Need some wisdom - 216 with cracked head, broken valve spring, and broken valve oiler tube.
Here is some background info on this sweet 1950 GMC 1/2 ton. It was bought new from our local small town GM dealer. Mrs. E. never licensed it and it never left the farm - probably never got out of first gear. Was outside and lots of rust, but very low milage. I am the 4th owner - bought it in 1999 - she was sitting on the side of the road, licensed and running - just couldn’t pass it by. 11,600 miles on the odometer - is this real? or has it gone around once. . . . Locals say it never left the farm.
I did a major tune up the first year - new plugs points condenser, cleaned the carb, new fuel pump. There was a very small leak of coolant from a small crack in the head on the left side below the rocker cover gasket near #5 cylinder. Removed valve cover & adjusted the valves - lots of oil coming from all rockers at that time. No evidence of any coolant inside - everything looked really clean - but that was 20 yr ago. . . . Flushed the cooling system, filled with antifreeze to -40, and added some Gunk Block Sealer (Sodium Silicate), and cleaned out the crack and sealed with high temp epoxy. Compression was great 110psi on all 6 cylinders
Since then I’ve done very little to it other than minor maintenance & change the oil and flush the brakes every year (did do a complete brake job - master to wheel cylinders) Constant oil leak from the pan, rocker, & side cover - always need to add oil “some day I’ll put new gaskets on them all” Monitored the oil on the dip stick and at each oil change - never even a hint of water in the oil. There has always been a few drops of coolant on that left head bolt, but never need to add coolant. Blissfully ignorant.
April this year I brought her out of the winter shed (only run her 6 mo in the summer) did a minor tune up, and it ran GREAT. 18,000 miles - so I’m averaging 300 miles a year - just to the dump and back. Compression #1-6: 130, 130, 98, 100, 100, 115 plugs all clean It ran so quiet and smooth that I didn’t pull the rocker cover. - note to self - should do this every yr. Idles real smooth & slow, and has good acceleration on the road. Hauled a few loads of manure, and it pulled well.
Early June, I did my first “big” trip - maybe 50 miles and it just ran quieter and sweeter - really likes 45 mph, so I take the back roads. I noted that there was no oil leak from the engine now - maybe I just need to run it more. . . . (note to self - no oil leak could mean no oil....) The dip stick still had clean oil and did not need a top up - hmm, usually it would need a quart after 2 months.
A week later (18,100mi) after sitting only 3 d it was hard to start and ran really rough. Compression: 105, 108, 108, 111, 0, 118 gulp spark plugs 1-4 were clean light white powder, #5 was black dry soot, #6 black & oily Pulled the rocker cover - oh no - thick oily orange gunk caked all over the inside of the back half of the rocker cover and all over the rockers and valves - but only on the back 3 cylinders - front 3 look clean and oily. The copper oil tube to the rocker is NOT connected - just hanging loose. Broken valve spring with piece missing on #5 intake - valve is loose Cracked spring on #5 exhaust but valve is tight.
I put a wood wedge under the #5 intake spring to pull the valve up - repeated compression = 118
Pulled the side panel - copper oiling tube had been rubbing on the pushrod of #4 intake valve and was broken clean off. The back of the block under the side panel had some orange gunk dripping down the side, but the mid and front were clean and oiled. It would seem that oil changes and top up would keep some oil on the front 1/2, leaving the back 1/2 dry.
After a long day of reflection, I removed the broken spring and cleaned up around it. The gunk cleaned up amazingly easily and underlying metal looked pretty good (I thought). I can now see that the hairline crack extends across the rocker cover seal area, and up to the edge of the valve guide.
Photos attached.
As this is all new to me, I would sure like to hear this group’s experience and wisdom . . .
1 - Is the orange gunk typical of what you see with oil and coolant mixed. I’m guessing so, but would like some confirmation.
2 - Can a crack in this location be repaired? - I’ve read the tech tip on Lock-N-Stitch - is that an option here so close to the valve guide.
3 - If I’m looking for a used replacement head, does anyone know what years would be compatible (this is a 1950) Would a 235 head fit from any years? Don’t know where to find this info.
4 - The gunk seems to be very localized, and it does not look like it has run into the drain openings. I’m guessing the tiny amount of coolant leak inside the rocker cover would evaporate, and there was no oil flow to sweep it into the drain openings. If some of this gunk got into the oil pan, how dangerous is it? (never saw anything in the oil change) Will the block need to be stripped down as well?
5 - Grasping at straws - The Gunk Block sealer (sodium silicate) did seem to stop the leak for the first few years. The ads for Bars Leaks sound magical. Has anyone had good experience with these products.
6 - If there is a very small continual leak of coolant into the oil, would you see this in the oil change? If you can't see it, does it still damage the engine.
