Is this 100% a blown head gasket?

[428Marauder]

So, years ago I purchased a used 428 that was running and according to the guy that sold it to me (in a car) it had less than 1000 miles on it. I've had lots of problems with it, finally replaced the carb with an aluminum holley, and the car runs great! There's just one problem. Over 180 degrees and the car starts to knock and gurggle. So, I was thinking that it was a good idea to burp the radiator. Since I replaced the radiator myself with a brand new aluminum radiator a couple years ago, I never have burped it, but I also have not driven it much. Anyway, my green coolant has turned into a more chocolate milk color. While trying to burp it, I noticed it was foaming up. I did not notice any abnormal smell.

I've ran a couple tanks through it with 91 octane, so that is eliminated. I just did an oil change and it looks clean, nothing weird coming out the tail pipes. Car runs and drives great, for about 5 minutes. At 70 MPH it will cruise just fine, and then you go up a hill and it starts to gurggle and knock.

So, I think a coolant flush makes sense, with fingers crossed and then I found these Thermagasket kits that is supposed to fix head gasket problems doing a coolant flush. Anyone ever tried this?

http://www.rxauto.com/products.php?cat=8

[cjshaker]

I'm not really a fan of gasket fixes that include sealers put into the engine, so can't really comment there.
HOPE that it is a head gasket though. The alternative may be that the internal oil tube leading to the deck surface is rusted through and allowing oil under pressure into the water jacket. They're fixable, but the entire engine must be dismantled.

[428Marauder]

FWIW, I not need to drive the car every day, and I am pretty broke. I would hate to waste the money on coolant flush and still have the same problems. If it costs me $115 more and it solves the problems, that would be a good thing.

I have a complete (seized) 390 in another car that would be correct for the car (the 428 is not). It might make more financial sense to have that motor rebuilt, but I would have to hire a good mechanic.

Pull one motor and trans, do complete rebuild. Pull other motor and and trans, put in other car, install rebuilt motor. What are we looking at here, $5-7K?

[428Marauder]

Im going to flush it several times with water, and once it has clean water in it, I will get back to you guys.

[66FAIRLANE]

Get someone to put a 'head tester' on it.

[Heo]

Put some dishwasher detergent in the radiator and run
It for a while then flush it out with a hose till
All the mud is gone

[428Marauder]

OK, so I opened up the valve on the bottom of the radiator and surprisingly the coolant looked fairly clean, not milky at all. Drained it out, ran some water through it. Put in some dish soap, ran water through it. Drained, ran water, drained, ran water. Still each time there would be some foam, but eventually I got it fairly clean. Ran it for about 5 minutes with the cap off, put the cap on, took it out for a test drive, right away when accelerating, "gurggle, gurggle, knock".

Going to flush it a few more times and try again tomorrow.

[428Marauder]

When engine is off and cool, it the water looks clear. Here is a video of the water with the cap off:

https://m.youtube.com/watch?v=7iFybx1vRcc

[machoneman]

Ouch! That vid of pulsating coolant is a textbook case, unfortunately. Once hot again, rev up the engine to say 2,000 rpm. Near 100% sure you'll see the pulsing increase rapidly....and then slow again as the revs drop to idle.

If not a head gasket, it could instead be a crack one of the cylinder heads (possible) or a cracked bore (less likely). With that much pulsing btw, a compression test should show a suspect cylinder down on PSI a lot or even two adjacent cylinder low (like 1-2, or 6-7, or any pair).   

https://www.youtube.com/watch?v=5zpNjYmmiYY

[428Marauder]

Welp, I'm not the kind of guy to sell the car and not be honest about the problems, so I guess I need to find a good mechanic.

[428Marauder]

I added some Bar's Leaks metallic block seal. Says "permanent" repair. $10. Should be good now. Phew!

Ok, the real reason is, like I said, the car runs fine. No water in the oil, no white smoke out the tailpipes, no weird smells, and the bubbles are very fine and foamy. I hope, that means it's a small leak, and a head gasket leak. My guess is, if that's the case, this will temporarily fix it. If it's a cracked cylinder head, or block, I don't expect this to do anything.

Will report back in a couple of days.

ETA: Also, I didn't put any in the overflow, or run the heater, as directed (so it didn't get into my heater core) and I am not going to leave it in, as directed. Ran it with just water, gonna drain it one more time, fill with coolant. Still have a little left, may add that at that point if I am still having the same issue, or it seems slightly improved.

[428Marauder]

Slight, weird question.

I have a pair of 390 4 barrel heads. Is there any difference between 428 heads and 390 heads?

Also, could be interesting, this motor has the 1U crank, externally weighted flywheel, webbed block, pretty much meets the requirement for a cobra jet, despite the fairly standard heads. Have not found a vin on it, I think it was a service block. I've pulled the top end off a 390 before, I could get this all the way down to the block, myself. The problem would be putting it back together, but it's not rocket surgery, right? The reason for doing this, would be to instead of spending money on a mechanic, maybe I can replace the heads with something better. Also, maybe I can do the job myself if I purchase a torque wrench. Watch a couple youtube videos, I'm there, right?

ETA: As long as I break it down carefully, bag and tag, actually that might save me some money on mechanic time, even if it means towing the car in, right?

[428Marauder]

I've actually never had the valve covers off on this car, and even though the oil is clean, at the very least, I have some Mercury pentroof valve covers I want to use anyway, so I will buy a torque wrench and check the head bolts torque next. Video to come.

[428Marauder]

Pretty much what I expected, made a temporary seal. I try and make it sound cool. And for $10 ... if it works for a day, I get a clearer picture. Gonna hafta get out there, put my foot in it, oh darn ... Will report back though.

https://m.youtube.com/watch?v=M9VkWKHhEnk

[428Marauder]

Post removed by author. Off topic.