Another Aluminum Engine Operating Temp Question

[63qcar]

Did a brief search and didn`t really see anything that helped me . So , I have a 482 FE aluminum block , heads , intake etc in a Cobra replica and am currently running a 180 degree thermostat . Summer here now and ambients are in the mid to upper 90`s and I`m seeing H2O temps in the 190 to 210 degree range and oil in the 210 degree range while in traffic ..... neither of which really concern me .
But I was wondering if I might be better off with a 160 degree thermostat instead .... and I do understand that the t`stat rating is where it starts to open and fully open will be in the 170 range .
I`m thinking that if the running temps are down in the 170 to 180 range , the engine might just like that better and might solve some carb problems I`m having . It runs good until the temperature gets in the 195 range and then it starts getting rough below 3000 rpm .
Running water and water wetter/lubricant in the cooling system and a manually and temp sensor controlled Spall pull through fan .

Thoughts ? Thanks

[PackardV8]

Once the engine is up to operating temperature and the thermostat is open, the thermostat has no control over running temperature. You'll be at 190 regardless of a 170 or 180 thermostat.

Are you running an exhaust heat crossover in the intake manifold? That is the source of many hot weather carb problems. I block them with a thin stainless steel sheet plate

Are you running an outside air intake? Underhood air temps are also a source of many carb problems.

Are you running a fuel return line to the tank? There are fuel filters which incorporate a return line and keeping the fuel moving through the line can prevent vapor lock carb problems.

Cobra/FE are tight, but is there room for a carb insulating gasket?

[dannobee]

If the water temp gets hotter than the thermostat's rated temp at idle in traffic, you need a better fan. If it gets hotter than the thermostat's rated temp at freeway or racing speeds, you need a better radiator.

[mag2555]

Get a insulator under the carb!
At slow speeds today alky cut fuel stays in the carb long enough to start to boil off the alky and get drawn down into carb which then makes the engine run ruff.

If you need further proof then just install a cool can loaded with ice before the carb!

[panic]

More detail about your radiator core size and shrouding.
Are you using vacuum advance?

[63qcar]

In no particular order .... Cool Carb insulator is under the carb . Current distributor is the MSD mechanical advance , but I have a modified Duraspark VA distributor on the bench .
No crossover on the intake and just the Cobra hood scoop and what comes in through the radiator and under car for air to the carb . Really wish there was a way to pull air from the high pressure area at the base of the windshield .
Also , no fuel return line .... pump is a Carter mechanical unit .

The temp at freeway and secondary roads ( 55mph + ) drops to 180 to 185 range .... around town is the problem .

Just got in from the garage and found that somehow the bypass hose between the water pump and the manifold has a plug in the water pump and the manifold . Maybe , because of the increased flow , my thermostat is now a restriction . So , I`ll be installing that bypass hose and may add another 1/8" hole to the thermostat .
I haven`t had this engine on the track this year ( HPD Events and road race ) , but the previous engine ran 190 to 195 in the summer at VIR and oil temps were 220 to 230 .
Since we`ll be in the low to mid 90`s this weekend , I should be able to find out if my "theory" is correct..... besides , I just love working on cooling systems in the Summer.

[PackardV8]

If the water temp gets hotter than the thermostat's rated temp at idle in traffic, you need a better fan. If it gets hotter than the thermostat's rated temp at freeway or racing speeds, you need a better radiator.

We'll have to agree to disagree on this one. The thermostat is there to restrict coolant circulation at startup and allow the engine to get up to operating temperature ASAP. Very few engines run exactly at thermostat temp, but your results may vary.

As a general rule, coolant temperature is directly related to ambient air temperature. I usually find after the thermostat opens, coolant temperature in a well balanced system will run approximately 100 degrees above ambient. Back in the 1990s, Corvette guys freaked out because the fan switch didn't trigger until the coolant temperature reached 220 degrees, but GM wanted it that way.

Oil temperature is directly related to engine bearing load. A big engine in a light car, such as OPs Cobra replica, can take forever to get the oil warm enough. It's impossible to load the engine for any length of time.

[dannobee]

The temp at freeway and secondary roads ( 55mph + ) drops to 180 to 185 range .... around town is the problem .

Check the fan and shrouding. There's a lack of airflow through the radiator. More/better fan(s) and more efficient shrouding will fix it.

[dannobee]

As a general rule, coolant temperature is directly related to ambient air temperature. I usually find after the thermostat opens, coolant temperature in a well balanced system will run approximately 100 degrees above ambient. Back in the 1990s, Corvette guys freaked out because the fan switch didn't trigger until the coolant temperature reached 220 degrees, but GM wanted it that way.

Oil temperature is directly related to engine bearing load. A big engine in a light car, such as OPs Cobra replica, can take forever to get the oil warm enough. It's impossible to load the engine for any length of time.

Technically, the thermostat controls the engine's minimum operating temperature. It doesn't know if the engine has been running 2 minutes or 2 days.

100 degrees over ambient means nothing. Coolant temperatures on modern cars can appear so stable that the needle looks to be painted on, with coolant temperature varying little if any from freezing outside to well over 100 degrees ambient.

Nearly all of my tow vehicles would maintain right at 195 degrees (give or take 5 degrees) climbing the Grapevine, even in the summer when towing race car trailers to Southern California tracks, with the A/C blasting away. When they started to get hot, I knew it was time to replace the radiator.

On the subject of Corvettes, let's go back to what I initially said; overheating in traffic is cooling fan related. I'd tell my Corvette customers who were worried about spiking temperatures when parked or in traffic to just turn the A/C on. The electric fan(s) would be commanded on when the A/C gets turned on, either by the PCM when A/C high side pressure exceeds 219psi or by grounding the fan relay when the A/C clutch is commanded on, depending on the year. This is done to cool down the A/C condenser. The same Corvettes have engine oil coolers located in the radiator tank. The reason for this is two fold; 1st is to help heat up the engine oil using coolant flow around the cooler, and 2nd is to obviously cool the engine oil when its temperature exceeds coolant temp.

[V12MECH]

On the hi-way, if the temperature is o.k, radiator is probably fine, I agree with the opinions that a fan upgrade may be required, forget drilling holes in thermostat, however you may consider 1 inch or so restrictor in place of thermostat, the coolant flow has to have time to absorb heat from block.
.

[V12MECH]

By the way, perhaps a simple water pump upgrade, various manufacturers offer improved flow designs .

[Geoff2]

Unblocking the bypass will probably increase running temp because you will be feeding hot coolant to the inlet side of the pump.
The bypass serves two purposes. Above, & a safety valve in case the stat fails to open. It should not be blocked.

What initial timing are you running? Too low, & the engine will run hot at idle.

I would also look at trying a smaller water pump pulley to spin the pump faster.

More cooling info here: www.stewartcomponents.com

[63qcar]

Geoff2 , I you just made a light bulb go off in my head . I need to check all pulley diameters as I think the engine had the March underdrive pulleys on it from way back . Wish I could find the paperwork on that , but no luck yet .
Going to measure them first chance I get .... if they are underdrive , I believe March has a set of what they call HiFlo , which is about a 5% overdrive on the water pump.

BTW , timing is 26 degrees at idle and 37degrees at 3500 rpm , so I don`t think that`s the problem and I don`t believe the shrouding/fan is the issue as that`s what ERA has used for years on cars in areas hotter than mine .

So , looks like some measuring is in order .

Thanks guys , I`ll let you know what I find .

[63qcar]

Update ... pulley diameters are ok , actually a slight overdrive . Next step is to remove plugs in water pump and intake and re connect the bypass hose (FE Engine ) . Got to thinking last night about not having the bypass connected and it seems to me that when the thermostat is closed ( and no bypass connected ) , with a fixed displacement pump , there is no place for the water to go ..... and water is basically incompressible . So , it deadheads and bypasses by internal pump leakage (?) , which would cause pressure and heat buildup ..... at least after several beers , that`s what I came up with .

So , next step is to remove the plugs , but it looks like the intake manifold one is frozen ( aluminum plug , aluminum intake and no neverseize ) . So heat with a torch , use PB Blaster , let cool and then repeat several times . Then heat and try to get it to break free . If not , then plan B .

Plan B ... calculate bypass hose/fitting internal area and then drill holes/slot in thermostat to equal bypass area . Yes , it will take longer to warm up , but this is a toy that isn`t driven in the winter and now our temps are in the mid to upper 90`s here . Might also gain some water flow if the thermostat is too restrictive .

So , that`s my two beer plan ..... unless someone sees any problems that could come up .

[dannobee]

Automotive water pumps are not positive displacement pumps like an oil pump or fuel pump. They're centrifugal pumps and bypass quite a bit internally when they need to (t-stat closed). But yes, reinstall the bypass hose and see if that helps at all. If nothing else, it'll help purge the system of air at the top of the water pump.