and reinstalling it is difficult.
I was later told to twist the choke rod to get it off and leave leave screw #46 alone and to reinstall twist again.
Anyone ever try that?
You must remove this part to get the top off. If you remove screw #45 then 46-47-48 come off and you can remove 12 but #49 comes out with it and reinstalling it is difficult.
I was later told to twist the choke rod to get it off and leave leave screw #46 alone and to reinstall twist again.
Anyone ever try that?
Thread Starter
Racer
Joined: Apr 2011
Posts: 471
Likes: 3
Guys, My QJet has a EGR valve that has been disconnected.
My questions are:
1) is it OK to just disconnect EGR or I've to do something else?
2) as EGR works only at low RPM, is this the reason of my problems at low RPM (a leaking EGR for example)?
3) is it true that EGR carbs have different primary rods and run lean if you remove EGR?
Thank you
My questions are:
1) is it OK to just disconnect EGR or I've to do something else?
2) as EGR works only at low RPM, is this the reason of my problems at low RPM (a leaking EGR for example)?
3) is it true that EGR carbs have different primary rods and run lean if you remove EGR?
Thank you
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
The Q-J does not have an EGR valve. The EGR is on the intake. It should not be open at idle & opens above that & closes at WOT. Your pic. shows a missing PCV breather on pass. side valve cover. There should be a PCV valve on driver side valve cover should have hose to carb. port. All carb ports should have hose or blocked.
Did you adjust idle mixture, change the fuel filter & clean the carb?
Using nos. from the pic. shown above:
The primary piston 22 holds the primary rods 23 up out of the jets. You can try through the vent tube gently pushing down on the primary piston 22 which should spring back up- if not post. Some spray carb cleaner down the vent tube also. You may need to start a Q-J topic.
Did you adjust idle mixture, change the fuel filter & clean the carb?
Using nos. from the pic. shown above:
The primary piston 22 holds the primary rods 23 up out of the jets. You can try through the vent tube gently pushing down on the primary piston 22 which should spring back up- if not post. Some spray carb cleaner down the vent tube also. You may need to start a Q-J topic.
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Thread Starter
Racer
Joined: Apr 2011
Posts: 471
Likes: 3
Here are some pics: I've just ordered a HP carb kit from Cliff and at first can you help me identify the steps in order to remove the carb from the manifold??? Thank you
Last edited by Iron_dog; Nov 1, 2011 at 10:04 AM.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
The PCV is basically a calibrated vacuum leak & that's the air source. Open can let debris fall in. Just use the tube to air cleaner or measure the hole & get a breather at the auto parts.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
At the carb front are 2 long bolts & at the back 2 short bolts. A flare wrench is normally used to disconnect the fuel line.
Advanced
Joined: Oct 2011
Posts: 68
Likes: 1
I have a carb question. I don't mean to hijack anyone's thread but it doesn't seem like it would warrant a new one.
I have 454 with a holley carb #7002-1. Apparently this is a double pumper, vacuum 650 cfm.
Anyway, the car idles rough, especially right after startup. It also doesn't seem to not have the power that it should.
I just got the headers replaced and a new exhaust system installed. 2.5" all the way back. It almost seems like it is "missing". Plugs, wires and timing were recently replaced/corrected but it still doesn't run quite the way it should.
I recently found out that my battery needs to be replaced but that wouldn't effect how it actually runs, right?
I guess what I'm asking is will rebuilding my carb fix the problems I am experiencing or does it sound like there is more wrong?
I have 454 with a holley carb #7002-1. Apparently this is a double pumper, vacuum 650 cfm.
Anyway, the car idles rough, especially right after startup. It also doesn't seem to not have the power that it should.
I just got the headers replaced and a new exhaust system installed. 2.5" all the way back. It almost seems like it is "missing". Plugs, wires and timing were recently replaced/corrected but it still doesn't run quite the way it should.
I recently found out that my battery needs to be replaced but that wouldn't effect how it actually runs, right?
I guess what I'm asking is will rebuilding my carb fix the problems I am experiencing or does it sound like there is more wrong?
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
I have a carb question. I don't mean to hijack anyone's thread but it doesn't seem like it would warrant a new one.
I have 454 with a holley carb #7002-1. Apparently this is a double pumper, vacuum 650 cfm.
Anyway, the car idles rough, especially right after startup. It also doesn't seem to not have the power that it should.
I just got the headers replaced and a new exhaust system installed. 2.5" all the way back. It almost seems like it is "missing". Plugs, wires and timing were recently replaced/corrected but it still doesn't run quite the way it should.
I recently found out that my battery needs to be replaced but that wouldn't effect how it actually runs, right?
I guess what I'm asking is will rebuilding my carb fix the problems I am experiencing or does it sound like there is more wrong?
I have 454 with a holley carb #7002-1. Apparently this is a double pumper, vacuum 650 cfm.
Anyway, the car idles rough, especially right after startup. It also doesn't seem to not have the power that it should.
I just got the headers replaced and a new exhaust system installed. 2.5" all the way back. It almost seems like it is "missing". Plugs, wires and timing were recently replaced/corrected but it still doesn't run quite the way it should.
I recently found out that my battery needs to be replaced but that wouldn't effect how it actually runs, right?
I guess what I'm asking is will rebuilding my carb fix the problems I am experiencing or does it sound like there is more wrong?
A double pumper has 2 accel. pumps. A vac. sec. has 1 accel. pump.
Should be a 650 spreadbore vac. sec.
"missing"
Check that wires 5 & 7 are not run together, well separated & cross.
It's possible it has more cam than stock giving it a loping idle. See
http://forums.corvetteforum.com/c3-t...post1578444578
Advanced
Joined: Oct 2011
Posts: 68
Likes: 1
You need to do another topic. Battery is not the issue.
A double pumper has 2 accel. pumps. A vac. sec. has 1 accel. pump.
Should be a 650 spreadbore vac. sec.
"missing"
Check that wires 5 & 7 are not run together, well separated & cross.
It's possible it has more cam than stock giving it a loping idle. See
http://forums.corvetteforum.com/c3-t...post1578444578
A double pumper has 2 accel. pumps. A vac. sec. has 1 accel. pump.
Should be a 650 spreadbore vac. sec.
"missing"
Check that wires 5 & 7 are not run together, well separated & cross.
It's possible it has more cam than stock giving it a loping idle. See
http://forums.corvetteforum.com/c3-t...post1578444578
http://forums.corvetteforum.com/c3-t...post1579108537
Last edited by det2orl; Nov 1, 2011 at 03:06 PM.
Racer
Joined: Aug 2008
Posts: 413
Likes: 22
From: Justin TX
I Purchased a rebuilt Quadrajet from Summit Racing. It is rebuilt by Holley and works great. My original 69 had issues with wear on the body where the throttle shaft goes through and needed bushings. The replacement bolted right on and works great.
Thread Starter
Racer
Joined: Apr 2011
Posts: 471
Likes: 3
Thread Starter
Racer
Joined: Apr 2011
Posts: 471
Likes: 3