Chevy SR Update
Posted: Sat Feb 18, 2012 2:18 pm
A quick update on my progress with the Chevy. My EGT is fixed. Silly me,
when seeing a red and black wire coming out of the gauge and a white and
black wire from the probe, I simply assumed black to black, etc. Well,
that's wrong. When I mentioned cherry red headers to an engine builder
friend, he said that's not right. He suggested the timing might be too far
retarded among other things. With the EGT working I was seeing the exhaust
temp pegged at 1600F or more (end of the gauge). I checked the timing at
about 2000RPM and it was only 10 degrees advanced. I made a slight timing
adjustment and tried again. At 30 degrees advanced I was only seeing about
900F EGT. Wow. I didn't know timing had such a great affect. I also
forgot how little movement of the distributor it takes to get a large change
in timing. (I don't move the distributor while the engine is running as is
normally done because I'm afraid of the big piece of aluminum channel bolted
to the prop flange that I use to turn the engine for valve adjustments. I
still have more valve adjusting to do and was too lazy to take it off.) At
about 20 degrees BTDC at 2000RPM the engine seemed to be running the best
and the EGT was about 1400F. I'll probably go a bit more advanced. Couple
of interesting things. If I shut down by simply turning the ignition off I
often get a small pop from the carb and a very abrupt engine stop. That has
stained the bottom side of the top cowl an ugly black. If I shut down by
pulling the mixture to idle cut-off it shuts down nicely - no pop, and
doesn't seem as abrupt. The other interesting thing is that the mixture
control definitely affects engine smoothness and you can lean to idle
cut-off. But I am not seeing any noticeable affect on EGT when adjusting
mixture as you normally see with an airplane engine. What's up with that?
I ran the engine long enough to get to operating temp (and beyond). I saw
engine oil reach a max of 210F while running. (It soared to 250F) after
shutting down.) Coolant temp reached 240F when I decided that was enough
and shut down. It didn't overshoot after shutdown the way engine oil did.
It just started cooling off right away. Once it came off the peg it
continued to rise quite rapidly until shut down. I saw a max coolant
pressure of 10psi. I was sort of expecting to see some tangible evidence of
when the thermostat opened, but all I saw was a steady rise in temp followed
by a steady rise in pressure. Since there was a short delay in seeing
pressure start to rise after the temp began rising rapidly, it could be that
the moment pressure comes off the peg is also the moment when the thermostat
opens. My block has no coolant bypass so when the thermostat is closed
there is no coolant flow anywhere. The pump is simply cavitating and
coolant is stagnant in the block and the radiator. No pressure in the
radiator until the thermostat opens. (That's where my pressure sensor is
located.) I'm assuming (hoping and praying) that the rapid rise in coolant
temp was because of no airflow.
I'm not very happy with my Autometer tach. It jumps around a lot. Even
when it's at it's smoothest, which isn't very often, I can only see RPM +/-
about 100. That's terrible. Either something is wrong or I am going to
have to get a better gauge.
My $12,500 CAM-500 gear reduction is leaking oil somewhere. It appears
where the gear box bolts to the adapter plate and I can't tell exactly where
without removing it. It also spewed a bit out it's breather. Dangit!
Lastly, and most importantly, did you know that the word "cavitate", and
"cavitating", are not in the dictionary. Only "cavitation" is a listed word
and even that is in only one out of three Webster's dictionaries that I
have. My spell checker only recognizes the plural - "cavitations". What's
up with that! (I'm starting to sound like Jerry Sienfeld.)
Mike Kimball
044SR
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when seeing a red and black wire coming out of the gauge and a white and
black wire from the probe, I simply assumed black to black, etc. Well,
that's wrong. When I mentioned cherry red headers to an engine builder
friend, he said that's not right. He suggested the timing might be too far
retarded among other things. With the EGT working I was seeing the exhaust
temp pegged at 1600F or more (end of the gauge). I checked the timing at
about 2000RPM and it was only 10 degrees advanced. I made a slight timing
adjustment and tried again. At 30 degrees advanced I was only seeing about
900F EGT. Wow. I didn't know timing had such a great affect. I also
forgot how little movement of the distributor it takes to get a large change
in timing. (I don't move the distributor while the engine is running as is
normally done because I'm afraid of the big piece of aluminum channel bolted
to the prop flange that I use to turn the engine for valve adjustments. I
still have more valve adjusting to do and was too lazy to take it off.) At
about 20 degrees BTDC at 2000RPM the engine seemed to be running the best
and the EGT was about 1400F. I'll probably go a bit more advanced. Couple
of interesting things. If I shut down by simply turning the ignition off I
often get a small pop from the carb and a very abrupt engine stop. That has
stained the bottom side of the top cowl an ugly black. If I shut down by
pulling the mixture to idle cut-off it shuts down nicely - no pop, and
doesn't seem as abrupt. The other interesting thing is that the mixture
control definitely affects engine smoothness and you can lean to idle
cut-off. But I am not seeing any noticeable affect on EGT when adjusting
mixture as you normally see with an airplane engine. What's up with that?
I ran the engine long enough to get to operating temp (and beyond). I saw
engine oil reach a max of 210F while running. (It soared to 250F) after
shutting down.) Coolant temp reached 240F when I decided that was enough
and shut down. It didn't overshoot after shutdown the way engine oil did.
It just started cooling off right away. Once it came off the peg it
continued to rise quite rapidly until shut down. I saw a max coolant
pressure of 10psi. I was sort of expecting to see some tangible evidence of
when the thermostat opened, but all I saw was a steady rise in temp followed
by a steady rise in pressure. Since there was a short delay in seeing
pressure start to rise after the temp began rising rapidly, it could be that
the moment pressure comes off the peg is also the moment when the thermostat
opens. My block has no coolant bypass so when the thermostat is closed
there is no coolant flow anywhere. The pump is simply cavitating and
coolant is stagnant in the block and the radiator. No pressure in the
radiator until the thermostat opens. (That's where my pressure sensor is
located.) I'm assuming (hoping and praying) that the rapid rise in coolant
temp was because of no airflow.
I'm not very happy with my Autometer tach. It jumps around a lot. Even
when it's at it's smoothest, which isn't very often, I can only see RPM +/-
about 100. That's terrible. Either something is wrong or I am going to
have to get a better gauge.
My $12,500 CAM-500 gear reduction is leaking oil somewhere. It appears
where the gear box bolts to the adapter plate and I can't tell exactly where
without removing it. It also spewed a bit out it's breather. Dangit!
Lastly, and most importantly, did you know that the word "cavitate", and
"cavitating", are not in the dictionary. Only "cavitation" is a listed word
and even that is in only one out of three Webster's dictionaries that I
have. My spell checker only recognizes the plural - "cavitations". What's
up with that! (I'm starting to sound like Jerry Sienfeld.)
Mike Kimball
044SR
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