[canehdian]

Yet another problem...The car has now developed a really weird tapping/rattling sound...It's most noticable at idle.

It almost sounds like a minor rod knock or a small repeated backfire something like that; i've done the old "screwdriver to the ear to the valve cover" trick and all 8 cylinders sounds perfect so i'm suspecting it's NOT the valvetrain...i pulled the distributor cap and there was a decent bit of moisture in there which i cleaned up, and the problem is obviously still there...if i were to guess as to where it's coming from based on sound i want to say it's coming from the carb, but since it increases speed with rpm i don't see how it could be coming from there?...I also suspected maybe an accessory so i pulled the belt and nothing changed there either...
so so far i've ruled out valve train, distributor, accessories...and i have no idea what else...i'm affraid to drive it incase it's more serious then i thought?

help please!

--Dave.

[meangreen92]

Possibly an exhaust leak, or a bad spark plug wire boot causing an arc to a
ground. If the car has headers, these are good things to investigate. The
best way to find the second possibility is to open the hood and look at the
engine as it idles. Do this in the darkest place you can find - but not in an
enclosed garage! If there's an arc, you will see it in the dark.

[canehdian]

You nailed it it was an exhaust leak!

Many thanks!