Is the mechanical cam of older sixes slightly "bigger" than the later hydraulic one? I ask this ,becose the older 1barrel slant had its power peak @ 4000 rpm ,instead of the 3600 of my super six. And is there any difference between 170 cam and 225 cam?

Hydrolic vers mechanical cam is difficult. You can't directly compare lift/duration in my understanding. The solid cams of the '60's are not quite as good as the ones used stock by the mid '70's, and it all changes when you go hydrolic.

Don't even think about using about using a solid cam with hydrolic lifters or the other way. You've got to convert the lifters and rockers to match the cam. You can make a hydrolic motor solid, but I don't think you can convert the other way, but why would you want to?

I think the 225 cam fits the same as a 170 (right?), but specs depend on the year, not the motor size. You might improve an early 170 by installing a mid 70's solid 225 cam, but a 170 cam won't improve a 225.

I'm not a cam expert in any way. This is just my basic understanding. Please don't build anything based on this information, it's just to help guide you on asking more questions, and hopefully someone will correct me if I got it wrong.

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1980 Aspen 225 super six

The cam's are the same 170/198/225 up to 1971. Then the 198/225 got a slightly better profile (a bit more lift, etc...). The only other 'change' to this would be the dealer installed HyperPak camshaft in the early 60's.

Hydraulics are different since the lifters have to pump up with oil and depending on rpm, oil, and quality of lifter your lift can vary. Slantzilla has run a hydro motor and found it to be very comparible on the drag strip to a solid bumpstick. The two reasons to run a hydro mill and cam for street only would be: 1)quieter lifter noise, 2) no more making messes in the driveway during your valve lash maintenance cycle...

-D.Idiot