IML: Timing Chain

["Eric" <gearhead@xxxxxxxxxxx>]

Kle,
The nylon coated cam sprocket progressively degrades until at one point 
there isn't enough material on it to hold the chain tight enough and then 
the chain will slip. I think the chain rarely fails due to breaking a link, 
though the chain will stretch some.
With a timing light, you can pretty well tell the condition of the timing 
set by looking for any skip in the timing mark. I experienced a surging at 
high speeds that was constant and rhythmic until the new chain set was 
installed. With the worn set, I would have to jab the throttle to the floor 
to get it off of high idle when cold, I believe that was a symptom of low 
vacuum based on the cam being out of time with the crank, causing not enough 
of an air rush through the carburetor air horn to open up the choke plate.
Someone mentioned that the chain set will fail at start up, usually. While 
this may be, mine failed on an exit ramp just as I fully lifted my foot off 
the gas pedal, creating an engine braking force. The motor died, then 
cranked irregularly. I could see the rotor skip when I cranked the motor 
after I finally got the car home.
In answer, the chain assembly will fully fail at once, but with plenty of 
clues that its about to go. The 440 is a non-interference motor.

Eric
Portland, Oregon
______________________________________________________
From: "Klebert L. Hall" <swampyankee@xxxxxxx>
Subject: Re: IML: Timing chain
Date: Fri, 4 Mar 2005 07:43:05 -0500
Reply-To: mailing-list@xxxxxxxxxxxxxxxx
> From: "Robin Giesbrecht" <robings@xxxxxxxxxxx>
> Subject: IML: main bearings, oil pressure gauge
>
> Next is the cam and timing chain.Looking at that timing chain(slack) from
> the crankcase while doing the bearings made me shudder.

  Correct me if I'm wrong, but when the timing chain goes in these cars,
don't they just stop? That's always been my experience with old pushrod
cars... The 440 isn't a valve-interference engine, is it?
   -Kle.
   '69 Crown 4DHT



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