Re: [Amc-list] Shroud for 70 Javelin?

[Frank Swygert <farna@xxxxxxx>]

If it cools fine going down the road and only heats up at idle you most likely have an air flow problem. You don't, however, need a "matched" shroud/fan/spacer. 
One thing to note -- it's common for a relatively fresh rebuilt engine to run hotter than normal for the first 500 miles or so. You might not really have a problem, it just needs to be driven enough to fully break in and stop producing as much frictional heat. Just keep it on the road and don't idle longer than necessary until it's got at least 200 miles on the engine, but after 500 miles if it's not running noticeably cooler there may indeed be a problem. 

First, test my theory! Run the car until it gets up to operating temp. Get an electric house fan at least 15" in diameter and set it in front of the grille. Let the engine idle until it starts to get above the middle of the temp gauge. Turn the electric fan on. If the temp stops rising, or at least noticeably slows rising (depends on size of fan), air flow is the problem.

Now for a recommendation on the cure. First, do you have a clutch fan? 70 shouldn't -- should be a standard six blade fan with fixed (not flexible) blades. If you have a flex fan it could be aftermarket or factory AC fan. According to the TSM it would still be six bladed if factory. If it does have a clutch fan (maybe from a later model car), replace the clutch. They get old and start slipping at low speeds when they shouldn't. 

No clutch fan? Install a universal shroud. The mechanic recommended a matched set because the shroud, spacer, and fan all need to work together. There are universal shrouds though. The flat type that curves around the fan will work with any (or most) fans. They come in 3" and 5" widths. Since the sides are flat you curve it with no more than 1" gap (1/2" is better!) between the fan and sides all around. At least the center of the fan blades should be inside the shroud, a little more won't hurt, but don't go more than about 1/4" in front of the flat fan hub. So you might need to change the spacers between fan and water pump hub. Pretty easy to find a universal spacer at any parts store, should have a universal shroud if many speed parts. You can find them at Jegs, Summitt, and even NAPA too (http://www.jegs.com/webapp/wcs/stores/servlet/KeywordSearchCmd?storeId=10001&catalogId=10002&langId=-1&N=4294933957&Ne=1147708&Ntt=shroud&Ntk=all&Nty=1&D=shroud&Ntx=mode%2Bmatchallany&Dx=m
 ode%2Bmatchallany&partTypeSelection=4294933957%3A1147708).

If you want a bit more of a "polished" look try one of these (http://www.metropartsmarket.com/catalog/classicmustangparts-c7s3.html). They are Mustang shrouds, don't cost a much more than the universals, but would look almost factory. Speedway has applications listed for common hot rods, but the shrouds are intended to be universal in nature. Just match one up to the room you have and size of radiator. After you get and mount the shroud you'll need to properly space the fan. The shroud from a six cylinder Concord, Eagle, or even CJ or full size Jeep (XJ and Wrangler use a short wide radiator, which won't work) should fit the radiator also, but you might have to space the fan. If you can locate a factory setup of course it's just a bolt in, but shrouds weren't common before the mid 70s except on AC equipped vehicles, and those weren't particularly common as they are now. 

A typical fan shroud works by improving the efficiency of the fan blades. As the fan turns it pulls air forward, but a lot of air "slips" off the ends of the blades sideways. Stick your hand on the sides of the house fan (assuming it's not a "box" fan!) and you can feel air blowing to the side a bit. The flat universal shroud "fixes" this, forcing the air to go through the radiator and not to the sides. A factory type shroud that covers the whole radiator works better, as it not only improves blade efficiency but also directs the air through a larger portion of the radiator core. Just improving fan efficiency makes a huge difference though. 


-------------
Date: Wed, 16 Jul 2008 19:42:00 -0400
From: "Chris Peters" <cpeters1@xxxxxxxxxx>

I had my 70 304 rebuilt for my Javelin a few years ago, and have finally
gotten around to driving it some.  

It seems to overheat at idle.  Radiator was cleaned professionally.
Thermostat is new.  Water pump is old but does not leak.  My car had no AC, and never had a shroud (at least when I got it in 1982).  It never had a heating problem before the rebuild, and I drove the car hard in hot Florida for years.  If I run on the highway, it seems to keep a steady temp.  When I come off it seems to immediately start to heat up.  If I idle for a prolonged time it will keep getting hotter.  It has never seriously boiled over, but does pee some out after I stop, and one time with some slower driving it did pee enough out that I had to add water (it was below the tubes).  

The guy who built the engine feels there is nothing that was done to the
engine to cause heating, especially on a 304.  He is recommending I add a shroud.  He says I need to get a matched shroud, fan and spacer. And I thought finding a shroud would be hard, now I have to find all three pieces. Of course I could get a 
new radiator, a new thermostat and a new water pump first.  

Anyone have any recommendations on where to start???

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
(free download available!)


_______________________________________________
Amc-list mailing list
Amc-list@xxxxxxxxxxxx
http://splatter.wps.com/cgi-bin/mailman/listinfo/amc-list