is actually involved in switching from a hyd cam to a full roller hyd cam setup? if i go from a crane energizer 278 (.467 lift/ 222 degrees) to a hyd roller with approx .510 lift/ 224 degrees in a 406 small block w/ 5.7" rods. i understand that it will have to be a retrofit cam with a small base circle but can it be done w/o machining or clearancing and will the roller rockers fit under standard height valve covers?

Buy a cam that does NOT need a bronze distributor gear. Pull out the old cam, put the new one in. Degree it to be sure it's where it should be.

Drop the new lifters in, drop on a few rockers, and check for proper pushrod geometry. Order pushrods the proper length.

Install pushrods, tighten rockers. Shouldn't be a clearance issue with standard rocker covers, my cast aluminum LT-1 covers cleared my 1.6 Pro Magnums although I had to knock off some oil drippers. You "might" need double gaskets for a bit of extra height. What won't clear standard covers is the stud girdle.

Will your valves clear the pistons? Will your springs tolerate the additional lift? Better check to be sure.

What kind of RPMs are you turning?

I ask because if you're running 6000RPM or under, you can get just about the same amount of power from a good solid cam, for about 1/8 of the cost.

you'll need a good timing chain cover or a preload bolt on the water pump for the cam button too.