Battling overheating new 360 build

-
The fan shouldn't be a problem if I'm cooling fine at idle, no?
 
DSMRossi said:
I've always tuned for max timing advance until detonation, then backed off. Once I find peak timing, I adjust the rest of the curve for best performance. I've never had cooling issued like this though. I find that a lot of people simply set peak timing for a generic number regardless of their setup and call it good, which leaves power on the table.
Click to expand...
Same.
38 is still a lot, not that it isnt the right setting for your motor. I believe your system isnt holding the necessary pressure is where I was steering you. Bad/weak cap can give this scenario. Best of luck!
 
I'm going with a restricted Radiator. I encountered a similar problem with my 360. I had my heads cut and installed thinner MLS head gaskets. It would idle and stay cool, but when I drove it it would steadily get hotter. Slow down and it would cool back off. I had the original 3 core radiator taken apart and rodded out. Guy said it was pretty clogged. Afterwards it runs cool as a cucumber.
 
SGBARRACUDA said:
I'm going with a restricted Radiator. I encountered a similar problem with my 360. I had my heads cut and installed thinner MLS head gaskets. It would idle and stay cool, but when I drove it it would steadily get hotter. Slow down and it would cool back off. I had the original 3 core radiator taken apart and rodded out. Guy said it was pretty clogged. Afterwards it runs cool as a cucumber.
Click to expand...
That's what I'm kind of leaning toward. It's an old core. I'll play with the timing tomorrow and take the car for a run, but I have a feeling I'll be looking for a radiator soon.
 
as one person said . spring maybe. 22 as compared to a 26 rad. first clean all 8 fan pump great. clutch fan great. if that does not work u got nastyblock. u r rebuilding ? so u screwed up. 2 dollars more . and get a new FAN CLUTCH. f the blade fan. clutch fan kicks in at temp needed. the fan I see one blade can come off and fuc? up life. flush or replace rad. is prob go stock and sue me if I me b wrong.
 
I once had an overheating problem on a 75 or 76 Dart 318 ex cop car. At cruise the rad couldn't flow fast enough, so it would fill up the overflow reservoir until it started pushing coolant out its overflow. Eventually it would run low on coolant and overheat. I was in Hemet, CA then, and had a shop there rod-out the radiator. Man, that car ran so cool after that, no matter how hot it was outside.
If you can find someone who can still do that work, I'd strongly suggest that.
 
rustycowll69 said:
I once had an overheating problem on a 75 or 76 Dart 318 ex cop car. At cruise the rad couldn't flow fast enough, so it would fill up the overflow reservoir until it started pushing coolant out its overflow. Eventually it would run low on coolant and overheat. I was in Hemet, CA then, and had a shop there rod-out the radiator. Man, that car ran so cool after that, no matter how hot it was outside.
If you can find someone who can still do that work, I'd strongly suggest that.
Click to expand...

There’s a couple shops near me, but I’d imagine that having it rodded out would cost more than just replacing it with a 3 core Champion. That’ll probably be my next route if I can’t make this work.

I also read that Ford contour fans fit the 26” aluminum radiators and move something like 3400cfm. That could be the end-all to overheating for Mopars.

Food for thought
 
charles mill said:
as one person said . spring maybe. 22 as compared to a 26 rad. first clean all 8 fan pump great. clutch fan great. if that does not work u got nastyblock. u r rebuilding ? so u screwed up. 2 dollars more . and get a new FAN CLUTCH. f the blade fan. clutch fan kicks in at temp needed. the fan I see one blade can come off and fuc? up life. flush or replace rad. is prob go stock and sue me if I me b wrong.
Click to expand...

This is a completely rebuilt engine and it cools great at idle. The more I read the more I don’t believe I have a fan issue. The car stays cool at idle or during warmup on fast-idle. It overheats under load which seems like more of a heat-soak issue due to inefficient flow or to excess temps that could be timing related.

I’ll be starting with timing reduction tomorrow. If that doesn’t do it I’ll be pulling radiator and replacing with an aluminum unit
 
DSMRossi said:
This is a completely rebuilt engine and it cools great at idle. The more I read the more I don’t believe I have a fan issue. The car stays cool at idle or during warmup on fast-idle. It overheats under load which seems like more of a heat-soak issue due to inefficient flow or to excess temps that could be timing related.

I’ll be starting with timing reduction tomorrow. If that doesn’t do it I’ll be pulling radiator and replacing with an aluminum unit
Click to expand...
I'm not personally familiar with Champion rads. But my experience on my Cherokee was this: oem rad cooled perfectly, but the plastic tank on the end cracked, so I bought an aluminum "HD" rad to replace it. It weighed about 1/3 of the oem copper/brass/plastic rad. It was quite reasonably priced, so I was initially happy. It never cooled near as well as the old rad, and I never could run the AC, when it was over 80deg outside, which pissed me off to no end. After the one year warranty expired, the rad started leaking where the tubes met the side tank. Eventually, I pulled the cheap rad out, and bought an ALL copper/brass rad for about 3x the price of the aluminum rad, but it runs cooler, now, than it ever has, and the efan rarely needs to come on anymore.
 
DSMRossi said:
View attachment 1715276913
Click to expand...
From the picture looks like your shroud is not covering the fan at all not pulling any air through it the radiator I'm not an expert just my thoughts think of the fan and shroud like this it's able to cool at idle because not as much heat generated and with your setup able to pull some air when going down the road the radiator actually becomes close to a solid item air will find the least resistant path and go around the radiator need to force air through it so that's why the proper shroud and fan setup is so important you probably have a combination of things causing this but I would tackle the proper fan and shroud setup first personally I don't like direct drive fans consider putting a clutch on it
 
Last edited:
DSMRossi said:
I didn't really consider that. The car only gets hot under load, so yes above 25mph. I could be in bumper to bumper traffic or sitting idling in a parking lot and not have a problem.
Click to expand...

Most time, overheating at speed is a flow problem. Get a thermostat with an 1 1/4" to 1 1/2" opening. You could try a good flush, but a scaled up radiator may not clean up without repeated flushing.
 
If you are using that dummy gauge, which is a scary proposition, use a temp gun to establish where on that gauge 200 is.

Mine was at 200 half way up the gauge in the normal range.
 
The rads not dumping enuff heat.
If you use a temp gun on the rad inlet and outlet when it's"overheating",
The difference between the upper and lower hose coolant temps needs to be min. 40*,. 50*+ would be better.
Shoot temps across the front of the rad, every inch, halfway down, you'll find cool/cold sections. Those are plugged tubes, the larger the cool area, the larger your problem.

If the rads only dumping 10*, that's about enuff to cool a 2 cyl lawnmower.

Do you have a spring in your lower hose, to stop it sucking closed at speed ?


Doubt me, go check the in/out temps on your daily driver.
 
Last edited:
Demonic said:
Most time, overheating at speed is a flow problem. Get a thermostat with an 1 1/4" to 1 1/2" opening. You could try a good flush, but a scaled up radiator may not clean up without repeated flushing.
Click to expand...

Wouldn’t you want the fluid to stay in the radiator slightly longer to allow it to dissipate heat? I’ve had a car with the thermostat removed and it actually caused a larger heat-soak issue because the coolant didn’t spend enough time in the radiator before it flew back into the engine.
 
inertia said:
The rads not dumping enuff heat.
If you use a temp gun on the rad inlet and outlet when it's"overheating",
The difference between the upper and lower hose coolant temps needs to be min. 40*,. 50*+ would be better.
Shoot temps across the front of the rad, every inch, halfway down, you'll find cool/cold sections. Those are plugged tubes, the larger the cool area, the larger your problem.

If the rads only dumping 10*, that's about enuff to cool a 2 cyl lawnmower.

Do you have a spring in your lower hose, to stop it sucking closed at speed ?


Doubt me, go check the in/out temps on your daily driver.
Click to expand...

I’ll be doing this this-afternoon. I’m also interested to see what I’m actually losing between inlet and outlet.

The lower hose does have a spring in it
 
Welp, I took car for a cruise and I have a decent drop across the rad. Top hose is around 185 coming out of radiator, lower hose is 150's. I will say that the thermometer isn't exactly the most accurate, it gives funny readings.

What I did notice was that there were a few areas on the radiator at the bottom driver's side mostly that were much cooler than the rest of the rad, like 60-70 degrees cooler. So I believe I have a compound issue that I didn't notice with my cool-running 318. It looks like a radiator upgrade is in my immediate future...

I did pull the timing back and I disconnected the vacuum advance so that part throttle cruising didn't have the added timing and that had no effect, so I don't believe I have a timing issue.
 
Also - the dummy gauge is showing me almost all the way to H, but the temp therm is reading me at 195, so I may not be as hot as I think. Regardless, that needle never moved that far on the old setup
 
DSMRossi said:
Welp, I took car for a cruise and I have a decent drop across the rad. Top hose is around 185 coming out of radiator, lower hose is 150's. I will say that the thermometer isn't exactly the most accurate, it gives funny readings.

What I did notice was that there were a few areas on the radiator at the bottom driver's side mostly that were much cooler than the rest of the rad, like 60-70 degrees cooler. So I believe I have a compound issue that I didn't notice with my cool-running 318. It looks like a radiator upgrade is in my immediate future...

I did pull the timing back and I disconnected the vacuum advance so that part throttle cruising didn't have the added timing and that had no effect, so I don't believe I have a timing issue.
Click to expand...

Wait, how many changes did you do at once?

Get rid of the second bypass, all it is doing is sending already heated-to-the-limit coolant, back thru the pump for a second go-round, displacing the cold water that shouldda been in there. It's bad enough the first bypass is there, (which I severely restrict..... and I drive from April 10th to October 10th.)
Whatever pump you bolt on, and I highly recommend an 8 blade, it should have an anti-cavitation plate on it.
And why in the world you guys always always wanna run max timing right out of the gate is beyond me. Get your support works up to speed first, and your fueling close first, and then;................ SNEAK up on the timing. I guarantee you this;Guaranteed; on the street, your butt-dyno will not know the difference between optimum power timing and 2 or even 3 degrees less. So why risk a nuclear meltdown of your expensive engine for 5 to ~7 hp?
And finally, your cruise timing needs to be between 42 and 56 degrees (perhaps even more) to prevent overheating, burning up the headers, and getting lousy fuel-economy. So by disconnecting the Vcan, if it was in fact working, you're just inviting trouble.
And double-finally; Like you said;The thermostat sets the minimum water temperature. It does this by trying to restrict the water flow to below it's set point. It's normal condition is CLOSED. If the water is going round and round in the dual bypasses, it's gonna take a while for the stat to catch on; And the slow-as-molasses-in-January factory gauge is gonna be two or three minutes behind as to what is going on.
The cooling system efficiency is gonna set the maximum temp. And that has already been covered in this thread. After 30/35 mph, YOUR rad is likely the least of your problems. My rad is a 1973 pos that I have had since the late 70s, never cleaned it her yet.
One change atta time, starting with; putting the Vcan back into operation, resetting the all-in power-timing to not more than 34/35,at over 3000rpm,then getting rid of that second bypass. Then make sure that the air hitting the rad core support, is ALL forced to go thru the rad, not under/over/ around/or between the rad and the core-support.Then the anti-cav pump. Actually just do all of these at the same time,lol.
After you get it under control........ then you can start to experiment..... yes, one thing atta time.

Oh yeah you asked; My minimum water temp is 205*F and my maximum is 207*F. How can I even measure that? Think about it.
How can you set your AFRs with the underhood intake air temp varying from 180* to 400plus*?.. IDK either. And neither did the factory. Hence the OSAC valve,the heat stove,the thermactor trap-door, and the fresh-air duct. What were they battling? You guessed it retarded timing.
Somebody said to get rid of that flex-fan, and I agree. Once the car is up to cruise speed, and the engine is buzzing along, those flex-blades are flung flat, or nearly so, and they present a wall, a WALL, to the incoming airstream.
I'll tell you what is guaranteed to not make a wall, and that is a large diameter, high-attack, 7-blade, all steel fan with a thermostatic fan clutch. Don't bemoan the powerloss, it's not what HotRod or anyone else preaches; and if you lose the engine to overheat you will bemoan that worse. Think about it. Somewhere after 35mph the ram air should be cooling your engine, and that 7 blader may be freewheeling, with the thruput,costing you almost nothing, just like the flex fan, but unlike the flexfan, not presenting a 5000 or 6000plus rpm impenetrable wall; 15 hp myazz..Don't you believe it!
In order for your engine to make power it first has to survive it's owner.
I'm harsh I know, do whatever you think is right,lol.
 
Last edited:
I hadn't noticed that extra bypass. Yeah, I don't like that, either. Another possibility is a bad thermostat. They are not created equal. The best I've found is Robertshaw brand. I understand for some specific apps, there are some hi flow t-stats sold, you might check them out. My friend, Brian and I had a boil off of about a half dozen different brands. You'd be surprised how different they all were. Some were not very accurately rated temp-wise, others didn't open very far.

Many t-stats are made now with a little 1/8" dia. bypass hole in the t-stat flange(not on the gasket surface, of course). The purpose is to allow trapped air in coolant system to more easily exit the block/heads and be vented so system can be filled with 100% coolant.

I doubt that this is the problem in your case, but I've even seen t-stats installed backwards. The symptoms were overheating at idle but only very, very slowly; and overheating at cruise.
 
I was wondering if anyone else knew about the inherent flaws of the "Hex Fan". I have friend that ran a brand new one two weeks on a home built 8500 rpm 302 in a '70 Nova and a blade cracked off and speared the battery on the second to third powershift. Two weeks to tear everything down, polish, replate... Dirt trackers in area also stated the propensity of those wonderful blades to fold flat and block airflow... may be okay if you want a racy looking box fan for your shop, but tragically worthless for anything of any real value...
 
AJ/FormS said:
Wait, how many changes did you do at once?

Get rid of the second bypass, all it is doing is sending already heated-to-the-limit coolant, back thru the pump for a second go-round, displacing the cold water that shouldda been in there. It's bad enough the first bypass is there, (which I severely restrict..... and I drive from April 10th to October 10th.)
Whatever pump you bolt on, and I highly recommend an 8 blade, it should have an anti-cavitation plate on it.
And why in the world you guys always always wanna run max timing right out of the gate is beyond me. Get your support works up to speed first, and your fueling close first, and then;................ SNEAK up on the timing. I guarantee you this;Guaranteed; on the street, your butt-dyno will not know the difference between optimum power timing and 2 or even 3 degrees less. So why risk a nuclear meltdown of your expensive engine for 5 to ~7 hp?
And finally, your cruise timing needs to be between 42 and 56 degrees (perhaps even more) to prevent overheating, burning up the headers, and getting lousy fuel-economy. So by disconnecting the Vcan, if it was in fact working, you're just inviting trouble.
And double-finally; Like you said;The thermostat sets the minimum water temperature. It does this by trying to restrict the water flow to below it's set point. It's normal condition is CLOSED. If the water is going round and round in the dual bypasses, it's gonna take a while for the stat to catch on; And the slow-as-molasses-in-January factory gauge is gonna be two or three minutes behind as to what is going on.
The cooling system efficiency is gonna set the maximum temp. And that has already been covered in this thread. After 30/35 mph, YOUR rad is likely the least of your problems. My rad is a 1973 pos that I have had since the late 70s, never cleaned it her yet.
One change atta time, starting with; putting the Vcan back into operation, resetting the all-in power-timing to not more than 34/35,at over 3000rpm,then getting rid of that second bypass. Then make sure that the air hitting the rad core support, is ALL forced to go thru the rad, not under/over/ around/or between the rad and the core-support.Then the anti-cav pump. Actually just do all of these at the same time,lol.
After you get it under control........ then you can start to experiment..... yes, one thing atta time.

Oh yeah you asked; My minimum water temp is 205*F and my maximum is 207*F. How can I even measure that? Think about it.
How can you set your AFRs with the underhood intake air temp varying from 180* to 400plus*?.. IDK either. And neither did the factory. Hence the OSAC valve,the heat stove,the thermactor trap-door, and the fresh-air duct. What were they battling? You guessed it retarded timing.
Somebody said to get rid of that flex-fan, and I agree. Once the car is up to cruise speed, and the engine is buzzing along, those flex-blades are flung flat, or nearly so, and they present a wall, a WALL, to the incoming airstream.
I'll tell you what is guaranteed to not make a wall, and that is a large diameter, high-attack, 7-blade, all steel fan with a thermostatic fan clutch. Don't bemoan the powerloss, it's not what HotRod or anyone else preaches; and if you lose the engine to overheat you will bemoan that worse. Think about it. Somewhere after 35mph the ram air should be cooling your engine, and that 7 blader may be freewheeling, with the thruput,costing you almost nothing, just like the flex fan, but unlike the flexfan, not presenting a 5000 or 6000plus rpm impenetrable wall; 15 hp myazz..Don't you believe it!
In order for your engine to make power it first has to survive it's owner.
I'm harsh I know, do whatever you think is right,lol.
Click to expand...

I have a few thoughts.

As far as how many things I've changed at once? It's a completely new rebuild with a zero-decked block.

The second bypass is simply because the heater core is temporarily disconnected while I'm breaking the new motor in. Assuming there's a slight exchange as the coolant makes it's way into the cabin and back into the motor, the second bypass should be negligent, no? I want to ensure that the motor can properly cool with the heater core connected, as I plan on driving the car with heat in the colder months.

My understanding of the primary bypass is to prevent cavitation in the pump to begin with, rendering an anti-cavitation pump unnecessary. As far as the water pump, flow is controlled by the thermostat, what would the benefit be to switching from a 6 to an 8 blade pump?

I run as much timing advance as safely possible because that's the most efficient way to run the engine. I HAVE had overheating issues due to retarded timing, so retarding a car that's on 93 pump gas and still not showing any signs of detonation (see spark plug pic in first post) could be in-turn hurting my digging here. I did however lower it to 34 as stated before your post and noticed no change in cooling performance.

The car is currently cruising around 3000rpm, so I'm not sure why anyone would think the flex-fan at that point is creating a wall, but fans are cheap and it's a simple swap to see if that makes a difference. I'm certainly not running the motor out as it's only got about 30 miles on it.

My basic plan right now is I've taken a 360 and bored it out, making the block that much easier to heat-soak. I've increased the compression and believe I'm simply overwhelming the factory cooling system (that's already old) that was designed for a low compression, volumetrically-inefficient engine, warranting at the minimum a radiator upgrade to something more suited to a 400hp engine. I've significantly altered the power this engine has made and left the components that comprise the support system in place.

At the same time, I don't think I'm running as hot as I believe. A quick check around the engine bay with the infared gun concentrating at the water temp sender showed my hottest point to be 195 while my temp gauge was showing me at the very top of the arc. Most people say they're running in the 200+ range
 
Last edited:
Like I said;
I run a minimum 205 and a max of 207, and with the tips I gave, my 4.04 bore 360 has ZERO heating issues, goes 93#3467pounds with 34* timing on 87E10 (OOTB Eddies),in the Eighth with a 230*cam, and will idle down to 550 rpm, parading at 4 mph@5* advance, all with a 45 year old rad, that has more patches on it than I can remember.
And, with a 223* cam, it has cruised over 580 miles on a tank of gas, at speeds between 65 and 85 with a final drive of 1.97.
I'll leave you with this final tip: if you installed your rings at the KB spec of .026, this was too tight for my top ring, to run at 205*F,lol. I had to open it up to .032 IIRC. And my KB107s are in at .004 and change....... so they would stop locking up every time I shut it off. I took that engine apart 5 or 6 winters in a row, fixing one step atta time, and the pay-off was the 93mph trap speed.
I'm not gonna argue with what you believe. I tell you what worked for me,so you may benefit from my experience, or not, as you wish.

Riddle me this; how long does it take for your factory gauge to tell you the engine is fully warmed up, after the IR gun says it is fully warmed up.............
Then think about that. when the gauge starts moving higher than it's normal. When it starts moving, it has already been "overheating" for perhaps a minute or perhaps two, depending on your particular gauge.
Furthermore with dual bypasses, what is your temp sender actually measuring? The pump has a much easier time pulling in the hot water from the top of the engine, than lifting the denser colder water up from below, especially if it doesn't have an anti-cav plate, and only 6 vanes. And you wonder why your rad has a 35* or more temp difference from top to bottom? Maybe, just maybe...... it ain't circulating because of what is going on inside the pump.................
 
I understand what you're saying, but "dual bypasses" means that I would have to eliminate the heater core from my car in order to take advantage of what you're saying works for you.

As far as the dense cold water, disconnect your hose where it connects to the water pump and tell me water doesn't force itself from the radiator outlet up and out of the hose at that connection. While I'm interested to see the effects of a 6 to 8 vein pump, I will give it a shot after I change radiators. I still feel that finding cold spots on my radiator tells me that I have blockages that need to be remedied regardless.

I was under the impression that a 35 degree drop wasn't enough as I've read it's not uncommon to see twice that on an efficient cooling system. I'll have to check what my truck runs at and compare.
 
You must log in or register to reply here.
-

Back
Top