Well, i've flattened another hydraulic lifter. I don't know what it is about my engine...or maybe just cheap tappets? Anyhow, i've got some new heads and a new cam to stick in it, so naturally i will be putting new tappets in. My cam is an Isky 280H Mega Cam (chosen due to a certain Hot Rod magazine article). It has a .517 lift, 232 @ .050 duration, and a 108 ls. My heads are trick flow twisted wedge, and they are going on a rebuilt 302 with flat top pistons. It is my daily driver. My question is what kind of tappets to use? I'm not very informed on tappets. Can i use a solid tappet on this cam, or does the cam have to be specifically designed for solid lifters? What about the "anti pump-up" lifters? I will be working in the higher rpms now, and i have a high volume oil pump...both of which i believe to be the cause for the demise of several of my current lifters. I guess i'm just not sure if i need to run a different lifter or if i just got some cheap ones with my last camshaft (Crane cam, came with lifters). I'm not sure which is worse...the work of pulling the manifold off just to replace one lifter, or the valve tick! P.S.--been playing with DesktopDyno, it seems to like the solid lifters (which includes the "anti pump-up" hydraulics, i assume) about 20hp more than the hydraulics, so that is the other reason for my asking. Thanks in advance!
Lifters Solids are the best way to go, hydraulics work ok but for serious rpms, they are limited. Of course rollers are even better but each type must be used on a camshaft designed for them for several reasons. Ran hyd's for years at 5500 to 6000rpm motors with no problems. Have you checked your spring pressures and are they compatable with the cam you have? Also pushrod geometry and coil bind on the springs. Just a few things I found in some engines that caused similiar problems as yours. I like Crane or Comp lifters for racing but have used TRW's over the counter ones with good results in street applications. With much of our parts now being mfgd. overseas, who knows what quality standards are being followed anymore. Sad for those in America out of work too.
So i can't just stick a solid lifter on this hydraulic cam. Maybe i will see about the "anti pump-up" hydraulics, they are supposed to be like a solid lifter. I haven't checked the spring pressure requirements for the new cam, but the old cam had springs that were right in its range. My springs are 110# closed. Pushrod geometry i never checked on the old heads, but will be sure to do on the new ones....but i was very careful not to reach coil bind. One of the guys at the local performance shops was telling me that the main manufacturer of lifters had gone out of business--guess that means i'll be buying my lifters from China now. Sad to see it happen.... Thanks old guy!
There used to be an outfit called "Rhodes lifters "that I always thought gave impressive performance . Maybe some of the other racers on this forum can tell you if the "anti pump up " lifters that cam manufacturers are using are the same . If they are not then you may want to check them out . If they are still in bussiness . The basic premise was a low rpm the lifters would reduce your cam lift and smooth out idle characteristics . At higher rpm starting around 1500 and ending around 3500 they would have less movement and gain valve lift . So there were two benefits to them , one was reduced lift ( duration for that matter ), at idle and easier on the cam and lifters ,at idle, because of less spring pressure .
no, you can't use solid tappets on a cam designed for hydraulic tappets. The reason for that is solid cams have what's called a "clearance ramp" built into the lobe profile. Basically it takes up the clearance between the rocker and the valve stem slowly as not to cause a whole lot of wear and stress. Run a hydraulic tappet on a solid cam and you'll find yourself with toasted lobes and tappets in short order. Also, the lobes on flat-tappet cams are not perfectly flat. They are ground at a slight angle. This combined with the fact that the tappet face is ground at a slight convex face causes the lifter to spin in its bore and keep it wearing evenly. Solid and hydraulic cams have different angles ground into them. Rollers are similar. You can't run a hydraulic roller lifter on a solid roller cam because of the clearance ramp, or lash ramp as some companies call it. Pretty much the same as a flat-tappet cam. Normally, the lobe design of a solid roller is so aggressive that a hydraulic roller lifter will not pump up and parts start to break. You cant run solid roller lifters on a hydraulic roller cam because the lash causes constant pounding on the lobe (no clearnace ramp on hyd. cams), thus eventually valvetrain failure. And a lot of you know how much fun dropped valves are.
That's the answer i was looking for! Very interesting too. I went ahead and ordered some "anti pump-up" lifters from Crane. They are supposedly the same design as a hydraulic lifter except that they are set to zero lash and do not "pump up" (thus causing the valves to hang open) at the higher RPMs. They have a heavier clip keeping the internals inside the lifter so that you can set them at zero lash. I figured that for an extra $10, and having spent so much on my combo already, i might as well....
When in doubt, consult your cam mfg as they are the ones offering the warranty anyway. When I installed a comp cam, I used their lifters as well. I have run both the Rhoads and the Crane lifters that offer variable rates. Be prepared, they make more noise than regular hydraulics. They also are harder to set with adjustable valve trains.
