OK I've always been told you cant use roller lifters on a regular cam......my question is why not? I know roller cams use more aggressive ramp rates so they need heavier springs but if using reg cam couldn't you use reg rate springs that match cam? I also know solid cams are different because the face of the lifters are different and would gouge the cam or lifters depending but roller lifter have - well a rolling wheel so that shouldn't be an issue. Can someone please explain in "idiot proof talk" for me please. Thanks. Robb
The harder steel roller will eat the cam lobes, same reason you can't use a cast iron dist gear on roller cam...
Flat tappet cam lobes are not ground flat. The lobes are tapered to force the lifters to rotate in the bores as they are run. Roller cam lobes are machined flat since the lifters don't rotate. You cannot use roller lifters on a flat tappet cam. You cannot use flat tappet lifters on a roller cam.
ok so basicly the roller lifters are made from harder steel(billet im guessing) to match the roller cams and being that flat tappet cams have a taper the roller lifters would gouge the cam. do i have it right?
In a nut shell, yup... I know back in the '60s Ford said the flat tappet lifters were tapered .002, never heard about tapered cam lobes... Would no doubt be easier to mfg lifters than grind cams with taper... Still even if lobes were(are?) flat, the metallurgy is incompatible... I've seen the result of using a iron gear dist in a roller 5.0 motor, it isn't pretty...
Not to mention the lobe profile itself is vastly different. Just a look at both lobes (roller and flat) will tell you the roller lifters would spend a LOT of time off the lobe once the lobe's peak has passed
Thanks for the correction!!! I did not know all of this! I deleted my post to prevent misinformation from being disseminated.
Now that you mention that, I'm not 100% sure that the lobes are tapered versus the flat tappet bases being crowned. I may need to dig my auto tech books out. Either way, something is not "flat" allowing the flat tappet lifters to rotate.
The flat tappet lifter bottoms are given a convex shape (very slightly domed) to allow the lobe to rotate it in the lifter bore. And the bores are not centered over the lobe, the lifter actually rides one side of the lobe. Poorly machined lifters are to blame for many of the cam failures of the past 10-15 years
If you're buying new flat tappet lifters, do a close visual inspection on them before using them, Pay close attention to the bottoms, if something doesn't look right, don't use em. Then when installing them in their bores, make certain they will rotated freely in the bore. If they do not, do not use that lifter or lifters. No rotation = a wiped cam lobe during the break in period.............guaranteed.
Some roller cams are designed to be used with cast iron distributor gears. They're generally SADI cores with a different heat treat on the gear.
Also if you are going to run a solid cam,run diesel oil such as Rotella or Delvac made by Mobil to have plenty of ZDDP in it for cam wear,I prefer Delvac myself as I always had the best luck w/ it in my 18 wheeler.
