I have an isky 270 mega hydrolic flat tappet cam (221/221 .465/.465 108 LSA), along with their anti-pump up lifters that came with it as a kit, and they're a bit noisy. Its done this since day one, and I did inspect the entire valvetrain (rockers, lifters, lobes, etc.) when I had the manifold off, and everything looked good. Im pretty sure its the lifters as its relatively quiet when the engine is cold and the oil is thicker. As it warms up, they gradually start ticking. Its not just a few, but ALL of them. It seems to be RPM dependant, too. The tick will come and go as the RPMs are increased. Aside from that, the car runs great otherwise.

Would switching over to some GMPP lifters quiet it down? This cam is basically isky's version of the XE/Magnum cams in that it has a steeper ramping rates. From what Ive heard, the XE cams are inherently noisy due to the quicker ramping rates at mid lift. Would I possibly run into this issue with the GMPPs as well? I have dual coil Comp 986 valve springs, so Im wondering if its an issue with the higher loads causing the lifters to partially bleed down.

Thoughts?

http://www.youtube.com/watch?v=wc2kaqXTh-M

That sort of shows what Im talking about. Ignore the rattling at idle. Thats just the gears in the trans. being kicked around. When I bring the RPMs up, theres intermittent valve clatter that comes and goes as the RPMs change.

What are you adjusting them to?

I know a lot of people say 1/2 turn down from zero (used to say it myself), but I've found 1 turn down, which is the factory setting, to be a lot quieter. No effect on performance.

It's usually not a good idea to put new lifters on an old cam. You might get away with it, but you risk wiping out your cam.

I adjusted them to a half-turn, using the standard I/E adjustment method. One full turn probably couldn't hurt. It will be that much less lash that can open up during operation.

I agree that its punishing on a cam to be forced to re-establish its wear pattern. Still slightly tempting to try it, though. The GMPP lifters are the quietest lifters out of all the aftermarket ones Ive used, although it was on a milder grind.

Yep, you where right about the factory setting vs. the usual 1/2 turn. Much quieter now. Engine runs a lot different, too. As I sort of suspected, the lifters where acting like rhoades lifters before reducing the duration and lift at the valve. With the valves adjusted properly, the vacuum dropped down into the single digits of mercury and the engine lopes more like it should. Also runs much smoother and has more power. Still some noise from the roller rockers but at least there is no more ticking.