Knock/rattle/tap at freewheel speed
 

I've got what's hard to describe, I'll call it knock/rattle/tapping at freewheeling speed, when accelerating or deceleration it's quiet, but at freewheeling speed it's there, I've tried changing the spark advance, adjusted GAV, just had the pan off and checked and adjusted the bearing clearances, went through the oil pump, visually checked the fiber timing gear and am just wondering what I'm missing. The only thing I haven't tried yet is somewhere or someplace I read that it may be necessary to raise the distributor just a tad to eliminate the rattle. I talked to a gentleman close to where I live today and he was saying that his A did the same thing. Anybody want to take a stab at it, I'm all ears. Oh, and I'm usually traveling around 35 - 40 or more mph when it shows up.
I had the head off when I dropped the pan and the valves looked good, pistons not hitting the gasket or head, I put about 4 oz. MMO in gas tank with every fill and when I first got the car I even put a few oz. of Seafoam in the fuel also because I know previous owner did pretty much only parade driving, but after having the head off and verifying the valves were good I backed off the Seafoam.

Re: Knock/rattle/tap at freewheel speed
 

I'm all ears too! Sounds like a common thing.

Re: Knock/rattle/tap at freewheel speed
 

Synchro909, are you saying that your's does this also?

Re: Knock/rattle/tap at freewheel speed
 

Might be the distributor shaft a tad long. Puts pressure on the cam. My fix was to get more vertical clearance, with the two piece distributor shafts.
You had the head off which makes this a possibility.

Re: Knock/rattle/tap at freewheel speed
 

Tonight I went down to the shop and loosened the set screw on the distributor and raised it a whisker then went for a drive, it may have helped a little but she still has a little rattle at freewheeling speed, is this typical for the A's or where do I go from here. You talk about a two piece distributor shaft ??? my distributor has a stub shaft approx 3-4 inches, then a longer shaft approx 6-8 inches into the cam gear, then of course the oil pump. I'm not sure if that's what's called a one or two piece shaft.

Re: Knock/rattle/tap at freewheel speed
 

Mine makes a noise when I am holding a steady speed at anywhere between about 30 and 50 mph. My wife describes it as sounding like a diesel engine but not as loud. I've checked all I can think of from end float of the rods, camshaft and crank to timing gears (I have an aluminium one) to pistons hitting the head gasket to a ring ridge in the bore. Nothing made the slightest difference so I have lived with it for the last 50,000 miles or so
My ears are still pricked!

Re: Knock/rattle/tap at freewheel speed
 

You have a 2piece shaft. When I fit a different distributor and made sure the distributor was seated in the head I tightenened the retaining screw on the side of the head to secured the distributor. I created a rapid noise at speed.
I took out the new replacement lower distributor shaft, and filed it and fit it so there was clearance when I replaced the distributor and snugged the retaining set screw on the head.
So when I test drove the car, no more rapid knock at speed.
I think when I replaced the first distributor, and replaced the lower shaft the new shaft had to be fit to the engine I have. Worked for me. Just raising the distributor a scootch would probably not be that effective.
But it is hard to second guess your situation.

Re: Knock/rattle/tap at freewheel speed
 

Have you tried to duplicate the sound while in neutral with the tires blocked by slowly raising the rpms? If you have someone in the car slowly raising the rpm until the sound presents itself, with the hood open, see if the sound is louder on one side vs the other.
If you cannot duplicate the noise while "freewheeling" in neutral, the noise may be coming from the drivetrain behind the engine.
If you can hear the noise while parked, take your fan belt off to see if it is still present.
Please try this and get back to us.

Poking fun at myself: I once had a severe main bearing knock until I removed the fan belt! Oops!
Good Day!