tbh, I've only ever serviced one slant six, and that was only very minor things. My friend's dad used to flip cars in the 70s, and he swore by the slant six. He said he had one that was going to the bone yard, so he decided that he'd blow the engine for fun. Revving at full throttle it took over ten minutes to blow. A lesser engine wouldn't have lasted one.
Here's a little story about the slant six that I thought was pretty cool.
It's the 60s and NASCAR (back when they still used cars that were stock, and not stockcars) decided they would have a race for midsize sedans. Ok, so Ford, GM, and Chrysler all entered their midsize, six cylinder, family sedans. The Plymouths and Dodges racing all had the slant six, which at the time, was a totally modern engine. They had also put their racing team on the cars to give them all the go they could.
Seven Plymouths and Dodges were in the race, and not only did all seven of them finish the race, but they all took the first SEVEN places! They had such an embarassingly massive lead over Ford and GM that NASCAR declared the race too boring, and never attempted it again.
While the legendary slant six was a completely modern engine, Ford and Chevy were still using ancient straight sixes, based on prewar engines. That, and they didn't really put any effort into making them fast. Meanwhile Chrysler's racing team came up with a simple but effective mod, the Hyper Pak. It's just an intake manifold with absurdly long runners. Gives the engine a ton of low end torque, at the cost of high end torque. But they figured that you need it on the low end to pull out of a corner. Apparently it worked.
And as is tradition with NASCAR, they screwed over Chrysler for winning too much.
