To much build up pressure in coolant system!

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nm9stheham said:
... The original does not have a hole there; it is solid there to block coolant flow. When they have been in a car for 30-40 years, they corrode through there, and allow some of the coolant to bypass the head and block ...
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I did that experiment when younger and dumber. When putting a rebuilt head on my 69 slant, I noticed that the head gasket blocked that "coolant passage". I thought I must have the wrong year gasket so "fixed 'er" by drilling a hole. Engine started up fine, but after idling 10 min I found the temp gage going toward pegged. That told me that passage was supposed to be blocked off, otherwise coolant flow can bypass most of the head (where needed most). I was able to lift the head 3" w/ manifolds on and swap in a new, unmolested gasket. Ran fine then. Those large holes aren't purposeful "coolant passages", but rather places where they shook out the sand and support wires, as were the side holes which are sealed w/ "core plugs" (not "freeze plugs" as greg r already explained). Not all shook out, which is why you find sand and steel wires inside the block passages.
 
If that head is not cracked, you should have it rebuilt and use it. It is the better slant six head. You can tell because the area between the spark plug and the combustion chamber edge is is "filled in" compared to the other type slant head. This decreases the chamber volume giving a little more compression
 
nm9stheham said:
As an FYI, one thing that has been going on is that the large irregular hole in the front of the head gasket is actually where the head gasket has corroded out. The original does not have a hole there; it is solid there to block coolant flow. When they have been in a car for 30-40 years, they corrode through there, and allow some of the coolant to bypass the head and block; most of it should flow to the back and the up through the 2 large holes in the back of the head gasket, so that most of the coolant flows through the length of the block front-to-back and then through the head back-to-front.

If I had to guess, I'd guess that is Bar's-Leak in the overflow, as suggested. It is pretty consistent and not quite like oil in the coolant. And there does not look like any coolant got into the crankcase, judging by the appearance of the lifter galleries. Drain the oil and check what comes out first.

It'll be interesting if the shop reports head warpage. BTW, what did the 'horrible noise' sound like?
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Thank you! I thought that hole looked pretty irregular and suspicious. Definitely could have been the case and why it overheated so badly. And it could just be the Bar's Leak....as I was flushing out the block I only found bright green coolant and not even a hint of any oil streaks. The 'horrible noise' was after I was driving on the highway and it sounded like something was hitting metal. I was very afraid it was my engine but after I turned the engine off the noise continued for another minute. I believe it was just my radiator overflow hose got so much pressure it burst off the fitting and was going wild under the hood, hitting probably the hood multiple times.

BillGrissom said:
I did that experiment when younger and dumber. When putting a rebuilt head on my 69 slant, I noticed that the head gasket blocked that "coolant passage". I thought I must have the wrong year gasket so "fixed 'er" by drilling a hole. Engine started up fine, but after idling 10 min I found the temp gage going toward pegged. That told me that passage was supposed to be blocked off, otherwise coolant flow can bypass most of the head (where needed most). I was able to lift the head 3" w/ manifolds on and swap in a new, unmolested gasket. Ran fine then. Those large holes aren't purposeful "coolant passages", but rather places where they shook out the sand and support wires, as were the side holes which are sealed w/ "core plugs" (not "freeze plugs" as greg r already explained). Not all shook out, which is why you find sand and steel wires inside the block passages.
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That definitely makes sense. It also explains why I couldn't really replicate the problem just idling, so since I don't have a working temp gauge (that's definitely getting fixed now) it probably kept going past the point of warning and just got too hot. Only worsened the problem right after driving too.

RustyRatRod said:
If that head is not cracked, you should have it rebuilt and use it. It is the better slant six head. You can tell because the area between the spark plug and the combustion chamber edge is is "filled in" compared to the other type slant head. This decreases the chamber volume giving a little more compression
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Definitely going to be rebuilding the head if it's all good. Good excuse to put a little work into it now and have it running better than it did (before the problems of course lol).


Thank you for all the help guys, really appreciate it. Now to wait on the verdict of my head (still no update from the machine shop) and get 'er all running beautifully again.
 
Finally will be getting my head back today providing there are no cracks. The head was warped, which doesn't surprise me, so if it isn't cracked I asked for a .030" mill to compensate for my Fel Pro gasket and to bump the compression a tiny bit. Coughed up for the nice Remflex manifold and exhaust gaskets, don't want any problems with that. Everything Should be here by Thursday meaning I have a couple days to prep everything else. Gonna clean out the block and radiator best I can. Is there any way to clean up the block deck and varnish in the cylinders? My dad told me a little acetone on a rag should do it. Very excited to get everything back together, fingers crossed that I have no issues.
 
Acetone or lacquer thinner works fine for cleaning along with a scotch brite pad, and I always go over the surface for a nice finish cleanup with a single edged razor blade just for reassurance.
Doing it with something that small gives you a lot of time to see any left over chunks or crap stuck to the deck surface.

On the block I mention to people that while the freeze plugs (core plugs, or whatever you want to call them) are out, a section of brake or cooler line adapted to a garden hose works pretty good.
Just bend the tip over so it can be shot around corners and run it all around in there as best you can and chase the junk out through the open plug holes.

I just got done setting my car back down due to a small trans fluid leak from my governor port line for the automatic 4th and 5th pressure switches.
Not too bad since they had not been retightened since assembly, but just enough to drip on the pipes and make a small puff of smoke on occasion at a stoplight.
Compression unions almost always need snugging up after a few heat cycles.
 
Got my head back, fortunately it was just warped and no cracks to be found. Got the thing milled so now the surface is flat and shiny. I still need to change out the valve stem seals since I can already see a couple ripped, and clean up the valves and chambers the best I can. I didn't opt for a valve job due to financial restraints. If the guides and valves are that worn however, I will end up doing it.



One concern is the condition of the coolant passageways. There look pretty worn, is this a big concern or something not to worry about?

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Thanks for the advice TrailBeast, gonna have to do that tomorrow morning when it's not so dang hot and sweaty outside. Why oh why do we not have a garage lol.
 
I don't have one either, and only gravel to park or work on things on.
It sucks.:D

The cooling passages are not that big of a deal really on how they look, but just make them as clear as you can within reason.
A sealant might not be a bad idea on the head and block both but just a small amount around the coolant travel holes.
You can use RTV for that but you want it so thin that you can hardly see it's color.
 
You should really check those valves and guides very closely. I'll be danged if I would put it back on without knowing about the condition of ALL the valve guides and seats. I completely understand your budget constraints, but imagine how much it will cost to do twice.
 
Oh I will be. When I replace the valve stem seals I'll be taking out the valves and checking them and the guides. If they are cracked or just too worn, I don't have much of a choice but to get them replaced.


I got a question for cleaning up the surface of the head combustion chambers and the tops of the valves: have any of you used paint stripper to remove that carbon build-up? I have seen some use gasket remover spray but I already have the paint stripper. Acetone I don't think will help that at all lol.
 
Dodge72 said:
Oh I will be. When I replace the valve stem seals I'll be taking out the valves and checking them and the guides. If they are cracked or just too worn, I don't have much of a choice but to get them replaced.


I got a question for cleaning up the surface of the head combustion chambers and the tops of the valves: have any of you used paint stripper to remove that carbon build-up? I have seen some use gasket remover spray but I already have the paint stripper. Acetone I don't think will help that at all lol.
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Heed these four words.
sharp steel scraper, patience. :D

Then finish up with the scotch brite.

If you can blow out the crap between the pistons and cylinder walls with a compressor I have used a wire wheel on a drill for that also, but you better be damn sure you don't leave any steel wires in there and rinse and blow the loose crap out.
It's not a bad idea to cover the other cylinders when doing it also.

I put the piston at TDC, wire wheel it all then blow it out with compressed air.
Then turn the motor backwards a little so the piston goes down a little and wipe any garbage off the cylinder walls.
After they were all done I went back and oil coated all the bores, and put her together.

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As far as my untrained eye can see the guides look okay, they're not cracked or feel very worn down by moving the valves around. Very little movement. The exhaust valve took a couple light taps from a rubber mallet and socket to push it all the way through, the intake was easier. My exhaust valve stem from #1 looks very worn down, and the valve stem seal from the intake valve was almost non-existent. I'm sure my other valves look like this....are they okay? Gonna have the machine shop check. If not....I'll go ahead with the valve job. I want her running for a long time coming. for I'm sure any visible wear on the valve stem isn't too good.
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Just my 2 cents but I just went through all of it. Lay it aside if you have to but come up with the money to have the head professionally reconditioned. You will be glad you did in the end. Next year you won't even miss the extra money you spent but you can cruise in confidence.
 
Well I took everything you guys said in consideration and finally went ahead to have the valve job done by the machine shop. This is really my daily driver and I ultimately want piece of mind for a long time. I regret not doing this when I had the motor out last year but I was only trying to quickly fix a few things and I wasn't as knowledgeable. Dropped it off today and he'll be checking guides, replacing exhaust valves (don't want valve failure in 10,000 miles), new springs, new seals, and if the intake valves are still good then recondition those. If not, then those will be replaced too. He said he's pretty busy at the moment (one man shop) but will try to get it done by Wednesday. But it'll be ready to pop back on the motor so then the rest is straightforward. :)

That's a pretty neat tool there Inkjunkie, I'll have to look into that to check out my cooling system to make sure that's 100%. Thank you!
 
Little update; the new valves said they'd be here today but I don't think I'll have time to run them over to the machine shop before he closes so I'll have to bring them over tomorrow. I've been cleaning up the block in preparation for the head, using some gasket remover just to loosen up the excess grime, then use a razor blade to get the rest off, then finished up with a scotch brite pad. Looks and feels fantastic, nice and smooth running it over with a fingernail. Gonna vacuum up whatever might've gotten into the cylinders. Core plugs, I'm having an awfully hard time getting the only real brass plug out to replace it. It just won't budge from me using a screwdriver and a mallet to try and make it turn to pull it out. Of course it's the only one left lol. Then it's just cleaning the passages up and installing new plugs before the head gets here so it's ready to go back together that day.
 
Good news and pretty bad news.....the Good news, I put I back together, fired it up and it sounds great! Idling smooth, everything sounds okay.


The pretty bad news....I'm smoking more oil than ever!! :( Under a blip of throttle a cloud of bluish smoke comes out the tailpipe. I pulled the brand new plugs and they look like they've been dipped in oil it's so bad. I did lightly coat the cylinders with oil prior to installation, but it's been doing this throughout warm-up. My head has new valves, Knurled guides, new seals, and new springs.....I don't understand! I'm not leaking any oil outside the head. Any help?


EDIT: I realize this isn't a cooling problem anymore, so I'll post this on probably the Slant forum. :)
 
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Dodge72 said:
Good news and pretty bad news.....the Good news, I put I back together, fired it up and it sounds great! Idling smooth, everything sounds okay.


The pretty bad news....I'm smoking more oil than ever!! :( Under a blip of throttle a cloud of bluish smoke comes out the tailpipe. I pulled the brand new plugs and they look like they've been dipped in oil it's so bad. I did lightly coat the cylinders with oil prior to installation, but it's been doing this throughout warm-up. My head has new valves, Knurled guides, new seals, and new springs.....I don't understand! I'm not leaking any oil outside the head. Any help?
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I don't know how much time you gave it but I would'nt expect it to burn off any possible oil out of the exhaust system for a little while, unless it was taken out and run on the highway for 10 miles or so.
Sometimes from disassembly or even left over from the way it was running before a lot of oil and crap can get in the manifold or pipes and can take awhile to burn off all the way.

Just recheck everything to make sure you got it all like it should be, and if it has a PCV disconnect it and see if it clears up.
It's also possible the rings got stuck from getting hot and having coolant in the cylinders, so I wouldn't think a bottle of seafoam or running 50% trans fluid in the oil would be a waste of money to try.
The only other reason it could continue would be rings and/or cylinder wall wear.
 
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Ditto. Don't judge until you have run it a while. Even a tiny bit of oil makes a cloud of smoke. One Ga Tech fraternity would drip ATF into a carburetor throat so their Rambling Wreck smoked like crazy in the parade.
 
Let it warm up completely and drive the thing. Might even need to warm up and cool off several cycles.

Oh and knurled valve guides SUCK. They will be worn slam out in 10K miles. Probably less. I would have had bronze liners installed.
 
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