Thank you for the excellent mod. I did that to mine and had enough material left for a second. So now I have it laying around...

 

Retarded ignition or cam timing will cause overheating.A broken chain tensioner failed cam sprocket ect. In extreme cases the exhaust manifolds will glow red. Easy test, lift the hood at night.

 

Hmmm...
I hadn't spent any time thinking about the timing as I, possibly foolishly, assumed that the car would take care that itself.
Is it possible for the cam timing sensor or the crank position sensor to go out of whack and report an incorrect timing relationship?
I haven't had a P0342 code so I assume that the CMP is fine. The car has been a little hesitant to start but I figured that it was a tuning problem.

 

Read your thread. Hope you can resolve it soon.

How about the AC condenser, that is mounted in front of the radiator?
How does that look? I had to replace mine recently because it was causing airflow issues to the radiator, and overpressuring the high side of my AC system.

They can get tons of crap embedded in it (same with the radiator), and since these cars are bottom feeders and suck up crap from the bottom).

This picture is from an LS1 fbody, but totally the same idea:





full post: http://ls1tech.com/forums/general-ma...bably-why.html

May be worth looking at. Good luck!

 

Well I jacked the bitch way up in the air and removed the thermal barrier material.
Now that the TAC codes are seemingly gone I'll go for a drive and see if the over-temp problem persists.

I pulled the A/C condenser out when I replaced the radiator and it was in very good shape. But, yes, it acts very much like an airflow problem. The fact that turning on the heater drops the temp so much seems to corroborate the idea.

I see that the tranni has a little leak.
I was looking at the torque-tube and wishing that I could check the condition of the couplers without having to drop the whole drive-train.
I am thinking that I could use a hole saw and a rubber plug. Has anyone tried this?

 

I have a bore scope that would easily fit threw a 5/16" hole. You might have to make several before you can see enough. I don't think it would be a good idea to drill multiple 3/4" holes, especially at your power level.

 

It turns out that the problem was in the wrong gaskets for the coolant bypass. When I bought the parts engine it had an LS6 manifold and bypass lines. Being the naive LSx mechanic I assumed that the gaskets were correct so I ordered new LS1 style plate with captive O-ring gaskets and put them onto my LS1 engine. They *worked* for several years.
Then I swapped out the heads for the RHS 54225 heads and, again, replaced the bypass gaskets.
When I started having the overheating problem that was one thing that I never considered checking because they had worked for over 3 years.
I tried everything else to cure the problem and, finally, gave up. I didn't drive the car for a while but then I decided to go over everything one more time.
Odd how, sometimes, fate can be such a determining power in things. I had decided not to put anti-freeze in the engine. I drove the car and then it sat for a while...
I opened the hood and just leaned on the fender staring at the engine going over everything that I had done. Then I remembered once upon a time I had something similar on my Cyclone GT that turned out to be a cooling system pressure leak due to a improperly tightened clamp.
So what would cause a pressure leak only after the car had warmed up completely and was being driven. The one, and only, thing that I had not really looked at were the bypasses.
I thought it was a long shot but I pulled one off anyways.
Fate was there to led my failing vision some insight.



Just a little calcite from the leak.

Ahah!
So I pulled them all off.
The plain water allowed the easily discernible rust to form showing me the problem.
I cleaned the bypasses and went to Ace Hardware to buy some O-rings.
After replacing the plate gaskets with O-rings I crossed all 10 fingers, 10 toes, and both eyes I went for a drive. After the usual 5 minutes of driving the temperature was dead steady on 170°. It stayed that way for the next hour of city and highway driving.

 

So the blocks were just leaking under pressure and depressuring the cooling system? You never smelled antifreeze from the leaks or anything?

Glad you found the problem and updated the thread!

 

don't get mad get even , well done mate .

 

Thanks everyone!

I smelled a very faint odor of coolant but I couldn't locate a leak associated with it.
The bypass blocks never had a red coolant residue on them to indicate a leak either.
Maybe the coolant molecule was just too big for the size of the leak. But when I just ran straight water then I found the calcite residue. Maybe the calcite is a smaller molecule?
I don't really know just why things were like they were.

 

Sooooooo....

What was the problem? Your bypass was not sealing?

 

170 is probably TOO cool... 197ish is ideal, but 190 to 210 is kinda the sweet zone. TOO cold is nearly as harmful and TOO hot

Copied from a post by Evil Twin

I've posted this hundreds of times over the last 12 years here. One of my pet peeves.
The coolant has a sweet spot and so does the oil. Coolant temp help to support the sweet spot of the oil.. Hot is your friend, cold is the enemy.. cold will give you more HP but Hot will give you much more engine life. You choose. Coolant sweet spot 190/210 F Oil sweet spot 210/230
Running cold oil and forcing it through tight clearances increases the thermal breakdown known as shear. this will destroy the component in the additive package and render the oil less than lubricious, that's why cold starts is part of the oil life monitor algorithm.

Also don't confuse cold air fuel mixtures ( dense winter air ) with engine coolant temps although as I've said many times tuners want cooler engine so they can get cooler combustion temps and be able to advance timing to give you more HP. ( that's what tuners do )These colder engine temps will indeed give you more HP but at the expense of engine life. Everything is a trade off. the Hot engine design was brought about Because Dave Hill wanted the first North American corvette engine to be bench marked at 200,000 miles, a first in the industry. Prior engine designs were benched at 100,000 Miles from every American Manufacturer.

 

It was my thermostat! Turns out it was stuck open and according to my mechanic, it was constantly recirculating the same coolent and unable to cool portions of it enough to stay cool under load or on really hot days. He claims to have let it sit, and run it in traffic and it didn't get above 205
Any how, I'll be picking it up today and reporting back.

 

Correct. From what I can see all four blocks were leaking pressure and reducing the cooling system's ability to transfer the heat out of the engine. I drove over to my local Ace Hardware and bought four perfect O-rings for just $0.80+.