Frank,
You might want to check out all 12 tappets (cam followers), not just 6. They
are notorious for eventually wearing through the .003" case hardening and
then eroding themselves and the cam lobe. If they are rotating around
slightly you can end up with quiet clearances one minute, and noisy
excessive clearance the next. Your marvel Mystery Oil is just doing a
temporary cover up. Check out the real problem before you chew up your cam
lobes.
Another place to check is the rocker arms themselves where they contact the
valve stems. These arms can become concave due to wear and give you a false
reading with the feeler gauge. If this is the case, the rocker arms will
need to be redressed with a machine shop grinder.
Rich Chrysler
----- Original Message -----
From: <fmags@cox.net>
To: <healeys@autox.team.net>
Cc: "David Porter" <frogeye@swcp.com>
Sent: Sunday, October 15, 2006 5:01 PM
Subject: engine noise - progress at last
> Got the noise to go away this afternoon. It has been a loud mechanical
> tapping noise at idle.
>
> Last weekend, I poured about a pint of Marvel Msytery Oil on the rocker
> shaft
> with the engine at idle and down all of the pushrod holes and let it run
> for a
> few minutes with no change in the noise.
>
> This afternoon, while doing some checks, I remembered that someone asked
> if
> the noise changed with RPM. I had not run it above idle so far as I
> didn't
> want to do any damage. But, I decided to run it at higher RPM anyway to
> see
> what happened. The frequency of the noise did increase with increased
> rpm. I
> gave it several hard raps of the throttle and the noise went away. Gave
> it
> several more raps and it came back to various degrees with more or less
> noise
> and a little rough running of the engine, and I got the noise to stop
> again.
> I stopped the engine, added the rest of the pint can of Marvel and added
> about
> 1/2 quart of oil and ran it with no noise for about 10 minutes at idle.
> Ran
> it a little higher in rpm (2,000) a few times and no noise.
>
> When I checked it with a stethescope last weekend, the noise appeared to
> coming from the #2 cylinder cam/lifter area.
>
> I suspect I had a sticking lifter (tappet), and since the noise went away
> it
> wouldn't be something more serious like a wristpin or connecting rod
> bearing.
>
> I think I will change all 6 tappets. If I don't change the tappets and it
> sticks again I sure wouldn't want to do any damage at highway rpms.
>
> Does it sound like I am on the right track?
>
> Thanks,
> Frank
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