Thanks a lot, Tom. It's a B&S 150112-2110-B8. Debris is certainly a factor with any shredder. My buddy and I decided to look at the gasket as a last resort, plus we heard a little whoosh of air coming from that direction. It's a fairly new engine (build date March 08), so I was surprised. Gary

Just a follow-up to my original posts. I called the Deere dealer after not hearing from him for a week. He still doesn't know how much it will cost to fix and whether he can do it. He says the water pump and cam are shot which is not surprising at 1400 hours (especially with plastic cam parts) but he also says the crank shaft is shot which sound dubious. He said he would call me back when he knew, but when I called him back to ask how much a new tractor was, his voice brightened considerably and he had the sales rep on the phone with me in 2 minutes. Given the chimera that will result from cobbled parts, we'll probably purchase a new x720. Thanks mownie 7, I believe you had it right in that the water pump was worn and potentially leaking into the engine (I did need to top off the coolant from time to time). Who would suspect that a water pump could cause the entire engine to go (if the dealer is telling the truth). Also, a water pump failure would cause the temp gauge to rise while the engine continued to run. I still think crank shaft replacement is dubious, but he has me over a barrel and clearly wants to sell a new machine. Ultimately, I had 11 exceptional years of service from this machine. I worked it hard and it never complained. I'm still a Deere fan in spite of NYC service deficiencies.

Tomplum is correct about the build date. Briggs & Stratton, like a lot of companies, will tend to be somewhat vague with details of WHY a change was made to a component. In your case, consider the new style head as an "upgrade". Often when a company makes this type of "production run change", it is because there was a problem of some kind with the original design. I think we can guess what problem caused B&S to implement this change.

Briggs vanguards (red ones) are still plentiful and IMO are the top two or three air coolded engines made. If it runs good, don't smoke, the price is right, and you like it Should be OK. 16HP to 23HP V-twins vanguards run from $500 to 1600 bucks depending on where you shop, ebay would be on the lower end, SEW in the middle, and the local dealers will be on the high end or higher. To know for sure price a new engine when you at the dealer. I would imagaine the current owner paid $600 bucks or more to have it fixed. He is probably gunshy now and looking to get some of his money back. Head gaskets are common repair and usually have a very high repair success rate. If you really want to know the condition of that cylinder, do a compression check. Should be at least 100 PSI to as much as 160. both cylinders should be with a few pounds of each other.