whats the max rpm for a stock type 4 1800. most books state max hp at 4200.

I think the factory available rev limiter was ~4500rpm.
I think many people are happy to rev to 5000rpm, but your better down changing before then in a stock set-up.

I don't go past 4000rpm because that's where my rev counter stops

4200 for my 77 Kombi = Max power.
I usually shift around 3800- 4000. unless I'm going up hill, or pulling a trailer, then Ill take it to 4200 before I upshift then it dosen't loose as many rev's and it stays in the torque band.
Rob......

For 'normal' driving I don't take it past 4500rpm, which just happens to be the redline on my type 3 tacho.:thumb

When I'm feeling silly I have been known to take it up to 5500-6000rpm :o, but it doesn't make the bus go any faster.