Thanks for those clarifications, Redeye. I don't have any confidence you can prevent any of the large Inteks from blowing headgaskets from time to time - IMO the design of the cylinder head and gasket has a weakness, in that there is insufficient support across the large span between studs, adjacent to the pushrod cavity. There seems to also be poor design in relation to the decompressor. These are areas where Briggs chose to make changes from the original Daihatsu design of the Vanguard, on which the large Inteks are based.
I have no experience with specific problems in the camshaft area other than a number of camshafts had lobes wiped off them, in fairly early production of those engines. I have been under the impression that this was overcome after a while. If you give us the Code we will know the date of manufacture, and should be able to establish whether your engine is early production.
Essentially, issues with blown head gaskets, decompressors not working due to exhaust tappet clearance being as little as 0.001" more than specified, camshaft failures in early production, and a fairly short fuel pump life, are the only characteristic problems I know of with the engine. The twin cylinder had a poorly designed air cleaner box and was prone to becoming dusted until the box was redesigned fairly recently, but that did not apply to the single.
The large Inteks seem to be cheap engines with questionable reliability due to the problems I've mentioned, but in general they can soldier on if they are repaired as often as necessary. For commercial service IMO you would have been considerably better off with a Briggs Vanguard twin, which is now and always has been manufactured in Japan to the original Daihatsu design. The Vanguard single cylinder engines have been made both by Mitsubishi and Briggs, and I am unclear on their quality record over time.
I suggest you have two alternatives here. You could verify that a V twin vertical Vanguard from their range (13 to 22 hp) is a simple drop-in fit then go that way, or you could dismantle the Intek, post pictures, and we could discuss what has gone wrong with its valve train. Time permitting, it seems more economical to find out what it would take to repair the Intek before making a decision.
