572 cylinder head overheating

[Denvervet]

I've got an overheating issue that an IR gun has narrowed down to one particular cylinder. I'm about to tear the top of the engine down for the third time and only have 100 miles on it. Cylinder ...#6... runs 30-40 degrees then comparable cylinder on opposite head
Setup
Crate 572 gm
Manifold single plane modded for fuel injection
Ron Davis radiator
Vintage air frontrunner with stewarts water pump

What I've done to diagnose:
Had to rebuild engine at first startup due to a metallic object being in #6 and had to replace entire head and piston
Ran into head heating problem and tore entire engine apart and had block pressure tested and deck cleaned up to insure true surface. Replaced all bearings,crank polished,etc
Same problem
Put bypass hose as well as tried without thermostat as per Stewart's advice....no change
Exhaust gas in antifreeze checked twice...negative
Plug showing real lean so bumpd fueling up 50% via efi...no change
Head in affected area gets up to surface temp adjacent to header of 270+
Intake water temp creeps up to 215-224 without pushing much and temps only drop 2-4 degrees on highway when 75 outside. Placed rubber seal between Rad support and hood
Sealed Rad to support
Changed out fuel injector to rule out lean cylinder due to faulty injector...nothing
driver's head commonly only runs at 205 when good and warmed up prior to entire system overheating
Thermostat stewarts 180 with bypass holes
Jacked front of car up to the sky and ran to be sure all air out of system as well as pulled head temp sensor while filling
Timing initial 17 degrees....advancing of no benefit
Used factory head gaskets...and only one way to put them on.
Tried the propane trick to look for vacuum leaks..nadda

At this point concluding something obstructing head coolant flow....head or block casting
I'm hoping someone has another idea of what to check before I start the tear down again!
__________________

[SparkyRnD]

sounds like a blockage in the cooling jacket around that cylinder. I had the same problem with one of our shop trucks, and just decided to replace the engine under warranty after a few months of diagnosing / testing things / replacing other parts.

[Denvervet]

Not what I want to hear.....no warranty here........backed by bank of me ;)
Took head off and probed all passages in head and block and all seemed good. Intake water port 30+ smaller than other cool side. Not sure if significant but physically would flow about half of cooler side.

[TheJDMan]

My first thought is, are you sure the pistion matches the others? Have you run a compression test on the engine to see if the compression in that cylinder is the same as or close to the others? I'm thinking that perhaps that cylinder is running at an elevated compression relative to the others causing excess heat.

[Denvervet]

Compression of that cylinder almost exactly the same as the adjacent ones.

[Vegas69]

When you increased the fuel to that injector, did the plug fatten up?

[BayouSS]

Is it possible that you have the wrong rotation Stewarts water pump? I also have a 572 with zero cooling problems, I have a Griffin radiator with double row of one inch tubes being cooled by twin 12" fans, this keeps the 572 cool with no problem. It rarely sees 205 and then only in traffic.. On the road it runs 180-185.

[Denvervet]

I took the water pump off and opened it up and sent pics to Stewarts and they confirmed it was correct for reverse rotation vintage air. I was sure hoping that was it.
Re Fuel injector....when I enriched it 50% I didn't drive more than a mile or so and didn't notice much color change but didn't expect with that short run. I just know the head temps didn't do a thing.
Took head and intake as well as pics to engine/machine shop. They are scratching their head also. That chamber looked leaner than the other rich ones but not like it was super lean or anything. Exhaust valve was brownish vs black on all the others. They really don't think the Lean thing is the original cause of heat production.
So, thats all the good new and bad news...nothing definitive. Someone suggested swapping the heads and see if the heat follows . If it weren't such a big pain in the butt I'd likely try that. On drivers side to get to lower head bolts with header in there I've have to disconnect hyraboost, clutch linkage, etc and that may still not be enough. The side I'm doing is barely able to get those bolts and got little in the way...except those headers. I too sick of chasing this to pull the motor again (3rd time in 5 months) to swap heads....lol....plus I don't think thats it anyway.

[BayouSS]

You have a pm

[Vegas69]

My thought was the computer is not increasing the pulse width on that cylinder correctly. Check the terminals in the connector for that injector as well. You should also see your oxegyn sensor go rich by fattening up that cylinder.

[Denvervet]

Todd I'm definitely going to chase down the electronics of that injector today when I get it all back together. What I've done so far is rule out the block for any coolant blockage and pretty much the head also. I ported out the water outlet on the head just in case. I never thought I'd ever be porting something like that but at this point without anything else jumping out to explain want to take that off the list of possibilities.... I moved the bypass outlet to the middle position on the intake rather than the heater outlet . I noticed that when the engine was hot the bypass hose was pumping( sucking actually) 215 degree water from that hot side of intake back into lower hose and really heating up that hose(195-200) which meant water pump was then pumping 200 degree water back into the block. Again I don't know if that will make much difference but trying to tweak anything to help me out.

[Vegas69]

The only time your bypass hose should be an issue is when the thermostat is closed. It was designed to allow coolant to recirculate through the block and prevent cavitation and an air pocket until the t stat opened.

It looks like your intake gasket slipped and was much to low last time around. OR, you have the wrong intake gasket/intake needs planed down to lower it. Look at the seal in your photos. Its low on your water outlet and air intake. I think a vacuum leak was a real possibility even though you couldn't nail it down.

[Denvervet]

The gasket was fairly centered on the holes but the floor of the intake water port was that much higher than the head floor...one more reason to open it up. On the intake air port it was maybe 1/8 " low is all. I'll try to make sure it is up better when I mount this time. When mounting the intake it can be centered vertically when setting in but once the bolts start to pull it down gasket wants to go with it.

[Vegas69]

Look at your upper right hand photo. Looks like a good .25. You have a **** hair of seal on the water port in that photo and I can't see the top of the air port but it looks super low. Make sure you are getting the intake on nice and square before you tighten down the bolts as well. Don't discount a mis machined intake. I learned that lesson the hard way a long time ago.

[xx_ED_xx]

I would swap injectors and see if it follows, also check wiring and injector driver

[Denvervet]

Already swapped inj..no change. After previous changes seems to be less discrepancy of temp but still gets overall hot. Today was 9 and overall got up to 222 and highway driving a couple miles made 0-2 degrees temp drop. Upon stop and go as well as idling no temp drop at all. So shut er down. I noticed at idle once hot it gun showed 225 at upper hose near intake yet near radiator was 208 as was lower hose. Makes me think reduced flow through radiator....but then why wouldn't Rad temps get even lower with fans blowing lots of hot air?

[Vegas69]

Have you made sure the t stat is opening at the proper temp and fully? Boil it or replace it. Also, pull the cap once the stat opens and watch the coolant flow. It should really be moving. Your upper to lower hose temp drop is suspect. It should be better than that. I'd say at least double. Big inch big blocks don't cool that great around town even with dual spals unless you have larger than 13" fans and an oversize radiator. However, my 489 ZL1 will run under 180 all day long on the highway even up to 100 degrees ambient. You have a cooling problem of some sort. I'd start with the basics.

[Denvervet]

Yep it was basic but not apparent. I finally decided to pull the radiator even though it looked good inside. Filled with dishwashing detergent solution a nd soaked an hour flushed and got lots of weird brown stuff out. Soaked with a triple shot of prestone cleaner, soaked and flushed and looked inside to lots of brown slime. My guess is previous owner ran dex cool. I fabbed up a way to flush each individual tube with water pressure. Worked like a charm and temps stay around 184 now.
I would have had done professionally but under the gun to get to transporter for power tour in 2 days.
I think the cylinder was one that runs warmer anyway and just exposed the cooling deficit.

[Vegas69]

The lack of cooling across the core was the key. Glad you found it.

[Denvervet]

OK, too optomistic too soon. Was 80 here yesterday so thought I'd test her out. Was great for 20 min. then just continued to climb. Ultimately was up to 212 idling in driveway not really cooling down much at all. Suspecting Rad gumming up again. Will pull it out and have professionally cleaned and hopefully flow tested. Power tour option mostly out now. Big bummer.