Tapping noise

[Dan30thz28]

Hello,

I have a tapping noise coming from the driver's side of the motor (1970 455 4-bbl), and it's coming from one of the rear cylinders. It's louder under load, and it's a consistent tapping noise. I wanted to know what could be the cause? Something in the valve train? An exhuast leak at the manifold? Thanks and I look forward to your responses.

Dan

[gmoney]

Dan: A noise can be difficult to isolate. First I would check for exhaust leak, look for tell tale soot or burned paint around the manifolds and heads. If you do not find any leaks do a compression test , this will isolate the cylender at fault. A collapsed lifter will tick and increase the rapidness with speed. Some mechanics use a stethascope or long screw driver to find the source of the noise. A collapsed valve spring will make plenty of noise. Lastly remove the valve cover and look for obvious problems in the valve train. Be sure to start with the simplest answers first and, move slowly to the more complex areas last. Maybe someone here has aspecific trouble shooting guide to help you out. Let us know what you find. Mike

[RocketDude]

Those engines were famous for frying the oil on the rockers by the ERG port. Very common to pull the vavle cover on that side, and you will find the rockers, rocker stand, and pushrods need to be replaced. The high temp of the exhaust going to the EGR valve heated the oil of the two cylinders on either side of the EGR to the point that the oil holes would fill with carbon and soon you had no oil flow to those two cylinders. Then the rockers, rocker stands, and pushrods are running dry and would soon start making noise. Just replace the worn components and you're on your way for another 30-40 thousaqnd miles.

Listen for the noise at the valve cover right by the EGR port. If you hear the clicking there, pull that VC, and if that's the problem, it will be very obvious. The oil will be burnt and nasty, and the parts sloppy and loose.

There are other possibilities for your noise, as mentioned above, but the problem I mentioned is very common on that engine. Cheap and easy to fix, too...!

[Dan30thz28]

Hey,

I took the car to Mufflex in Trenton, and he heard the car. He immediately told me that it was an exhuast leak at the manifold on the driver's side which I had suspected. I'm really relieved to hear that, because I was afraid it would be something in the valvetrain. He's having the manifold machined flat, and reinstalling it on the car along with an H-pipe and bringing in the trumpet tips an inch or two because they were sticking out too far. Thanks so much for all your advice, and I'll let you know how it's going once I get the car back.

Sincerely,

[streets]

Hi Dan,

I have to lean towards agreeing with RocketDude. These engines had a problem with the driver's side valve train bank. The key question's are:

1. have you lost power?

2. Does the noise go away occasionally?

#7 cylinder also has a great tendancy to collapse it's exhaust lifter. As mentioned a mechanics stethoscope would initially narrow that down. It is hard to tell even with removing the valve cover if a lifter is functioning properly. Because these are non-adjustable, it may look like the pushrod is traveling, when in fact it might be just flopping around. A compression check on the entire engine would also add some clues.

Depending on your miles (and ambition,) you might want to consider getting into the top end deeper based on your findings.

Worst case, without pneumatic tools, it took me 2.5 hours to replace all the lifters.

An exhaust leak as also mentioned could be a real possibility. Withoiut hearing it, its hard to tell.

Good luck with it,

Dave

[Dan30thz28]

Hey,

It was an exhaust leak, and now the motor is silent, and running great. Thanks for all your advice guys it was greatly appreciated.

Sincerely,