|Rambler American Restoration
Fixing Six Cylinder Rough Idle And Surging
One of the problems I've had with my American most of the time I've had
it is a very rough hot idle. Through some investigation, I found out that I
had a loose intake manifold. I tightened it down and the problem got much
better but was still there (and has slowly been getting worse again). As it turns out, I'm not the first person to
experience this problem. AMC actually issued a service bulletin on this
problem back in 1969.
Basically, the fix is to replace the intake manifold gaskets and torque
the manifolds in a specific sequence. Here's what you need to do (Note:
The way I'm describing installing the manifolds deviates from the factory
method but I found this to be much easier when doing this with the engine in
- Disconnect the negative battery cable.
- Remove the carburetor and any heater hoses going to the intake
- Remove the intake and exhaust manifolds and clean the manifold and
cylinder head mating surfaces. Note that AMC did not use an exhaust
manifold gasket so don't be surprised if it isn't there.
- Separate the intake and exhaust manifolds. WARNING! If the manifolds
haven't been separated before or if it's been a long time, chances are
good that you'll have a least one stud break on you during this
- Clean the intake to exhaust manifold mating surface to remove all of
the old gasket. WARNING! The factory gasket
was made of asbestos. If you are not 100% sure that it has been replaced
with one that is non-asbestos, make sure that you wear a respirator and
clean up all of the debris to prevent exposure.
- Install a new exhaust donut gasket and place the exhaust manifold on
the engine and exhaust pipe making sure that the donut is centered in the
end of the muffler. Just start the bolts that go into the exhaust
manifold. They only need to go in a turn or two for now.
- Install a new intake to exhaust manifold gasket.
- Install a new intake manifold gasket on the engine (make sure it stays
on the alignment pins) and loosely install
the manifold. You will need to wiggle the manifolds around quite a bit to
get the intake manifold over the alignment pins.
- Install the remaining fasteners and snug them up in the sequence shown
- Torque each fastener to 25 ft. lbs following the sequence show below.
- Install the carburetor (be sure to use fresh gaskets) and any removed heater hoses.
- Set engine idle speed and fuel mixture.
02/09/06 06:56:04 PM