Re: [AMC-list] caspers motor may be ok, but need advice/suggestions

[Joe Fulton <piper_pa20@xxxxxxxxxxx>]

--- On Wed, 4/21/10, tom jennings <tomj@xxxxxxx> wrote:


From: tom jennings <tomj@xxxxxxx>
Subject: Re: [AMC-list] caspers motor may be ok, but need advice/suggestions
To: "AMC, Rambler, Nash, Jeep and family" <amc-list@xxxxxxxxxxxx>
Date: Wednesday, April 21, 2010, 9:55 AM


Even after disassembly I never found the source of the odd mild at-idle
"knock" from the crankcase! It came out of the oil filler neck, so it was
definitely down the bottom end. It behaved exactly as if it was the fuel
pump cam hitting the fuel pump lever. If you revved it or even just blipped
the throttle, it went silent, then a few seconds later it would gently get
louder. Not loud though, just tank, tank, tank, tank, ...

If you picture what the fuel pump diaphragm is doing down there, the lever
pushes the diaphragm up against the spring, and it fills with gas. Lever
falls back down, and the gas tries to press out towards the carb. But at
idle the carb is full, the needle is against the seat, so the gas only seeps
out of the pump. Next time the lever comes up, the diaphragm is still full
of gas, and there's a big gap 'tween it and the lever. >TAP< as the lever
moves through open space and just taps the almost-full diaphragm just a tiny
bit.... rev it up, the carb takes fuel, the diaphragm drops, the lever hits
it earlier, it's quieter. That's all I could figure was going on. All the
bearings were very worn, copper showing and abrasion, but nothing broken,
gouged out, loose, etc, just lots of years and miles. Cam had that mild fine
black pitting from wear with no oil filter, no fuel cam wear, etc.
,snip
 
Now that I think about it, my 62 Classic wagon (195.6 OHV) made that same noise at idle.  That noise, plus the fact that it had pretty bad a-pillar rust led me to scrap the car a couple of years ago.  There was also a brazed place on the bottom of the oil pan, which let me to suspect that it had thrown something (rod nut, whatever) previously and had not been properly repaired.  Maybe I put two and two together and got five.  I don't know.
 
Joe Fulton
Now that I think about it
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