Can this be done?

Helping a friend with a non-Mopar

Sbc stuff. He has new mushroom tappets but his cam it's a non- mushroom -flat tappet cam

I'm assuming this can be done but it's not the most ideal ???

All parts are new.

On a Mopar it won't work. The 1.00" lifter foot will hit the wider adjacent lobes designed to clear a .904" lifter.

Don't know anything about SBC's but in general, even if they fit it would be a waste of time to use mushroom lifters (which have to remove and install from underneath) with a solid cam that does not require the larger lifter.

I wouldn't attempt it, even on a Chevy SB

I'm not seeing a reason why you would do this.

If you aren't running a lobe profile that requires a larger than stock lifter diameter ie roller type lift, what's the point?

Kevin

So the lobe in the mushroom cam love is typically narrower?(for a Mopar)

I believe he wants to use these parts because he has them but also clings to the idea that the larger lifter alone will increase performance. Not sure that's really the case but I could see the mushroom lifter getting on cam sooner.

I'll measure the lobe width and look for interference.

Does anyone know what tool is typically used to spot face the bottom side of the lifter bore incase he really wants to go through with it ?


Thanks for the replies.

It's no different than using a .904 lifter on a lobe designed for an .842 lifter.

With the MR lifter their will be ZERO gain unless the lobe was designed to use the MR lifter.

That said, as long as there is room between the lobes so one neighbor lobe doesn't lift its neighbor when it's not wanting to be lifted then you can use them. He will see ZERO performance.

Also, you have to keep cam thrust to .005 at most and even less, all the way down to .003 would be better.


You can buy a back spot facer from any big tool house. Try MSC or similar.

With as cheap as a set of SBC solid lifters are...... I really see no up-side to this situation.

Yes, the lobes on my cam (P3690588 Mini-Express) are visibly narrower than a .904 flat-tappet. Even so, there is not much lateral clearance from the lifter foot to adjacent lobe sides.

On a Mopar BB it is not necessary to back-spotface the bottom of the lifter bores, despite what the Direct Connection "bible" said 35 years ago. Some recommend it to give the mushroom a flat place to hit if it floats off the lobe. I did not grind on my 400 block and every lifter has miles of clearance between max lift and contacting the block. I've never been inside a SBC so no idea what the underside of the lifter area looks like.

As everyone is saying, there is no reason to do this. It may not even fit, mushroom lifters are more trouble to remove and install, and it will NOT increase power or reliability.

Thanks for all the insight. It's not my ride but I'll pass along what I've learned.
Hopefully I can save some time.