'66 Valiant Running Hotter than Expected

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Jim Kueneman

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The '66 Valiant I recently finished went on a long interstate trip last weekend and it was rather a "cool" day for us in the low 90's. It is a 360 that has aluminum Edelbrock heads and a 4 core radiator by Bob at Glenray.. factory shroud, correct factory direct drive 7 blade fan, all lower factory grill area filler panels, and hood seal. It ran right in the middle (NOS gauge and sender) of the temp gauge till it hit 90F. After that I could modulate the temp by how fast I went.. the faster I cruised the hotter it got. Cruising around 80 MPH it got up in the 75% of the gauge. The car has AC but I have a leak to fix so I was not using it. From what I experienced I would not have been able to use it anyway. I stopped to get gas and it hit the upper normal line at the red light (about 95F outside). I was disappointed, I was sure the aluminum heads and radiator would be fine.

Now the interesting thing. On the way home at dusk through farm land there were a lot of bugs. The next morning I got them off the front of the car but when I opened the hood the BOTTOM of the hood around the fan was almost black from bug guts. The where thrown everywhere around the fan... I am scratching my head about if there is some weird aerodynamic of the '66 that causes a vacuum to first suck that many bugs up from.... ??? under the car????? and second if that is part of the cooling problem...

Anyone seen anything like this before?

Jim
 
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Alum is much weaker than steel/cast iron. The deck thickness on an iron head might be 3/8"; 5/8" on an alum head. Ports are also often bigger on alum heads, with more metal for porting.
Guess where that additional metal intrudes into. Yup, the water jackets, so less water....
 
It might not make much difference, but when I used to have cooling problems I would try running the heater wide open. If the temp dropped significantly, I knew I needed some more cooling. If it didn’t, I had a restriction in the cooling system like a sticking thermostat, etc. Not a fool proof trick, but useful sometimes. The first time I saw a heater used in the summer was in a friend‘s new 427 Cobra. It was an early model and didn’t have the dual cooling fans, which he added later. This was in Oklahoma, which get pretty hot in the summer, and feels even hotter with the humidity. There are probably better ways to trouble shoot cooling problems than this, but it just came back to me. I also had an early Econoline with the 177 inch motor that the heater barely worked in. Turning on the heater made no difference in temperature, so I checked the heater control valve. It was plugged. Replaced it and the heater worked… and it would drop the motor temp a couple degrees in hot weather.
 
You didn't mention how hot it really got just where the needle was on the gauge. Of course bugs can cause blockage and heating issues. What's your 360 block like? Stock bore, has it been rebuilt. .030 over or more? What degree thermostat?
 
Put a spring in the lower radiator hose to keep the water pump from sucking and collapsing the hose.

Most people think with the modern hoses that they are not needed........but the factory thought they were needed....must've been a reason and this sounds exactly like what the reason might very well have been.
 
You didn't mention how hot it really got just where the needle was on the gauge. Of course bugs can cause blockage and heating issues. What's your 360 block like? Stock bore, has it been rebuilt. .030 over or more? What degree thermostat?

0.030 over, totally rebuild, cleaned decked, line bored, etc, etc... 180 high flow ... blanking out of the manufacturer....
 
You didn't mention how hot it really got just where the needle was on the gauge. Of course bugs can cause blockage and heating issues. What's your 360 block like? Stock bore, has it been rebuilt. .030 over or more? What degree thermostat?

And it was toasty... based on how it restarted at the gas station.
 
I have a forty-over 360 with alloy heads, set up at about 11/1 Scr. It has run three different cams. It is in a 68 Barracuda with a 4 speed. I used to cruise it at 65 =3000 rpm, but she used to run hot; and I couldn't cure it.
So I got to thinking that either the pistons were tight or the rings were.
So I pulled the engine and stripped her down.
I sent the Block to the Machine shop to hone out the bores about a half a thou, then opened up the gaps on the top ring about .005, and the second about .002. Then slammed it all back together. No other changes were made.
After that, she has been impossible to overheat.
My guess is that my thinking was right.

BTW
On a side note:
adequate cruise-timing is essential.
With the current cam (276/286/110), my 367 likes 56 degrees at about 2400@70 mph in overdrive. She runs at exactly 207*F as measured at the stathouse with an IR gun. Hot day/cold day/fast/slow/idling, cruising, or racing; 207*F.

>If yur timing is retarded, and you have a long-period cam running headers, it is easily possible that the combustion gasses do not finish burning in the chamber. So, two things happen; 1) the expanding gasses chase after the falling piston, heating up the cylinder walls, and 2) the Headers will pull still-burning gasses out into the alloy ports, which then transfer more heat into the water jackets that encircle it.
> if yur timing is overly advanced, the pressure peak may occur too early, and result in detonation.
>Your exhaust system has to be able to deal with the hot gasses too. Any restriction will negate the work of the headers, and the hot gasses have additional time to heat up the ports.
>If your cruise fuel mixture is too rich, not all of it will find oxygen in the chamber to react with, so it/the raw fuel, goes out with the hot gasses. If it finds oxygen in the headers up near the head, it will spontaneously combust right there! This will muck up the work of the headers by causing the exhaust pressure to spike, and so the burning mixture will probably sit right there until it is burned up. If the WOT mixture is also rich, this kind of activity, will also kill some power at WOT, from the torque peak and higher, cuz it kills the overlap cycle. So then, you gotta make sure the header flanges at the heads are not sucking air, and lean out at least, the cruise AFR.
>If/when you get the timing right, you will be surprised at how lean she will run. Don't lean it out so far that the valves burn, lol.
>If you are running a Multi-strike ignition system, try not to cruise at the switchover point, which, IIRC is 3000 rpm.
> make sure the head gaskets are not allowing pressure into the cooling system.
 
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Four things if you don't mind, Jim. What's the static compression ratio? Where is the initial timing set? What carburetor? What camshaft?
 
Four things if you don't mind, Jim. What's the static compression ratio? Where is the initial timing set? What carburetor? What camshaft?

About 9:1 (maybe a little less), have a FBO plate so 18 initial and 30 all in and about 52-54 with the vacuum. Edelbrock 1405? Oregon Cams... basically what I use for the slants, aimed at low end torque low duration moderate lift. Dynamic compression about 180.
 
I have a forty-over 360 with alloy heads, set up at about 11/1 Scr. It has run three different cams. It is in a 68 Barracuda with a 4 speed. I used to cruise it at 65 =3000 rpm, but she used to run hot; and I couldn't cure it.
So I got to thinking that either the pistons were tight or the rings were.
So I pulled the engine and stripped her down.
I sent the Block to the Machine shop to hone out the bores about a half a thou, then opened up the gaps on the top ring about .005, and the second about .002. Then slammed it all back together. No other changes were made.
After that, she has been impossible to overheat.
My guess is that my thinking was right.

BTW
On a side note:
adequate cruise-timing is essential.
With the current cam (276/286/110), my 367 likes 56 degrees at about 2400@70 mph in overdrive. She runs at exactly 207*F as measured at the stathouse with an IR gun. Hot day/cold day/fast/slow/idling, cruising, or racing; 207*F.

>If yur timing is retarded, and you have a long-period cam running headers, it is easily possible that the combustion gasses do not finish burning in the chamber. So, two things happen; 1) the expanding gasses chase after the falling piston, heating up the cylinder walls, and 2) the Headers will pull still-burning gasses out into the alloy ports, which then transfer more heat into the water jackets that encircle it.
> if yur timing is overly advanced, the pressure peak may occur too early, and result in detonation.
>Your exhaust system has to be able to deal with the hot gasses too. Any restriction will negate the work of the headers, and the hot gasses have additional time to heat up the ports.
>If your cruise fuel mixture is too rich, not all of it will find oxygen in the chamber to react with, so it/the raw fuel, goes out with the hot gasses. If it finds oxygen in the headers up near the head, it will spontaneously combust right there! This will muck up the work of the headers by causing the exhaust pressure to spike, and so the burning mixture will probably sit right there until it is burned up. If the WOT mixture is also rich, this kind of activity, will also kill some power at WOT, from the torque peak and higher, cuz it kills the overlap cycle. So then, you gotta make sure the header flanges at the heads are not sucking air, and lean out at least, the cruise AFR.
>If/when you get the timing right, you will be surprised at how lean she will run. Don't lean it out so far that the valves burn, lol.
>If you are running a Multi-strike ignition system, try not to cruise at the switchover point, which, IIRC is 3000 rpm.
> make sure the head gaskets are not allowing pressure into the cooling system.

Interesting thought... I will ask my machine shop buddy how he set that up.. he documents everything.
 
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About 9:1 (maybe a little less), have a FBO plate so 18 initial and 30 all in. Edelbrock 1405? Oregon Cams... basically what I use for the slants, aimed at low end torque low duration moderate lift. Dynamic compression about 180.
And this is a 360, correct? That's not a lot for a carburetor. If it's running lean that could certainly do it.
 
And this is a 360, correct? That's not a lot for a carburetor. If it's running lean that could certainly do it.

500 CFM, what I wanted good to any RPM I would ever care about and good drivability (it runs and its drivability is like a Swiss watch compared to any of my other cars). I tuned it with an AFR meter. It is running around just a bit richer than ideal 14.7 (high 13's) at cruise and 11's at WOT (I think... I have slept since then). Oh and the last time it was at WOY was when I tuned it. :).
 
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About 9:1 (maybe a little less), have a FBO plate so 18 initial and 30 all in and about 52-54 with the vacuum. Edelbrock 1405? Oregon Cams... basically what I use for the slants, aimed at low end torque low duration moderate lift. Dynamic compression about 180.

I believe it was a 819 cam... I would have to dig through the paperwork but it was in that range.
 
The best part is the temps dropped 30 degrees in the last 2 days (the length of our fall) and it won’t be that hot again till June.
 
The '66 Valiant I recently finished went on a long interstate trip last weekend and it was rather a "cool" day for us in the low 90's. It is a 360 that has aluminum Edelbrock heads and a 4 core radiator by Bob at Glenray.. factory shroud, correct factory direct drive 7 blade fan, all lower factory grill area filler panels, and hood seal. It ran right in the middle (NOS gauge and sender) of the temp gauge till it hit 90F. After that I could modulate the temp by how fast I went.. the faster I cruised the hotter it got. Cruising around 80 MPH it got up in the 75% of the gauge. The car has AC but I have a leak to fix so I was not using it. From what I experienced I would not have been able to use it anyway. I stopped to get gas and it hit the upper normal line at the red light (about 95F outside). I was disappointed, I was sure the aluminum heads and radiator would be fine.

Now the interesting thing. On the way home at dusk through farm land there were a lot of bugs. The next morning I got them off the front of the car but when I opened the hood the BOTTOM of the hood around the fan was almost black from bug guts. The where thrown everywhere around the fan... I am scratching my head about if there is some weird aerodynamic of the '66 that causes a vacuum to first suck that many bugs up from.... ??? under the car????? and second if that is part of the cooling problem...

Anyone seen anything like this before?

Jim
How hot is it getting? What does your gauge read? Is it puking coolant?
 
How hot is it getting? What does your gauge read? Is it puking coolant?

It never over heated but it was getting there. Like I said if I had the AC working it would have been game over. I’ll have to carry the IR gun or put a temp sensor in it next year. The motor will be more broken in and looser by then too. This is all reminiscent of the trouble that I had with the Coronet in the heat. I thought I could avoid that with the aluminum heads and the four core radiator. I had good luck on the duster with the Toth heads and four core radiator. That Car never gets hot ever. The gauge was right at the max normal range when I was at the off ramp red light after cruising for 80 miles an hour three hours. Once I hit the highway it would come down to about 3/4 to seven eights of the way to the max normal range. The Duster in the Dart typically have a hard time, even getting up to the middle of the normal range
 
It might not make much difference, but when I used to have cooling problems I would try running the heater wide open. If the temp dropped significantly, I knew I needed some more cooling. If it didn’t, I had a restriction in the cooling system like a sticking thermostat, etc. Not a fool proof trick, but useful sometimes. The first time I saw a heater used in the summer was in a friend‘s new 427 Cobra. It was an early model and didn’t have the dual cooling fans, which he added later. This was in Oklahoma, which get pretty hot in the summer, and feels even hotter with the humidity. There are probably better ways to trouble shoot cooling problems than this, but it just came back to me. I also had an early Econoline with the 177 inch motor that the heater barely worked in. Turning on the heater made no difference in temperature, so I checked the heater control valve. It was plugged. Replaced it and the heater worked… and it would drop the motor temp a couple degrees in hot weather.

Yes, I was running the defroster experiment and it would bring it down quite a bit, but it brought me up quite a bit ha ha
 
It never over heated but it was getting there. Like I said if I had the AC working it would have been game over. I’ll have to carry the IR gun or put a temp sensor in it next year. The motor will be more broken in and looser by then too. This is all reminiscent of the trouble that I had with the Coronet in the heat. I thought I could avoid that with the aluminum heads and the four core radiator. I had good luck on the duster with the Toth heads and four core radiator. That Car never gets hot ever. The gauge was right at the max normal range when I was at the off ramp red light after cruising for 80 miles an hour three hours. Once I hit the highway it would come down to about 3/4 to seven eights of the way to the max normal range. The Duster in the Dart typically have a hard time, even getting up to the middle of the normal range
So you are going off the factory gauge with no numbers on it and it isn't overheating and it is a fresh engine that hasn't really been broken in yet? That all sounds pretty normal to me.
 
So you are going off the factory gauge with no numbers on it and it isn't overheating and it is a fresh engine that hasn't really been broken in yet? That all sounds pretty normal to me.

Yea, maybe but like I said this is starting out like a carbon copy of the Coronet that struggled similar and that was with a factory 26" radiator and small block. If it struggles now at 95F even when broke in it will struggle next year at 105. There is a tipping point that has become clear in our heat.. If you can't do 90F without seeing the gauge move on the highway you will not make it with the AC on and 100F in the summer.
 
I'd be wondering what actual temperature it's getting up to. Factory gauges really don't tell you much, and aren't that accurate anyway. I run a mechanical temperature gauge in everything for that reason. Find out what it's really doing, then go from there. My very amateur experience is that if the car is running hot at interstate speeds, it has a coolant flow issue somewhere. I'd get the radiator flow checked, then check the thermostat to see if it's opening when it's supposed to and as much as it's supposed to. That said, I have two nearly identical small blocks, one a 340, the other a 360. Same cam, same intake, same carb, same exhaust and same heads. Both have three core factory type radiators. The 340 does have a bit higher compression ratio, 360 of course has 20 more cubic inches. The 340 never gets over 180. The 360 when fully warmed up on a hot day likes to run at 210. Never have been able to figure out why, but new cars routinely run that hot, so I have just lived with it for 30 years.
 
500 CFM, what I wanted good to any RPM I would ever care about and good drivability (it runs and its drivability is like a Swiss watch compared to any of my other cars). I tuned it with an AFR meter. It is running around just a bit richer than ideal 14.7 (high 13's) at cruise and 11's at WOT (I think... I have slept since then). Oh and the last time it was at WOY was when I tuned it. :).
Up there ^^^^^ you said 1405. That's a 600. The 1404 is the 500. IMO Jim, either of those is WAY too lean for a 360. I think that's possible that's some of your issue, especially if it really is a 500. Again, just one peon's opinion.
 
So you are going off the factory gauge with no numbers on it and it isn't overheating and it is a fresh engine that hasn't really been broken in yet? That all sounds pretty normal to me.
I agree. That's entirely possible. I would be verifying with an IR temp gun.
 
The factory 2 barrel is 350 so I’m already way bigger than that (I’m likely wrong on the part number I know it’s 500)
 
I guess I don't understand how just because it is a 500 CFM it would be too lean? Driving down the highway at at 3000 RPM is using around 270 CFM. Any carb should work if it is jetted correctly and this one is jetted very close.
 
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