I just hooked up with a roller block, and i'm in the process of rebuilding it, I have a slightly used hyd flat tappit cam that I wan't to put in there, can I still use the roller lifters? or do i need to go and buy another hyd roller cam?

and btw, what is the difference between the two camshafts?

 

yeah you can run the roller lifters on the flat cam, just not for very long then you'll need a new cam and lifters. the cam and lifters have to match, it's all in the way the cams ground.
solid cam = solid lifters
hydrolic cam = hydrolic lifters

you can run a hydrolic cam in your block, with the correct lifters if you don't want to spend the extra money on a hydrolic roller

 

Not to be contrary, but let me expound a little on what Ed said.

There are actually 4 different types of cams, because there are 4 different types of followers (lifters): mechanical flat, mechanical roller, hydraulic flat, hydraulic roller. Each cam must be ground for the type of follower to be used - period. Like the Chinese restaurant, no substitutions allowed.

The differences come down to this: With a flat tappet (follower, or lifter), you want it to rotate in the bore so that you don't wear a groove into it from the cam. This is accomplished by making one side of the lobe slightly higher than the other, on the heal portion, so that it rotates in the bore a little with every turn of the camshaft. You don't want that little ramp on a roller follower, because the wheel on the bottom of the follower takes care of the wear problem - having a ramp on the lobe would put an unbalanced load on the roller, lunching it.

The cam lobe shape is also varied depending upon the type of follower, whether roller or flat, mechanical or hydraulic. The lobe contacts the follower differently on a flat tappet than it does on a roller, so mixing and matching would cause a drastic change in the way the cam opens the valves. And, with mechanical lifters, there is a lash take-up ramp at the opening, which you don't want or need with hydraulic.

That's the theoretical side. From a practical standpoint, you can put a flat-tappet cam and lifters in a roller block, but you'll need to use flat-tappet-type timing set and pushrods, because they are different between the two different cam types. You'll be giving up the advantages of a roller cam, but frankly, for the street, the performance differences are minor. You should, though, since the cam is used, reuse the lifters on exactly the same lobe that they were used on before because of the wear pattern that they have made with each other. For roller lifters, that isn't an issue.

 

yes of course that makes perfect sense.
I don't know why I didn't realize that before

Thx guys