Differences between a roller and non-roller block??

Maybe a dumb question, but I just don't know. What exactly are the differences between roller and non-roller? Are heads interchangeable between? I know the cams are different. What is the advantage of roller over non-roller?

I'm looking at buying an old Boss 302 block which was originally a non-roller, but the guy says it has been machined/adapted to be a roller block, but you could still use it non-roller. Would it be better to use it roller or non-roller, cause I heard a block machined to be a roller you can't use as agressive cam?

roller tapped has rollers on the tappets, less friction

A factory "roller block" has taller lifter bores. Roller lifters are longer than flat tappet lifters.

Vizard has done testing on flat tappet vs roller tappet cams......up to about 270* duration (advertised) the flat tappet performs a little better. Above about 270* the roller cam will out-power the flat tappet in most cases. I have not personally done any dyno or Spintron testing on roller v flat, but I normally listen to what Vizard has to say.

A roller cam can be used in a early non-roller block. Most people opt for the link bar lifters to accomplish this.

You can also drill and tap the block (in the lifter valley) for installation of the factory spider and dogbone setup. But going this route requires a small base circle cam. Many engine builders don't like the small base circle cam for stability reasons. Additonally, cam profiles are limited as well.

You need to factor in the additional cost of converting to the roller cam and decide if it's worth it for you.

Ok so just to be clear, when you use the link bar lifters you do not have to use a small base circle cam, right?

The block I a am looking at buying, the guy says is machined for for roller lifters or flat tappet. Does that mean that I will be forced to use either a small base circle cam or flat tappet cam or could I still use the link bar lifters and a roller cam?

Correct.

If you don't use the factory spider and dogbone setup, there's no need for a small base circle cam.

And if you want to stay with a flat tappet, you should be able to.

I'm assuming the "machining" he's talking about is nothing more than 2 threaded holes in the lifter valley that would hold the spider.

Ok, thanks for your help!

Here's a couple scans of the Vizard article:


http://www.fordmuscle.com/pictures/mstngjoe/Vizard1.jpg

http://www.fordmuscle.com/pictures/mstngjoe/Vizard2.jpg

Thanks again man, I really appreciate it!