Quad-jet carb
Thread Starter
Instructor
Joined: Sep 2012
Posts: 178
Likes: 26
From: Blue ridge Georgia
Quad-jet carb
Hello, so my 75 coupe has been sitting in storage for over 10 years, I put it in storage shortly after I got it so I have not driven it but maybe 5 miles. Now it back in my home garage and I am wondering if I should rebuild the carb or get some other carb.
p.s. since going over the car I found a ton of problems that will need to be corrected. I hear rebuilding a quad- jet is a nightmare
thanks for any advice
scott
p.s. since going over the car I found a ton of problems that will need to be corrected. I hear rebuilding a quad- jet is a nightmare
thanks for any advice
scott
Popular Reply
Mar 20, 2023, 11:19 PM
Melting Slicks
Joined: Nov 2006
Posts: 3,370
Likes: 1,792
From: Apple Valley, MN
If you want it done right, send it to Lars. No one more knowledgeable than him. He recently posted a highly detailed step by step account of a full rebuild. If you have the time and patience, you can do it but if you don’t have either, then reach out to him.
Melting Slicks
Joined: Nov 2006
Posts: 3,370
Likes: 1,792
From: Apple Valley, MN
If you want it done right, send it to Lars. No one more knowledgeable than him. He recently posted a highly detailed step by step account of a full rebuild. If you have the time and patience, you can do it but if you don’t have either, then reach out to him.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 8,946
Likes: 4,113
From: US-PNW
I say, give it a go as is – may operate just fine – or not. Then make decisions on rebuilding. To clean and re-gasket one isn't difficult. To properly tune requires experience (Lars) or expert reference sources (Cliff Ruggles Q-Jet book).
Melting Slicks
Joined: Feb 2018
Posts: 2,315
Likes: 717
From: Marietta GA
Trying to do it yourself can be accomplished, if everything goes right. My friend is a copier repair technician, with 30 plus years experience. He rebuilt his quad first thing when he bought his C3. His car runs great as long as he doesn’t have to start it when the engine is hot. If I tell, you all the parts, and numerous fixes he has tried, you would not believe me. Some new parts he has bought twice. He is a wonderful person, but no matter what I send him about Quadrajet rebuilding, he blames the hot soak on something else. He could have had Lars rebuild 4 Carbs with all the money he has spent, not to mention his many labor hours. There are plenty of other things to fix on your Corvette, and if you are like the most of us, you can do the repairs twice to get it done correctly. Good Luck.
Thread Starter
Instructor
Joined: Sep 2012
Posts: 178
Likes: 26
From: Blue ridge Georgia
Thanks for the advice, now for the stupid question where can I get in touch with Lars. I found so much wrong with the car I have decided to do full frame off restoration.
thanks again
scott
thanks again
scott
Melting Slicks
Joined: Nov 2006
Posts: 3,370
Likes: 1,792
From: Apple Valley, MN
Melting Slicks
Joined: Feb 2018
Posts: 2,315
Likes: 717
From: Marietta GA
Scott
SMART Move, I guarantee you will be extremely pleased with his work and all the testing / adjustments made to your carb. I would have to say … way more than Rochester did when the thousands of carbs game off the production line back in 1975!
SMART Move, I guarantee you will be extremely pleased with his work and all the testing / adjustments made to your carb. I would have to say … way more than Rochester did when the thousands of carbs game off the production line back in 1975!
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Instructor
Joined: Apr 2000
Posts: 196
Likes: 32
From: Il
Scondo, I'd give it a try as 67:72 said. You never know..... I just pulled a 79 out of 20+ yr hibernation. Replace tank, blew out the fuel lines, changed oil, new plugs and wire. Primed the oil pressure. Fired right up. Carb operates fine. I couldn't believe it. Every car is stored differently and I've certainly had my share of carbs that required a rebuild.
Worse care you pull it off and rebuild it or send it out.
Worse care you pull it off and rebuild it or send it out.
Tech Contributor
Joined: Aug 1999
Posts: 14,356
Likes: 6,332
From: At my Bar drinking and wrenching in Lafayette Colorado
If you're doing a full frame-off, you do not want to have the carb rebuilt as a first-step operation - a rebuilt and tested carb that has been fuel soaked has a shelf life of a month-or-so at best. The carb should be the last thing you have rebuilt just prior to firing up your newly rebuilt engine at the end of your restoration project.
Lars
Lars
Racer
Joined: Nov 2020
Posts: 265
Likes: 76
Lars just did my carburetor after I struggled to get it right for Months. It will be the best money you ever spent. There's a big difference between getting it okay or alright and getting spot on.
Melting Slicks
Joined: Nov 2006
Posts: 3,370
Likes: 1,792
From: Apple Valley, MN
Fiberglass repair is a lot easier than working with bent/rusted metal. If you do decide to do it yourself, be sure to invest in a commercial grade particulate respirator.
Seam repairs like your situation is straightforward. Grind out a tapered “v” about 1 1/2 inches either side to the crack, down to the bonding strip. Layup with fiberglass and resin that is suitable for use with SMC (Sheet Molding Compound) panels. Do NOT use polyester resin as that is for earlier cars. Sand the new glass to contour.
Seam repairs like your situation is straightforward. Grind out a tapered “v” about 1 1/2 inches either side to the crack, down to the bonding strip. Layup with fiberglass and resin that is suitable for use with SMC (Sheet Molding Compound) panels. Do NOT use polyester resin as that is for earlier cars. Sand the new glass to contour.
Thread Starter
Instructor
Joined: Sep 2012
Posts: 178
Likes: 26
From: Blue ridge Georgia
Thanks 69L88, I am really thinking about it. I got a quote from the only body shop that said they can do fiberglass body work. 25,000 for body repair and paint. I fell of the chair in disbelief of the price. I am no body man by any means so I am afraid of destroying the body contours. The frame needs a lot of attention first , so it’s going to be step by step
thanks
scott
thanks
scott
Instructor
Joined: Oct 2022
Posts: 201
Likes: 68
From: Washington
I decided to rebuild mine instead of sending it to Lars. It’s been taken apart for a few weeks now. I’ve been waiting on throttle blade screws. I tipped it upside down and the screw had broke off. It was rattling around in there. Would have been catastrophic if it landed in the brand new engine. ☠️. After having it apart a few times it doesn’t seem that complicated now that I understand it. I’m gonna send it to Lars if I can’t get it to work after rebuilding it.
Tech Contributor
Joined: Aug 1999
Posts: 14,356
Likes: 6,332
From: At my Bar drinking and wrenching in Lafayette Colorado
I decided to rebuild mine instead of sending it to Lars. It’s been taken apart for a few weeks now. I’ve been waiting on throttle blade screws. I tipped it upside down and the screw had broke off. It was rattling around in there. Would have been catastrophic if it landed in the brand new engine. ☠️. After having it apart a few times it doesn’t seem that complicated now that I understand it. I’m gonna send it to Lars if I can’t get it to work after rebuilding it.
The throttle blade screws are #3-48, and they're peened to lock them into the shaft. If a screw is broken off, you're going to need to machine the remnant portion of the screw out of the shaft, and you may end up needing to install a #3 HeliCoil to repair the shaft threads after you've machined the broken remnant out if you don't nail the broken screw centerline. The screws are a unique low-profile fillister head screw, and are best obtained from a donor carb - the vendors that I've seen selling the throttle blade screws are selling round head screws, which are not correct.
It's also generally a bad idea to install a new or a freshly-rebuilt carb on a new engine. You want to fire up a new engine with a known-good carb that you know is running correctly. Based on the problems I know that you've had with your carb I would strongly recommend against using it to fire up your new engine, even after you rebuild it - that's a recipe for a flat cam and washed-down cylinder rings. Use a carb off of a running engine.
Lars
Last edited by lars; Mar 22, 2023 at 02:46 PM.
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
Carter -
The throttle blade screws are #3-48, and they're peened to lock them into the shaft. If a screw is broken off, you're going to need to machine the remnant portion of the screw out of the shaft, and you may end up needing to install a #3 HeliCoil to repair the shaft threads after you've machined the broken remnant out if you don't nail the broken screw centerline. The screws are a unique low-profile fillister head screw, and are best obtained from a donor carb - the vendors that I've seen selling the throttle blade screws are selling round head screws, which are not correct.
It's also generally a bad idea to install a new or a freshly-rebuilt carb on a new engine. You want to fire up a new engine with a known-good carb that you know is running correctly. Based on the problems I know that you've had with your carb I would strongly recommend against using it to fire up your new engine, even after you rebuild it - that's a recipe for a flat cam and washed-down cylinder rings. Use a carb off of a running engine.
Lars
The throttle blade screws are #3-48, and they're peened to lock them into the shaft. If a screw is broken off, you're going to need to machine the remnant portion of the screw out of the shaft, and you may end up needing to install a #3 HeliCoil to repair the shaft threads after you've machined the broken remnant out if you don't nail the broken screw centerline. The screws are a unique low-profile fillister head screw, and are best obtained from a donor carb - the vendors that I've seen selling the throttle blade screws are selling round head screws, which are not correct.
It's also generally a bad idea to install a new or a freshly-rebuilt carb on a new engine. You want to fire up a new engine with a known-good carb that you know is running correctly. Based on the problems I know that you've had with your carb I would strongly recommend against using it to fire up your new engine, even after you rebuild it - that's a recipe for a flat cam and washed-down cylinder rings. Use a carb off of a running engine.
Lars
I was going to ask where to get some.
the throttle shaft bush kit came with silver philips head.
