Inliners International Forums General Discussion Engines 250 motor still overheating.

I'm hoping someone can tell me what the problem is here.
Last year I was having overheating problems with my Chevy 250 motor.
After getting the head checked and was told it was fine, they figured it was a cracked on the motor. I decided to purchase a crate motor. Basically another 250. Since 6 months ago I have replaced the water pump twice, the thermostat twice, I also drilled a hole on it. I checked all of my hoses which I use the stainless chrome ones. I had it timed several times. It was timed almost to like a 12, then we backed it down to about an 8. Because at 4 like the book says didn't worked either. So I decided to buy a new radiator also, still over heats. What am I missing here guys? Everything has been changed under the hood. The timing set at anything isn't doing it. So can someone please send some knowledge my way.

Is it actually boiling over or just showing high temp on the gauge? What is the pressure rating on the cap? Is the heater connected? What kind of fan are you running? Is there a fan shroud? Over heating Is not usually and issue with these.

The gauge is showing about 200 when it reaches temperature, then as I drive it will reach about 220. When I finally shut it off it will reach about 240. Running stock fan, no shroud. I'm using a chrome cap, can't really remember the lbs. I did checked the cap spring to see if it moves freely and it's fine.

I an not running the heater. I thought about bypassing it. Can it be clogged?

Once when I was having a heating issue with a totally different engine (Studebaker V8) if I turned the heater on it would cool down. I think it was just the little bit more cooling that the heater core & fan produced. Not a fix and very uncomfortable to drive in the summer but it let me know I didn't have enough capacity in the cooling system. Also a fan shroud helped. I can not see this as being your problem. It is a puzzler. Is there sufficient air flow through the radiator? Once I had an engine that did not over heat until I put a pusher electric fan on it.

Well I just got in from the garage. I had a small amount of hope left and that went out the window. I bypassed the heater core and it still overheated. At this point I really don't know what else to troubleshoot. It's just odd to me that both motors would overheat. Now I'm wondering if there was anything wrong with the old one in the first place. Probably didn't need to replaced my radiator.
Don't know what else to test or look at.

Overheats at what speed?
What fan shroud? Fan?
Where is the fan w/r/t the radiator core?
Bypassing the heater makes it worse.

It's overheating at idle sitting in the garage.
I never had a heater in this car. Never hooked it.
I meant to say I don't have a radiator shroud.

Timing or carb lean are about the only things that can make it overheat in a garage with no engine load on it. A fan too far away from the radiator might make it run warmer, but not excessive. Have you been through the distributor to check the advance isn't stuck and is functioning properly...?

How do I check to see if the advance is stuck? As far as the fan distance to radiator I think it's fine. It's pretty close.

Exactly what is the engine and what is it in? If it has the original GM distributer advance the whole body will twist when you hit the throttle. If it is something later only the point plate moves. If it is HEI or some other electronic crap you need some diagnostic equipment.

Yes, I meant that the heater core gave added cooling capacity, extra to the regular cooling .

Are you just going with the gauge reading or is it actually boiling over. Is it some sort of stock gauge? Old GMs had a 168 degree thermostat. This was moved up to accommodate emissions standards to 190-195. Old gauges will show overheating in this range. Water boils at 212 degrees F with no pressure. The more pressure the higher the boiling point until the whole thing blows up. If it does not look like a steam engine waiting to load passengers at the station get it out on the road and see what happens.

The further the fan is from the radiator without a shroud the less air is pulled through the radiator core especially sitting still at idle. The tighter the & deeper core the worse it is. Extra space allows the fan to pull air from around the radiator not helping cooling and just adding fan drag to what work the engine is doing.

The car is a 1950 Chevy. It has a 1972-74 camaro 250 4.1L. I just recently bought it about 6 months ago. I haven't even broken the motor yet. I drove it probably twice since the motor was put it. My concern simply has been that the temperature reading from my aftermarket gauge is about the same when my old motor started giving heating issues. The fan isn't too far from the radiator.
I did drive it tow days ago. It stayed at about 200 and occasionally would go up to 220. Once I shut the car off the gauge would go up to 240. And you can definitely smell burning as well as feel a lot of heat from the radiator and hoses. Sorry, I hope this gives everyone enough info.

I forgot to mention, I am running an HEI distributor.

A couple of thoughts I haven't seen yet posted: 1 - check to make sure the aftermarket gauge/sensor are reasonably accurate. Remove the sensor from the engine and place in actively boiling water. Gauge should read 212� (at sea level). You can't necessarily infer too much above and below that temp, but should give a ball-park idea if you're seeing an accurate temperature reading around 212�, which is your concern.

2 - Regarding the timing. This motor likely should be using non-ported (manifold) vacuum as opposed to ported vacuum for the vacuum advance (lots of internet references on this; ask more here if more help needed). The initial timing at idle should be set with the vacuum advance disconnected (vacuum line removed and plugged). 8�BTDC is likely fine. Idle speed (and idle air/fuel mixture) needs to be correct when setting the timing. With the initial timing at idle speed set, reconnect the vacuum advance. If you check the timing at that point, you'll find the timing will have advanced - that is ok and normal (do not reset the initial timing!), and should help the motor to run cooler at idle.

Oops, just realized these issues were addressed in your other thread! Just double check this timing thing, seems the most likely culprit.

Another thought, you could also remove the radiator cap when the engine is cold, start it, let it warm up, and verify you see water circulating in the radiator as you look down the into the radiator.

These are all great suggestions, I appreciate it. I will check everything.

OK, A '50 Chevy with a new stock 250 and auto transmission. I was thinking of the older vac advances. You have and HEI. Is it a stock GM or aftermarket? It doesn't really matter. Can you check if the previous owner was having this issue? With all you have done we know a lot of what it is not. If you are sure the timing is right, there are no air pockets, and the pump is moving coolant it makes me think about restricted flow or too high temp thermostat. I don't think a fan shroud is an issue here since the car didn't have one. The first easiest & cheapest thing would be a 185 degree or so thermostat. If that doesn't help some then the radiator is likely the problem.

Does it actually boil over before or after you shut it off? Do you have a recovery/overflow tank? It is not unusual for the temp to climb after shutdown especially with high temp thermostats. A 195 degree stat opens at that temp. The engine is going to run at near 200. This is an emission thing not necessarily a good for your engine thing. This is where the pressure rating of the radiator cap comes into play. When the pressure in the cooling system exceeds the rating of the cap it pushes against the spring and allows the expanded coolant to get out hopefully into the overflow tank. It can be drawn back in as needed with no loss of coolant or mess on the ground. This is a more modern concept than the '50 Chevy used.

You have a new engine and parts with new paint and grease and sealants. It is going the give off "burning" smells for a while. The hoses and other parts will feel very hot that is why we don't take 200 degree baths. All of this heat stuff is relative.

I'd like to see some pictures of this cool little ride.

So my thermostat is a 180, which is strange why is running so hot. How do I post pictures here? The car never boils, just very hot. It reaches 240 once I shut it off.

If you let it get to 240, The temps will get higher than that from heat soaked.

Since you mentioned HEI, they are notorious for having the advance stick over time. Just pop the distributor cap off and try to turn the rotor by hand. It should turn a few degrees with ease. If its stuck/frozen and wont turn, you'll need to pull the distributor out and have it rebuilt....

Thank you. I will check the distributor tonight.

I checked my HEI and the motor spins freely.

I have read much of this posting. A few questions.
Where is the temperature sensor located?
Which vacuum port are you using for distributor (live or ported)
When checking the dist, did you pull the cap and twist the shaft to make the counterweights move?
Have you verified the vacuum can is functioning?
How old or new is this dist?

Timing and fuel mixture can be super critical for the issues you are having. You brought all this up in another post and then dropped it. Months ago.

The HEI distributor it's pretty new. I did removed the cap and turned the motor. It did spin freely and the spring moves it back fine.
I did took it to see a car guy, kind of guru old timer. He noticed after removing my radiator cap that no fluid was moving. He assumes it's either my water pump or upper hose. I'm using the stainless chrome hoses and because my distance from radiator to water neck is so close, it seems like the hose is kinked a bit.
I did removed it and it seems fine. I did noticed my antifreeze is pretty brown and almost looks like it has something mixed.

https://quickshare.samsungcloud.com/7mUq0dpucP2c

Hoping this picture works.

It looks like the top bend in the hose is above the top if the radiator & cap. That could fill with air and cause flow issues, cavitation.

Ok so my pictures went through. That's a great observation man. Thank you. I am going to test the system with a regular longer hose. Hopefully that is the issue. It would be a easy fix. I thought about cutting the chrome end adapters in half to allow the hose to go in better.

I would say try and find a upper stat. housing that goes straight up and find a shorter 90 deg. hose that will reach. And just simply try and get rid of all the un-needed bends.

I am ordering one tonight and trying a regular 90 degree rubber hose. This will at least tell me if it is the problem. I have also removed the water pump to inspect it. I'm having someone check it for me.

Will the way the heater hoses are routed make a difference? I did noticed I had them crossed. So what used to go through the heater core and so on were wrong.

Why are you refusing to check the temperature gauge?
Running an engine inside a garage for long periods, without good airflow could cause an engine to over heat. You should have a fan set in front of the grill or better yet, drive the car and see if it is actually overheating.

>>I had it timed several times.<<

You had it timed? Get a timing light and a tach.

Take the cap off and FIDDLE with the rotor? NO. Connect the timing light, rev the engine and watch the timing as it advances.

If the hose is kinked, fix it, don't debate it.

Check to see if the engine is actually overheating and check the temp gauge.

The timing is set with a timing gun. It does not overheat to the point that it boils. It gets to 200 while driving and at lower speeds or when coming to a complete stop, the temperature will then rise to 220.
I have ordered a new straight up water neck to fix my hose issue, and I have removed the water pump to have someone look at it to see if if maybe it's bad. Hopefully by Thursday I'll know what the problem has been.

Questions I asked and never answered. All in a effort to help.
Where is the temperature sensor located?
Which vacuum port are you using for distributor (live or ported)
Have you verified the vacuum can is functioning?

The temp sensor is located behind the intake manifold, on the head.
And I am using the ported for vacuum.
Sorry I'm not very mechanical when it comes to older motors. How would I test the vacuum can? I can take pics of where my vacuum is connected to my carb.

My preference is to use live vacuum hooked to distributor. The extra timing it gives will keep the engine cooler.
The temp sensor in head can give erratic measurements. A better location is in the lower thermostat housing. GM quit putting the sensor in the head (near a exhaust port) for just that reason.
The vacuum can can easily be tested using a live vac line and a timing light. Hook the live line to can and watch the timing increase, unhook it and watch it go down in timing.

Thank you tlowe, I truly appreciate your time. I am having someone that knows their way around these old motors on Sunday and I will show him your reply. I did however changed my water neck to an upright style with a shorter hose. It worked pretty well. But this this still got to high in temperature too quick. I ran it without the radiator cap for about 5 minutes, then everytime I raised the rpm it burped water out of the top of the radiator. So after a couple of times I decided to put the cap on. The temp then went up to 220 so I shut the car off. That caused the water to burst out of my heater hose and steamed out pouring a lot of water out..
It's like it built pressure and the only place it found it's way out was my heater hose.

Well that looks better and we know another thing it is not. If it is not the vacuum port I don't have a clue where else to look. Could there be a blockage in the head? I know you had it pressure tested but did the check for obstructions? This is crazy! (as I'm sure you know)

Sorry, the picture is a bit small. This shows where my vacuum line hooks up from my HEI distributor. It's the one with the chrome end on the bottom. The top port is plugged.
https://quickshare.samsungcloud.com/y4hyPARL97LL