MUSHROOM LIFTER CAM

I know that these were the hot set up for NASCAR, MP and Pro Stock. Other that turning the engine over for installation anything else to be aware of? These lifters still being made? Thanks

Check the block for lifter clearance at full lift, some blocks need clearance ground . And a cam button is recommended

The old MP cams seemed to work fine in the old day.

But a now a regular mech cam has as much lift/duration as the old mushroom cams

I never had to turn the engine over to install them. As a matter of fact 35 years ago I installed a Mopar 695 lift mushroom tappet with the engine in the car. I made up a rounded U-shaped piece of thin aluminium and slid it in the cam tunnel. Them starting with the rear lifters I slid them to the rear of the block and fished then up into the lifter bores with my fingers and a small screwdriver. As I got each one up in the bore I held them up into place with my Mothers cloth pins, slid the cam in, and removed the cloth pins. My 69 dart ran 10.20's with that cam, stock cam and rods, and 906 heads back when 10.20's were pretty dog-gone quick. Pretty cheap way to go fast.

I think I'd be inclined to stick with using more "commonly available" parts.

The question that comes to mind is, are you trying to achieve something that you don't feel you could do with a traditional flat tappet cam?
Perhaps some rules in place where roller cams aren't allowed?

Are mushroom lifters still readily available? What kind of $$$$ are they?

Is anyone still making the lifters?

I always thought the lifter bores needed to be spot faced on the bottom for mushroom tappets?

I just found 2 cam kits on the shelf. I had run a 273 in modified production and I think these came with the car.

My 440 block didn't but I tend to spend a few days deburing and grinding on my engine blocks before assembly and like I said mine was only around 695 or so lift

I've put my 451 together with that cam and hand-ported iron heads. My block did not need any machining. I've read that if you float the valves you could be in big trouble because the lifter will smack the underside of the lifter bore area and could break something if there is not a smooth back-spotfaced area for it to hit.

I'd be ecstatic with 10's of any kind! As I posted elsewhere this is a used set and I'm getting more nervous as startup time approaches. I think I'll pull it out and buy a brand new cam/lifters if I can find the B/RB package (P3690588).



More lift with a given duration compared to most solid cams. Although more modern grinds with higher lift rates are available nowadays, I would be less concerned about lifter wear on a 1.00" mushroom compared to the standard .904" diameter.

I honestly think it was a great idea at the time so many years ago. If I had one laying here I wouldn't be afraid to use it. Heck I'm still holding on to a few of my old 286 duration @.050 750 lift roller cams that we stepped up to after running that cam. They didn't require the CRAZY spring pressure that we run on cams now and our parts lasted forever.

The maximum lift per degree of rotation is a function of tappet diameter. A .970" (a common size) can be bigger & faster than a .904".
Now obsolete, only useful where rules prohibit a roller.

How old is it?
.970" is the tappet diameter of the Ford Model T.

They do need facing... I ran one years ago on a
destroked 383
EDIT
and its way easier to load the cam and lifters in
it with it upside down

My 1937 designed continental engine has mushroom lifters, they redesigned the cams in the late 40's and required the lifters to be changed. Steel cam, cast steel lifter, cast steel cam, steel lifters. screw it up and it wipes the lobes. Tim

I didn't mean tryng to achieve mechanically, I was asking if there was a performance goal in mind that wouldn't be able to be reached without going to a mushroom style cam.

Depends on how much casting flash there is along the underside of the lifter bore area. Mine and most other posters over the years (here on Moparts and other forums) did not require any block machining...

Yep, it's easier to install with the block upside down and the crank removed. A bit tricky with the engine in the car though Somebody else on here did the same "half-pipe" trick inserted the length of the cam tunnel, but he used a magnet on a flexible stick that made it easier to drag the lifters to the proper bore.

Don't forget it's quite a bit cheaper than buying a roller cam and a good set of roller lifters, too. My 1982 DC books claim "very close to roller cam performance at about half the cost".

I'm set up for about 140# on the seat and 430# at full lift (.654 gross with the 1.5 rockers). That shouldn't be hard on parts and I'm not going to turn 7000+ anyway.

Ah. I see now... guess that will be up to the original poster

And again it's a significant cost saver over a roller and not hard on parts with reasonable spring pressures, if you're willing to put up with the inconvenience of the mushrooms. Someday I'll have it going and report back!

How much cheaper than a roller is it really, if someone wanted to buy new parts today?

I don't think mushroom lifters for a mopar are all that common anymore, but I could be wrong.

In addition to that, there aren't nearly as many profiles available to choose from, and even less(if any) that have the benefit of Spintron developement.

hi ,

my 98 cummins has mushroom lifters from the factory !

I don't think mushroom lifters for a mopar

If you bush the tappet bores you can use any mushroom.

BTW: an extreme example of "larger lobe contact surface with the same tappet body diameter": 1941-52 Harley-Davidson WR. Tappet is .731" OD, the "ice skate" (foot) is over an inch; note the asymmetry.

Assuming that the sliding forces can be dealt with, the maximum velocity of a flat tappet (which partially determines how much valve-open area you can “fit” into a specified cam duration) is roughly proportionate to the tappet’s contact surface length (not its area).
The math:
VM = (tappet diameter - .040”) ÷ 114.6 (.040” is a safety margin to prevent edge contact)
Solving for common tappet diameters:
.842" = .00700" lift per degree (GM)
.875" = .00729" lift per degree (Ford)
.904" = .00754" lift per degree (Chrysler, AMC)
.921" = .00769" lift per degree (Olds diesel)
.970" = .00812" lift per degree (mushroom)
.990" = .00829" lift per degree (stock GMC L6)
1.220" = .0103" lift per degree (VW Type I 30mm replacement)

A .970" mushroom is about 7.7% greater than the Chrysler .904".

Important: a larger tappet has NO EFFECT on valve motion, it merely makes it possible to design into a new lobe.

Well, for those of us that bent pushrods & popped a lifter = zero oil pressure, mushroom tappet, that don't happen, #2- at the time, was roller cam performance at mechanical cam price. Ran mini express for 5 years .654 lift 316° dur. Sweet cam

Back then I ran a .750 lift... that was about the
biggest I could go back in those days