Steve, the Vanguard is the engine that formed the basis for the Intek. Daihatsu was commissioned by Briggs to design the Vanguard. A Daihatsu-Briggs joint venture factory in Japan makes the V-twin version. Briggs decided they would make the single cylinder version themselves, but found they couldn't, so they contracted Mitsubishi to make it. Then they had commercial conflicts with Mitsubishi, so they reverted to making it themselves. Meanwhile when they first found the Japanese design too difficult to make, they redesigned both the single and twin themselves to make them easier to produce in their own US factories, and called them Intek. Unfortunately, in my opinion their design changes were not for the better. The Vanguard engines, especially the twins, have good reputations. The same cannot be said of the Inteks.
I doubt there would be any difficulty in replacing your 28 cubic inch Intek with your 28 cubic inch Vanguard, which is also a better engine. However I cannot believe you would want to discard the Intek just because it needs to have its exhaust tappet adjusted. The tappets should have been adjusted regularly ever since it was new - personally I think it is unreasonable to condemn the engine just because you didn't do it. No harm has been done, once you spend a quarter of an hour making that simple adjustment, the engine will probably run like new.
By the way, are you sure it is a 280777, not a 28Q777?
