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I can put my own questions to rest finally on MY
heat riser. Thank you Fred, Paul, Dave and others who have offered what
they knew.
I went out to my '67 Imperial motor today. I
believe mine is missing the spring mechanism, the anti-rattle spring, and who
knows what else. Anyway, I have dual exhausts on my car, fired her
up, and moved the heat riser in both directions & then checked at the
passenger side tailpipe.
Definitely a noticeable difference - (looking at
the manifold from the passenger's fender) with the heat riser turned clockwise /
forward - a noticeable increase in sound and exhaust. Turned
counterclockwise / towards the rear - a definite reduction in sound &
exhaust.
To throw one last bit of info in there - I checked
a Mopar exhaust manifold in my Mom's basement and the heat riser was mounted in
front of the head pipe - not alongside it as is on my '67 440. Not sure if
that has any significance, or if that was even a big block manifold - it was an
arched "magnum" type manifold, though..
Anyway, my problem / question is solved, and it
agrees with Dave's input. Perhaps Fred & Paul's '69s are
different? Or who knows what manifold is actually on my '67?
Thanks again for everyone's input on this repeated
question.
Dan Richardson
300L Family Heirloom
----- Original Message -----
Sent: Sunday, August 26, 2007 3:56
PM
Subject: IML: 69 heat riser
revisited
There have been some questions about the heat riser valves.
On my 69 Lebaron I had locked the heat riser valve open because of a
rattle.
I just did an experiment to check the function of this valve. Upon removing
the hose clamp that I have to hold the valve open, the valve rotated clockwise
about 100 degrees to rest against the stop.
I started the car and the valve began to bounce to about 10-15 degrees back
from the stop in a counter clockwise direction. I could hear it rattling. As
the engine warmed the RPM increased to probably about 1500 RPM, but the
position of the valve did not really change. It was within a few degrees of
being closed. As the engine warmed more and I kicked off the fast idle, the
valve bounced less, but was still almost closed. I had my son get in the car
and hit the gas. He had to give it quite a bit of gas (> 2000 RPM) and then
the valve would open very quickly about 45 degrees. It would slam shut as soon
as the engine slowed, again to within a few degrees of being closed. The
slamming shut was accompanied by the rattle.
From this I conclude:
1) Rotation of the valve counter clockwise opens the valve. Clockwise
rotation closes it.
2) The valve has just over 90 degrees of rotation.
3) The valve is very close to being closed at anything below about
1500 rpm or higher irrespective of engine temperature.
4) On my car the valve is open when the counter weight is at the top
pointing forward and closed when the counter weight is to the front of the car
pointing down or a little bit back.
Fred Joslin
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