junkyard 396ss coolant advice, The answer........

[Julia Wakeling]

You're not "too far off topic" for me.  That's where I'm coming from.  The
Good O'l days.

Your answer is..........
"Air flow".

Your supposed "1900 CFM" 16 inch fan.  Well....... isn't.

One of my many projects in the garage currently is a '67 Chevelle, Marine
Block 502 Big Block Chevy (siamese cylinder walls) with an 8-71 weiand
blower and dual Holley 950 mech. sec. dbl. pumprs.  Needless to say, it runs
hot.  My problem was trying to get an engine designed to suck up 70 deg. F
lake water, and get it to run in the confines of a radiator system that
doesn't require an onboard 100 gallon kiddie pool.  No matter what electric
fan I tried, none worked.  So, I went testing.

I found that nearly ALL fans that give their ratings in CFM overboasted by
at least 40%.  My dual 2200 CFM electric fan setup pulled no more than 2400
CFM together.  Many of the ratings given are at 16 volts, free spinning.
Not at the opperating 13.4 volts, snuggled close to the radiator.  In
essence, you're only pulling about 800-900 CFM through your radiator in
"actual" numbers.  And that number is about 600-800 CFM LESS than what the
stock 396 requires for air flow.

Here's my suggestion on how to cool a Monster.

Contact Bee-Cool Radiators.  You can get then at most of your local hop-up
shops etc...  Get a 2 core aluminum radiator for your GMC, or anything close
enough to be fabbed up.  A Griffin would work too.  Run a 195 thermastat.
Then, run a standard clutch fan, or aluminum flex fan (prefered) off the
waterpump pulley.  The horsepower loss is negligable.  On a dyno, my engine
lost a whopping 9 horsepower spinning the flex fan fan.  (ohh, it's a 978
horse engine, by the way.)  However, the lower coolant temps showed more of
a gain than the loss from the fan draw.  At 205, the engine ran it's best
with 978 horse, while at 220 F, it pulled only 952.  The lower the temp got,
the horsepower was slightly lower, (140 F, 965, and steadily climbed to 978
at opperating 205).  Carb set-up and timing final advance is most likely the
reasoning for it making the most power at 205 F.  But you'll find the power
where you need it and want it with enough tuning.

The CFM air flow is RPM relevant on a clutch or flex fan, and will pull the
air needed as RPM's increase.  AND it won't block air coming through the
radiator at speed like most electric fans do.  While you're cranking down
the highway, the electric fan is actualy PUSHING air away from your radiator
that would normaly flow right through under it's own velocity.  But since
the electric fan can only pull the ammount it's capable of, any additional
air gets caught in the high pressure area in front of the radiator, and goes
right around it.  So at 65 mph, you're pulling in the same amount of air you
would pull at idle.  Everything else is waste that never gets through the
fins because the fan bottle necks it.  While a clutch fan, or flex fan will
pull exponentialy as engine RPM increases.  And at speed, there is no
"blockage" (aka, the fan on the radiator pulling ONLY what it's speed will
allow) on the radiator itself to hold back additional air flow that naturaly
wants to flow through the radiator.  Once you eliminate the high pressure
area bottle neck, your fan on the water pump will have an easier time
pulling the air charge, as it's already moving through the fins.  Thus,
you'll loose less horsepower than you think you would be loosing by driving
the fan with the engine.

With a Bee Cool 2 core, a flex fan, and a 195 thermastat, my Chevelle runs
205 F all day long.  Even in 105 F weather in traffic.  And it makes the
most horsepower at that temperature.  It's all just a combination of air
flow, and heat transfer.

Tim Wakeling
Unleaded Racing Technologies

Additional notes below:

----- Original Message -----
From: "James Northrup" <james_northrup at yahoo.com>
To: <diy_efi at diy-efi.org>
Sent: Tuesday, August 28, 2001 10:03 AM
Subject: junkyard 396ss coolant advice


> i have a '73 gmc sprint with a 396ss motor in it.
>
> its from a 68 chevelle SS with oval ports, according to the kid who sold
it
> to me, and the heads have been ported leading me to beleive it very well
> could be a factory job and either the 325 or 375 horse edition.  the GMC
> sprint was in NO WAY set up for performance at any point when i got it.
it
> had a th350 with a 2:73 and a 2nd hand holley 600.
>
> presently it runs a holly vaccuum 750, with stock intake, no AC, bypassed
> the heater, and the water-pump is directly belted to the crank pulley.

                why direct?  No alternator???  May be slipping??

> Accell coil atop a new HEI.
>
> it has a mechanical lock-up-in-4th 700r4 with 4:10 richmond ring& pinion
in
> a 10(.5?)"  housing, a 1900 cfm 16" electric fan, 2 core radiator from its
> original 350 4bbl.  the thermostat is a 195 degree, the fan kicks on at
180
> deg+ via a 1-wire copper thermostat and adjustable dial in the radiator
> intake.


                Mount the coolant temp sensor at the left side cylinder head
coolant passage pipe fitting.  It's Under the header, in the center of the
cylinder head.  That gives you a more accurate reading of what the
temperature coming OUT of the head and cooling system is.  That point is the
closest point to the center of the cooling system that you can read fairly
accurately.  It's actualy on the way out of the engine at that point, but
unless you put a boss somewhere inside the pan, you can't realy get closer.
You might not be as hot as you think you are INSIDE the engine.  Or, you
could be a LOT worse.  Use a laser pointer style temperature gun to find the
efficiencies in the radiator and cooling system.  Also, hit the pointer at
the hoses too.  Yes, the hoses even act as a part of the cooling system.
They DO dissipate heat.  With good numbers at several points, you can make a
VERY close guestimation as to the "actual" mean temperature of the coolant
as it enters and exits the engine, and come up with a number that IS, or is
as close as you can get to "THE" actual mean coolant temperature of the
engine.  If you're showing 220 at the center of the left head, you're REALY
hot.  As it still has some time in the engine left untill it reaches the
water neck.  While you might be only at 185 at the head, and going up to 205
at the water neck, and 165 at the lower hose inlet past the radiator.  Read
the WHOLE system.  One point will just tell you what it's doing at that
location.  Rememebr, a cooling systems job is to let the water cool down the
engine block, heads, and intake manifold.  The water takes on the heat from
the engine metal, and then transfers it to another location to dissipate
that heat that it's transfered from the block etc...  All of those
"engine"areas BUILD heat in the coolant.  Once it's out of the engine water
neck and on the way to the radiator, the coolant is COOLING, not heating up.
Once through the radiator and in the lower hose, it makes the trip again.
Take ALL of those numbers, and go from there.  Build the BIG picture.  Even
the volume of coolant being transfered by the pump can be traced with
reading.

                If you think you might not be moving the coolant fast
enough, you might want to try a factory style high volume water pump.
Without good numbers to build a story on, it's all a guess.


>
> I'm curious if anyone can comment on said cooling configuration, the
> radiator likes to dump out the recirc hose when i shut down the motor.
the
> mechanic who installed the longblock tells me the small radiator warrants
> the higher thermostat to keep the coolant in the radiator cooling longer
> before it kicks into the engine.


                True...............But if it won't be cooled by air flow
while it's in the radiator, it's only going to go back into the block Hot!!
As for the overflow bottle popping off, sounds like you could be hotter than
you think, or, you might have an inadequate coolant overflow tank.  I use a
Barry Grant tank with a shutoff valve and vent valve also.  You may consider
an aftermarket tank.

>
> yet another mechanic tells me to take the thermostat out entirely, still a
> third tells me that the smaller radiator warrants a higher temp and both
> mechanics are right, depending on the size of the radiator.


                Totaly incorrect.............a "lo-tech" falacy.  You'll
never end up using the air flow to cool the coolant (as it's just winging
through as fast as it can go), and thus, you'll keep bulding temperature in
the water untill boilover.  Although it will build up temperature Slower
than with a thermastat, there is nothing to keep it from continuously
building temperature.  "Tuning" the thermastat is sometime neccessary.
Drilling a few or one small hole (1/32 to1/16 diameter inch etc..) in the
T-stat to allow continuous coolant flow has been one of the many little
combo's I've come up with.  But as for dropping the T-stat entirely??  Bad
idea.  Tell that technitian to go take cooling systems 101 over again.

>
> according to mechanic#1, who replaced the intake and carb, he leaned out
the
> mixture, so it doesn't "dog out" the new longblock.  this just smells
> suspicious in light of all its ferocious cooling deficiency.


                "Dog Out"?  What exactly is "Dog Out"?  Did he lean out the
idle mixture, or rejet the carbs?  If he rejetted the carbs, how did he do
so, since you've only got 100 miles on the engine for testing and tuning?  I
put triple that mileage on an engine during tune time to get the absolute
BEST possible mix at ALL RPM's and driving conditions.  Did he check each
header primary tube with a lean/rich gauge yet?  What do the plugs look like
if he's jetting it "Old School"?

                Idle mix won't do a thing for you once to crack open the
butterflies.  At that point, a Holley runs primarily through it's main and
secondary jets, and not the idle jets.  Leaning the idle mixture would only
change idle quality, and keep it from "Loading Up" the spark plugs with
carbon at idle.  What exactly did he do?  And how did he do it all in only
100 miles?

>
> i haven't even got 100 miles on the new motor, would hate to boil it,
anyone
> else's experience would help.  do i just need a new 4-core radiator?  or
> should i be suscpicious that mechanic#1 is lining up his next longblock
> replacement revenue at the  expense of my new rings and bearings?


                    No.  He's just coming from the "Lo-Tech" old timers
guild.  Just because he doesn't know doesn't make him a crook who wants your
money.  It just means he doesn't know, and doesn't have the heart to tell
you.  Or worse.  "He THINKS he knows".  Once again, suggested courses are
"Cooling systems 101", and "Combustion 101".


>
> I'd like to solve the issues with the coolant so i even have an engine
that
> could bear soem fun stuff, like an efi project. apoligies if its too far
off
> topic.
>
>
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