Greetings all,
As some of you might remember I burned up my #4 piston at Watkins Glen this
season. Inspection of the other cylinders upon teardown showed pistons 1, 2
and 3 were perfect. Because 3 and 4 share a carb, I wondered how #3 could
show no signs of running lean, and #4 ran so hot it failed. Couldn't find
any vacuum leak on #4.
I talked with several of my FOT buddies about the well known problem with
TRactor engined TR's poor coolant circulation, especially around #4. Right,
wrong, or indifferent, here is the basic conclusion I came up with.
The stock water pump pushing water into an unmodified cooling system
doesn't have a prayer to circulate coolant to the back of the engine.
Cylinder #4 will run hotter than the rest and be more susceptible to
detonation. There are two reasons for this, the coolant circulation path
and water pressure.
I'll start with the water circulation through the block. I wanted to see
who the coolant comes out of the block into the head. I took one of my
engine cores, removed the head and pounded out the piston sleeves. I
scraped the lions share of the rusty crud off the liners and the interior
coolant passages in the block and slid the liners back in place. I took my
garden hose stuck it into the water inlet on the water pump and let the
water flow.
I was looking at a classic case of the water taking the path of least
resistance. The water shot up out of the block a few inches in the front of
the block, highest through the passages between the front of the block and
#1, and progressively less and less until at the rear of the block the
water barely trickled out of the block. Then I screwed in a few head studs
and set a steel shim head gasket in place. The steel shim gasket is
designed to block a portion of the passages between the head and the block.
The water flow at the rear of the block was minutely better, but still
almost non-existent. I then took one of Mordy Dunst's copper headgaskets
and put it in place. Mordy identified this issue and mentions it briefly in
his chapter in Kas's new book. The water flow through the holes in Mordy's
gasket is pretty much uniform across the deck. Now we are on to something.
There is a need to restrict the water flow through the passages from the
block to the head at the front of the engine, and progressively open the
passages up towards the rear of the block.
It appears one of Mordy's gaskets accomplishes the task, but I have always
run the steel shim head gasket with great success. Not wanting to mess with
something that works well for me I needed to come up with a way to restrict
the coolant flow in the front of the engine. I talked to my machine shop
about tapping the holes and screwing plugs in the head, but they came up
with one better. They pressed small freeze plugs into the water passages in
the head. Two in the front and two in the teardrop shaped holes between 2
and 3. The two in the front they drilled a 1/8 inch hole in each. They
pressed round plugs into the two in the middle teardrop shaped holes, so
the narrow end of the hole is still open.
I feel I get much better water flow to the back of the block now, but am
wrestling to come up with a way to actually measure it...
Now on to the water pressure issue. The stock pump with it's four straight
impeller blades does not make great pressure. I bought the latest
generation racing water pump from Ken Gillanders. The impeller is radical.
I am running Ken's latest generation harmonic dampener and water pump
pulley, so the water pump is not geared down. Ken was concerned it might
cavitate at high rpm, and suggested I run a water pressure gauge. I plumbed
the gauge into the hole for the block drain at the rear of the block. At
1500 rpm the pump produces almost 20 psi. of pressure, and at the end of
the back straight at Mid-Ohio it pinned teh gauge at 35 psi. That is some
serious pressure for a coolant system. There was concern that I would blow
the pressure cap on the radiator and dump my coolant into the catch bottle,
or possible blow off radiator hoses Didn't have either problem, nor did the
pump show any signs of cavitation.
Kas theorizes that running high pressure in the block will effectively
quench the steam bubbles that are trying to form around the liner, thus
allowing the cylinder to run cooler.
I installed a Griffin aluminum radiator earlier this year. I ran a few
events without a thermostat, just a gutted thermostat plate as a restricter
and a stock water pump. I never saw over 140 on the gauge with this setup.
When I went with the racing water pump, I installed a 160 degree
thermostat. On track at Mid-Ohio, the temp gauge never went above 175-180.
The 16 pound radiator cap never vented any coolant into the catch tank, so
the thinking is the thermostat is providing the resistance in the system to
keep the high pressure in the block. Word of warning, the stock radiator
probably could not handle this kind of pressure.
I have run one event with these changes. I pulled the plugs after each
session, and while I thought I might have seen a little detonation on #4, I
didn't have nor could I find a magnifying glass to see for sure. I was
still seeing high EGT's, but Ken and Kas assure me they are were not too
high. I finally looked the plugs after running very hard in the feature,
and they showed no problems at all. I already put a magnifying glass in my
trailer.
Many thanks to Kas Kastner, Ken Gillanders, JK Jackson and Jack Drews for
the time spent on the phone and the emails, and to Mordy Dunst for his work
on head gaskets and his resizing of the coolant passage holes.
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