My second hand ZZ454 came with a 180* thermostat installed. My temp sender is in the manifold (air gap) crossover at the rear of the engine.
I have an aluminum radiator, stock BBC shroud, 69 7 blade fan and clutch.

Temps have always been really low. Like 150-160. I thought maybe the the thermostat was failed so I replaced it with a Stant 180* thermostat. Now temps are higher, normally 170-180. Yesterday however I was in stoplight rushhour traffic and the temps got up to 210 ish before I got moving again...which was as hot as I've ever seen it.

So, since I never throw anything away :clonk: I found the original thermostat in my garage and tested it in pot of water on the stove...it worked fine, but it seemed to have much bigger holes to flow water...maybe this explains why it kept the engine 20+* cooler.

1. The Stant thermostat seems to get the engine up to operating temp faster, but can't control the heat in traffic. How hot is too hot?
2. The large flow thermostat keeps the engine cooler...is 150-160 too cool? I saw 150, because that is where the gauge starts...it sometimes takes quite a while to come off the peg.
3. Is the temp sender location a problem?

its better to have it right at the thermostat. but some manifolds dont have the hole for it. or you cant put it in manifold cause hose hits it. I got a combo if that is the problem.than theres a drivers side in block or head to put the sender in too.

I would switch back to the high flow thermostat
and move the temp sender, like he said

I have an AIR GAP manifold also and there is a port for a temp sensor or a fans switch right at the thermostat. I used my factory location for my temp sensor which is in between #1 and #3 cylinders. My car came with an idiot light for temp so I had to get rid of that. I used the port at the thermostat for my electric fan switch. I originally had my fan switch in the rear passenger side port, but I could not get the fan to activate. I switched it to the front drivers side port and presto, activation.

You should be careful not allowing the car to reach a certain temp. As condensation builds up in the oil pan, the only way to get it out is to allow the oil to get hot enough to burn it off. We all know what water in the oil does to an engine. It passes by the rings as steam and condensates in the pan. If you don't take your car out on a long cruise every so often to allow the oil to get nice and hot, the condensation will continue to build. Just a suggestion I heard from another Team Camaro member. I would stick with the 180 degree thermostat. I have the same stat and my car runs at 180-190 all day. Traffic or not.

Reading your post, a couple things come to mind: bigger clutch fans don't typically come on until at least 210, not all thermostats are created equally, and I wouldn't think that 210 would be too harsh for your ride. I don't think I would want the temp to get any hotter than that though. I f it were me, I would swap thermostats back to the original and call it a day. If you can, figure out what brand/p/n the original one was for future reference and keep one on hand. I just went through the same thing with my Ram truck... Was keeping a cooler themp, decided to do some heating/cooling maintenance, then started running hotter (mine was more like 220-230) I switched back to the other thermostat and it worked much better. Hope this helps!
Dan:beers:

Thanks to everyone for their responses. I drove the car yesterday and again it started to get 210+ in traffic, so I put the original high flow stat back in last night...
I bought a cheap laser temp gun at a car show for $20. (I'm a toy addict :clonk:)...I'll take some spot temps and see what temps are around and about the engine.
My original thought with the original high flow stat was that it wasn't getting hot enough to get condensate out of the oil like Charlie said...or even if the mixture was a little rich, could you get cylinder fuel washdown since the temps weren't high and combustion wasn't efficient and end up w/ fuel in the oil...(that might be extreme, but I'm still learning...)
I'll laser beam the oil pan as well to see what I get with the high flow back in there...also would be curious to see what the different temps are at the different potential sender locations...
I'll post back w/ results...
Scott

I have an oil temp gauge, I dont think you really need to worry about the oil temps,
On my car the oil reaches 250 (about where it levels off at) at almost the same time the coolant reaches 180

Scott, do you have any obstructions either in front or behind the radiator or fan? If you have anything behind it the air can't be moved away from the core thus making the temo rise. Make sure you don't have a blockage in the core. You may also want to consider going to an aluminum radiator. I did and it dropped the temp about 10 degrees. You may want to put the sending unit in the factory location instead of in the manifold. I removed my idiot light sender and replaced it with the one for the gauge. It may just be giving a false reading. How far from the radiator is the blade? I changed out my clutch fan and went to a Flex-A-Lite electric fan that has its own shroud and I use a fan switch in the manifold to activate it so it's not running constantly. If your motor is producing more power than it did from the factory, your radiator may not be sufficient anymore. You may need to go with a larger radiator. I put the largest unit I could in mine that was still a direct fit unit. Just some suggestions. Good luck. Keep us informed.