ecklers sells the hose with the spring for $18

 

the tempos have never stayed with the tstat, even before I had the new engine out in. the engine was alwaays at 220 with the old l48. Now it goes even higher. the temps do come down as soon as I slow down. Street driving is not a problem it only goes up on the freeway. I will try to get an ir gun this week and check with ecklers aabout the hoses with the spring.

 

my thinking on removing thermostat is that its pretty simple to do and even a thermostat that is opening fully still restricts substantially the water flow(compared to size of hole that thermostat sits in). if water flow is the problem that would solve that...just a thought

 

I have a big block with exactly the same issue. I have a new Dewitts radiator, air dam intact, new foam seals, new (correct) clutch fan, new hoses with spring, new (complete) engine rebuild with 2000 miles on it, checked the temp with IR gun, 195 degree thermostat.

At speed, over 70, the gauge starts to creep right up to the red and won't back down until I get off the fwy.

I had a suggestion from a buddy who restores '56 chevs. He mentioned high flow water pumps causing these issues. And guess what? When I rebuilt I put an Edelbrock long nose high flow pump on. the theory is the pump is not letting the water sit in the radiator long enough.

Any thoughts or comments? not hijacking but adding another possibility. But, as mentioned, I have a big block

Added: i would love to hear Tom Dewitt's thoughts on this matter. And Tom, I love the radiator. It was so well made, it was worth every penny.

 

I hope this isn't true. I just put a Stewart stage 2 (and a Dewitts) on my 454. But haven't run it yet. I've heard the opposite, that higher flow pumps help with cooling.

 

My 78 stock L-82 4 speed always has run hot on the highway from the day it was new and cooled off once off the highway, just like many have described above. Chased the high speed heat problem for 25 years and finally cured the problem with the combo of 79 heavy duty cooling rubber spoiler extension on the stock chin spoiler on my 78, Dewitts aluminum radiator, Stewart Stage 2 aluminum water pump, and making sure all the radiator insulation was correct and intact. It runs too cool now sometimes with the Robertshaw modified 180 thermostat that is required to be used with the Stewart Stage 2 aluminum water pump. Max temp on the highway on a 95 degree day now is 180 degrees!!

The BB's have the problem because of the obvious problem a hugh engine in a confined space with limited airflow capacity for the biggest radiator that can fit in the nose. The smog small blocks like my L-82 have the problem due to the 882 smog heads which were designed to RAISE the combustion temperatures to meet emissions regulations.

Hope that helps!

 

i was wondering what happened to this thread and how he was making out?

 

There are no two engines alike and what works for one person is not to be considered the global cure all for everyone. When you drive at high speed it takes more power, your engine RPM goes up, water flow is higher, and timing is advanced. Since you are going to use more power, it is normal to create more heat, and hopefully the radiator has additional capacity to remove it. Of course you have to eliminate all the obvious stuff like weak/old hoses, spoilers, and debris. I'm not sure a brand new lower hose "needs" a spring but it won't hurt.

HF water pumps have been known to cause high temperatures. This is because every radiator has a optimum flow point or sweet spot. GM matched the water pump to the radiator so it works at it's best. Too much flow or too little flow and the heat rejection can be reduced.

Our aluminum radiators have more tubes and they are wider than the stock radiator, so the flow path is bigger and less restrictive. In this case, a HF water pump may actually be a better match. If you have this combination I wouldn't be concerned. I am NOT saying you need a HF pump with our aluminum radiator, I just saying it won't hurt and you could see a slight improvement because of the larger flow path.

When chasing a temperature issue, do not focus only on the cooling system. There IS two sides to the equation... the engine creates the heat and the radiator gets rid of it. Often we tend to bandage an engine problem with increases in the cooling systems. Most of the combustion heat goes out the exhaust but when something is wrong with the timing you can add a lot of heat to the coolant. Timing issues could be frankin motors with weird cams, wrong distributors, or worn out distributors, HEI mods, vacuum cans, offset timing gears, and all kinds of stuff. I find that totally stock engines very rarely have any of these cooling issues.

Replacement temperature sending units can cause a false alarm when they read high and your engine temps are normal. You have to get an IR gun to check this but make sure to check the switch at all levels. Some replacement senders will read normal up to 190, then they go off exponentially. Like this...

Gauge/IR gun

180/180
200/190
240/200
280/210

Make sure you shoot the motor at the highest gauge reading and compare that with what the gauge is telling you.

 

I retimed the motor and replaced the seals around the radiator. I took it out yesterday morning when it was 75 degrees out in the morning and it didn't go near 220 on the gauge. On the way home from work it was 95 out and the temp climbed toward the red. Cooled right down as soon as I got.off of the freeway. Still need to purchase an ir gun to check everything. I have a new water pump with the rebuild but I'm not sure if it is high flow or not. If the ir gun shows everything correct I'm taking the motor back to the builder. This is rediculous

 

bloody hell, have you taken out the thermostat, even if just for fun?

 

I had a 160 tstat in when I started everything. I have a 195 in now. I tested them both to make sure they opened before i installed it and they both did.

 

That should have been the first thing you did. What if you don't have a temperature problem at all? The sender could be misleading you.
You could just look at the switch and if it looks brand new, find the old one, install it, and go for a drive.
If you can't find the old one, make sure to check (IR gun) the gauge when it reads at the highest reading, even if you have to pull over and jump out to do it. If the motor cools down when you get home and you check the reading it might tell you it's accurate when it not at the high end.

 

still restrict flow, working one's too.

 

update????

 

Just got it out today and took it to a show. It is the original sending unit. i guess they used the one out of the old motor and not the new one. Temp on the radiator was 150ish. temp on the heads was 217 temp on the little silver disk on the front of the motor was 220. temp on the intake was 200ish. temp on the oil pan was about 257-260. all of this was when the gauge in the car read 220 deg.

 

So are my only next options to get hoses with springs and remove my thermostat? When I had it out the other day I ran it up to 90 for a very short period and it actually seemed to cool the engine instead of heat it up so it seems the hot spots might be between 70-80mph. Is this a clue to something?

 

Azguy,

Is your vacuum advance hooked up and working?

I have same overheating issue. Just noticed yesterday that mine runs hotter between 70 and 80 mph. Above 80mph, it started cooling back down to 200F.

I don't have vacuum advance hooked up, but am going to try it and see if the additional timing helps. Worth a try.

Roger

 

Yeah the vacuum advance is hooked up. I guess its a possibility that it isn't working somehow

 

How would I test it?

 

It should be pretty easy, there is more than one way.

Simplest-quickest, with engine running at normal temperature, pinch the vacuum hose that goes to the distributor with vise grips or clamp, then unplug vacuum hose from distributor. The engine rpms should decrease. However, this isn't 100% accurate because some vacuum hoses are hooked up to ports on the carb that do not provide vacuum at idle.

So, if the test above didn't change anything, do this another way. With the engine running, connect full port vacuum to you distributor and you should hear the engine rpm increase if the vacuum advance is working.

If you have a timing light, I would check the timing with and wihtout the vacuum advance connected.

Let me know what you find.

Roger