One and all, this edited email was on the Alpine list and has some
interesting comments about radiators, fans, etc. The author talks
about Alpines but the general ideas apply to all cars.
Jeff
______________________________ Forward Header __________________________________
Subject: Jarrid,Bill and Chris reply
Author: GDWF22A@prodigy.com (MR RICHARD T TRENK SR) at INTERNET
Date: 9/8/97 7:09 PM
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Bill Lewis wrote on his overheating with the quad row core he installed.
>From the tests done it appears there is a lack of air flow at idle and this
would indeed be expected for an unshrouded core.
Deep, multi row cores require high air speed against the forward face in
order that the air molecules dont become so heated (as they flow through)
that they are too hot by the time they reach the last row of tubes and
fins. For race cars and aircraft, we can use some very thick cores because
the vehicle is never expected to encounter slow air speeds.
Passenger car cores of 2 or 3 row design do not require any suplimental fan
action if the air flow is approx. 15mph or higher. With a 4 row core you
simply need a bit faster air flow in the region of say 18-20 mph through the
core. The stock fan, at idle rpm likely makes around 15-16mph through
the core and if you happen to be facing the wind, then it's speed it added in.
A simple shroud should do the job as you already learned.
However.......I come back to basics as usual! If the radiator is truly
known to be CLEAN, the pump action normal, engine timing normal, water
passages KNOWN to be clean and normal....Then...there was no need to
install a 4 row core in the first place....unless you have a increased
output engine which just might make more heat losses than a stock core
could handle.
On the race engines which pump lots more BHP than stock, we do use a 4 row
core without fan, but then we do not idle this engine for long and we also
use a 15psi cap as well as having screw retainers acting as safeties on all
core plugs in the block and head. We also race with a 60/40 ratio
water/antifreeze mixture in order to obtain a bit more heat transfer than
50/50 would give. A specially modified stat is used to give us 215 deg.
coolant temp. as this is worth about 8-10 BHP (for free) on the dyno.
The engine has no problems running at this coolant temp and with a big oil
cooler radiator in place of the dinky stock series V oil cooler, we can
keep oil temp below 240 deg. on a 90 deg day and we accept oil temp of 250
deg on a 100 deg day. Oil which has seen over 250 deg is never reused
after the race. Enlarged oil pan is used and this has internal baffles to
minimize side slop in curves. This big pan and large cooler increased total
cap. to about 7.5 quarts.
The car ran it's last events under my ownership in about 1992 and finished
up in the vintage car class (Rocky Mt VCC) with a record of 17 first places
in 21 starts. Trying to finish first overall and catch a fast AC Cobra,
the engine threw a rod at 8100 rpm. It has been rebuilt and then sold to a
chap in CO but I don't know if he runs it as he also has a Bug Eye which he
does race.
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