One BBL Carburetor Runs Rough at Idle

Check your intake manifold bolts for proper torque settings. This may sound off the subject, but it happened to me. We were going over the car and happened to check one of the manifold bolts. It was loose, then we checked all 12, half needed tightening. Noticeable difference in performance. Don't know your torque settings but my 351C 4V with Edelbrock manifold needs 25 foot lbs. Follow the tightening pattern.

mike

could be something else, read the plugs, change the fuel filter, check the spark, change the points and cap

6 bangers are almost bulletproof, carb should be good, cause it is so simple, I rebuilt several, no problems where does it run rough, what speed or RPM?

Larry Lindstrom wrote in news:2tudnUpLVPnsdm_bnZ2dnUVZ snipped-for-privacy@comcast.com:

I would. You never know how many times these things have been "rebuilt" or what was done to it. Something with as low a demand as that may have been sitting on the shelf for years. Gaskets and seals dry out.

You need to tell us what the carb is. Autolite, Carter, Holley, etc.

the jets may need replacing, needle valve worn, floats bent could have a passageway partly plugged, throttle plate may not close all the way,

Yes. I've been through this before with a friend who worked at an auto parts store in high school. Essentially what we learned was that all the rebuilt carbs they had came from Mexico and all were crap. They were all crap in varying degrees, IOW number 2 may barely run and number

3 runs a lot better but still crappy. I went through that with a 70 and 75 Cadillac and his 67 Thunderbird.

Grab the carb near the top.

Then try to wiggle it

There are screws that hold the body of the carb to the throttle plate that loosen over time due to vibration.

If it's loose, you'll need to remove the carb from the intake to tighten the screws . . .

You've gone through 5 differant carbs, all have been bad. Assuming you're buying a quality part from a reputable source, what are the odds of that?

If you're absolutly convinced the problem is the carb, buy a new Holley and set it up right. If the problem persists, it's not the carb.

Short of that, buy a rebuild kit from one of the major suppliers (likie Mustangs Plus) and rebuild the carb yourself.

Has anyone thought of adjusting the idle mixture? How about the base engine... compression is even? Ignition is in good shape? Vacuum leaks?

Wife has a 65 6 cylinder and had same problem. Found the problem with the intake manifold was warped and allowed vacuum leak. Replaced that and its been fine the last 5 years or so.

Yes, check the intake manifold bolts for proper torque. Can't hurt.

you can run an on, unlit propane torch around the manifold to find leaks.

Thanks everybody:

Dave's mechanically inclined, and does most of the work on his cars. He did take the car in to a shop with the last carburetor, it had the wrong jets.

He had come to the same conclusion WinsorFox expressed about the Mexican source and quality of the rebuilds.

He's going to try the wiggle test and other suggestions, but he's expecting to buy a new carburetor.

The carburetor is a Holley.

FYI, Dave has a '65 289 convertible and this '65 6 cyl. coupe.

Your advice is appreciated.

Thanks Larry

Ponycarburetors.com

Might pay a little more, but each unit leaves there properly rebuilt and tested

CD

Are you sure it's not something other than the carb? Like an airleak in the intake manifold to head sealing surface? A vacuum hose disconnected?

Jan

test wrote: