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| [GMCnet] Radiator Fan Woes [message #269447] |
Mon, 12 January 2015 08:54  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma:
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Senior Member |
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When I installed the Cad500, I designed and built a custom front mounting
bracket to use the Olds motor mount instead of using the conventional 68-72
Cad bracket and motor mount. That may have raised the engine as much as
1/2", causing the fan to no longer be centered in its shroud.
Consequently, I've had trouble with the fan hitting the shroud at the top
when I "get on it". To alleviate some of the problem, I adjusted the
shroud up so far that it actually touches the aluminum frame of the engine
hatch.
Still, I had to feather the throttle to prevent fan racket. Finally, I
figured out that one of the transmission mounts must be bad, allowing the
engine to rotate too much. Raising the hatch and accelerating in gear with
the brakes locked almost proved that theory -- except that the front mount
was the weak one.
After debating whether to cast a new mount from urethane, I decided against
trying to learn a new skill at my advanced age. JimK sent me one of his
large inventory of new mounts. Even installing that proved a bit of a
challenge: The new mount had threaded sockets for the bolt up through the
crossmember. But the one that was installed had studs protruding down thru
the crossmember. With the tight vertical clearance above my center-mounted
A/C compressor, the mount would not come out. Figuring the studs were
threaded into the old mount, I tried securing the nuts on them with red
Locktite. Even after setting overnight, the nuts came off easily. Then I
tried JBWeld. Again, the nuts came off. I finally used my reciprocating
saw to cut between the crossmember and the loosened mount; that worked, at
the cost of damaging the powder coating on the crossmember. The new mount
then went in easily.
With the new mount in place, I can "get on it" with only the screeching and
smoke from the tires -- no more fan interference.
With that problem "solved", I decided it was time to order John Biwersi's
new fan and did so about 10 days ago. He shipped me the last one he had in
stock and it arrived last Tuesday. On Thursday, I tried to install it and
discovered a problem: It hit the fan shroud. It turns out that the fan
I've been running is about 1/2" smaller in OD than the 19" of John's new
fan and I don't have that much clearance at the top -- due to the way I
mounted the Cad500.
Besides the new one, I have 3 fans to fit this engine. The smallest is
about 1" smaller than the new one, another about 1/2" smaller, and the
other about 1/4" smaller. I've always run the 1/2" smaller. After the new
one didn't fit, I installed the smallest, which is a "flex fan", though I
believe it came from the factory on a GM engine. I'd never tried it
before, because of the flex feature which I don't generally endorse.
A short test drive proved that the fan clears and seems to be quieter than
the one I was running. I'm going to run it for a while, including next
week's trip to Florida, before deciding what to do next. My options
include using the 68-72 Cad front bracket (probably modified to use my new
Olds mount), continuing with the flex fan, or ordering a custom, smaller
diameter, fan from John. He's checked with the manufacturer and that is an
option. At the moment, that seems to me the best option because I'm very
favorably impressed with the design and construction of the new fan. But
if I can lower the engine 1/2" or so, I can get the benefit of the full 19"
diameter fan. Decisions, decisions -- I'm getting too old for all these
decisions!
In the meantime, I'll be offering the new Biwersi Fan for sale at Lazy Days
next week, or Patterson in March (unless I figure out by then how to use
it). Not because I don't like it, but because I've got too many spares
laying around already. :-)
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc.
www.gmcwipersetc.com
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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