Hydraulic is just easier to deal with, but solid will make a bit more power. It's a trade off in that regard. Also with solid, the harder you run it and the more often, the more adjusting you need to do to keep the lash right.

 

What about solid rollers then......or are all solid lifters rollers?

 

no there are traditional flst tappet solid asnd the newer roller style rollers are heavy are have a tendacy to float at higher rpms but the solid roller helps to aleviate some of this

 

I don't think anyone exactly answered your question:
Hyd lifters have a tendency to bleed down at high rpm (they can't fill with oil as fast) and as a result, the valve lift goes to sh*t.

Wow what a brain fart I had! Thanks to MY77 for clearing it up. Here's a web link to Crane cams that has some more info of hyd lifters and cams:
http://www.cranecams.com/?show=faq&id=3

 

actually, hyd. lifters pump up in high rpm situations and can actually pop the clips out of the top and completely come apart. its NOT being able to pump down (due to high rpm and oil pressure) that causes the problem.

 

Hyd are also heavier, so they need more valve spring pressure to be controlled at higher rpm. Then the higher spring pressure tries to compress the lifter more etc. It's a rather nasty cycle. Hyd do tend to pump at at high rpm though. Solid rollers will rev like a ****** though, you have the right spring pressure with a solid roller cam, and you can turn 9-10,000rpm. Hyd roller is the best for street use in terms of power, reliability and ease of maintenence. Solid rollers work nice on the street if you don't mind adjusting valve lash every so often. Flat tappets work too, but modern oils are starting to make it a pia to deal with them.

 

solid rollers on the street are cool...i want one, but i would have to get new valve springs and alot of engine builders are using beehive valve springs so seated pressures are much lower...

also, if you are going to build a solid flat tappet, i would recommend trying to borrow "break in" rocker arms with a much lower ratio..like 1.3:1 so alot of initial stress during crucial break in periods.

 

You don't necessarily have to adjust solids all the time. I doubt anyone would put them on a daily driver, or any car that really get a lot of miles put on. Adjusting every 10k miles or so would be about right based on old data. Use of modern oils (especially high-end synthetics) would extend the adjustment intervals.

 

I had to adjust them pretty often at first, but less frequently as I got more miles on the engine. FWIW, I had solid roller lifters in a 351W in an '85 GT vert that saw 80 miles commuting a day ... back when fuel was a lot cheaper!

 

Yeah, when you're getting things seats, there would be more adjusting. I wouldn't mind having a DD that needed solids, butt it's hard to swallow that 10mpg bill.[&:]