[Tigers] Overheating

Sun Apr 22 14:20:40 MDT 2018

I am always amazed by overheating issues.  Mainly because there are so many
ex0lanations and fixes as there are members of the various lists! Heck, I am
one of them lol, and I have and have my thoughts as well.  Where I am coming
from is the overheating event itself and the causes and maybe not so much
the fixes.  I know my car, now a box stock OEM 260 that came in the car when
manufactured along with the header tank and stock radiator. Over the years
the cooling system has remained the same despite several serious motor
upgrades over the years which have been uprooted and morphed back to the
260. It has never been opened!  

Now one of my engines was a 5 bolt 289 that had heads made into hipo heads
long ago, in the later part of the 60's.  Got the whole treatment, cast iron
suckers. Screw in studs after modifying the head stud bosses by shortening
them  (space needed for the screw in stud wrench flats) and then ported for
flow. 11 + CSR pop up pistons;  forged, Jahns as I recall.  Small combustion
chambers in the heads.  0.030 bore, 0.010 under crank mains, "hipo" crank
which means a good inspection.  I had the pleasure of a Holman and Moody rep
chatting with me at a Drag Race in Santa Maria CA. He was impressed by the
rpm capability and the fact that with my gearing I could pull the front
wheel off of the track on launch.  I sure that was fairly common back then.
I drove that engine as a daily driver for a couple of years, out to VAFB, up
to Paso Robles, San Luis Obispo and all around Santa Maria. Before that, I
once drove the Tiger to Hollywood and to the Playboy Club on a week end
night. WOW. What an experience that was: more people than should be allowed
to congregate in one place at one time. TRAFFIC, can you say. Movement
measure in inches for a good long while. I once surrendered a forward move
when a heavy revolver came out of a passenger window of a car full of
gentlemen who wanted to get in front of me. Certainly so, no problem, lol.
The important part of this is that so far, and I have owned this car since
1967, January, and I have not yet had an unexplained overheating issue. Not
once, not with any engine put into the car. 

I think that some of the issues are due to poor maintenance, poor driving
habits, and mismatched components and missing pieces.  Yes, there are known
factors that come into play when and engine is being assembled, such as
those mentioned by Bugz.  Things like piston clearances, ring gaps, thin
cylinder walls.  We usually mitigate those during design of an engine and
then during assembly making all the necessary checks.  The engine guy most
often makes good engines. Where some of the problems arise come from
mismatched bits and pieces.  Coupled with mismatched power expectations.
What?  Sure, how many of us have lusted after the super spiffy high output
engines making north of 400 or more hp in our little cars?  When we do that
, we seldom consider our driving habits and whether or not this is a daily
driver. Even a high output engine in safe in a daily driver because of a
number of factors.  Daily traffic is the pits for getting up to speed so the
excess power the engine has simply does not come into play. We generally
sedately accelerate at a small rate to match traffic speeds. And guess what,
you really do not use more hp to get that from your high HP gee whiz engine
than the old 260 produced doing the same job at the same loads. HP is HP and
it takes a certain amount of gasoline to make that HP, no more. Yeah, we all
find the occasion to stomp on it and we accelerate a bit more than we should
or need to but not often. We can pass a bit faster on the freeways but most
of the time we sedately motor down the road with our friends in the other
lanes.  So why do we overheat? Well consider that our vehicles are old and
that over time things have been removed or left off or changed to
accommodate changing driver wants and styles. In this thread I have heard
notions of higher flow rates and higher pressures in the systems, and bigger
or smaller radiators or missing header tanks. SO lets reason out what
happens when we take a stock system designed to use a radiator that came on
a car with a small low output engine. Higher flow means a few things and one
is that the coolant flow is thought to flow faster though the engine
carrying away heat better, but is it?  It could, but that stock radiator may
not be up to the higher flow rate and so all that excess water flow goes
into pump cavitation because you cannot push the water fast enough through
the straw of the radiator. And older radiators are even worse for flow. So,
while your mileage may vary, it is likely that you just spent money for the
honor of owning a high flow pump.  Further, most on our cars have had
plumbing changes made.  Header tanks seem to be removed way too often. But
those suckers play an really important role. One is that they are a source
of extra cooling water. And the manner and location in the system permits
the radiator to be as full as it can be if you keep the tank topped off.
Next is finding a replacement radiator for your car or mine for that matter.
Are the tanks the same size as OEM? Is the surface area the same how about
then number of rows and  fin spacing? I expect that an  Alpine rad will fit
but it is not adequate for flow or hp needs.  Put a high flow water pump on
that and nothing improves.  And new car radiators are smaller because they
want the engine to be more efficient. Thermodynamics says that hotter is
better for efficiency. So with the mostly aluminum engines and the ability
of that material to shed heat like a banshee they can use very thin
radiators.  Other issues crop up as well, as I personally ascribe to.
Instrumentation.  Can drive you bonkers trying to get sorted out. Old gages,
old sensors, old wiring, old voltage regulators can make your life and
expectations miserable.   My temp gage and fuel gages worked but were not
correct.  I actually had two issues: a poor voltage regulator and I had
removes and cleaned the gage faces and put in new o-ring gaskets between
glass and instrument case. I  miss clocked them just a tiny bit. That
permitted the connection post on one to short out on the case. Just enough
for faulty readings. 

So where is al tis going? Well only to cautionary notes. Look carefully at
your expectations before, during and after any modifications and make sure
that the bits and pieces you have installed or want to install are
compatible in size and capability. Make notes of everything that the errant
system does and what the conditions are that might have cause the issue:
like oh yeah, I had my foot into it for 10 miles and golly gee it overheated
with my small pump and radiator. Well, yeah.  Sh*t does happen and sometimes
it can be a full on bugger to sort out. I think a lot of the issues are
coolant quantity issues. A cup of water is not as effect as a swing pool of
water so make sure the radiator is full to the top.  And for goodness sakes,
when asking for help, on any issue, give every bit of information you can on
the bits and pieces and conditions and ambient conditions that you can
remember and dig up right up front. In the past I have seen some like , "my
motor quit running as I was just driving down the road. What's wrong with
it?" And this group is the most helpful of any I have ever seen, so a round
of applause to the key  knowledge folk who help to keep our LBC running
happily. 

Now back out to the shop to do some welding on my radio telescope mount. 

Flame wars on, ok to shoot the messenger (me), etc. 

Mayf

_________________________
drmayf
Worlds Fastest Sunbeam, period.
204.913 mph flying mile average speed
210.779 mph exit (not top)  speed

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