Quadrajet Question
Thread Starter
Le Mans Master
Joined: Apr 2013
Posts: 5,001
Likes: 1,056
From: Arlington TX
2024 C1 of the Year Finalist - Unmodified
2023 Restomod of the Year Finalist
2023 C1 of the Year Finalist - Unmodified
Quadrajet Question
I normally post in the C1 section but I have a '69 sbc w/Quadrajet, so any questions about that probably belong in this area.
Lars told me to stick with the quad that came with my engine, and it's running good, but it would be better for my configuration if there was an outlet on the aft side of the throttle plate so I can connect my PCV valve to, rather than the front (existing plate is not drilled on the backside).
Also, my air adjustment screws on the front are frozen, corrosion I guess.
My question is, can I replace my throttle plate with one from another carb without messing up my carb? If so, any particular one?
My carb is a 4MV 7029202.
Lars told me to stick with the quad that came with my engine, and it's running good, but it would be better for my configuration if there was an outlet on the aft side of the throttle plate so I can connect my PCV valve to, rather than the front (existing plate is not drilled on the backside).
Also, my air adjustment screws on the front are frozen, corrosion I guess.
My question is, can I replace my throttle plate with one from another carb without messing up my carb? If so, any particular one?
My carb is a 4MV 7029202.
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
Cliff Ruggles has a section in his book showing the method of drilling and tapping the base plate. Get his book and Lars papers on qjets and rebuild your carb. If you're hesitant to open your carb up, send it to either of those two experts. Or if you're the adventuresome type, buy the cheapest, junkiest and dirtiest qjet on ebay you can find (less than $20) and tear it apart first for the experience before you open your carb up. That way, if you break or bend something, you won't have a heart attack.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Im not seeing why u should swap locations? That would be a lot more work to even just replace the carb than to change the PCV hose.
I think if u take a solid wire and poke through the PCV port it will go directly into the base of the venturies meaning its just port to the intake w/o and special function. I could be wrong though and need to get to the garage and look again. But what im saying is that really any intake connection should do for the PCV though u would want a port common to both cyl banks on a dual plane intake.
As for the idle adjustment screws u could soak them in penetrant and use deep socket on a flex shaft 1/4" drive for more torque to try and free them before u round the slot with a screwdriver.
Swapping throttle plates would be a mess and a lot of work. Even just rebuilding a qjet for the first time is gonna be more than one headache. Yes getting a junker carb to learn on is really a good idea and maybe u could locate one with your PCV connection location and the correct choke for your car too. That way youll have a spare tool box carb for trouble shooting also.
Hope this helps more than it hurts.
I think if u take a solid wire and poke through the PCV port it will go directly into the base of the venturies meaning its just port to the intake w/o and special function. I could be wrong though and need to get to the garage and look again. But what im saying is that really any intake connection should do for the PCV though u would want a port common to both cyl banks on a dual plane intake.
As for the idle adjustment screws u could soak them in penetrant and use deep socket on a flex shaft 1/4" drive for more torque to try and free them before u round the slot with a screwdriver.
Swapping throttle plates would be a mess and a lot of work. Even just rebuilding a qjet for the first time is gonna be more than one headache. Yes getting a junker carb to learn on is really a good idea and maybe u could locate one with your PCV connection location and the correct choke for your car too. That way youll have a spare tool box carb for trouble shooting also.
Hope this helps more than it hurts.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
It would be better for my configuration if there was an outlet on the aft side of the throttle plate so I can connect my PCV valve to, rather than the front (existing plate is not drilled on the backside).
Also, my air adjustment screws on the front are frozen, corrosion I guess.
My question is, can I replace my throttle plate with one from another carb without messing up my carb? If so, any particular one?
My carb is a 4MV 7029202.
Also, my air adjustment screws on the front are frozen, corrosion I guess.
My question is, can I replace my throttle plate with one from another carb without messing up my carb? If so, any particular one?
My carb is a 4MV 7029202.
For your seized mixture screws, give them a good soak-down with penetrating oil and then heat up the throttle plate at the screw area with a propane torch. Once nice-n-hot, you can wiggle them back and forth carefully, and they will eventually free up so you can remove them.
You can send me your entire throttle plate if you'd like me to do the modifcations for you.
Lars
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Thread Starter
Le Mans Master
Joined: Apr 2013
Posts: 5,001
Likes: 1,056
From: Arlington TX
2024 C1 of the Year Finalist - Unmodified
2023 Restomod of the Year Finalist
2023 C1 of the Year Finalist - Unmodified
You can simply drill and tap the back of the '69 throttle plate so it matches the configuration of the later model plates. You'll need to remove the plate to do that.
For your seized mixture screws, give them a good soak-down with penetrating oil and then heat up the throttle plate at the screw area with a propane torch. Once nice-n-hot, you can wiggle them back and forth carefully, and they will eventually free up so you can remove them.
You can send me your entire throttle plate if you'd like me to do the modifcations for you.
Lars
For your seized mixture screws, give them a good soak-down with penetrating oil and then heat up the throttle plate at the screw area with a propane torch. Once nice-n-hot, you can wiggle them back and forth carefully, and they will eventually free up so you can remove them.
You can send me your entire throttle plate if you'd like me to do the modifcations for you.
Lars
