Engine Coolant Additives

don's 37

don's 37

Senior Member
I see a lot of advertising on additives that you can buy that you add to your radiator and "your engine will run 20% cooler!" Does this stuff really work? Is it safe for Flatheads? On a warm day my '37 runs hotter than I would like it too. The engine is completely clean and the radiator top was removed and rodded through. I have no blockage. I also heard rumors that a Flathead will crack when run under extreme temps. I have the 85 HP engine.
 
I tried some mixed with water only in mine an didn't notice any improvement at all so I went back to a 50/50 anti-freeze/water mix. I have noticed that if I keep the engine at 2200 rpm or below it won't exceed 200 degrees even when it's 95-100 outside and it normally stays around 180. 2200 rpm is ~55 mph with the stock 3.78 gears so I don't do any interstate driving but that's ok with me. My cooling system is unpressurized and I am running t-stats (160s).

Rich
 
I've read a lot about flathead cooling systems and different tricks to get them to run cooler, ie; no t-stats, washers instead of t-stats, etc. I tried most of them and found that they really didn't work for me where I live. What did work was to get the timing and carb jetting right and keep the rpms down out on the road. The new gas with ethanol in it made setting up the carb a challenge but staying on the slightly rich side and raising the float level a little higher than spec helped. It gets hot here in the summer and its been ok for the past few years.

Rich
 
The biggest difference that I made in the coolant temperature of my 59ab was to advance the timing. It made a noticable difference. I am running leaner than stock .049 carb jets and that made the throttle response much better. I've contemplated richening the mixture with .050 jets but the engine runs nice and I'm reluctant to mess thing up. If it's not broke . . . .
 
Henry/Kokomo said:
I've contemplated richening the mixture with .050 jets but the engine runs nice and I'm reluctant to mess thing up. If it's not broke . . . .
Click to expand...

Rich/Alabama said:
What did work was to get the timing and carb jetting right.

Rich
Click to expand...

I just replaced the .049 jets in my 94 carb with the stock .051's and lowered my engine temperature by at least 20 degrees. No noticeable change in engine operation. And that's at 4,800 feet where I live. Still not too rich. My plugs were light tan before changing. I'm going to check them after the change and see how they look.

I also have my timing advanced as far as it will go as well as the vacuum advanced to maximum. No ping at my elevation and runs great.

As for Water Wetter, I put it in just in case it helps. Can't hurt and isn't that expensive. That is, of course, in addition to 50/50 antifreeze and stock 160 stats.
 
Skip recommends "Purple Ice", although I haven't used it(still building motor). But I doubt I'll need to worry about it up here, although we do get an occaisional heat wave in the 80's!
 
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