MagnaVelocity SBM mushroom Direct Connection camshaft?

[Bighead440]

Just curious if anyone here has ever run or had experience with the only (to my knowledge) Direct Connection mushroom cam offered for small block engines? It's specs are pretty formidable, 324 duration with .633" lift (1.5 rockers) and a 110*LSA. The Mopar Performance books never mention it, but the old DC bulletins list it for NASCAR Grand National use on long tracks and other 355" Kit Car applications. I want to build a 4" crank SB with high compression and W2 heads for a nostalgia build in a really light chassis, possibly manual trans, and I think this might fit the build. I have a new set with lifters, and means to bronze bush the lifter bores, or the tube/peen kit to block the galleys. Any info or thoughts?

 

[Lefty71]

Any info or thoughts?

Don't know, but really curious to hear what people with direct experience have to say.
I always thought that mushroom lifters and the cams that used them were old tech....they were a stepping stone to the next technology.... which is high quality mechanical roller lifters and the aggressive profile cams that can make best use of them.... this passes up the usefulness and trouble associated with a mushroom setup. Again, just my thoughts, I'm curious to hear what others say as well.

 

[493 Mike]

Is spot facing the bottom of the lifter bores required for "mushroom" clearance? Seems like a gamble to use. I agree with Lefty71 though with modern roller lifter grinds and newer technology, more gains to be had.
Mike

 

[wagonman]

I think for a Nostalgia build to say you have a mushroom cam would be Cool. The machine work $$ to use it maybe not so Cool. Would be a screamer for sure. For Me it would be Wall Art.

 

[Bighead440]

Is spot facing the bottom of the lifter bores required for "mushroom" clearance? Seems like a gamble to use. I agree with Lefty71 though with modern roller lifter grinds and newer technology, more gains to be had.
Mike

Clearance is not a problem as much as having a machined (flat) surface for the lifter to contact IF the valves float (missed shift/driveline break, etc.). I do have the cutters, and a friend has agreed to lathe me up a block bushing to pilot the tooling with.

 

[66Satellite47]

I'm not a small block guy, but my favorite cam in my big blocks is still my mushroom cam that was not as big as the Mopar version. Not sure what machine work is needed on the small block. In my BB nothing was needed like the mags said. In my BB the mushroom was about equal in power to the best of my solid roller cams. My bet is with good heads the small block would love it. IIRC the mushrooms were designed to meet the NASCAR Grand National rules, no roller cams. Good luck.

 

[Rusty34]

I'm not a small block guy, but my favorite cam in my big blocks is still my mushroom cam that was not as big as the Mopar version. Not sure what machine work is needed on the small block. In my BB nothing was needed like the mags said. In my BB the mushroom was about equal in power to the best of my solid roller cams. My bet is with good heads the small block would love it. IIRC the mushrooms were designed to meet the NASCAR Grand National rules, no roller cams. Good luck.

You are correct. I am a retired NASCAR engine builder, 28 years building engines for Hendrick Motorsports. I was hired in 1993 by Randy Dorton to become HMS Engines 4th engine builder. I got my start in the late seventies helping build engines for a couple of the smaller Chrysler teams. At that time all NASCAR Winston Cup Grand National Teams were just a few years in trying to make the smaller 357 engines work after NASCAR banned Hemi's and Big Blocks. We used the mushroom tappet cams because at that time roller cams were not permitted mainly because good roller lifters which could endure 500 miles of 200mph racing at high RPM and high valve spring loads without breaking could not be found. Mushroom cams allowed for a more aggressive profile to be run over a conventional flat tappet grind. The undersides of the lifter bores need to be spot-faced for mushroom tappets. It is absolutely critical that you mock up a dry assembly of cam and tappets in the block to rotate the cam and check for clearance. You must map out adjacent lobe interference with respect to the installed camshaft running position. This will tell you where to position the cam. You adjust position by machining parts to either move the cam forward or backward to get clearance at the closest interference point. The relationship of all cam lobes to all lifter bore centerlines varies due to allowance of production tolerance variations. Every block and every cam will have different clearance numbers. We used to chart them in each engine's build book.

 

[66Satellite47]

IIRC I switched to the mushroom cam in my 446 BB in 1978. I used the General Kinetics grind with 6.35/6.45 lift with 276/[email protected] with 1.5 rockers, witch as little less lift than the Mopar version. My GK mushroom made a bunch more power than the 720/274 Comp roller I tried.