I once chased the same symptoms you are describing in a Pontaic GTO ...
Brand new engine ... bad block casting! Stuff happens. Found it by checking
each individual water jacket until the dead end was discovered. A one in a
million shot, because I suspect air somewhere trapped in the system.
On 7/30/2006 4:57 PM,
mkimball@gci.net wrote to rebel-builders:
-> Yeah, I have heard about needing a restrictor when removing the
thermostat
-> from someone on this list a while back. My next run will be with the
-> thermostat back in place. Running without was a bit of an experiment. In
-> Skip Jones conversion book he suggests running without because a stuck
-> thermostat made him find a place to land real quick once. But I agree that
-> the odds of that happening are very low. I measure water temp in the
-> thermostat housing. I have a thermostatically controlled 16 inch fan on my
-> 20"x20" Ron Davis custom radiator that produces 2500cfm of air movement
(the
-> largest amount of air movement for any fan offered by Summit Racing).
It's
-> supposed to turn on at 180 and off at 170 deg F. It operated as
advertised.
-> I'm pretty sure my water pump is turning at the proper speed. I have
-> standard size pulleys and all my runs have been at 2000 rpm. I did have a
-> retarded timing problem on my initial runs that I saw right away with high
-> EGT. I advanced the timing until EGT settled at about 1300 deg F at 2000
-> rpm. I am running a full dual MSD ignition with a dual pickup distributor
-> using centrifugal advance. Thanks for your comments. I'll let you know
-> what happens when I run with the thermostat back in place. I've got a
-> couple of local engine builders meeting me this week as well. Hopefully,
-> we'll get this solved soon.
->
-> Mike
-> 044SR
->
-> -----Original Message-----
-> From:
mike.davis@dcsol.com [mailto:
mike.davis@dcsol.com] On Behalf Of
Dave
-> Ricker
-> Sent: Sunday, July 30, 2006 4:03 PM
-> To:
rebel-builders@dcsol.com
-> Subject: Re: [rebel-builders] V8 Cooling Problem
->
-> Mike
->
-> One of the things we learned as "gospel" when we were running small block
-> Chevs
-> in race cars was to not run without a restrictor (or a thermostat) becaue
-> the
-> water doesn't have time to cool as it passes through the rad unrestricted.
-> This
-> was according to Smokey Yunick who apart from helping to develop the
SBC had
-> plenty of success in professional racing. He recommended a diameter of
-> about
-> 11/16" for the restrictor.
->
-> He also had some definite views on the efficiency of the cooling system of
-> the
-> SBC and via Moroso marketed a coolant re-routing system to make sure
the
-> coolant
-> ran evenly through both banks of the engine. He also felt that the water
-> pump
-> could be turned too fast under some conditions losing pumping efficiency.
-> He
-> said running the system at about 220F with up to a 25 lb cap would give
the
-> highest output but this is for 2 HP/cu in kind of tuning. See "Smokey
-> Yunick's
-> Power Circuits" ISBN 931472-06-7.
->
-> Another book I have says the same thing about the thermostat in
performance
-> applications, basically if it was designed into the engine by GM then it's
-> there
-> for a reason. I expect the reason for leaving it out is to remove one more
-> item
-> that "could" fail but in all my time I've never seen it happen on the street
-> or
-> track.
->
-> Where are you measuring the water temp? I presume you're sure it is
-> measuring
-> water temp and not in an air pocket? Coming from the engine or going to
it?
->
-> BTW we ran a standard copper 4 core GM double crossflow (over & back)
rad
-> like
-> yours and a "flex" fan. I'm guessing you have an aluminum 4 core rad and
-> you
-> kept "good" airflow on it during the test?
->
-> OK, enough about the wet end of the system, what are you running for
timing?
-> Fixed, variable, settings? I have definitely seen engines overheat with too
-> much timing and run badly because of retarded timing. The timing wants
to
-> be
-> tailored to the RPM and load as well.
->
-> OK, down off my soapbox, hope all this helps!
->
-> Cheers,
->
-> Dave
->
->
->
->
->
->
->
-> Mike Kimball wrote:
->
-> > I know that I should probably be on a hot rod list for questions like this
-> > but I also know there are people on this list that know about high
-> > performance V8 engines. And it is on a Super Rebel after all. Anyway,
-> when
-> > I run the engine the temperature rises steadily over about a ten minute
-> > period. The pressure starts rising about 5 minutes into the run. The
-> > pressure continues to rise until reaching 16psi as the temp passes about
-> > 190-200 degrees and then my 16psi cap opens and coolant starts
spewing
-> out.
-> > The temp continues to rise until I shut it down shortly thereafter. Any
-> > idea why the pressure builds steadily and doesn't level off before
-> reaching
-> > 16psi? I checked an auto supply manual at the local auto store and
Chevy
-> > 350 equipped cars and trucks for decades have used 16psi caps or less
-> except
-> > for a rare 18psi application. There are only a couple of things different
-> > about my installation versus a car/truck. My radiator is under the
-> engine,
-> > roughly horizontal. It's tilted about 30 degrees with the inlet and
-> outlet
-> > on the high side. I have no thermostat installed per Skip Jones' Chevy
V8
-> > aircraft conversion manual. The thermostat housing is taller than usual
-> and
-> > the cap mounts there.
-> >
-> > Mike
-> > 044SR
-> >
-> > -----------------------------------------------------------------
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-> > -----------------------------------------------------------------
->
-> --
-> David A. Ricker
-> Fall River, Nova Scotia
-> Canada
->
->
->
->
->
->
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