Overheats on the freeway but not when cruising around town?

[68 Sport Satellite]

KD, did you select a water pump yet? That plate shown on the 6-blade pump is an anti-cavitation plate to minimize bubble formation and bubble formation is bad for cooling. One with a plate is best. The number of fins that is ideal depends on the water pump pulley diameter. In general, I've found the higher the fin count (with cavitation plate in place), the faster the coolant flow. I had an overheating issue on my 451 with all new parts and tracked it down to the speed of coolant flow. I went from a brand new 6-blade pump to a higher fin count brand new Flowkooler pump and the problem went away.

However, now that I'm about to install A/C which requires downsizing the water pump pulley , there's a chance that this new pump will move the water a bit TOO fast. I plan to test this and run that new setup with the high fin count pump. If the overheating returns, I'll swap back in the 6-blade pump and it should be good.

I spoke at length with the tech guys at Flowkooler about this. There's an old theory that big blocks or A/C cars got the lower fin count 6 blade pump to slow down the coolant and keep it in the rad longer for better cooling. This is not always true. It depends on what your motor needs and is highly dependent on the water pump pulley diameter.

Also, I know that you collect a lot of used parts and re-use them a lot. Water pumps are one thing that do wear out and need replacing. I would install a new pump if I were you. When my dad and I had the '67 Chevy 327, in the 43 years we owned it, we had to replace the water pump about 4 times. The bearings wear out. One way to test this is to carefully hold a metal rod (we used a tire iron) and place one end against the water pump housing and the other end to your ear with the motor running. A good pump will make a nice smooth whirring sound. You can hear the difference with a bad pump.

 

[Kern Dog]

I did use a new GMB pump when I built this engine. I reused it when I changed the radiator.
I don't claim to know everything but it seems that the concept of slowing the coolant flow so it stays in the radiator longer also allows the coolant to stay in the engine longer, generating even MORE heat.
I have a Flowkooler in the red car because I have A/C and wanted the best. For Jigsaw, I figured that a standard pump would be adequate. It probably was. I saw no obvious flaws in the thermostat, water pump, fan or the radiator. The radiator is 23 years old and spent 18 years in Ginger, the red car. I never overheated out on the road with it. Both cars received new radiators simply for the ability to use stock shrouds and hoses.

 

[68 Sport Satellite]

I did use a new GMB pump when I built this engine. I reused it when I changed the radiator.
I don't claim to know everything but it seems that the concept of slowing the coolant flow so it stays in the radiator longer also allows the coolant to stay in the engine longer, generating even MORE heat.
I have a Flowkooler in the red car because I have A/C and wanted the best. For Jigsaw, I figured that a standard pump would be adequate. It probably was. I saw no obvious flaws in the thermostat, water pump, fan or the radiator. The radiator is 23 years old and spent 18 years in Ginger, the red car. I never overheated out on the road with it. Both cars received new radiators simply for the ability to use stock shrouds and hoses.

nice. So with the red car you've got a Flowkooler with the small A/C pulley and all is well. That gives me hope that when I add A/C I won't need to swap the old pulley back in. Thanks.

 

[68 Sport Satellite]

Someone else mentioned it and I'll also concur - a bad rad cap that doesn't seal or meet the stated pressure rating can also cause an overheating issue. I think it's rare, but I've seen it happen.

KD - on the aluminum rads, I installed a zinc anode plug insert where the drain petcock normally goes. This combats corrosion due to dissimilar metals of iron and aluminum in contact with one another via engine coolant. The zinc corrodes more readily than the aluminum or iron, hence the term "sacrificial anode", protecting the iron and aluminum (cathodic protection). Summit sells them. I recommend. They also sell one of these built into a rad cap, but I prefer the lower rad plug. Coincidentally, my first job out of college was a Cathodic Protection corrosion specialist for underground tanks and pipelines, so I know the science and the zinc plug is legit.
Fluidyne High Performance FHP32004 Fluidyne Zinc Anodes | Summit Racing

 

[matchek]

I have seen this in print before but still don't understand.
When I refill a cooling system, I squeeze the upper hose as the radiator gets close to full to burp out as much air as I can.
I'll often run the engine with the cap off to watch the flow and then top it off as needed. I will get it up to operating temperature and check the coolant level occasionally. If there is some other way to rid the system of air, I'm willing to learn.

The radiator arrived last week.

View attachment 1463121
Pretty nice looking unit for a beat up car!

View attachment 1463122
Transmission cooler at no extra charge….

View attachment 1463125

Nice thick mounting flanges:

View attachment 1463124



I went through my stash and picked a shroud. I have 2 from the 85-89 Chrysler Fifth Avenue cars. They had 26" radiators but also used bigger fans. The opening in the shrouds that I have are approximately 22", compared to around 20" in the stock shroud I have in the red car. I'll be using a bigger fan and shroud with this radiator. I've used a 19" 5 blade fan but I'm switching to a 20" 7 blade fan from that Fifth Avenue.

View attachment 1463127

Since the shroud isn’t stock, I had to clearance it a bit where the hoses will go.

View attachment 1463129
View attachment 1463130

By the way did you mention the brand, price , width, and # or rows? Was just curious what you selected. Interesting my current radiator has the oppostive configuration with the entry port on the upper right (drivers) and the exit on the bottom left (passenger). I am a little baffled on these configurations. I guess my water pump is backwards.

Sorry if I missed this above, but was your prior radiator corroded inside and / or did you try to clean it first?

 

[Kern Dog]

Your radiator is configured like a 273-318-340-360 LA series engine. The big block engines of 1970 had the bottom nipple on the left/driver side with the top nipple on the right/passenger side. Somewhere around 1974, they switched to using a water pump housing on the passenger side.
In 2001 when I did my first 440 swap, I didn't know that the big block was built with water pump outlets on one side for most years and then the other side to the end of production. I bought a 1977 440 from a New Yorker and just ordered a radiator to work with the passenger side lower nipple.

I called ECP and ordered a factory replacement style radiator for a 1970 Charger with a big block. It was right at $300 shipped to my home. I have another one in my red car that I installed in 2018 or 2019. It has been great.

 

[1 Wild R/T]

The change of waterpump housings was 73.... But you can't just throw a 72 & earlier water pump on the engine.... The timing marks are in a different location, so that would mean a different timing cover & damper... Plus the alternator-A/C bracket is different because the bolt boss on the water pump near the thermostat is moved about 3/8"...

Another one of those situations of Do you want to chase the details to make it right? Or do you want to do what it takes to make it work?

Like Greg mentioned, a small block radiator will have the inlet & outlet locations you need...

 

[Kern Dog]

The change of waterpump housings was 73.... But you can't just throw a 72 & earlier water pump on the engine.... The timing marks are in a different location, so that would mean a different timing cover & damper... Plus the alternator-A/C bracket is different because the bolt boss on the water pump near the thermostat is moved about 3/8"...

How did I get lucky? I've used the same harmonic damper and timing cover from the previous water pump housing setup in the red car, Ginger.
I've verified TDC. The timing mark isn't easy to see but I've grown used to it.

 

[matchek]

Your radiator is configured like a 273-318-340-360 LA series engine. The big block engines of 1970 had the bottom nipple on the left/driver side with the top nipple on the right/passenger side. Somewhere around 1974, they switched to using a water pump housing on the passenger side.
In 2001 when I did my first 440 swap, I didn't know that the big block was built with water pump outlets on one side for most years and then the other side to the end of production. I bought a 1977 440 from a New Yorker and just ordered a radiator to work with the passenger side lower nipple.

I called ECP and ordered a factory replacement style radiator for a 1970 Charger with a big block. It was right at $300 shipped to my home. I have another one in my red car that I installed in 2018 or 2019. It has been great.

Yeah that makes send. Well the engine block is stamped Oct 1972 so I believe I have a 73 Engine and now a 73 water pump. From the 70 manual, a 440 w/ Air Con took a 26" wide radiator and w/o 22" wide. The 318 took a 19" without Air Con and 26" without. I currently have a 26" and have the ports reversed like Kern said.

There are not a lot of places that sell a 26" rad with the ports reversed like mine with 3 rows but did find it for $300 as well.

At this point, I am just interested in making it work. By the way since my water pump is supplied from the passenger side does that mean I would need to order a 73 Water pump and housing? I am just looking into in case I need a water pump. It is not currently leaking but have not tested the flow yet. Thank you!

 

[1 Wild R/T]

How did I get lucky? I've used the same harmonic damper and timing cover from the previous water pump housing setup in the red car, Ginger.
I've verified TDC. The timing mark isn't easy to see but I've grown used to it.

Greg, is your timing tab on the passenger side or the drivers side? I would expect early water pump should cover/hide the drivers side timing tab...

@matchek When you buy a big block water pump you only get the pump, not the housing.. And the pump fits both designs... The the question becomes the quality of the pump & how much coolant it moves..

 

[RemCharger]

How did I get lucky? I've used the same harmonic damper and timing cover from the previous water pump housing setup in the red car, Ginger.
I've verified TDC. The timing mark isn't easy to see but I've grown used to it.

Greg, is your timing tab on the passenger side or the drivers side? I would expect early water pump should cover/hide the drivers side timing tab

Any pics of a drivers side tab?
Never seen one myself.

 

[1 Wild R/T]

Any pics of a drivers side tab?
Never seen one myself.

I don't have one... I also rarely work on anything newer than a 70 anymore... Back when I turned wrenches on a lot of early 70's stuff I dealt with plenty, along with vehicles that the timing tab on the passenger side along with the lower hose but use what was called mag timing where you slid a magnetic pickup in a sleeve attached to the timing tab..

Have you seen a early vs late small block timing cover? Same deal...

 

[Kern Dog]

The LA series has had timing marks on one side or another. I have not seen a big block with timing marks on the drivers side. I am not claiming that they don't exist, just that I have not seen one.

 

[5.7 hemi]

If it was in a RV, the big blocks would have it on the drivers side as the bottom radiator hose is the passenger side.

 

[Sixpactogo]

If it was in a RV, the big blocks would have it on the drivers side as the bottom radiator hose is the passenger side.

I don't believe that to be true. I have never seen any big block mopar engine with the timing marks on the driver side. Here is a pic of my 78 440 engine. You can clearly see it is on the passenger side. Way too much stuff on the driver side like the PS pump, oil filter and AC.

 

[Sixpactogo]

The change of waterpump housings was 73.... But you can't just throw a 72 & earlier water pump on the engine.... The timing marks are in a different location, so that would mean a different timing cover & damper... Plus the alternator-A/C bracket is different because the bolt boss on the water pump near the thermostat is moved about 3/8"...

Another one of those situations of Do you want to chase the details to make it right? Or do you want to do what it takes to make it work?

Like Greg mentioned, a small block radiator will have the inlet & outlet locations you need...

This is not so. When I built my Nieces 70 Challenger, I used a 77 Motor home engine. Swapped on the water pump housing from a 68 440 engine with no issues at all.

 

[5.7 hemi]

You may be right.

 

[1 Wild R/T]

Well maybe my memory is fading, don't think so, I know the hose swapped sides in 73, clearly you can see the timing marks on the 78 engine posted above.... I remember lots of 76-77-78 cars with mag (magnetic) timing.. I'll shut up & go home now...

 

[RemCharger]

The mag timing slot was on the pass side .
They're hard to see and frankly, undesirable.
But to my knowledge, there has never been a balancer with a different tdc slot.

 

[matchek]

I don't believe that to be true. I have never seen any big block mopar engine with the timing marks on the driver side. Here is a pic of my 78 440 engine. You can clearly see it is on the passenger side. Way too much stuff on the driver side like the PS pump, oil filter and AC.

View attachment 1467092

That looks like my water pump housing setup. What is your alternator belt connected to the upper right of it - that large black component? Is that the air conditioner? I don't have A/C and thing my alternator belt connects to my power steering pulley. Nice engine. Thanks for posting.