360 Tune Up

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If there is an opening at the top and bottom of the shroud, not sealed to the radiator, it's going to reduce the effectiveness of your fan.

Take some tape or foam and seal those areas. See if it works better.
 
I know I have a better tune up now with the modified distributor and the working vacuum canister. I will have to test mileage at some point but I found out today that 87 octane won't work in this engine, regardless of the change in timing. I believe I have a stock cam with higher compression pistons, which gives me a high dynamic compression situation that can't be handles with less than 93 octane. I can live with that.

I also did extensive testing today on temperature and tested 3 different modifications designers to improve airflow and none of them made any difference. This tells me that I am not dealing with an airflow problem and I'm starting to believe it may be a coolant flow problem.

I know Chrysler played around with two differnt waer pump and pulley configurations but im not up to speed on them. I am running an AC, have a 5 speed AX-15 transmission and 3.55 rear gear.

I have a 7" pulley and I don't know which water pump I have. I do know that I've changed 180 degree thermostats twice and as long as the ambient temp is 80 or less, it will stay at 180. Today at 90 degrees, I was running at 200 in 5th gear and 70 mph. I know that is not "too hot" but it concerns me that the cooling system can't keep me at thermostat temperature.

Got any ideas? Am I thinking right on this? Should I start a different thread? Thanks for all the help you've given me.
 
Rock Able said:
Got any ideas?
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The thermostat sets the MINIMUM coolant temperature. It has nothing to do with the maximum unless it is restrictive or stuck closed.
The cooling system efficiency sets the high point. At 70 mph=~2450rpm in 5th gear, your cooling system should be at or near peak efficiency....... if it was working right.
At 70mph the cooling fan and shroud can be,or should be able to be, shut off or even removed. Ram air should be sufficient no matter what pump you are running and no matter what stat is in it, and no matter what coolant you are running. But this assumes the rad is of sufficient size and capacity and that the 70mph column of air the car is plowing, is all or mostly all passing thru the rad.
 
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AJ/FormS said:
The thermostat sets the MINIMUM coolant temperature. It has nothing to do with the maximum unless it is restrictive or stuck closed.
The cooling system efficiency sets the high point. At 70 mph and in 5th gear, your cooling system should be at or near peak efficiency....... if it was working right.
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It's not. That's why I'm trying to figure out what is limiting the cooling. The radiator is a Champion 3 row and is rated for WAY more HP than I have.
 
AJ/FormS said:
Well maybe the condenser in front of it is acting like a sheet of plywood.
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I don't think so. When the fan kicks on, there is a lot of hot air coming through. Ram air at 70 mph should be even more. Trust me, I've beat the air flow thing to death.
 
With the 5 speed gearing, the engine is running relatively slow, but not sure that's of any significance since there were overdrive 4 speeds and highway geared cars.

Accurate air temperature measurements are difficult.
Conductive temperature measurements aren't so difficult. If you have a multimeter with thermocouple or some thing like that you could clamp it to the radiator outlet.
Do a feezing water, and more important a boiling water check so you know roughly the accuracy. most termperature measuring devices are repeatable but not too accurate unless calibrated.
Anyway the point here is to get a sense of how much radiator is dropping the coolant temperature.
 
Why don't I just pull over and shoot both of them with my IR thermometer . They can't cool off that quickly.

Isn't there a smaller pulley available for the water pump? That seems easy enough to try, given all the crap I've already done. The delta T will change with increased flow rate.
 
Lets do a couple scenarios.
As long as the heat going into the coolant can be removed by the heater core the thermostat stays closed.
Just making up easy to remember numbers in the illustration.
upload_2019-5-26_19-8-40.png


Lets say at 45 MPH the engine works harder and the coolant now has to get rid of more heat.
The radiator takes over and even with 90* air temperatures, it brings the coolant through it down to 100*F
upload_2019-5-26_19-15-4.png


And lets say at 65 mph 150 BTU per minute are going into the coolant.
Even if the heat exchange at the radiator is still good enough to bring the coolant down to 100 F, its not too surprising that additional energy transfered into the coolant would raise the temperature at the sensor.
upload_2019-5-26_19-31-34.png


At least that's how I see it. If it keeps creeping up while driving, that's a different story.

That's also where I was going with the coolant temperature at the radiator outlet. If its increasing on par with inlet temperature then you'ld be right to suspect heat transfer at the radiator has been maxed out. Whether thats due to coolant flow, or air flow or fins would still have to be figured out.
 
Rock Able said:
Why don't I just pull over and shoot both of them with my IR thermometer . They can't cool off that quickly.

Isn't there a smaller pulley available for the water pump? That seems easy enough to try, given all the crap I've already done. The delta T will change with increased flow rate.
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My recollection is yes, there are different pulley combos for a/c and non a/c and maybe for trailer package too. last pages in the cooling section of the shop manuals.
 
Thanks. I don't have a shop manual. This is my first Mopar build and I have learned EVERYTHING the hard way.....it seems.
 
This is from a digital '73 Dodge FSM
It shows the pully ratios but not the diameters.
The smaller impeller A/C water pumps get a different drive ratio.
upload_2019-5-26_23-10-26.png


There are a couple of threads here on the topic of OEM pulleys.
I'm not much help on that.
 
Mattax said:
This is from a digital '73 Dodge FSM
It shows the pully ratios but not the diameters.
The smaller impeller A/C water pumps get a different drive ratio.
View attachment 1715340461

There are a couple of threads here on the topic of OEM pulleys.
I'm not much help on that.
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Almost all of them are shown as over driven and the first things guys want to do is slow the pump down.

That's a killer for sure. It's all about flow. Coolant flow and air flow.
 
My crank pulley is about 7 3/8" diameter and the water pump pulley is about 7" or so. (It's hard to get to with all the belts on.) I am definitely turning the water pump slow, especially with overdrive in my transmission. Looks like the 3418227 pulley would speed me up. Is that correct?

It looks like I have the 225 pulleys....... Go figure......
 
7.375/7=1.054 and crank is bigger than the WP so you are good to go, IMO. Yeah you could spin it faster, but with overdrive you are not working the engine as hard so shouldn't need more Rpm. Run it in direct and see what happens.

My no A-C system is underdriven to keep the belt on at 7200. I am geared 65=2240 and my rad is from a 73Dart 318/A-C, with zero problems since 1999. I have run as slow as 65=1600 and as high as 65=2970, still with zero problems.
Are you by any chance running hypers at .0015inch clearance? I found that to be too tight,in spite of what KB says. I can't find my last assembly specs but I'm pretty sure I went to a tic over .0025, and that loosened her up. It rattles just a bit on cold mornings. In compensation I cranked the minimum running temp up bit by bit and finally hit 205. That's the sweetspot on my combo.
 
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I am running hypereutectic pistons. Summit P/N SLP-8KH116CP30. I can't find the specs on them, however. (You wouldn't happen to know would you?) They must have changed them. This one pings hot or cold with low octane fuel, even with my new timing setup.

Maybe my water pump is not as efficient as yours. Also, I am running AC. I'm at the end of my rope chasing this and a $75 pulley is the easiest thing I could try. Remember, I am pushing an old car body with a lot of wind resistance. It sits high and doesn't flow well. In 5th, it's not turning many rpms and I'm stuck with my radiator or a similar design.
 
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Waitaminite I got an idea
What does it do when cruising in direct? at same speeds as before in od.
And what are the secondaries doing?

Here's where I'm going;
What if
in od, at cruising speed, the 360 is so underpowered that you are deep enough into the throttle that the secondaries are opening? I mean you said the temps start creeping up at 70ish right. I know any 360 should pull that with 3.55s relatively easily in direct gear. But what about yours in .79od? If your secondaries are not opening, it's gonna take more throttle in od than in direct to cruise at the same speed. In direct, at 60mph the carb should still be on the transfers, with a very small throttle opening. By 70 the mains may be contributing, it depends on your cylinder pressure and fuelling.
But in od the throttle may have to be opened more to get enough power to cruise with. So maybe the mains are flowing. This would simultaneously point to both the lack of fuel economy and the engine is working harder to maintain 70. Just thinking. Now throw in the possibility of the secondaries being cracked, and that would be another can of worms.
What if is all I'm saying.
 
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AJ/FormS said:
Waitaminite I got an idea
What does it do when cruising in direct? at same speeds as before in od.
And what are the secondaries doing?

Here's where I'm going;
What if
in od, at cruising speed, the 360 is so underpowered that you are deep enough into the throttle that the secondaries are opening? I mean you said the temps start creeping up at 70ish right. I know any 360 should pull that with 3.55s relatively easily in direct gear. But what about yours in .79od? If your secondaries are not opening, it's gonna take more throttle in od than in direct to cruise at the same speed. In direct, at 60mph the carb should still be on the transfers, with a very small throttle opening. By 70 the mains may be contributing, it depends on your cylinder pressure and fuelling.
But in od the throttle may have to be opened more to get enough power to cruise with. So maybe the mains are flowing. This would simultaneously point to both the lack of fuel economy and the engine is working harder to maintain 70. Just thinking. Now throw in the possibility of the secondaries being cracked, and that would be another can of worms.
What if is all I'm saying.
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I'm definitely nowhere near opening the secondaries. The poor mileage was because my vacuum advance wasn't working, I'm sure. Haven't verified that yet but feel pretty confident it will be improved. Plus, was able to go to a leaner setup with the changed timing.
 
Mattax said:
First thing I'd do is check the advance on the other distributor. If its a shorter advance, then swap vacuum cans and be done with it.
Again. 7* BTC on a stock engine isn't out of line with what you would have got from the factory. So what you'll be doing by bringing that up is making it more efficient.
Articles. When you find 'em, many are half sales pitches and regurgitations of the same.

Your goal is to cut the bottom off the curve.

Disassemble the distributor. Hardest part will be removing the snap ring that's under the felt pad. Second hardest part is removing the reluctor. Take a photo or notes before removing it to remind yourself of which slot the roll pin uses.
With the snap ring and reluctor removed, the rest is straightforward. Slightly lift the plate to free the vac can arm.
Here's a cam plate (aka slot plate) in the initial position. Zero advance.
The primary spring's tension holds the weights against the inside of the slots.

Remove the cam plate. If you were me, I'd measure the slots and distance between for baseline reference. Or you can go from the internet alone if you prefer. LOL.
The stamped number represents the advance distributor degrees allowed by the slots.

Your distributor #2 seems to have about 28* in it. (It may be stamped 14)
You're looking to reduce that by 5 or 6* to 22* advance.
My notes show that 22* will require slots 0.410" long. You can find some other folks findings on the net and their similar.

Weld a tack on one or both of the slots. On the inside! carefully file it back to slot length needed.

Reinstall.

(if you see differences in the photos, its because the photos are of several different distributors)
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You might interested in this. Worked great on my distributor.

How to limit mechanical advance in a mopar distributor, tuning for street, strip or all out racing, cure that rich stinky idle, win races
 
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