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Hotter than hell and poor performance

1K views 24 replies 10 participants last post by  pityocamptes 
#1 ·
I live in Tucson, Az (AKA as hell). Today I went 4x4ing, been a long time being in school and all, and found that going down the highway my rig temp got up to 195 F and held steady. Its a '74 scout ii with an amc 258. The thermostat is 160 F and in the cooler weather it seems to work just fine. Well today performance sucked as the temp was higher. I picked up a higher T stat thinking that the 160 F was staying open and not allowing the water to cool in the radiator. Picked up a 195 F and that was worse. Temp got up around 205 before it dropped down to 190-195 F. I was wondering if anyone else had similiar problems in hot weather. Also I noticed that oil pressure dropped but was within specs, wasn't happy about that either but oh well. I was wondering if anyone had installed a spray bar that sprayed misted water through the radiator? Would that work? Any suggestions? Radiator is brand new, 4 core as is the water pump and antifreeze mixture is good. Thanks.
 
#2 ·
Good info to suggest from...

As you found out the 195 F stat is not your friend in the heat. Remember that the stated temp is the temp that it opens up at. So a 195 F thermostat is best suited for winter conditions when you want that water to get really warm fast and stay warm...being heated by the block.

The 160 F thermostat should be fine as long as it is not sticking.

The oil pressure will drop as your viscosity becomes lower. The fluid does not take as much energy to move at the higher temps. thus a lower overall stated pressure. Another thing to remember is that it is best if you get an aftermarket or auxillary pressure gauge. The stock ones are not known for their proper reading.

My question to you is...Does your rig have a shroud? If not that might help some. Second question would be which fan do you have...CLUTCHED or direct drive? It can make a difference.

As for oil...I personally prefer to run a 15 or 20w-50 oil in the summer months. Takes a lot more punishment for the oil to become water thin versus a 10w-30.
 
#3 · (Edited)
Harvester of Sorrow said:
Good info to suggest from...

As you found out the 195 F stat is not your friend in the heat. Remember that the stated temp is the temp that it opens up at. So a 195 F thermostat is best suited for winter conditions when you want that water to get really warm fast and stay warm...being heated by the block.

The 160 F thermostat should be fine as long as it is not sticking.

The oil pressure will drop as your viscosity becomes lower. The fluid does not take as much energy to move at the higher temps. thus a lower overall stated pressure. Another thing to remember is that it is best if you get an aftermarket or auxillary pressure gauge. The stock ones are not known for their proper reading.

My question to you is...Does your rig have a shroud? If not that might help some. Second question would be which fan do you have...CLUTCHED or direct drive? It can make a difference.

As for oil...I personally prefer to run a 15 or 20w-50 oil in the summer months. Takes a lot more punishment for the oil to become water thin versus a 10w-30.
I'm running synthetic 20w 50. I don't have a fan shroud, rig never had one. Would it make that much of a difference? Oil gauge is an aftermarket mechanical and water temp gauge is an aftermarket electric. The fan is direct drive not clutch. I know some RV's have spray bars that help cool the engine. I don't think it would be very hard to fabricate one but didn't know if it might be more harm than good (rust, etc.). Has anyone rigged a spray bar? Any other ideas for keeping the temp. down? With air temp being well over a hundred I can only assume that road temps must be close to double. My brother has a laser temp gauge (used for his work) and read a temp off his truck the other day and it was over 180 F. Sucks being here in the summer :eek: Thanks for the help.
 
#6 ·
Engine temp of 195 degrees, in Tucson, in the middle of summer, while wheeling.... Doesn't sound bad to me. If your temp is staying under 200 while wheeling down there. You are not even boiling, without a pressurized cap. With one, you have a good ways to go....

You sure you need to be worrying about 195 degree engine?

When you say it does not perform well, what symptoms does it exhibit? Might not be a cooling issue at all. Could be carb related, i.e. gas in carb bowl boiling, etc..
 
#7 ·
Hooper said:
Engine temp of 195 degrees, in Tucson, in the middle of summer, while wheeling.... Doesn't sound bad to me. If your temp is staying under 200 while wheeling down there. You are not even boiling, without a pressurized cap. With one, you have a good ways to go....

You sure you need to be worrying about 195 degree engine?

When you say it does not perform well, what symptoms does it exhibit? Might not be a cooling issue at all. Could be carb related, i.e. gas in carb bowl boiling, etc..
Yesterday I experienced power loss from the excess heat and at times the temp gauge was over 200 (for the most part it settled a little over 195 on gauge) especially when creeping along. Since $$ is low I probably take a stab at making one. Has anyone made a shroud? My brother works with sheetmetal so materials would be relatively cheap. If I do make it out of sheetmetal how close to the engine should the shroud come? Thanks for the help.
 
#8 ·
pityocamptes said:
Yesterday I experienced power loss from the excess heat and at times the temp gauge was over 200 (for the most part it settled a little over 195 on gauge) especially when creeping along. Since $$ is low I probably take a stab at making one. Has anyone made a shroud? My brother works with sheetmetal so materials would be relatively cheap. If I do make it out of sheetmetal how close to the engine should the shroud come? Thanks for the help.
You might try ducting to cool air. Some folks have commented that they saw remarable performance improvement by drawing air from outside the overheated engine compartment.

Others have said that adding louveres in the hood helped a lot.

The shroud fits tight against the radiator, and extends to about even with the engine side of the fan blades. It does not need to be particularly close to the engine. The object is not to funnel air over the engine, as much as it is to ensure that air drawn by the fan is pulled *through* the radiator, not around it..
 
#9 · (Edited)
200 degrees?? Is that all? I seen 220 on mine! :flipoff2: Three things. Add a shroud, electric fan and make sure the coolant is BLOCKED going to the heater core. When I have my heater core valve open my truck runs 15* hotter in this weather. I'm in Phoenix.
 
#11 ·
Shadow man said:
200 degrees?? Is that all? I seen 220 on mine! :flipoff2: Three things. Add a shroud, electric fan and make sure the coolant is BLOCKED going to the heater core. When I have my heater core valve open my truck runs 15* hotter in this weather. I'm in Phoenix.
What do you think causes that? Water getting trapped in that loop and not being fed through the radiator as fast?

Seems like if you run your heater, it would help cool things...? Of course, not many of us are going to turn out heater on when things are that warm outside, and I doubt it helps the cooling *much*... Just curious why having flow through the heater core would heat things up even more...

Obviously running an AC is going to heat things up a lot more...
 
#12 · (Edited)
Pat, its not exchanging heat "IF" you don't have the heater fan running. All it does is recirculate hot coolant from the engine, to the heater core and back into the engine. This is especially true on Chevs. There is alot of systems like this so you can have heat even before the themostat opens. If its open you also have less coolant flow thru the rad. Something else I also know for a FACT that a heater running full bore on a Scout II will completely cool a 304 down to nothing when its -30* in Mt. with the rad completely blocked too! :D
 
#13 ·
Shadow man said:
Pat, its not being cooled "IF" you don't have the heater running. All it does is recirculate hot coolant from the engine, to the heater core and back into the engine. This is especially true on Chevs. If its open you also have less coolant flow thru the rad. I also know for a FACT that a heater running full bore on a Scout II will completely cool a 304 down to nothing when its -30* in Mt. with the rad completely blocked too!
OK. I have not looked at that cooling circuit carefully. After it dumps back into the block, it does not route through the radiator, so it just goes round and round, getting hotter and hotter...? I'll need to double check to make sure mine is closed. Actually, thinking about it, I know that it is an open loop, since I took the valve out of mine when it rusted open. Guess I'll go pick one up and throw it in there.

So, you are saying the heat exchanger in the heater is actually pretty efficient...

Maybe I will leave the loop open and just run the heater... <chuckle>

Thanks
 
#16 ·
pityocamptes said:
I live in Tucson, Az (AKA as hell). Today I went 4x4ing, been a long time being in school and all, and found that going down the highway my rig temp got up to 195 F and held steady.
A fan shroud probably won’t help on the highway. Going 60 mph down the freeway should be more than enough CFM. Having said that, you still need a shroud for traffic and trail work. Are you sure it's not running too lean and that the timing isn't retarded?

pityocamptes said:
Its a '74 scout ii with an amc 258. The thermostat is 160 F and in the cooler weather it seems to work just fine. Well today performance sucked as the temp was higher.
Not too much you can do. Hot air is less dense and makes less power. Cold air induction (i.e. ram or snorkel) would help some.
 
#17 ·
Hammerlock said:
A fan shroud probably won’t help on the highway. Going 60 mph down the freeway should be more than enough CFM. Having said that, you still need a shroud for traffic and trail work. Are you sure it's not running too lean and that the timing isn't retarded?



Not too much you can do. Hot air is less dense and makes less power. Cold air induction (i.e. ram or snorkel) would help some.
Well, the air fuel gauge shows that I'm running stoich down the highway and on trails. Timing is around 5 degrees BTDC. I do have a snorkel system set up just for this reason but it doesn't seem to be doing a whole lot with the hotter weather. I think I'll fab a shroud but probably won't hit the trails again until the rains come and cool things off.
 
#19 ·
desertfabmotorsports said:
195 is not hot, you get above 230 you are getting warm. As for oil pressure, I run straight 50w racing oil. Helps alot.
If you are experiencing power loss you might check fuel line location. Sometimes fuel will start to boil which could cause loss of power. :D

Todd
www.desertfab.com

The carb is an open bowel Weber and the fuel line runs up the passenger frame rail (rubber hose) and then wraps over the valve cover (steel tubing for this part), partially goes over the exhaust manifold (this is a 258 inline six - exhaust and intake manifolds are meshed together on the driver side) and then goes back to rubber fuel line which plugs into the bowel nipple. Should I reroute it? If so where? I was thinking I should replace the plugs. Its been about a year since I've changed the plugs out. Any comments? Thanks.
 
#20 ·
pityocamptes said:
Well, the air fuel gauge shows that I'm running stoich down the highway and on trails. Timing is around 5 degrees BTDC. I do have a snorkel system set up just for this reason but it doesn't seem to be doing a whole lot with the hotter weather. I think I'll fab a shroud but probably won't hit the trails again until the rains come and cool things off.
5 Degs btdc is ok, but your timing will still be off if the mechanical or vacuum advance isn't advancing properly. A 258 is working pretty hard in a Scout anyway so any minor problems are compounded.

You can probably eliminate boiling fuel as the problem unless it's stumbling and cutting out.

Don't lose any sleep over this. Even though it's running hotter than the stat rating 195 isn't bad and is actually cooler than a lot of engines are designed to run at.
 
#25 ·
Well with the addition of the shroud my rig doesn't seem to be running the same?!? The shroud extends 6" past the four core radiator and my air filter is the open style filter housing. I did notice that the shroud seems to blow air over the engine (directed air flow) and I'm thinking it might be forcing air through the open filter housing? Somethings different with performance but I just can't put my finger on it. Could the shroud have changed anything as far as performance? It almost "feels" like a huge sheet of plywood is in front of my rig making it less "aerodynamic" if you know what I mean. Thanks.
 
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