Motor is a 360/408 stroker with single groove pulleys, and a high volume water pump. Currently the crank pulley is approx. 5-1/8" OD outside, and the water pump pulley is approx. 6-3/8" OD outside. -- A local radiator guy suggested that I go to a 1:1 ratio or possibly overdrive the water pump by making that pulley smaller than the crank pulley. -- He says that this would aid with cooling. -- Is it possible that doing this could cause other problems ? -- Comments ? -- We've already dealt with radiator, thermostat, coolant, shroud, timing etc., so let's not get into that, on this discussion. -- Thanks

 

That's exactly what I did by using pulleys from a 440 on my 383. I believe Chrysler sized pulleys according to engine size and accessories like A/C to enhance the cooling system. The results are basically a bit higher coolant pressure in the block as you try to force more coolant through a predetermined sized hole, namely the thermostat. A bit higher pressure in the block's passages inhibits the formation of small air bubbles on the cooling jacket walls, the flow volume is determined by the thermostat opening and coolant pressure. I have to admit that I didn't just re-engineer the pulley ratios, rather I used the ratios Chrysler had already figured out. The 440 crank pulley I used was 4 groove and quite a bit larger in diameter than the original. You might be best to just purchase a slightly smaller water pump pulley keeping the ratio change in mind. I don't know what combos are available for your engine size but that may be worth researching. I've run my combo for 2 years without issue and the engine actually runs cooler than previously. You will probably have to figure out custom lengths for the belt(s) if you go smaller in pulley size and make sure that the grooves positively line up to prevent pump shaft fatigue and breakage.

 

I think one of the biggest things that gets over looked is air flow. You can have the biggest radiator that fits your vehicle, but if air can't go any place after it gets past it doesn't do it's job. Headers can restrict air flow past the motor .

The Shelby Mustangs with ac had vents in the hood for air movement, the opening in the back of the teardrop tbolt hood was for hot air going out.

Your system might be fine just needs more air flow.
Try running with out your hood and see how it works.

 

I agree with Iowan when it comes to air flow so in my case I used a Spal 16 inch high flow electric. It is set to run two minutes after shut down to prevent hot soak. When on, and the car stopped you can feel the hot air coming out of the engine compartment all the way to the back of the car. Fortunately it's a paddle blade and not noisy. To address frontal air flow, I fabricated a left and right scoop behind the grill that extends on an angle 7 1/2 inches to either side of the rad. These funnel the air into the rad at higher speeds. Past 40 mph my fan does not come on at all. I run about 185 degrees at idle in traffic and 180 on the highway. There are many ways to get engine heat under control but I guess you'll just have to experiment to find which method(s) work for you. I would definitely start with the pulley resizing and take it from there - you can do no harm.

 

-- I, also, fabricated L & R scoops, behind the grille. -- The local radiator guy said the same about a big radiator not always being the solution.

 

---- I've been reading more about pulley ratios and cooling on other forums, so I re-checked my pulley diameters. The water pump pulley is 6.5" and the crank pulley is 5". By my math the water pump is being UNDER DRIVEN by 30% -- . Based on all of the info that I have found, this is near the opposite of what it should be for effective cooling, especially at slow speeds, in slow moving traffic. -- In other words I should have a smaller water pump pulley than the crank pulley. This would create a OVERDRIVE of the water pump and fan. -- I plan to look for pulleys to create the OVERDRIVE situation, but since it is so late in the year, weather wise, here in the N.E. I may not report on the results until next spring/summer. --- Thanks for all of the input.

 

----- Current pulleys are from Summit/March Performance. --- I called Summit and they have a matching 6-1/2" crank pulley. - This will not create a OVERDRIVE, but a 1 to 1 ratio is much better than I currently have (6-1/2" WP to 5" at crank). --- It's on the way here. --- It's getting too cold, here, to have a good test, but I'll put it on, anyway. -- Progress, I hope.

 

-- Got it and it's on, but too cold, here, to tell if it helps. ---NEXT QUESTION -- Will a 7 blade all steel mechanical fan pull more air than a 6 blade, with all other factors remaining the same ? -- Let's not get into electric fans, that may come later. -- Thanks

 

Let's do get into electric fans and their advantages over metal blade fans of years gone by. Nowadays many people are hopping up their engines to run at very high rpm's unlike the day they were created. Acknowledging this issue ( and with the arrival of offshore four bangers that ran at fairly high rpm's) manufacturers started to make the blades out of plastics and composites. Over driven metal blades had a habit ( albeit rare ) of coming apart from fatigue and the owner ended up with a new vent hole in the hood along with a new rad. Shafts on water pumps were just too small and couldn't support high rpm's or any imbalance. Then came the viscose fan unit that just about guarantied the top speed of the fan through slippage and a multiple of fan blade designs and number of blades. Now you can purchase an unlimited design of electric cooling fans that save fuel due to lack of drag, come wrapped in their own shroud and air flow is guaranteed at any speed, will remain on after the car is stopped, are light and strong, don't overload the water pump shaft, fit damn near anywhere, push, pull and evacuate and allow cooling to tranny's, engine oil and fuel. It's getting damn hard to find a metal blade on anything these days - even my F150 FX4 has a plastic fan blade mounted to a viscose interface. Now I'm not an engineer or a deep thinker in a design lab or R&D facility but I'm smart enough to realize that these people just might be on to something that I never thought of. I'll put my trust in them and see what benefits I can get from their professional disciplines to enhance my everyday driving. Come to think of it, and by reading online magazine articles, so do a lot of everyday shade tree mechanics.

 

------- Any info re my question ? -- Thanks

 

logic would say it should help, give it a try if you have one it sure can't hurt.

I still think you have to much air pressure under the hood for the radiator to get good air flow.

 

-- Probably do - I'm going to try the Old Trick of raising the hood, in the rear, by adjusting the hinges in a non-normal way. - Won't know result until warm weather returns. -- It's interesting that Dusters, Barracudas etc in the late 60s had 7 blade fans, and they are still available here & there. -- I really don't care about loss of HP, with a mechanical fan, and only have about 3" between the radiator and the water pump pulley for a electric fan. - There are some low profile electric fans available, but I'm not going there yet. ----- Also, I just bought a digital, infrared, laser thermometer, and will be playing with that.

 

You might read some of Bills Findings and see what you can come up with Magoo....
https://moparforums.com/forums/f7/radiator-help-15174/
I have had good luck with the 7 blade fan.....I run the 1977 Dodge 360 Now A/C pulley set up.....

 

Bob --- I sure hope that I don't have Bill's problem. I'm not up to a tear down. - I doubt that I have that problem - it starts & runs very well. -- I now have 1 to 1 pulley ratio, crank to wp/fan pulley, and today I ordered a 7 blade, Mopar, all steel, non-clutch, fan from Ebay. -- Soon heading to Florida and the Valiant will rest in the garage in Pa. until spring. At that time I'll be back into the project and I'm sure that with the info gathered from you guys, on The Forum, I'll lick the problem of getting hot in traffic. -- When the weather warms up again, I'll give an update on the results of all of this. -- Thanks -- Dick

 

Mr. Magoo,

You probably have a Hotrod parked in Florida waiting for you, if you don't you should.

 

-- Had a 65 Valiant there for a few years. -- Brought it back to Pa and sold it.

 

I hope not nether...... That thing is sweet...