Rebuilt Engine High Temp Issue

[The Swed]

I should have trusted my gut... the rebuilt engine seemed to be running hotter and told the shop to make sure to put a 160 F thermostat... I have 700 hundred plus miles on the rebuilt and I was hauling a load to the dump the line was long and slow, it was a moving every five minutes a truck length and the engine started to get hot... then run ruff... then quit... I really wanted to dump the load but not at the cost of my engine so I turned around so I could get moving to allow some air flow. I stopped at the auto parts store and I bought a 160 F thermostat and hope they put the wrong one in. Yep they put in a 195 F which is 35 degrees higher. I replaced it but I'm not sure why the engine had such a hard time at the high temperatures. Any thoughts... See attached pictures... the first is the temp gage at 195, the second is at 160, the third and fourth pic is both thermostats, and the fifth is the mess. BTW the temp gage was a little pass the center when the engine shut down so I'm guessing at was around 400 F? I'm tired and I hope this makes sense... As always I'm very grateful for all the replies! Thanks for taking time to read this.

[Mick Je]

Well what I would do first is run another water temp gauge with numbers on it, and have the sensor on the manifold closest to the thermostat housing. I say this because I don't really trust the stock water temp gauges because actually the quarter mark is actually 185-190 degrees on not 160.
Also is your choke fully open when warmed up?
Explain more on how it runs at high temps.

[Alex V.]

I think if it was 400 degrees it'd have boiled all the water off and there'd be obvious permanent damage. My 350 has, IIRC, a 180? thermostat in it and it lays just a hair below your 195 spot, but I've seen it climb to more than straight up when I was sustaining 70 for miles on end or pulling a long hill at 65+. I'd say if your cooling system can't keep up you need to sort out the problem - thermostat won't help after the capacity of the cooling system is exceeded. I have 180's in both my trucks, logic being that a little lower temp won't hurt them in the long run and during stints where I'm pushing it real hard (like long hills pulling something where my 454 will barely sustain 55 working full-out) I have more head room before the temp gets to a dangerous point. Overheating at idle needs addressed. Do you have a fan shroud? Clutch or straight fan? Original radiator or aftermarket? Where's your timing set and how certain are you the fuel mixture is fairly close?

[cdowns]

thermostats don't cool engines

[engineer_gregh]

In your pictures of the gauges, neither shows an over heat condition. If your truck never boiled over then I would say you never really over heated. Mick gave the same advise I would give, install an after market temp probe and gauge from any local parts store to verify your actual engine temp. I would double check timing, carb set up to make sure you're not too lean, pull out a spark plug to see if its wet or too black. The look of your spark plug can tell a lot. After I had my BB 402 rebuilt I had to add a large aluminum radiator and electric fans to keep mine from running hot. Mine was bored .30 over and I used a Comp Cam 268H so it's not stock. Chasing an over heat condition can be very frustrating.

[Boog]

Swed. Straight water basically boils at 212*. A 15# radiator cap raises that boiling point to 257* A 50/50 mix water/coolant with a 15# cap generally raises that boiling point to 265*. It's not likely your engine reached 400*
If you didn't experience boil over it wasn't all that hot. Hotter than you are used to seeing maybe but not dangerously hot.
As far as the engine running rough and shutting off, that could have been vapor lock. The fuel/air mixture and ignition timing will affect engine running temp as well.
Idling in summer heat the engine temp will go up some. Be sure your radiator is adequate, run a 7 blade fan and thermostatic clutch with shroud like it came with and it should be fine. Or you may choose to go with a dual electric fan setup like our late model trucks come with.

[68 IRON]

To add to the troubleshooting plan, you might try using a laser thermometer. You can see the the different temps around your block and radiator. For instance, if your radiator is very cool and your block is hot you may have a flow problem at idle. But my guess is the fan isn't drawing enough air through your radiator. As Cdowns said, the thermostat doesn't keep the engine cool.

[haysonj]

All the thermostat does is control the flow of water through the engine and radiator. The newer fuel injected engines use a 195 Tstat and a carb. engine should have a 180 Tstat. If you are getting any temp over 200 you have a coolant flow problem or your fan is not pulling enough air. I tow all over California in 100 degree heat and my truck has never went over 210 degrees. Do you have a shroud on the fan?

[The Swed]

Yes the fan has a shroud see attached picture. I hope to remove the the spark plugs today and have pictures of them.
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[The Swed]

To lay a better foundation the truck was a farm field find. The engine had a Carter carburetor. I had the TH350 transmission rebuilt then I had engine rebuilt. The carburetor is now an Edelbrock performer carb with an Edelbrock performer intake it had existing full length headers and cherry bomb mufflers. The new build has an RV cam for more low-end torque, the radiator was rodded and a new water pump was installed. FYI I put in 160 F thermostat before the rebuild and the truck ran great with no heat issues whatsoever but a lot has changed. While in college getting my mechanical engineering degree 161 F was the best temperature to run an engine with the least amount of metal to metal wear. Yes that was in the late 70's... No I didn't wear platform shoes or angel flight pants!
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[garyd1961]

I know you don't have a vortec engine but you might want to try running a bypass hose from the water jacket on the front of your intake (you have a plug right next to your thermostat housing) to the plug on top of your radiator. I think the 400 sb ran one and all vortecs should have one. It increases the water flow through the heads which will make the engine run cooler especially sitting in traffic or at low rpm.
My vortec 350 would climb all the way to the hot side before I installed a bypass now it never leaves the cool side. I had drilled a hole in my thermostat before I installed the bypass and it helped but not sitting in traffic on a hot day.

[geezer#99]

Originally Posted by garyd1961

I know you don't have a vortec engine but you might want to try running a bypass hose from the water jacket on the front of your intake (you have a plug right next to your thermostat housing) to the plug on top of your radiator. I think the 400 sb ran one and all vortecs should have one. It increases the water flow through the heads which will make the engine run cooler especially sitting in traffic or at low rpm.
My vortec 350 would climb all the way to the hot side before I installed a bypass now it never leaves the cool side. I had drilled a hole in my thermostat before I installed the bypass and it helped but not sitting in traffic on a hot day.

He has a bypass. It's the heater core. Hooked up wrong but a bypass all the same.
Should have intake hose to bottom of core, top of core to water pump.

The motor quitting when it got hot was likely fuel percolation. Boiled the fuel right of the carb. He needs a heat insulator under the carb.

[garyd1961]

Originally Posted by geezer#99

He has a bypass. It's the heater core. Hooked up wrong but a bypass all the same.
Should have intake hose to bottom of core, top of core to water pump.

The motor quitting when it got hot was likely fuel percolation. Boiled the fuel right of the carb. He needs a heat insulator under the carb.

I saw the heater hoses but it's possible the core could be partially clogged plus I'm talking about adding extra flow to what he has now. Doesn't fuel percolation usually happen after you shut the engine off? (I have an insulator gasket ordered for mine now.) It seems more like vapor lock to me.

[custom10nut]

When you say you rebuilt it, how much did you bore it out? The reason for asking is that all the parts you said the engine came with are not run of the mill bolt ons, I've had many 350s throughout the years, and know that boring one .060 over and running it in normal traffic do not mix well. They make great drag racing motors. They will run hot because of the thin cylinder walls.

[The Swed]

Here's one of the plugs. 700 miles

[The Swed]

It was bored out to .020
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[leftybass209]

Doesn't sound like overheating is your problem. A thermostat is just a general guideline for coolant to start flowing. Your engine was already at temperature by the time you were at the dump, so it wouldn't matter if you had a 100 degree thermostat, or a 195, you were sitting idle and if it was in fact a cooling issue, it didn't have sufficient air across the radiator. A properly cooled engine would run fine at 205-210 degrees.

My stock temp gauge reads higher than yours at the supposed 195 temp, and I'm running a 180 also verified with an infrared temp gun.

[engineer_gregh]

That plug looks like the engine is running lean. Any idea of your initial timing or advance timing?

[engineer_gregh]

It looks as though you have a spacer between the fan and the water pump with no clutch?

[geezer#99]

Originally Posted by engineer_gregh

It looks as though you have a spacer between the fan and the water pump with no clutch?

Good eye!!
And the fan looks too small and too far into the shroud.

Plugs can get deposits like that from being too cold(heat range) or from retarded timing.

[haysonj]

While in college getting my mechanical engineering degree 161 F was the best temperature to run an engine with the least amount of metal to metal wear.

This has since been proven to be false. 95% of engine wear occurs in the first two minutes of startup when the engine is cold and there is no oil on the cylinder walls. The 70's engines ran at 180 degrees and lasted 100,000 miles. The new engines run around 200 degrees and last over 200,000 miles if maintained properly. Your 160 Thermostat will open at 160 and never close as your engine temp is over 180. You might be better off with a 195 Thermostat which would allow the coolant to stay in the radiator longer to dissipate more heat.

[The Swed]

I'm going to recreate the same conditions to see how the truck responds with the lower thermostat. BTW the engine would run in the 195 range on hot days in stop in go traffic before the rebuild with the 160 F thermostat, 160 F is where it opens not what the temp is. I always make one change to see if it made a difference because I know many that do two or three changes at once and never know what fixed the problem. I'm always looking for root cause. BTW I know my fan is not stock so what should the blade to shroud clearance be? How far should the fan be in the shroud? My fan is a reflex fan with no clutch. Thanks again for all the input!

[GASoline71]

Originally Posted by leftybass209

Doesn't sound like overheating is your problem. A thermostat is just a general guideline for coolant to start flowing. Your engine was already at temperature by the time you were at the dump, so it wouldn't matter if you had a 100 degree thermostat, or a 195, you were sitting idle and if it was in fact a cooling issue, it didn't have sufficient air across the radiator. A properly cooled engine would run fine at 205-210 degrees.

My stock temp gauge reads higher than yours at the supposed 195 temp, and I'm running a 180 also verified with an infrared temp gun.

I agree. People tend to freak out when an engine gets to 200 degrees. But in reality that's not overheating at all. It's why the system is pressurized, so the temp can climb to the boiling point and slightly beyond and still be just fine.

I run a 180 degree T-stat and have a 2 row aluminum radiator. The stock fan shroud and the stock fan with my SBC 350. Sitting in stop and go traffic on a 90+ degree day, it can climb close to 200 degrees, but the system is efficient enough to maintain that and keep the engine from overheating.

Gary

[geezer#99]

Originally Posted by The Swed

I'm going to recreate the same conditions to see how the truck responds with the lower thermostat. BTW the engine would run in the 195 range on hot days in stop in go traffic before the rebuild with the 160 F thermostat, 160 F is where it opens not what the temp is. I always make one change to see if it made a difference because I know many that do two or three changes at once and never know what fixed the problem. I'm always looking for root cause. BTW I know my fan is not stock so what should the blade to shroud clearance be? How far should the fan be in the shroud? My fan is a reflex fan with no clutch. Thanks again for all the input!

Flex fan!!
Stock type or aftermarket. Aftermarket ones are useless for drawing air.
Otherwise your fan tips should be 1/2 inch from the shroud and the fan half in/ half out at the shroud lip.

[garyd1961]

Originally Posted by haysonj

You might be better off with a 195 Thermostat which would allow the coolant to stay in the radiator longer to dissipate more heat.

This^has also been proven false.

Get rid of the flex fan and get a good clutch fan.