CK5
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FNG here.....Wasn't sure where to make the first post.

Some mechanics I know used WD-40 or brake fluid to absorb the water and coolant in the crankcase...they did not run the engine with that in it,just let it sit & soak awhile,to displace the moisture,so it would hopefully flush out ..unfortunately enough of either of those to fill the crankcase would cost like $50 now..

Years ago there was a nitrocellulose based chemical made specifically for this purpose,but I haven't seen any for sale in many years at parts stores...
 
Man sorry to hear your luck on this one, but it looks like you have motivation to keep at it.
 
Some mechanics I know used WD-40 or brake fluid to absorb the water and coolant in the crankcase...they did not run the engine with that in it,just let it sit & soak awhile,to displace the moisture,so it would hopefully flush out ..unfortunately enough of either of those to fill the crankcase would cost like $50 now..

Years ago there was a nitrocellulose based chemical made specifically for this purpose,but I haven't seen any for sale in many years at parts stores...

Gives me motivation to clean my shop real nice so I have places to organize what I take off get them parts/brackets sanded painted etc., not a huge job on an old 350. Just going to take a while since my free time is limited. Money isn’t the object here as much as time is. My wife won’t like me working on the truck everyday but it has to be done. After I get my shop all cleaned up and sterile I’ll start the tear down.

Diesel fuel is what I have used to clean crank cases in the past. Works great. Just let it sit in the engine 24-48 hours and drain it and drop the pan to let it air out. Pretty much going to re gasket everything and put some new goodies on. Hell, if the head is toast I’ll just get some new ones.

The interior can wait for now. Just want this thing moving under its own power again.
 
A mechanic I know who was an old sage and has since passed,used diesel fuel for many uses ,like a parts cleaner and engine flush before an oil change..
One truck a friends dad had,an '86 C-10 with a 4.3 was smoking,using oil,and spark knocking..we all assumed the engine was on its way out..
But that mechanic took it in for 3 days and all he did was fill the engine up all the way to the valve covers with diesel fuel,and let it sit 2 days..

On day #3 he pulled the drain plug out and what came out of the oil pan was amazing..coal black oil,with some chunks and blobs of carbon & soot looking sludge!...he poured a bit more in with the drain plug out and after it came out clear looking,he filled it with 15W-40 diesel rated oil and started it up...
It smoked like a tire fire for about 15 minutes,then it slowly tapered off,until it wasn't smoking any more out of the exhaust..then he took it for a ride ,and gunned it getting on the highway several times..when he returned,he removed the EGR valve and cleaned all the gunk out of the passages,had to use a drill bit by hand to open up the passages..

After that the engine ran much better,smoother,and had a lot more power,and no more spark knocking..I guess the thing was just all coked up from the owner putting around on back roads with it all the time he owned it..
The mechanic claimed when he worked at a GM dealership in the 80's quite a few of the early 4.3 V6's with carbs would carbon up badly,some he said the intake valves had so much crud stuck on the undersides of the heads and stems hardly any fuel could get into the cylinders..and they often did that procedure to "fix" them..

Maybe you could just pull off a rod & main bearing cap and see if copper is showing on the bearings..if not,you may be able to get away with not doing any lower end work...
 
A mechanic I know who was an old sage and has since passed,used diesel fuel for many uses ,like a parts cleaner and engine flush before an oil change..
One truck a friends dad had,an '86 C-10 with a 4.3 was smoking,using oil,and spark knocking..we all assumed the engine was on its way out..
But that mechanic took it in for 3 days and all he did was fill the engine up all the way to the valve covers with diesel fuel,and let it sit 2 days..

On day #3 he pulled the drain plug out and what came out of the oil pan was amazing..coal black oil,with some chunks and blobs of carbon & soot looking sludge!...he poured a bit more in with the drain plug out and after it came out clear looking,he filled it with 15W-40 diesel rated oil and started it up...
It smoked like a tire fire for about 15 minutes,then it slowly tapered off,until it wasn't smoking any more out of the exhaust..then he took it for a ride ,and gunned it getting on the highway several times..when he returned,he removed the EGR valve and cleaned all the gunk out of the passages,had to use a drill bit by hand to open up the passages..

After that the engine ran much better,smoother,and had a lot more power,and no more spark knocking..I guess the thing was just all coked up from the owner putting around on back roads with it all the time he owned it..
The mechanic claimed when he worked at a GM dealership in the 80's quite a few of the early 4.3 V6's with carbs would carbon up badly,some he said the intake valves had so much crud stuck on the undersides of the heads and stems hardly any fuel could get into the cylinders..and they often did that procedure to "fix" them..

Maybe you could just pull off a rod & main bearing cap and see if copper is showing on the bearings..if not,you may be able to get away with not doing any lower end work...

My father is a 40 year GM mechanic now retired. He taught me all the tricks.
 
Managed to clean my shop up tonight and this is as far as I could get with my limited time. I’m going to give it a month/month and a 1/2 worth of a project.

B71BCC86-92A4-4634-9396-A2E6B4A58FC9.jpeg
 
Upon further inspection I now believe the thermostat stuck shut and starved the engine of coolant.

I drained the oil and it wasn’t too green or white which makes me satisfied that I caught it early enough to not have caused major lower end damage. I will still do the diesel fuel trick just to be thorough.

I believe so far it was a head gasket failure and not a cracked head however only the machine shop will be able to tell me for sure. Luckily my cousin runs the best shop in town and I will get honest work for honest money.


These casting marks scared the bejesus out of me....AF19C581-60E4-47E4-8BE2-C0D15D982656.jpeg
 
Upon further inspection I now believe the thermostat stuck shut and starved the engine of coolant.

I drained the oil and it wasn’t too green or white which makes me satisfied that I caught it early enough to not have caused major lower end damage. I will still do the diesel fuel trick just to be thorough.

I believe so far it was a head gasket failure and not a cracked head however only the machine shop will be able to tell me for sure. Luckily my cousin runs the best shop in town and I will get honest work for honest money.


These casting marks scared the bejesus out of me....View attachment 316295
Good pressure check does wonders

Check the block good too
 
Good pressure check does wonders

Check the block good too

Yeah I did a pressure check on the cooling system which is how I found out the thermostat was stuck shut. After I get the heads and intake removed I’ll clean the engine with oven cleaner to see if there is a crack somewhere near cylinder 8. I’ll also inspect the bores thoroughly. Im still thinking it was just the head gasket at this point.

All the plugs looked great sans cylinder 8 which was soaked in coolant. Hopefully I’ll have the heads off tomorrow or the next day and then in the shop the next day getting tested. Can’t wait to get all the custom brackets this thing has painted back to their former glory. Definitely going to replace all the gaskets on the engine. Might even get a new intake and carb. All depending on the shape the heads are in.
 
Decided to take the day off. Here’s the progress so far from this morning. Started at 8:30 so been an hour. These foam things I got are great for keeping things organized

0B22B4F6-6689-41C6-A246-FC23AE227C83.jpeg49C87D79-A35B-488E-B744-3434FDE59206.jpeg
 
Well, I think I found where the gasket broke.


Among other findings....

Cylinder 8 took a good beating. EF32FA7E-D350-4EE0-BA3C-919421D31105.jpeg1BA5600C-7974-4E3E-AF57-900793B12A5A.jpeg061735C3-131C-4424-A7D2-316920EFEDFD.jpeg
 
I’m thinking someone broke the end of a spark plug inside the cylinder some how.
 
You weren’t the original installer of those heads?
 
Could you have a possible broken ring or rings in that cylinder?
 
You weren’t the original installer of those heads?

Nope. I bought this truck about a month ago.


Could you have a possible broken ring or rings in that cylinder?

I didn’t see any metal in there. I also didn’t purge this cylinder. So I think someone else broke something in there and purged it out.
 
Could you have a possible broken ring or rings in that cylinder?

The shape of the imprint in the head surface reminds me of a ring or also a spark plug end.

I’m sure anything is possible.

Time to pull the motor. If it’s not a high nickel block I may try to have it bored out. I’ll check the casting # when I get back.
 
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