Hot-running LS6

mmcporter · #1 08-28-2003, 01:51 AM

Anyone have any tips on lowering the highway speed temp on an LS6 with 4.10 posi, M22, polyglass rubber and otherwise stock? The car runs at 190-210 at speeds of around 65-70. Plenty of coolant in the radiator, car has never overheated or belched up coolant. Everything seems to be functioning okay. Am I driving too fast with this gearing? Any thoughts?

**Mr70** · #2 08-28-2003, 01:59 AM

Is Your Fan Clutch working properly?
What is your Thermostat rating?
What weight engine Oil are you using?
Also try Flushing the Entire Cooloing system.Get it all out of there.You'd be amazed what kind of Crap can accumulate.

mmcporter · #3 08-28-2003, 02:04 AM

[ QUOTE ]
Is Your Fan Clutch working properly? I think so 
What is your Thermostat rating? Don't know, good question 
What weight engine Oil are you using? 20W50 nonsynthetic 
Also try Flushing the Entire Cooloing system.Get it all out of there.You'd be amazed what kind of Crap can accumulate. Makes sense, although the coolant looks fine and it was changed recently 

[/ QUOTE ]

**MrMotion** · #4 08-28-2003, 02:14 AM

This seems to be the normal heat range for an LS6. If someone knows how to get them to run cooler I'm listening.

**Mr70** · #5 08-28-2003, 02:38 AM

My 70 L78 TH400/4:10 was running 210+.
I checked all I mentioned earlier,and then Changed my gas blend.I run highest the station has at the pump,then add Protek Lead/Octane boost.By verying the mixture,I found it actually showed an Increase/decrease in my cooling system Temp.
Albeit slight,but still a difference.
Today I found the best is 20 Gallons of Mobil gas,with 11 oz.Protek additive.
I only run 185-190 degrees now.

hvychev · #6 08-28-2003, 02:47 AM

Interesting guys. I am running between 200-210+ with my LS5 TH400. Rick I have done all the fixes you mentioned including boiling the tanks & recoring my original radiator, changing to a Mr. Gasket 160 thermostat, and am running 20W50 Penzoil. Would the timing be an issue?

**k92** · #7 08-28-2003, 04:16 AM

I have similar setup as yours,but with more cam, 11.5:1 no clutch on my fan and my car never over heats,I have a 160 degree thermostat,38 degrees total timing and run pure 100 octane fuel, the car never gets over 185 degrees no matter how hot it is....

ORIGLS6 · #8 08-28-2003, 04:24 AM

190 to 210 isn't unusual for these cars. If I recall correctly the OE thermostats were in the 185-195 range. I replaced mine early-on to bring the temp down.

We attended the Street Machine Nat'ls the year it was held at Gateway in E. St. Louis and were trapped in the gridlock trying to leave on Saturday afternoon. My battery wasn't doing well and I was afraid the car might not restart so we let it idle for over three hours. The car never once got above 165. That was with Turbo Blue in the tank and timing at 2 degrees advance. Yes, timing can be a factor.

Another thing to check out is your water pump. I have a friend who built an L-88 for his '69 Chevelle and had similar trouble. He installed a new four core radiator but still no help. Finally tore into the water pump and found the fins on the impeller were about half the size of the ones on the other pumps he had used. Changed pumps and the problem was fixed.

Just some thoughts. [img]/ubbthreads/images/graemlins/dunno.gif[/img]

Dennis

mmcporter · #9 08-28-2003, 01:11 PM

Interesting responses with some good tips. Sounds like MOST folks are saying that "these cars run between 190 and 210 (and up)" so that performance shouldn't be shocking. However there are things one can do to chip away at the cooling system performance. I appreciate the tips and hope to see more; I'm sure we could all learn a thing or to about the "norm" of these cars. I have owned an SS396 for years but am new to the LS6, so I don't yet have a "vibe" for the "norm" for the car. [img]/ubbthreads/images/graemlins/confused.gif[/img] I'm getting there though...

Chevy454 · #10 08-28-2003, 01:36 PM

Lots of good answers on the topic at hand. Thermostat, good system check, and timing check should all be on order. Timing plays a big factor, but if it starts/runs well, then you should be close. And, the range you describe is normal for these cars. Heck, that's actually a little cooler than where some of the newer cars run. One thing that is easily overlooked, though, is "pressure". Any idea what radiator cap is on it?

Care for some food for thought...?

Low coolant temperatures DO NOT necassarily indicate a well functioning coolant system. If there is no heat transfer between the metal and coolant, then you've got the low coolant temp you're looking for, but you're engine's temp is actually higher. If there is heat in your coolant, then it's doing it's job. Something else that is of help is to get an infrared temp gun and check and see what the engine's temp is actually at, versus what the coolant temp is. If the coolant isn't taking the heat away, but is giving you a low guage reading, then that's really just a fasle sense of security...