First, backstory.

1988 L98, 700R4. Summit 8803 cam, Edelbrock EPS intake, Edelbrock Thunder AVS 650 carb, fresh bottom end with stock style standard bore pistons, plasma moly rings, stock pressure oil pump, tri metal bearings, FloTek 200cc heads, BTR Chromoly pushrods, 1.5 cast roller rockers, Accel billet HEI distributor, long tubes, 3000 stall, new Delco water pump, etc. etc. etc.

Stock engine was badly overheating at idle. Discovered bad head gaskets and a head with a casting flaw around the #4 cylinder that was inhibiting coolant flow causing the head to warp longitudinally. I located the original owner from 1988 (he is 82 years old!!!) and confirmed a long history of blown head gaskets and even an dealer installed short block. Not one time.did they suspect a head being bad.

Installed the rebuilt engine to find it overheating when attempting to break in engine under no load at 2k rpm. Pulled radiator to find it completely clogged. I blew out and washed both the radiator and condenser. A ton of debris was removed from both.

Now it's cooling much better, but after about 15 minutes of 2k rpm (no load) it tries to overheat again.

Both fans are wired to a 180° on 165° off thermo switch and they're working correctly. I have a 160° thermostat installed. It claims it begins to open at 160° and is full open by 180°.

​​​​​​It will idle forever and not overheat. When run no load @ 2k, it will get to 205° easily, but after about 15 minutes. Even with A/C running, it refuses to overheat at idle.

Am I setting this up properly? How can I get this thing to sustain about 170°?

I'm confused about how this system should operate. Obviously the radiator coolant should be far less than the coolant in the engine, so is this 180° on/165° off thermoswitch adequate? I'm beginning to believe the stock single core radiator doesn't have the actual capacity to cool this engine properly. I have ordered a "Frostbite" 2 core radiator today from Summit racing. I assume this will likely cure my cooling woes.

What do you think?

Lastly, this thing sounds NASTY. Super quick revving, a good amount of lope but completely manageable, good vacuum. I love this head/cam combo. It sounds like a NASCAR engine.

 

If you're only seeing 205 at idle or slow speed with A/C I'd say you are operating pretty well... its a relatively sealed engine bay and it is cooled only by the electric fan at low speeds. The dual core will help some but it's the nature of the car. If you're running at no load and 2k rpms and it is "over heating" what temperature are you seeing... 235 degrees Fahrenheit, while hot, is the upper end of what these cars are designed to run....

 

Get a real radiator and problem solved. I have a 383 and a dewitts radiator and im actually looking to get the engine a little bit warmer. Im also running 2 stacked plate coolers - 1 for engine oil and 1 for trans. I have zero cooling issues what so ever.

 

I agree. The new radiator will make a huge difference. I have a Griffin Racing in mine and it only gets to around 200 degrees at most with the factory fan and a 180 degree thermostat. Also I use a plate cooler for the transmission fluid. I don't pass mine through the radiator at all. Its debatable but I think this helped lower temps quite a bit.

 

You can test that front fan by unplugging the bullet style connector (cyl head 1 & 3) and grounding it. Somewhere I found the number 239° for that front fan as well. The main fan behind the radiator comes on at 226°.
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They're both working. They're also no longer connected to the ECM and are exclusively controlled by a 180° on/165° off thermoswitch and relay.

This being said, I've received the new radiator. I'm installing it now.