Husqvarna snowblower with Briggs engine valve guide issue

[Auto Doc's]

Thanks for the update picture.

Now, I think that picture better confirms the exhaust valve guide has moved up in the casting due to an overheat condition. (Poor B&S design) I can see that the exhaust valve guide is not sticking very far at all on the combustion chamber side.

At the moment, I do not have a used head to inspect and verify.

I suggest you temporarily reassemble the head and install tight with the old head gasket, set the valve lash and rotate the engine by hand slowly to see if the valve rotor (spring retainer) is close making contact with the top of the valve guide has the exhaust valve operates.

Just driving/pressing the guide back down, just means it will do it again.

 

[slomo]

I removed valve cover and found exhaust pushrod disconnected and intake valve bent.

Are you clear on what caused this issue? Lack of valve lash checks or over heated the block, maybe both? Both of these are YEARLY maintenance items in every engine manual out there. Just letting you know this was all preventable.

 

[grumpyunk]

Have you removed the intake valve guide seal to compare guide heights? One other thing that can help cause guide migration is having clippings and critter nests above the cooling fins on the cylinder and head. The detritus blocks cooling air and causes overheating, which can allow the guides to move. A secondary cause of those parts overheating is running the engine while it is low on oil. Besides lubricating the bearings, the oil splash continuously carries away heat from the hottest parts and mixes it with the other oil to spread the calories so it can be radiated from all the surfaces of the engine. If the oil level is low, or the engine run regularly at low rpm, there is minimal splash, and thus minimal heat carried away. The heat carried by splash applies to fully pressure lubricated engines as they also get splash helping to cool things.
There are multiple guide re-positioning videos on YT. You basically drive the out of place guide back to original as noted by witness marks, then use a pointed cold chisel & hammer to dimple the area around the guide, causing the metal of the cylinder head to deform towards the guide to grip onto it. It seems to work pretty well as those who have used the tactic have reported they have not had repeat problems.
My theory is you can slide a hand under the cylinder & head with the engine running to feel the output of the blower on the flywheel. Lots of warm air should blow down onto the chassis that has passed over the cylinder & head. If the flow is rather weak, then the cooling airflow may well be obstructed.