LT1 experience? Step inside please

[1wild-horse]

So, I recently purchased a nice 95 Z28 convertible from a guy who spent a wad of cash trying to get an overheating condition resolved.
So the shop that did the work ran down the gambit of cooling system parts, 2 water pumps, and had the heads off twice.
I removed the radiator after I purchased the car to find it plugged solid through the center portion. Its a 39 tube radiator and only 6 tubes actually flow water real well. So I bought a new rad, installed and vac filled the system. Both rad hoses get hot. Heater core is always flowing hot water because the air stays hot out the vents.
Now, question is, ect sensor will read 220's and continue to climb, gauge will follow suit. After the rad install I never let the Hi fans turn on and see if it would cool down. Been reading all over the Ls/lt sites that for a stock t stat and fan settings this is normal. I have ZERO experience with LT1's and wouldn't know. Seems pretty damn hot for an engine to be running. Anything over midrange on the gauge would seem out of the ordinary, and I think most people would complain.
So anyone with firsthand experience would be helpful. Did these cars actually run this hot when new? Would they really get hot enough to turn on the hi speed fan if you just let it idle in the driveway?

 

[T.Man]

Might be a dumb question but did you burp the system? Sounds like it might just have air that's trapped?

 

[03Sssnake]

These cars are bottom feeders. Make sure the lower radiator air damn is still there, if it’s not you won’t get sufficient air flow while driving.

 

[1wild-horse]

I believe it's bled sufficiently, have none of the signs it has air like radiator hoses being cold or no flow to the heater core. I have checked for the air dam and the plastic shrouding and its all intact. Going down the road with the a/c running it takes about 10 miles before it starts to climb above 220. Never see it come down. I did throw a tstat at it just because they are cheap. No change there either. Seems like its not circulating, even though its running water through the heater core enough to keep the air constantly hot.
I've tried the block tester to look for combustion gases but after it warms up it blows coolant out of the rad neck and ruins the test.
Thinking I may have a cracked block or the machine shop missed a crack in the heads.

 

[StrayBullitt]

I feel like Hypertechs were a big deal back in the day for these cars due to you could program for a lower T-stat and change your fan on temps since they run hot. Reading that you should expect fan on at around 220-223 degrees and if there is a problem and you reach 235 the aux fans should come on.

 

[1wild-horse]

I have read low speed fan should trip at 227, off at 218. And 235 for hi speed. I would expect to see temps climb to that low range to kick the fans on sitting still in traffic, but not cruising down the road.
But thats why I ask, I've never been around these cars to know what normal is. Can't believe they would run 220 230 normally, that seems plenty hot.

 

[StrayBullitt]

I would tend to agree with you, but it is August and you were running the Air conditioning it sounds like.

If it only ever goes to 227 and your fan is functioning correctly and the temp drops like it should I think it sounds like you are fine. That said I would be temped to drop the coolant level enough that you can perform the block test, just to be sure no issues there.

 

[1wild-horse]

I actually tried draining it down about halfway in the radiator. Warmer the engine got, the level started to rise in the radiator neck side. Which is also strange because the pump should draw from that side.

 

[03Sssnake]

They do tend to run on the hotside. I have had 4 4th gen F-boats. Was not uncommon to see 220ish in the summer with AC on. I always did the colder t-stat and tuned the car kick on the fans sooner. I wanna say it stayed around 200-210 after that. My 99 shitcan has no ac and is track duty only these days, so it stays around 190-200.

 

[IronSnake]

My 97' anni Z28 was the Lloyd Elliot stage 2 kit on it. Luckily, with an electric waterpump and fans, I had it setup to keep the car in the 180-190 range. Worked pretty well. Even had AC still and the car never struggled even in a dead heat. I'd consider looking into the aftermarket to help control the fans.

 

[Black2010]

They run hot and what you described doesn't sound that off bases. It's been 15 years or so since I've been around an LT1 and it was on a Corvette. Good friend had a Z-28. Both suffered from the same issue, lack of airflow while sitting still. First thing I would do is hook it up to a scanner to validate that the temps are as high as you are seeing on the dash. It's not uncommon for the dash to be off quite a bit. Next, if it really is running hot and you want to get it running cooler look at having the fans adjusted. Forget about a lower T-stat. The stock should be 195 (unless my memory fades again as well) so at 210+ it's already fully open. A 180-160 stat is going to be just as open at that point. It will just take longer to get to that equilibrium.

Keep in mind though that normal operating temp is around 210ish so 215-220 in a hot summer day sitting in traffic with AC blowing (should be turning the fan on with the AC anyway) is really not abnormal. Running a car to much cooler can actually be a problem as well as the tune wont be right and it may not get warm enough to burn off the moister in the oils.

Lastly, (again trying off memory). I don't recall if the LT1 or it started with the LS1. Their may be a crossover tube for the heads. It could be blocked which would prevent coolant flow across the heads.

Honestly, from what you describe it sounds pretty close to normal so cooling things more would just go into the mental comfort level (been their as well).

 

[Black2010]

Would they really get hot enough to turn on the hi speed fan if you just let it idle in the driveway?

To be specific to this question. 100% yes, especially with the hood closed on a 95+ degree day. Best way to test a cooling system is while moving. If things look good while moving your cooling system is generally OK, it's the airflow that's the problem. On my Corvette (I added a pusher fan in front of the AC condenser/radiator. If I get stuck in traffic I flip it on for piece of mind. My current corvette as an L-98 but as with the LT1 corvette and my friends camaro they run hot too.

 

[1wild-horse]

All great info, thank you guys that replied. I bought the car just to flip it and when I found that the radiator was plugged I was excited, but then after bringing the car to temp, I was hoping to see it fluctuate temperature. Well with the fans kicked on hi and the temp not coming down I decided not to drive it down the road. I did however compare the ECT temp on the scan tool to the gauge and found the ECT to be higher. It is also within 8-10 from an infrared temp gun pointed at the water pump.
If I am to sell this car, the last thing I want to do is screw someone over on it. So I want to be sure that it's cooling at least as good as expected to from a factory stock standpoint.
Just don't think its quite there...

 

[Double"O"]

Delete opti, spray house down, replace factory rear, replace stock heads for real heads on it and spray some more


OK ok ...I'd burp the coolant system and go from there

 

[1wild-horse]

Lol, there is supposed to be profit left when you're flipping one.
My Chevy friends already said LS swap. To which I replied, Coyote?

 

[Corbic]

Junk the LT1 for a 5.3.

 

[BigPoppa]

Oh how i remember the days of replacing opti after opti.....

Yes, they run hot. By design. 230 isn't unheard of.

383 LT4 that pos and let it rip.

 

[nxhappy]

u could always sell the chebby =)