[Chrysler300] Freeze Plugs Continued - Help

["Richard Osborne" <richard@xxxxxxxxxxxx>]

Good Afternoon,

While driving home from cruising at the Mopar Nationals last night, the
right front freeze plug popped from the G's engine block. It was late,
we had the baby in the car and were in a less than desireable part of
town so I drove the 3 miles home, pretty much non stop. We had driven
almost non-stop for 80 to 90 miles at between 50 to 75 mph. It popped
while slightly accelerating to change lanes (very slight acceleration,
didn't even open secondaries).

I just installed a temporary rubber plug in and pressure tested the
system. After 20 minutes of measuring, it dropped 1 psi from 25 to 24
psi. I see in the 1961 service manual that you are to pressurize to 15
lbs. I am not sure of the conversion to psi? My results, however, seem
to be acceptible. Do you agree?

If you remember, a couple of months ago while breaking the motor in,
the plugs in the cylinder heads popped. It is interesting that the first
plug to go in the head was also right front, coincidence? After mic'ing
everything, I was confident that the machine shop had installed plugs
that were slightly too small. I have driven the car maybe 500 miles
since fixing the head freeze plugs. The temperature has seemed to be
good, never pinged, never had a problem starting when hot. No evidence
of water in the oil, even now. The same machine shop installed the plugs
in the engine block. Could this be the same problem of too small plugs?

I am concerned as the car has now lost several cylinders (I just got it
out to wash all of the antifreeze off of it). It will not idle now,
where previously, it idled very smooth. It is also backfiring slightly
through the carb (I think right side carb (which feeds the left side of
the engine), but not sure) a little.

I will pull all of the plugs and do a compression check on all of the
cylinders. Who knows, maybe something will become obvious once the plugs
are removed. 

What am I missing? What else should I be looking at? Can the freeze
plugs be replaced while the engine is in the car? I didn't have time to
survey as I need to watch our little boy, he loves riding in the G, so
this is motivation to fix it. No Woodward Dream Cruise for me...

Please advise of your thoughts and experiences.

Best regards,

Richard Osborne
Columbus, OH


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