The Dodge Challenger Message Board

I just read you still have the problem with your overheating 440. Well you help us all the time, so I to tryed to figure out your problem. I haven't any clue so I talked to my mate to find out if he has a couple of suggestions to help you out. And he had.

- check your ignitial timing.
- check your total timing. May not be above 38-40@3000rpm
- check the distributor timing curve.
- use a 160 degree thermostat. (DON'T RUN WITHOUT ONE, THE ENGINE WILL JUST BE WARMER)
- use a 18 psi radiator pressure cap.
- the radiator inlet/outlet should be left/right side, not both on one side.
- check the cfm of your electric fan.
- the best is a mechanical fan + an extra electric one at the front.
- check if your waterpump flows enough.
- check your heads. (thought you already did)

Don't know what else you already tryed, but these are the one the most common problems causing a overheating engine he said. Good luck!

I have checked total and initial timing but will re-check the timing curve.

I want the engine to run at 170-190 degrees so I need a 180 thermostat and the cooling system has to be capable of cooling well below that so the thermostat acts as a temp regulator.

The radiator does have the in/out the same side. Cap is 16psi and that is enough to stop it boiling below 240 degrees.

cfm of the fan is about 2,500.

Waterpump is a high flow/output special.

Heads are fine.

From what I've heard the radiators with the in/outlet on the same side were used in Canada because of the low temperatures there. It would let the engine run a bit warmer because the radiator will not use 100% of it's cooling capacity, but something like 80%.

Does it also overheat when driving or just when idling? If it's only with idling, maybe it's an idea to use a solid mechanical fan in combination with your electric fan at the front of the radiator. Don't know if your cfm is enough for your 550 hp. Will check it out later on.

It can't be the waterpump assuming it's a 'like new' one, but you could check if it flows well by pulling off the upper radiator hose to be sure.

Dave, maybe your engine run lean?

The engine is not very lean. I have jetted it so that I have about 14:1 air/fuel ratio at idle (it is uneven at idle) and 13:1 at all throttle positions. I need to increase the secondary jets to give me 12:1 at wide open throttle.

It overheats no matter what speed you do but the harder you drive and the warmer the air temp the faster it overheats. It will stay stable at idle I think but it could just be that I have not left it idling for long enough on a hot enough day.

Increasing the cooling capacity has improved things a LOT (I had an extra row added to the radiator). It has dropped the water temp about 20 degrees from what it was so I am sure that a better radiator could cure this. In fact it takes a very long hard drive to get the temp up above normal now. But I am worried that a long motorway(freeway) journey with traffic jams on a hot day would push it to boiling.

I think my problem is that the system is only just coping and once the temp is high there is not enought reserve capacity to bring it back down.

I know a guy who had overheating problems in his Dodge '55 with a 354 Hemi engine. It took some time for him to solve the problem... Previous owners probably had run the engine without enough glycol (anti-freezing solution) so one cylinder sleeve had been so affected by rust that it had created a tiny little hole through the cylinder wall. (You could not see the hole with only your eyes, on the backside of the cylinder sleeve it was a large rust affect). Once he changed the cylinder sleeve for a new one, the overheating problems were gone. A bit tricky to find if you not are familiar with these kind of problems. In Dave's case it can for instance be a small crack in the block that makes life a misery (Hopefully not! I have no idea if anybody with a 440 has experianced these kind of problems).

More likely: I think the most common cause of overheating problems is leaking head gaskets. Are the cylinder heads straight? Are the surfaces straight? Do the head bolts show any signs of strain? Are they of the correct quality for the application?

You can´t get enough of good (?) ideas, can you?

dave have you done a pressure test on the system maybe theres a slight leak from head gaskets.check the plugs for coolent.

By the way how hot does it get over there in the uk.

Pressure is fine. I am sure there is not a 'fault' as such. I think Hans had a good point about the radiator in/out. It can't be good that a good deal of the hot water just drops vertically down the side of the radiator (where airflow is lowest) and goes straight back into the engine again. Looking at the radiator this afternoon I can see that a lot of water could be circulating straight around without really getting cool at all. Feeling the radiator it does feel cool enough in the centre.

Also I wonder about these March Performance pulleys. They underdrive the alternator slightly to free up horsepower - which is not a problem when the idle is higher than stock. But I wonder if the water pump speed is effected at all? Depends on the size ratios of the crank and water pump pulleys I suppose. I wonder if the idiots at March got their sums right?

But the water pump I have is supposed to flow 30% more anyway so that should more than make up for any losses there (if indeed there are any).

During the cooler weather the engine was fine which supports my theory that there is not a 'fault' as such. The problem gets slowly worse week by week as the air temp slowly gets higher. Making the radiator less efficient. Average air temp at the moment in my area is around 16-20 degrees C. It can get as high as 30C during July and August. Hotter than that only rarely.

I think a new radiator will have to find it's way into my car soon.

Dave, Christer,
I'm with Your fot inlet/outlet radiator disposition....
The cooling capacity of water (and any liquid) depends by his speed. With in and out in the same side there are pipes very short that offers little resistance, in that the water speeds.... The other pipes offers a much longer distance and there the water flow more slowy. So You have a good radiator only on the in/out side.... The other side is nearly "only for look"...
Good luck!

Dave, your problem is the radiator, for sure. I talked about it with a mopar doctor and he explained me it.

Your waterpump sucks the coolant out of the radiator and pushes it through the block back into the radiator as normal. When it comes back into the radiator, the coolant will be sucked down to the outlet right away so it has no time to cool down.

When in/outlet differs the coolant has to go through the whole radiator which cools it down enough to cool the engine. I thought you only uses 80%, but now I talked about it, I rather think you do not use the 80 but the 20%.

And he also said, change to a 160 thermostat or drill 6 holes (3 on each side) in your 180 thermostat plate for a better coolant flow.

Hope this all helps you, otherwise we're on the Nats and you couldn't make it...

I fitted a new alloy cross-flow radiator today and every thing is fine. It was a hot day today here but the temo stayed at a rock solid 180 degrees. I am very happy.

For all the reasons outlined in the thread above, I just swapped my
radiator over from one which had the inlet/ outlet on the same side, to a
Year One HD big block radiator, with the inlet/ outlet on opposite sides.
Rather than the anticipated improvement in lowered temperature, it's now
running worse than with the old radiator on. I swapped the thermostat down
from 180 degrees to 160 degrees to see if it made any difference. On a
steady run yesterday, with air temperatures at around 18 degrees, and the
car travelling at 55- 60mph, the temperature would sit at around 172- 174
degrees for about two minutes, then steadily climb to 180-185 degrees, sit
there for a minute, then gradually descend back to 174- 176 degrees. Once
the car came to a halt, or into traffic, the temperature climbed very
quickly up past 190 degrees, before the fans cut in.

I'm using MP thermostats, an uprated water pump which supposedly improves
cooling by 30% over stock, a standard belt driven fan, and two Kenlowe
electric fans. My thoughts are:-

- air locks working their way round the system.
- the water pump is outperforming the thermostat (?)
- cylinder head/ head gasket problems.
- I'm installing the thermostat's upside down
- all of the above.

Any thoughts, based on the symptoms described above?
As an aside, my carb's running very rich (any time now Dave, honest ). How
much would this contribute to overheating?

Any advice gratefully received.

Thanks

Tim.

You want your fans coming on at 185-190. The question is are they bringing the temp down once they are on? If not why not?

Stop doing things arse-about-face Tim! Tune those carbs FIRST! They are WELL out and you are not running on the idle circuits at idle in traffic.

THEN and ONLY THEN start looking at other problems.

Make sure you are getting a full 12+ volts at the fans.

I know you're right Dave, but it's Catch 22 now. I can't drive more than a few miles without the fans coming on, and the temperature staying up. I get the impression I need to give it a good long drive to properly set up the jetting etc? Plus, would the higher engine temp give false readings to the air/ fuel mix?

Regardless, I'll drill the throttle blades and at least set the idle mix at the weekend. I'll even take photos to prove I did it.

Seriously mate, how much of a temperature increase could I expect due to the carb running very rich?

I had to reset the electric fans to come on at about 190 degrees, otherwise they would have been permanently on, and drained the battery. I'll move them back down to about 185 degrees once the problem is sorted. When the car was moving above 40mph, they were bringing the temperature down after about a minute. In traffic they were just stopping it going higher until I moved. With the old radiator, they would bring the temperature down after about 20 seconds, regardless of whether the car was moving or not, so there's something fundamentally wrong somewhere.

Check the voltage at the fans. Check the radiator is hot all over (before it is too hot to touch). Look inside the filler cap to see if there is evidence of coolant circulating.

It can only be a blockage (ie hoses or upside down thermostat) or the fans not getting max volts.

try running without any thermostat in at all and see what happens.

When I had my 70 R/T, with a 440, Ihad a similiar over heating problem. The lower radiator hose would draw shut with higher RPM's. Could be a weak hose, no coil in hose, or lower hose is too long and is pinched against the K-frame. Thought you may like a few more possibilities to add to the pot.

Thanks for the pointers gents. I'll check through each of your suggestions in turn. I'll let you know how it goes.