Cooling Strategies

[Roy]

It seems to be non-ending topic here and I hate to re-hash this but in trying to make radiator decisions the question keeps coming up. Will the "stock" CJ V8 conversion aluminum radiator provide for adequate cooling of the 468 BB Chev? The old, general, basic "rule" I seem to remember is "1 sq. inch of core for each cubic inch of displacement." The CJ-conversion rad roughly measures 372 square inches of core. Comes up way short.
I plan on running hooker headers, wrapped in thermo-tec, separate coolers with fans for auto trans and power steering and have an Edelbrock hi-flow aluminum water pump. While those may help, will it be enough or should I figure on modding the core support to accept a larger rad? I have a source for alum cross-flow rads in 19 tall by 22,24,26,28 and 31-inch widths at 129 bucks each, no price diff for width. Looks like a 19x26 would be closer (estimate the core less tanks from the aforementioned dims)....
or go even larger with the 28 or 31 inch....once the cutting begins why stop for a 26?

[randyscycle]

Well, here's my experience: Others' results may vary.

I am running a CJ to V8 conversion aluminum radiator in front of my 396 Chevy. I have around 10:1 compression and a marine cam with just under .5" lift and around .280 duration give or take. I am running the Holley TBI. I have a 195F thermostat installed and use a Ford Taurus electric fan (4500 CFM on high input) with a thermostatic fan control. I also have an aluminum hi-flow water pump. I run a trans cooler in front of it, plus use the radiator trans cooler as well for my TH400.

With all that, on a 95-98 degree day (the worst I ever see here in VA) the temp stays around 210 degrees idling in traffic with the fan running pretty much constantly after a decent stretch of road speed with stock gears. It will slowly creep upward to around 230 if I really sit a long time. On the trail, the temp never gets above 200 or so, and the fan will cycle off and on all day.

Loaded or unloaded seems to make no difference, and even with my S250 shelter in the bed, it doesn't seem to change. I don't tow with it, so I can't say how that would affect things.

One thing that I've always had a hard time wrapping my head around though, is that no matter how big a radiator you stuff into the core support, there is still a limited amount of air that can get to it, due to the size of the hole in the front sheetmetal. Many tell me it doesn't matter, but I can't see how it wouldn't matter. I also think that ventilating the hood wouldn't be a bad idea, especially if you start adding multiple coolers and fans and such.....

[Roy]

Randy...I appreciate your input. You have always come across as knowledgeable and experienced. I am not disputing your truck's history. I am leaning towards a similar setup. But, my main concerns are the 20% larger displacement, and clearance and fitment issues. I have no problem enlarging the opening for entry air, and have some things in mind for flow and exit. The trans and p/s coolers will be located behind the cab below the bed to help exit air streams and reduce engine bay temps.
I expect to do lots of low-speed trail riding and idling during use of the on-board air and welding systems. These situations are influencing me to consider some overkill on the cooling system.

[Doug]

Randy, roughly estimating...the radiator is, lets say 50% fin and tube, 50% air space. The opening is 100% air space. You could easily have twice the radiator behind the small opening and still get enough air through the radiator. This also fails to account for the turbulence through the radiator and the cleaner flow through the opening.



Roy, in know it's not apples to apples, but just for info: I'm still running a sad stock 230 radiator with a few tubes pinched shut on a 327. I ran a 400 for a while too. I had trouble cooling the 400 when I'd get the bottom third of the rad plugged with mud. Some days when wheeling in a lot of mud I'd retard the timing as much as I could and could get along okay.

FSJ brackets are at least a couple inches wider, were you closer I'd give you the whole front. I have a couple to spare.

[Roy]

I appreciate the insights and the offer Doug. I am probably gonna go with the CJ-conversion rad and see what happens. I am not ready to go against the insights of two 'Zone Gurus.........

[Doug]

Oh, I run a stock clutch fan, no shroud. The 400 cooled better when I had the shroud in, but somewhere along the line it started making contact with the fan and I ditched it. Just haven't taken the time to make a new one with more room. The 327 doesn't seem to mind.

[Roy]

Due to motor placement within the frame rails and the 1-1/2" or so of body lift I am planning on running dual-electric cooling fans mounted in a shroud.
What do you think about that Doug and/or Randy?
I will proceed full speed ahead upon your approval. I figure that conditionally releases me from criticism if it doesn't work out........

[randyscycle]

I think you'll be fine with the dual fans. What CFM are they?

I only ask, because so many of the aftermarket ones I see are actually pretty low compared to some factory ones I've seen. And a lot more spendy too. Not to be biased, but the Ford Taurus shrouded fan I use is 4500 CFM on the high speed setting. It literally sucks bugs into the radiator sitting still! Plus I picked one up off of e-bay for around 60 bucks shipped.

The shrouded type (in my personal experience) definitely work better than the open fans. Honestly, I can't say the open style fans do much good at all except as auxiliary/supplemental fans on an A/C condenser, or trans cooler.

I think its a solid plan, and having the body lift should also allow slightly more exit area for the hot air too. I know my truck tends to build up a lot of underhood heat at lower speeds. I keep considering a Waggy hood with a couple of vents in it, just 'cause. Still though, I haven't really needed it yet.

[2ndA]

Just my 2 cents: Friend had a 715 with a basically stock 472 caddy. Used the core support and factory radiator from a J. Used a GM electric fan for cooling and a 180 degree thermostat. Drove a TH400(or maybe it was a 700R4), NP205 and modern danas with gears in the 4's on 38's or so. The truck never ran over 200 with the big block putting out 350hp+, even when doing light towing.or running high speed(around 100mph). I know he had a cooler for the PS and another for the trans, but both were mounted somewhere else besides directly in front of the rad.

So it's neither that tough or expensive to keep things cool.