Roller cam conversion or new engine

[PlayingWithTBI]

As you up the psi it over comes the ability of the lifter to stay pumped up.

I'm confused here, when the valves are closing, the springs are pushing them closed with very little pressure exerted on the lifters. That's when they load up again so, on the next stroke, they pump oil up through the push rod. When you set lifter preload, you're setting them at partial compression to facilitate the proper pumping of the hydraulic lifter. The seat pressure doesn't change with the same valve springs whether you have .400" or .600" lift. You just need more pressure at max lift at higher RPMs so, the valves don't float when going over the top of the cam lobe.

Hydraulic lifters are pumps, they need to collapse and pump up or, no to hardly any oil will reach the top end. Solid lifter lash is set to act like hydraulic ones so they can pump oil up to the top too, thus the tappet noise from them. It's not how much lift you have, it's how many revs you run. I can run .540" lift @ over 5400 RPM with these springs and keep a fairly low seat pressure.

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[shovelbill]

For us, it's setting stack height and proper seat pressure and preloading the lifters. On high-performance builds, say with .650" and high rpms, some of us use limiters to have a bit better control of float. We also have horrific pushrod to lifter geometry that can cause side loading in the lifter bores. I've never had a lifter collapse if it wasn't faulty and that's very rare.

https://larrysmcymachineinc.square.site/

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[1989GMCSIERRA]

I wouldnt hold your breath waiting for your cam to go bad. I have a1989 GMC that’s got 396,000 miles on original TBI 350 v8 and it’s never been touched Internally. The most I ever did was replace a alternator and a waterpump. Other than a oil and filter changes or a tune up I’ve never touched any internal part of the engine. It’s finally starting to burn some oil. But almost 400,000 miles later…

as firvthe coolant loss it’s probably a intake manifold leak.

 

[Pro439]

It’s just kinda of a conscious by guys that build a lot of engines. Once you get over 400 psi open psi that you can overcome the oils ability to keep the lifter pumped up and when you set the lash at 0 it is with the lifter pumped up. Crower likes their lifters set to 0 + .020 - .050 When you get that much cam you are going to be running 6500 + rpm’s and over 450 hp. To my knowledge there is only 2 companies making hydraulic lifters nowadays. Same with rods and cranks. Not to many here in the states doing there own stuff anymore