Hughes cam?

The benefit of .904 lobes for flat tappet cams is you can decrease seat to seat timing and keep the same or quicker @ .050 numbers.

Thats a big deal because let‘s say you have two cams, both 230 @ .050 and one is 265 off the seat and the other is 258 off the seat. The slower lobe off the seat will have less vacuum at idle and clearly valve speed is lower.

On top of that, the 265 off the seat lobe is 131 degrees @ .200 while the 258 off the seat is .150 degrees @ .200!!!

Not only is the .904 lobe later opening by 7 degrees, it’s caught the .842 lobe to .050, but its 19 (NINETEEN) degrees bigger at .200 lift.

Thats HUGE area under the curve and it makes power. And you’ll have a cleaner, smoother idle with more vacuum.

Thats why using .904 lobes is always a better choice when you can do it.

It matters with roller lobes too. You can only get a roller wheel of .750 diameter with an .842 lifter. That’s a small wheel AND because the unit loading is higher and because the axle of the roller is a smaller diameter you are limited to about 280-300 pounds of spring load on the seat. That’s not much.

On the .904 lifter, you can get an .815 diameter wheel, with a larger axle and that means you can get to about 350-360 pounds of spring load on the seat and have the same or better reliability as the .842 lifter.

So lifter diameter matters with both flat tappet and roller lifters.

Its too bad Chrysler guys still don’t take advantage of the .904 lifter more often. I guess it’s because it’s too easy to get on the web and order an off the shelf Comp or Lunati or whoever else stocks cams than it is to pick up the phone and get a cam ground for .904 lobes.

The cost is the same whether you get a cam with .842 or .904 lobes so that’s not a reason not to use .904 lobes either.

Any cam regrinder, any of them do not make their own masters. They copy lobes from a cam. So the only way they’d have lobes for .904 lifters is if they’ve already copied a lobe from a cam that was ground for .904 lobes.

I know for a fact that Oregon Cams does have .904 lobes. I’ve seen some of them and I know he has had to weld a regrind several .904 lobe cams because we couldn’t get the cam replaced quick enough.

I don’t recall what lobes those were, but I’m sure there are more of them than those two.

And yes, they weld up cast iron cores and then regrind them. Some cores are nonexistent.