Hello again Z community,

Ran the motor today on my recently purchased 73 and I hear loud and snapping sounds around the intake and exhaust manifolds. Sound increases when throttle is opened. The car has a history of running hot in stop and go LA traffic.

Questions:

1. Does this kind of sound mean that I have an intake or exhaust leak?

2. If it is an exhaust manifold leak, does it mean that my exhaust manifold is warped and needs to be replaced?

Thanks much in advance.

Check to see if the exhaust manifold nuts are tight. They will work themselves loose sometimes, especially towards cyl 6. I wouldn't worry too much about the manifold being warped just yet.

Does sound like it could be backfiring either thru the carbs or the exhaust, though. How do the plugs look?

Be cautious when tightening the exhaust manifold nuts & intake manifold bolts. The max. torque is 8.7 lbs. per the FSM.

Both systems are original, so they're pretty old. The nuts and bolts look crusty and corroded especially at the exhaust manifold. I don't think it's backfiring because the snapping is constant. But, I'll try to tighten and see what happens.

Maybe its time to replace with a header?

Thanks again

Squirt the crusty stuff with 50/50 Acetone and Automatic Transmission Fluid over and over for a couple of days. That concoction is the best homemade penetrating oil ever. Maybe then they won't snap off, if they do you'll be in deep dew dew (French words).

Edited August 30, 201311 yr by siteunseen

Be cautious when tightening the exhaust manifold nuts & intake manifold bolts. The max. torque is 8.7 lbs. per the FSM.

That is FT. Pounds

Sure sounds like an exhaust leak.

Don't try to tighten exhaust manifold nuts on a HOT engine. You will almost certainly snap the studs.

Decided on a new MSA set up consisting of the coated 6 into 1 headers and premium exhaust. Just arrived. Got the new intake and exhaust stud kit too. Might have a resonator installed at the transmission section later. Hope this system works correctly in the end...

Edited September 11, 201311 yr by gtom

Have you checked the valve lashing, timing, and made sure all the emissions parts are working. All these would case what you explained.

Have you checked the valve lashing, timing, and made sure all the emissions parts are working. All these would case what you explained.

Yep, it's not the valves or timing. Car sounds like 'chitty chitty without the bang bang'. As for the emissions parts, I'm sure that's part of the problem.