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[T3] Some engine noise diagnosis/advice solicited


This is being cross-posted to the Type 3 list and the Type 34 Registry
list.

I am looking for some advice on an odd engine noise.

Data: 1965 type 34, stock, single port, dual carbs (I think 1500S, but
don't know for sure).

Problem (?): I have a low knocking sound that has no discernable
pattern and is generally only noticeable at idle. It is definitely
coming from the engine somewhere, but seems to be centered in the
area around the base of the distributor and fan housing.

I thought perhaps that the sound was a cracked fan. So, after Daniel
Baum's fan replacement with the engine in the car, I decided to have a
go at getting to the fan for investigation. Unfortunately, my impact
wrench will not loosen the fan/pulley bolt (I suspect my wrench is
weak). Obviously the problem is not a loose bolt there; but the fan
could still be cracked. BUT, having taken off the generator and
bellows, I cranked the motor and listened carefully. The noise is not
noticeably louder when listening at the air intake (bellow off) or
listening in the generator cooling hole. I assume a fan issue would
sound louder when listening in those places. Also, a visual inspection
of the outer edge of the fan from the generator cooling hole reveals
no problem. The motor can be turned by the fan without any apparent
slop or clunking.

I conclude so far that the sound is coming from inside the crankcase.
Does this seem fair? A "stethoscope" test using a screwdriver on the
engine with the handle to the ear is inconclusive to me. But from the
outside, the noise still seems concentrated in the rear of the engine.

Sooo ... my big fear at this point is some kind of problem with the
cam gear or a similar internal problem. I read all of the Type 3 list
archives I could find on strange noises, and found a couple possibly
relating to this problem, but the noises were described differently.

This noise has been present since I bought the car in late 1999. It
has not gotten worse from what I can tell in the 3000 miles I have put
on it since then. The engine runs fine and stays in tune with no
erratic timing issues. The noise is not loud, only really present at
idle and goes away with even a minor RPM increase. Perhaps I am being
overly sensitive? Should I just drive the car and hope for the best?
Driving habits: I rarely drive the car any great distance; generally
only the 6 miles via back roads to my office on nice days. Mechanical
habits: I am not generally one to yank the engine unless I absolutely
have to; i.e., I would prefer to avoid a tear-down without a really
good reason.

Advise is appreciated!

-Dan Browning
1965 343 

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