Requesting cooling/radiator/fan help for a slant six

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halfafish

halfafish

Damn those rabbits, and their holes!
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Gurus of the forum, I am soliciting some real-world feedback on radiators, fans, and cooling. Opinions and theories are also happily accepted!

My car is an almost completely unmolested 66 Valiant, currently sporting the original /6 with 3-speed column shift. I am in the process of building this into a fun sleeper, keeping the slant but upgrading all the undercarriage systems, and swapping to an A833OD and 8-3/4 rear end. It is projected to make about 170 HP and about 230 ft/lbs of torque when done.

When I got the car, it was leaking badly everywhere, so I got everything fixed including a new radiator as documented in this thread.

Radiator Swap:

66 Valiant slant six radiator upgrade/swap

Then while cruising forums in my eternal quest for knowledge, I found this video dealing with HP loss due to the type of fan. The bottom line was, if using a belt-turned fan a clutch fan setup has the least drain on performance.

Engine Masters fan test:



This test made me think with HP and performance coming at a premium for the slant, minimizing HP loss would be a good idea. Further digging indicates the only hope for an early A and a clutch fan came in a few threads stating a setup from a late 70’s MB 280SE will bolt right up, and is much more compact when trying to get it to fit between the water pump mount and the radiator. So, I order the clutch and fan, which sure enough are quite a bit thinner. Together they measure only 2-1/2” total depth. This would be great news, except the Champion radiator I installed is a 3-core and quite thick. I have only 2” clearance between the water pump and the radiator.

So, this brings me to my questions on radiators, fans, and cooling. If I were to repair my original radiator, I would have plenty of room for the MB clutch and fan. The factory unit measures 19”x17”, and only two cores. The Champion is 22”x17”, and is a 3-core. I can run the Champion with a fixed factory 4-blade or 7-blade fan (big HP drain). I can run the repaired original radiator with the MB clutch fan (very little HP drain).

My experience with slants back in the 70’s was they just about never overheated, but that was with a stock engine. Would my mildly built slant do OK cooling-wise with the original two core radiator and the MB clutch fan? If so, that would be my preference as it would drain less HP, and look much more stock to fit in with the sleeper mode.
 
There were two different width radiators for the 66 "A" bodies. I forget the width off the top of my head. The standard slant six radiator was smaller (it had a large mounting flange on the pass side. The heavy duty radiator was wider. The core was the width of the core support opening, and had a smaller mounting flange. In your case, I think the standard radiator would work OK. The larger HD radiator would give you an added safety factor. Just make sure either radiator is in good condition.

PS: I would fab up a shroud, to increase the effect of the fan. Ever see a clutch fan without a shroud?
 
That test is biased to a situation that barely exists. How often will your engine be spinning at redline? And how many of us are running direct drive fans?
And how often will you be running it up to 100mph?
No, if you are a streeter, your run is 1.5 to 2 gears long; from zero to 60 and then you are done.So you will hit redline probably just once with that super-wide-ratio box. It would take at least 3.73s to hit redline twice.
Put a thermostatic fan clutch on it and call it done;
Or, on a slanty which barely makes any heat in the first place, you can get away with a viscous clutch.
As you may know, the viscous coupler allows the fan to lag behind the coupler quite a bit, and during a WOT run it will never reach pulley speed. I wonder if it would even reach 50%. So the power loss is minimal. But you can prove it; stick it in second gear and make a run from say 2500 to 5000 and time it. Take a best of 3. Then take the fan off and repeat. Run the car at 25mph to cool it off if the temp starts to rise. Let us know what you discover,
I cool my 225 with a 4 blade direct-drive low attack-angle fan, a teensey rad, and no shroud at all.This engine is only warmed a little with 9.5 SCr and a small cam.
Good luck.
 
I think your stock rad has an excellent shot of cooling this enough; /6 rads typically had plenty of capacity. Blocking them in winter with cardboard is not uncommon just to keep enough heat in.
Plus:
- the /6 block sides shed a lot more heat directly into the air than the V8's
- your Champion radiator in nothing particularly great.
- your HP level is not all that high
So if you want to do the MB fan, then I think you will be OK.
 
nm9stheham said:
I think your stock rad has an excellent shot of cooling this enough
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I don't.

/6 rads typically had plenty of capacity
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Nope. Without the heavy-duty cooling package or the trailer-tow package or factory A/C, they had minimally, barely adequate capacity for average driving conditions when everything was brand new. These were cheap cars, and Chrysler squeezed every last fraction of a cent out of them that they could.

Blocking them in winter with cardboard is not uncommon just to keep enough heat in.
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LOL! Only on cars that aren't maintained properly. That halfaѕѕedness doesn't mean "Wow, that car has a super great radiator! And its engine doesn't put out much heat!", it means the car's owner either can't afford to buy a thermostat, or is lazy and ignorant.

- the /6 block sides shed a lot more heat directly into the air than the V8's
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This is a made-up factoid with no basis in reality. I'm not saying you made it up, necessarily, but somebody did. I will happily eat those words without ketchup when someone shows me valid data backing up the claim. Until then: no sale.

your Champion radiator in nothing particularly great.
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I agree.

- your HP level is not all that high
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Agree.
 
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AJ/FormS said:
That test is biased to a situation that barely exists. How often will your engine be spinning at redline?
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That's only one of several basic flaws in this "test". See here (especially 3rd paragraph and beyond) and this other thread starting here.

And how many of us are running direct drive fans?
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Most of us with early A-bodies with Slant-6 engines.

And how often will you be running it up to 100mph?
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How else am I spozeda get the kids to school on time?

Or, on a slanty which barely makes any heat in the first place
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They make plenty enough heat to overheat in a hurry if the radiator, fan, thermostat, and rest of the cooling system are inappropriately specified or in poor condition.
 
As to that test; I lost all faith in those guys the day I saw that video.
Ok ;Edit
how many of us are running direct drive fans on our performance engines, in order to try to incur as much power loss as possible?

Or, on a slanty which barely makes any heat in the first place.
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Ok, maybe that blanket is a bit big;
I've only had 4 slantys. None of them ever made decent heat in winter; -25*C to -38*C up here in Manitoba.I think that converts to -13*F to -35*F. Up here,that little 4 blader is more than sufficient in winter to air-cool the beast with the rad completely blocked, a proven 195 stat, a recently overhauled engine,and a new heater core. At least that was my experience.
During one winter, I even took the 4-blader off, during the coldest part of winter.The heater core was the sole heat-exchanger! I don't recall how hot the engine ran, but I could finally see out the window. Ok that's a bit of an exageration, so; I could finally take my mits off.lol
But maybe 4 slantys is too small a sample. I don't know why I got all of them tho.

And I'll concede that in summer I have overheated one of them. But it still ran 11 miles @ about 40mph, with very little water in it and didn't seem to suffer any long-term damage.
That one was my fault tho, I put a 13# cap on the 1980 radiator, and 11 miles later; POOF!, it popped a 3 inch rupture in the top tank.I don't know what I was thinking,lol. So now after the repair,it runs a 7 pounder, like the rest of my Mopes.
 
There is a new Spectra brand A body HD radiator for sale in the mechanical parts section right now. Looks to be a 22" one with a shroud. Not mine....just sayin'
 
Thanks to all for the help so far. I've read every thread indicated, probably 50+ pages with lots of good info! As with anything, opinions vary...in the interest of science I'm going to give a shot to using my original radiator with the MB clutch fan and see what happens. If it's not enough cooling, I will re-install the Champion with the fixed blade and call it a day.
 
I swapped mine out of a 80s Dakota. Idling for fifteen mins waiting on my slow kids to drag *** out of school the temp gauge goes from p to the m. 170 slant in a 65 Val and direct drive fan. I constantly worry it'll overheat. I know it won't because i keep constant watch on it. Used to puke fluid from time to time but since I added a reservoir out of a newer galant (nicely tucked away and hidden) it has amazingly kept the temp from fluctuating as fast. Having to put fluid in it every so often gets old. Champion makes good radiators, worry about the price later.

About the motor trend test though, how many of us have swapped a motor and went out banging away at it??? I have. To broke from buying parts to get an electric fan or different fan at all. But by god I got a new Holley!!!! That carb was more important than the fan blade imo. Lol.
 
I run a 3 core radiator aluminum
and a 6 blade fan from a a/c car
all is great
 
Dan, If you ever lived in some good cold temps in IN in the winter, you would indeed have seen that the engines needed cardboard to get any sort of heat in them. Well maintained, coolant up to snuff, t'stat just fine. I thought you were in CO for a while....

As for engine surface being large, well it just IS LOL. You are welcomed to measure and let us know, but it is pretty obvious. Heat output direct from the engine block and heads just is.... So maybe it is not a LOT more heat...I have never had any heating issues from a stock /6. And my family and inlaws had 6 of them from 68-76, all A's.
 
nm9stheham said:
Dan, If you ever lived in some good cold temps in IN in the winter
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Michigan…Ontario…Colorado…yep, I think I know a little bit WTF I'm talking about when the subject is wintertime.

you would indeed have seen that the engines needed cardboard to get any sort of heat in them.
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Nope. I drove seven different Slant-6 A-bodies through numerous winters that got down to numerous degrees below zero, and the heaters worked fine without need of any cardboard or other such riggings. I won't claim the heaters were as fast or as hot as those on newer cars, but they were adequately fast and adequately warm. The one exception is when we took the '62 out to the middle of nowhere in the middle of winter in Colorado to photograph Comet Hyakutake. It was about -25°F without including the wind chill. We left the engine idling so we could periodically bring in the camera and put it in front of the heater outlet to thaw the frozen-open shutter; it was up to that, but only got warm enough to help our toes and fingers with the engine sped up.

I've also had the misfortune to be driving Slant-6 A-bodies when they overheated...just like any other car with any other engine would, for the same reasons: faulty radiator, or extreme conditions (real hot day, running the A/C in a traffic jam). Slant-6 cars are not magically immune; the laws of thermodynamics apply equally to them as to any other car.

As for engine surface being large, well it just IS LOL. You are welcomed to measure and let us know, but it is pretty obvious.
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Sorry, no. The world stubbornly refuses to work according to what you or I or some other guy might think is "obvious", because that word really just means "what I think I remember of what I think I understand of what I think I saw". That's why it's not helpful to make claims we can't back up with facts, i.e., science and data.

First you'd have to demonstrate that there's a significant difference between V8s and Slant-6s in the surface area of external engine walls that have coolant on the other side of them. Then you'd have to demonstrate an actual difference in heat loss through that path, because there are other factors at work. For example, "mud" (rust/dirt/crud) tends to gradually build up starting at the bottom of the coolant bath on the inside of that Slant-6 engine wall you say is so big and sheds so much heat. Eventually this mud can reach to (or above) the freeze plugs. Engines thus mudded up have overheating problems not because the heat path through the engine's exterior wall is impeded, but because the heat path from the cylinder to the coolant is impeded.

Until you've got that data, there's more than enough meat and potatoes to go around in a discussion of things that really, actually affect engine heating and cooling; we don't need to pull imaginary ones out of thin air.
 
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FWIW. I cruised Woodward Saturday in my 64 225 Valiant. Not sure what the temp was in the afternoon but probably in the low 80s. A few hours of bumper-to-bumper traffic, like 35 mins to go one mile. Maybe I'm whistling past the graveyard, but the original temp gauge barely got to the first mark. Also endured about 3-1/2 hrs each way at Interstate speeds. Saw a few cars puking coolant but no Mopars.

Slightly warmed up rebuilt 225 +.040, 3-on-the-tree, fuel line mod, Oregon cam, .080 off the head, original radiator and 4 blade steel fan, new replacement water pump, cast iron exhaust manifold.

Never skipped a beat. If it ain't broke......
 
53 year old temp gauge, 53 yr old sending unit, thermostat you recommended.

Sincerely,
Alfred E. Neumann
 
A high-performance engine will not generate more heat in daily driving if it is as efficient as the standard engine. That is basic thermodynamics. The reason many tuners have over-heat issues is that they get 8 mpg, with the extra energy going into heat load. Max HP is due to maintaining torque at high rpm, and mainly from how well you can minimize pressure drops if the gas flows into and out of the engines. Improving that doesn't necessarily ruin low rpm operation.

I understand that 3 cores gives minimal improvement over 2 cores. I suspect the M-B clutch fan with the thinner radiator and shroud would cool adequately, and give less power rob than a fixed fan. Of course, what you need depends on conditions. The OP lives in SW Washington, near the Pacific. Somebody who regularly drives out of the LA Basin (steep 4000 ft climb at 70 mph) on 115 F days certainly needs better cooling, and new vehicles barely meet that. I understand manufacturers test their new designs there. With a little age, most vehicles no longer suffice which is why you see one (often fairly newish) on the side w/ hood up every 1/2 mi on summer days, along I-5 N (Tejon Pass) and I-15 N (Cajon Pass).
 
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