Tom400CFI

^The OP doesn't have an LT1. (?)


240* under what conditions?

The cooling system should keep the engine temp below ~240*F under all operating conditions. What does that mean? To ME, it means up to 115*F ambient air, and then what ever operating scenarios GM Engineers could for see.

Using one of your "tests" as an example. to ME, holding the engine at 4000 RPM for an extended period of time with the car not moving is not an "operating scenario" that engineers would design around. Who would do that? When? Why? Basically, no one would. IOW, I don't think that the fans were designed to provide enough airflow, to accommodate a sustained 4k RPM, no air flow situation. I feel that you are creating an "unnatural" situation with your..."test" at least with that test.

You mentioned "overheating" doing a 1/4 mile run...but I don't recall seeing specifics, or details on the conditions.

ch@0s

Use the block tester it doesn't have to be at 4K.

DanielRicany

The best conditions that I'd be able to tell you is that it was about 50 or 60 degrees outside, I started getting on it at about 190-200*F, as I'm going, it got up to 238* then I let off and the temperature came down within 20 seconds.

Also, when I'm on the highway, if I'm cruising at 4,000 RPMs, the temps get high, and when I drop down the RPMs by either slowing down or switching into overdrive, it takes a while to come down. I was cruising at around 2300 RPMs at 190*, it took about 2 minutes for it to drop 1 degree. I only got down to about 187 before I got off the highway. Shouldn't it drop down to my thermostat rated temperature pretty quickly from the time that I get onto the highway?

Thanks!

T. Wayne Nelson

I have AFR heads on a 400 block. Now these 400 blocks are supposed to run hot.(don't believe it) The only condition where my car gets a little hot is sitting at a stop light in Vegas on a 115 degree day with the A/C running. After a while it may get to 240, at which time I roll the windows down and turn off the A/C. At no other time will my car run hot, drag racing, track time, never.. I have a performance motor with 500 hp at the flywheel which will run a lot hotter than a normal car. I kinda think you should let someone who knows these cars test it for you....

powerpigz-51

If you are leaking gases into the coolant, at any RPM, the gas tester will pick it up, as your coolant will be saturated with gas bubbles. They do not just "go away" below 4k rpms. If this was your problem, I would not be surprised if you could smell exhaust in the coolant with your nose. So the test will be valid at idle, due to contamination of the coolant.

ch@0s

I still don't get why you are cruising around at 4K when you have another gear left.

DanielRicany

Because I am still testing out my build, tuning, etc. So I like the be able to have the power readily available when I want to get on it.

Tom400CFI

wholeheartedly!! Your "Testing" procedures" are not good. Your explanations of what's happening are vague, and you aren't really following (or at least responding to) peoples test advice. You did w/the garden hose, so that's something, but this diagnosis is taking way too long.

I'd say that the HEADS are in the clear now, after your water test. Why don't you perform the gas test that several have suggested?

If that passes, I'd suggest video taping an 'overheating event' and the driving leading up to it.

powerpigz-51

And trying to find out where the heat is coming from with IR thermometer was a dang good idea. Look for cool spots as well, especially in the radiator. (I know, it's new).

Baller

These two things are an interesting contradiction. No load 4K rpms temp drops almost immediately on rpm reduction, under load 4K rpms temp takes much longer to drop on rpm reduction.

I'd going to go with the two best suggestions of it being either a slipping impeller on the water pump or a lean condition. Only other thing I could think of would possibly be some sort of cavitation issue. Look at the impeller blades, if they're pitted then you've got cavitation.

Edit: One other thing that should be verified and easily enough - are you *sure* the fans are staying on above 4K?

Tom400CFI

Which is why I agreed with Wayne above. The OP isn't doing any real test! He just throwing out WAD (wild assed "data") that confuses an already unclear situation!

A test that produces conclusive data, is also REPEATABLE. Show us some data that is concise, and repeatable...or get the car to someone who knows what they're doing.

powerpigz-51

Full disclosure here....it took me 4 years of owning my 85 to figure out why my car overheated at anything over 90 ambient, as my radiator fins were clogged up with Retriever hair and sand. and Daniel is off to a good start tearing his car apart over and over. That is how I learned my car (still learning). Hang in there, you will get it.

DanielRicany

What Do You Mean "Pitted"?

DanielRicany

Here are some pictures of what the water pump looked like on the inside and on the cover plate.

Baller

Baller

That's an interesting water line in there... Maybe someone else can verify but shouldn't the impeller *always* be fully submerged?

Is it possible that when you changed the heads you didn't get the system fully bled when you refilled with coolant and at the higher rpms you're just pumping in excess of what's in the system so it *runs out* of coolant?

Again, simple thing but simple things are easiest to fix/verify and also tend to get overlooked a lot in my experience...

HTH

383vett

If you are boiling over at 240* you either aren't using antifreeze, your radiator cap is no good, you have a cracked head or a head gasket not sealing.

ToniJ1960

Are you running it with water only for your testing? Just curious sorry if its been asked

powerpigz-51

Is the clean portion of the cover top or bottom? EDIT: Dumb question! Looks like it sat for a long time at one point, if the corrosion line indicates the level of the coolant (water?).....I thought you had a new pump.....

Black89Z51

I was going to say the same exact thing. A full 1/4 of that pump isn't submerged.