Carb Overhaul

[ChevyMan]

I plan to have my carb overhauled. It was overhauled few years ago and I feel the need for another on my 30 plus-yr. car. I called the parts dealer and asked for an "overhaul kit". When I looked at the box, it said "carburetor repair kit". Is 'repair' and 'overhaul' one and the same?. I can't return it for a refund or replacement if I open the package.

What I see through the cellophane are many black or dark-colored gaskets, more than half a dozen or so, plus a few smaller metal or plastic parts. I am wondering if they are all I need to overhaul the carb? ???

[Eric]

I plan to have my carb overhauled. It was overhauled few years ago and I feel the need for another on my 30 plus-yr. car. I called the parts dealer and asked for an "overhaul kit". When I looked at the box, it said "carburetor repair kit". Is 'repair' and 'overhaul' one and the same?. I can't return it for a refund or replacement if I open the package.

What I see through the cellophane are many black or dark-colored gaskets, more than half a dozen or so, plus a few smaller metal or plastic parts. I am wondering if they are all I need to overhaul the carb? ???

What you've got is probably a generic "refresh" kit - with air horn and throttle body gaskets, new float/needle and seat, etc.

This may be sufficient - but a couple of cautions:

* Do you know enough about working on carbs to confidently disassemble your Q-Jet, perform the adjustments and put it all back together? If not, I strongly recommend you far m this job out to an expert. Q-Jets have many small, easily damaged parts - for example, the spring-loaded primary metering rods, which have to be very carefully lowered into the primary side jets and held in place while you re-install the air horn (top part of the carb). These are very, very easy to bend/break. The secondary air valve spring tension adjustment is also critical.

* Your 30-year-old Q-Jet probably has leaking main wells (they almost always do) . These can be epoxied by someone who knows how to do this (see above). If you don't, all the "rebuild kits" in the world won't cure your ills.

A proper rebuild involves total disassembly. The carb body, air horn, etc. are thoroughly cleaned in solvent. The unit is then re-assembled with factory relacement parts (gaskets, springs, float/need and seat, etc.) and adjusted per specifications before final adjustment on the running engine... .

[ChevyMan]

What I don't seem to understand is when the engine is fully warmed up at idle ...the temp gauge showing approx. 210, or more specifically, the needle reaches maximum point on the gauge....the carwill run as if there is no problem with the carb, although at times when I'm stopped at a red light, the engine sounds slightly erratic, which might be the MMO in the fuel system, though I may be mistaken (about the MMO, that is) ??? ??? ???

[Jim Rose]

>>What I don't seem to understand is when the engine is fully warmed up at idle ...the temp gauge showing approx. 210, or more specifically, the needle reaches maximum point on the gauge....the carwill run as if there is no problem with the carb, although at times when I'm stopped at a red light, the engine sounds slightly erratic, which might be the MMO in the fuel system, though I may be mistaken (about the MMO, that is) <<

What you need is an OLD GREY HAIRED mechanic who worked on those old gutbuckets. You may be chasing the smoke instead of the fire--- The best way to a repair is to find out what needs repair before you dive in and arbitrarily fix what you think is wrong instead of what is really wrong.

[Eric]

What I don't seem to understand is when the engine is fully warmed up at idle ...the temp gauge showing approx. 210, or more specifically, the needle reaches maximum point on the gauge....the carwill run as if there is no problem with the carb, although at times when I'm stopped at a red light, the engine sounds slightly erratic, which might be the MMO in the fuel system, though I may be mistaken (about the MMO, that is) ??? ??? ???"

I'll "amen" Jim; it'll just be frustrating (and expensive) to pull parts and do "repairs" without having first figured out what needs to be repaired. Don't assume you have a carb problem - or just a carb problem. This is a 30-year-old car. You could easily have ignition-related problems, a collapsed lifter, worn rings/valve guides (either f which could cause erratic running). The best thing to do is find a mechanic who knows older stuff and let him have at it. Probably it is a relatively simple thing - like adjusting the carb or ignition - and you'll be right as the rain.

[Eric]

Are you familiar with JET Performance? These guys sell rebuilt/recalibrated Q-Jets (as well as small parts for the do-it-yourselfer). Here's the contact info:

JET Performance Fuel Systems
17491 Apex Cir.
Huntington Beach, CA 92647
714/848-5515
www.jetchip.com

(click on "performance carbs," top left)

[ChevyMan]

Quoting Eric:

"Probably it is a relatively simple thing-like adjusting the carb or ignition-and you'll be right as the rain"

If you must know, I"ve had stalling problems when I tried to move forward after coming to a stop at a stop sign or a red light, so I took car to my friendly mechanic and he did something to it ( no parts involved)and that seemed to temporarily stop the stalling episodes, but he did warn me afterwards that the carb will definitely need overhauling. On his word, I gave him the go ahead to do it.

We'll see how things turn out.

[ChevyMan]

I plan to have my carb overhauled. It was overhauled few years ago and I feel the need for another on my 30 plus-yr. car. I called the parts dealer and asked for an "overhaul kit". When I looked at the box, it said "carburetor repair kit". Is 'repair' and 'overhaul' one and the same?. I can't return it for a refund or replacement if I open the package.

What I see through the cellophane are many black or dark-colored gaskets, more than half a dozen or so, plus a few smaller metal or plastic parts. I am wondering if they are all I need to overhaul the carb? ???

What you've got is probably a generic "refresh" kit - with air horn and throttle body gaskets, new float/needle and seat, etc.

This may be sufficient - but a couple of cautions:

* Do you know enough about working on carbs to confidently disassemble your Q-Jet, perform the adjustments and put it all back together? If not, I strongly recommend you far m this job out to an expert. Q-Jets have many small, easily damaged parts - for example, the spring-loaded primary metering rods, which have to be very carefully lowered into the primary side jets and held in place while you re-install the air horn (top part of the carb). These are very, very easy to bend/break. The secondary air valve spring tension adjustment is also critical.

* Your 30-year-old Q-Jet probably has leaking main wells (they almost always do) . These can be epoxied by someone who knows how to do this (see above). If you don't, all the "rebuild kits" in the world won't cure your ills.

A proper rebuild involves total disassembly. The carb body, air horn, etc. are thoroughly cleaned in solvent. The unit is then re-assembled with factory relacement parts (gaskets, springs, float/need and seat, etc.) and adjusted per specifications before final adjustment on the running engine... .

I've had no problem having the carb overhauled by a 30-something mechanic. He used the repair kit I supplied, replaced the fuel filter, removed the carb and did what an overhaul called for, that is, completey cleaned inside and out. It's warrantied for 90 days anyway.BTW, I intend to keep this car as long as I am able to get replacement parts for it. I like the smooth ride from driving it (weight: 4380 pounds) and still have the original factory paint job and few original parts like the fuel pump, rear brake shoes, gas tank and maybe a couple more parts I couldn't recall at this moment. Yep, it's a great car and I'll be driving it until I "drive it into the pond"!!!

[ChevyMan]

What I don't seem to understand is when the engine is fully warmed up at idle ...the temp gauge showing approx. 210, or more specifically, the needle reaches maximum point on the gauge....the carwill run as if there is no problem with the carb, although at times when I'm stopped at a red light, the engine sounds slightly erratic, which might be the MMO in the fuel system, though I may be mistaken (about the MMO, that is) ??? ??? ???"

I'll "amen" Jim; it'll just be frustrating (and expensive) to pull parts and do "repairs" without having first figured out what needs to be repaired. Don't assume you have a carb problem - or just a carb problem. This is a 30-year-old car. You could easily have ignition-related problems, a collapsed lifter, worn rings/valve guides (either f which could cause erratic running). The best thing to do is find a mechanic who knows older stuff and let him have at it. Probably it is a relatively simple thing - like adjusting the carb or ignition - and you'll be right as the rain.

It's been quite awhile since my carb overhaul, and since then I had a minor choke problem a week later so I took it back (under 90-day warranty) and they advance one click toward "rich" on the QJet. No complaint after that.

What I want to know is: is the choke valve inside the choke housing supposed to open up after the car warms up, or is it necessary to manually open it by tapping on the gas pedal? I've had to tap it on many occasions.

[Eric]

"What I want to know is: is the choke valve inside the choke housing supposed to open up after the car warms up, or is it necessary to manually open it by tapping on the gas pedal? I've had to tap it on many occasions."

When the engine's cold and you depress the gas pedal, the choke coil (which is heat sensitive) causes the primary air valve (the plate on top of the carb's front bores) to snap closed. It is held in position by a cam when the engine's cold.

This will result in "fast idle" - around 1,800 rpm.

Once running, a slight tap on the gas pedal will knock the engine speed down a few hundred RPM - but the Q-Jet's choke typically stays on for another little bit (it varies, car to car). As the engine temp. rises, heat is funneled into the choke housing (on the passenger side of the car) by that little metal tube you see running from the intake manifold to the choke housing (that round thing with the black plastic cover you can rotate to make adjustments).

As the engine warms up, tension on the coil element inside that housing decreases and the cam/tang releases - which "opens" the choke and allows the primary air valve plate to open fully. The Q-Jet's secondary "lock out" is also disengaged at this point - so the carb can run on all four barrels when you floor it.

This process happens gradually, as the engine warms - which was a designed-in feature of the Q-Jet to provide smooth transitions from cold to warm engine - but it's sometimes necessary to tap the throttle a little to fully release the choke.