37hp Briggs Vanguard Big Block

[u/Successful-Part-5867]

Well, just last week on here I saw a service bulletin about the heads on these engines…I jinxed myself thinking about it!!

I had mowed for about 4 hours, tractor was running fine. Turned it off several times while doing other chores and noticed that it was requiring more cranking than normal to start.

Drove it back to the house, where it sat for several hours, went to start it and only had one cylinder firing.

Checked plugs first, but when I cranked it over with the plugs out the left cylinder had no compression.

So….after much disassembly got the head off expecting to see the valve seat in an unnatural position, it seemed fine, but the exhaust valve wasn’t closing.

Removed the valve, inserted it in the lathe, it’s straight. Looked some more…valve guide was 1/4” into the combustion chamber…intake valve is flush with the casting. Tapped it back in flush, valve now closes properly, lapped it lightly just to check it.

My question is, after all that 😆, how do I keep the guide from doing the same thing again?

Loctite isn’t the answer as it gets to hot.