overheating overheating HELP....!

[Last Indian]

Dr. Jones, sorry for your dilemma and sorry if I miss step here, but I didn’t have time to read the whole post. So if I suggest or repeat what has been said already my apologies.
A couple things strike me though! Electric fans really don’t work that well for big motors or big HP! The pitch on the fans is not that good, small blades, no length to the foil, physics law! So a four row radiator is actually a lot of resistance, so the air tends to spill off and not go through even when it seems to. I’m not saying you can’t do it, but it’s difficult. Also fans pushing and pulling not a good idea, causes way to much turbulence. If you were going to try to run electric fans, the ones you have in front (black) should be the only ones. They have a bigger pitch to them, but I would run them on the pull side. Then still follow the advice I give below about the short nose pump and making or buying a shroud. So the shroud, I apologize up front for saying this, is bad! The air moving through a radiator is like a carb, the straighter the more efficient it is.
In my opinion, which is based on the work I’ve done for years in racing and specifically with my Z/28, which are notorious for this problem. Likewise the Z ran a big oversized 4 row radiator and overheated! Why? Because I put electric fans on, 1983 or somewhere in that time frame. It was new and I thought clean and cool. Took off the shroud and whalah overheating. So my 2 cents worth, get rid of the electric fans, get rid of the current shroud covering the radiator, buy a short nose water pump, put the stock size pulley back on the pump, I like the one you have it just needs to be the stock size, buy a good clutch fan and buy or build a shroud that basically cones from the radiator to just about an 1” past the tips of the fan blades. See example of the Z.

 

[DrJones]

Block was hot tanked. the deck was surfaced by only a few thousandths 2 or 3.  Heads milled .010 did not enlarge spring pockets they are stock. Head gaskets are Felpro FEL-8518PT. No sealer on head bolts. Pontiac do not need thread sealant since the bolts do not break into the water jackets, did lube them.  I did all the assembly myself. I'm feeling like there must be a blockage of some sort inside the block. I'm gona get my buddy's infrared thermometer and check different ares see if I can find any hot spots.

I'm really running out of ideas. Maybe the Gen3 just won't let enough air pass to satisfy.

Frosty, thanks for checking back. I did not find any hot spots on the block or heads. We have come to the conclusion that the gen3 body just will not let enough air to pass to counter the amount of heat that big engine creates. I'm sad to say but we're pulling the Pont 400 and dropping in a LQ9 from 07 Escalade with 4L80 trans. I have a 02 F150 that is going to get the Pont 400 & TH400. The F150 has plenty of open front grill to do the cooling job.

[Last Indian]

Wow! That’s a lot of work to throw in the towel! You do have enough cooling area, you just have close to 50% blocked! No matter what you do with fans, thermostats, lines or the like you’re trying to exchange heat in a radiator that’s up against a wall. That aluminum plate is not a shroud it's blockage and creates turbulence in the air flow that is trying to move through the two openings that are there. Take off the aluminum plate! Than run the car on the road or at least run a large fan in front of the car, leave the electric fans on the front in place, than see what you get.

[Old guy44]

I have been busy with life that has gotten in the way of everything. I have seen the posts and recently found out something, electric fans do a lousy job of moving air through a thick radiator. I have a '63 Catalina that was built during GM's weird days, it does not have a temp gauge! I can have a temp (and oil pressure gauge) installed by classic instruments for around $2500.00. I chose to go another way and put in a 4 row aluminum radiator to insure that it just does not overheat. I also installed A/C. To cool the condenser I have a large electric fan between the radiator and the condenser. I said all that to say this. The A/C works well as long as the ambient temperature does not go above the mid 90's. I had a lot of thoughts what to do and figured that the easiest thing was to put a bigger fan on to see what happens. I purchased a 7 blade flex a lite flex fan and put it on replacing the factory 4 blade. Wow what a difference. I need to agree with last indian, electric fans just don't do a great job of moving air through a thick radiator. The flex a lite not only has improved the efficiency of the A/C there is a noticeable difference  in the under hood temperature after a run in 100 degree temperature. It seems like a relatively simple and inexpensive thing to strip all the shrouding off of the radiator install a high volume engine driven fan and see what happens. A FACTORY type shroud that funnels air from the entire radiator without restricting flow like what you have would probably help but if the fan is close enough to the radiator may not be necessary. Seems to me that it is worth a try, after all you have been through.

[Kurk_Kurk]

i mean, a trick i used is a bypass kit for the coolant to cycle around the intake manifold better. it's a 400 and i've heard that they are prone to overheating and this bypass trick worked for me.

just 2 hoses from the thermostat back to the rear of the manifold. pulls hot coollant from the back and back to the front where it's cooler