help with '67 396 spitting and sputtering - Team Camaro Tech
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post #1 of 7 (permalink) Old Sep 22nd, 01, 07:53 PM Thread Starter
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My '67 with a 396 has been running great until today on a short trip, it started to sputter and spit and act like it wanted to die unless I kept the RPMs up at idle. Everything is rebuilt and replaced back to factory original. Two things to mention, it is running very rich or something, the smell of unburned fuel will make your eyes water. The second is if I disconnect the plug wire to the number 2 cylinder, the idle increases and smooths out. What's up with that?
The dwell is set at 30 degrees and all ignition components seem ok. The timing is at 8 degrees initial but the engine idles better with more advance. Any thoughts on what could cause the miss? the super rich condition? the spitting and sputtering at idle? It drives me crazy, it was running well one minute and like a piece of doo doo the next. Thanks for any suggestions to get this back on the road again.
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post #2 of 7 (permalink) Old Sep 23rd, 01, 02:58 AM
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Maybe #2 plug wire is crossing with another cylinder. Also check the other bank of cylinders and see if you have a fouled plug.You have to pull all the plugs and check them out.

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post #3 of 7 (permalink) Old Sep 23rd, 01, 04:23 AM Thread Starter
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If the #2 cylinder is "crossing" with another, is that due to the routing of the wires? What should I do to correct that? I did pull all the plugs to check them and they were all a nice ashey gray except #4 that was a little black. I pulled the points also to check them and they look good. I have only driven the car about 250 miles since getting it all back together.
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post #4 of 7 (permalink) Old Sep 23rd, 01, 09:18 AM
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David Pozzi
 
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Sounds like a plugged idle jet or maybe a plugged idle air corrector.
Pull the idle mixture screws and squirt some carb cleaner in there to clean them out. You can blow some air from an air compressor in there too if you have that.
Squirt some on the air bleeds inside the air horn too.
It is probably on the drivers side of the carb since that side feeds the opposite cyls if you have a dual plane intake.

You can also "suck out" the jets by revving the engine and closing the choke while the throttles are open. this applies vaccum to all the jets and air bleeds.
David

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post #5 of 7 (permalink) Old Sep 23rd, 01, 06:43 PM Thread Starter
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David, your thoughts make a lot of sense. The motor does not idle well on the "idle system," but if I advance the timing enough or bump the idle speed enough, it does ok. I think that it is running well on the secondary system, but not on the primary idle system. May be time to rebuild the old Q-Jet? I did pull the carb off tonight and cleaned the idle screws and passages and it made a big difference but not perfect. Thanks for the post. I think you have me on the right track.
Are the Quadra Jets hard to rebuild? I am not so concerned with the rebuild as with the adjustments. There is a guy here in Denver that specializes in GM carbs and would charge $90.00 to rebuild. Do you think it's worth letting him do it or can I get decent results?
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post #6 of 7 (permalink) Old Sep 24th, 01, 08:35 PM
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A lot depends on how mechanicaly inclined you are.
the Q jet is more complicated than a Holley if you have done one of those.
You have to be careful not to lose the power valve spring when the carb comes apart. The metering rods are tricky to get back in. the choke lever link is sometimes a pain.

I'd get the part number off the carb left rear side, get a good kit for it with NEW float. They go bad a lot, and are not included in the kits. Here in California with the alcohol in the fuel, the floats get soaked with it and get heavy. This raises the fuel level and can cause richness problems too.

Take a good look at the kit instructions and read mine below and see if it makes any sense to you.
The primary idle jets need to be blown out real good, and are buried an inch down inside a passage in the front of the carb.

REBUILDING A QUADRAJET CARB
Here are some instructions that will give you an idea of the work needed to rebuild a Q jet carb.
Iím sure Iím leaving out some info or steps here, this is just off the top of my head.

Most rebuild kits come with instructions and a cheap float guage. The plastic floats can get fuel soaked and get heavy, but if your carb has been off and dried out you won't know if it is a bad one. I usually replace the float due to the type of fuels we have now.

The tricky stuff is getting the accelerator and choke linkage off and removing the carb top, setting the float, and re- installing the carb top without having the metering rods slip out of the jets.
Most of the other adjustments are probably correct allready, like choke pull off, secondary air valve, etc. Don't take the carb totally apart, concentrate on the fuel passages and major gaskets and such, not on every little link and lever on the outside.

A good carb man could do it in an hour. A first timer, much longer, maybe a day.
If you aren't good at taking time and reading all the instructions, and keeping all the little parts organized, I'd pay the mechanic to do it.
Think of it this way, if you make one mistake, you will probably have to remove it and take it to the carb guy anyway.

Any chance you could find an extra carb to practice on?

Maybe you could buy a kit and read the instructions and see if you think you can do it.

Place the carb on a block of wood (2X4) for a steady surface.
Use a small punch to punch out the roll pin that holds the accelerator pump arm at the top of the carb.
You can also use a small nail for this, you can grind down the tip to fit the pin size.
Punch the roll pin in towards the carb air horn, but stop about 1/16" short of the air horn. This will allow you to remove the arm - when replacing it, you can pry the pin back in with a screwdriver.

Remove the air cleaner stud, and the secondary metering rods.

When you remove the choke blade link. look down inside the carb to where it attaches, some carbs have two holes.
Make shure which hole is used. Even if you don't remove the link from the lower hole in the arm it might fall out later. If you want to remove it lift up and twist gently and move the link toward the carb center.

Remove the carb top attaching screws.

When you take out the primary metering rods, there is a spring under the piston that will fall out if you turn it over, take it out now.

there is also a spring under the accelerator pump piston.

The accelerator pump check ball is under a screw next to the float valve.

When you get the top off, check the small tubes in front of the secondaries, they can plug up or fall out, make sure air blows thru them.

Spray the passages out with carb cleaner and blow out with air.

Some early Q jets are prone to leaking at the bottom of the jet passages on the bottom of the carb body. It would be a good idea to put some epoxy on them to seal them. If they leak it will make the car run rich at idle.

The kits come with several top gaskets, make absolutely shure you choose the right one.

Same deal with the bottom gasket. Get them both right side up too.

Make shure the float pivot pin goes back the same way it came out. The loop goes toward the passenger side of the
carb.

Replacing the top is the hardest.

Get the choke link back in now (bottom end)

Hold the primary metering rods down in the jets, sometimes the plastic bushing does not hold it down properly, if it does, count your blessings. Don't forget to insert the accelerator pump thru the gasket and top.

when you get the top on, make shure the metering rods go up and down by pressing on the piston head with a small screwdriver. Insert it thru the front vent hole.

The fuel filter does not come with the kit. Get one, a new plastic gasket for the nut does come with the kit. Use a little lube on the threads and be VERY careful here it is too easy to cross thread the very fine threads there, also someone may have been there before you and screwed them up.

I've probably missed some small stuff, it's been a couple of years since I've done one. But I have done 20 or more before.

You can't get away with any mistakes on this job, if you make a mistake, either the carb won't go together, or it will run
like crap.

Like most things, the first time is the hardest!
You still wanna do this?

------------------
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer
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post #7 of 7 (permalink) Old Sep 25th, 01, 06:48 AM Thread Starter
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David, thanks for the great post, I may try to clean out the passages one more time before going for the rebuild. I have done Holleys and some Autolites, but this sounds much more involved. $90 for a rebuild sounds like a bargain! Thanks again for the guidance.
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