All About Cams and Special Head Bolts

[Bernica]

Kind of an interesting article regarding cams and special head bolts. I learned some things here about the bolts that I certainly didn't know!

What to Know About Lifter Reliability and Mysterious Bolt Heads

[Gaz64]

I've seen the special bolts before, but I have never seen a dished lifter for a flat tappet cam.

That would fail within 5 seconds of startup.

I don't know of any flat tappet cam that does not have lifter rotation.

[Jac Mac]

Originally Posted by Gaz64

I've seen the special bolts before, but I have never seen a dished lifter for a flat tappet cam.

That would fail within 5 seconds of startup.

I don't know of any flat tappet cam that does not have lifter rotation.

Landrover, the old 4 cyl model, but they have a curved bronze sled rather than a round lifter, Nissan L series, Ford Pinto & Cortina SOHC have curved arm running directly on cam.

FWIW the article was poor, did not mention dedicated lifter/tappet oiling or grooved lifter bores which have been the real breakthrough in lifter reliability in recent years

[Gaz64]

Originally Posted by Jac Mac

Landrover, the old 4 cyl model, but they have a curved bronze sled rather than a round lifter, Nissan L series, Ford Pinto & Cortina SOHC have curved arm running directly on cam.

FWIW the article was poor, did not mention dedicated lifter/tappet oiling or grooved lifter bores which have been the real breakthrough in lifter reliability in recent years

I'm talking about flat tappet cams operating a lifter or bucket (shim or hydraulic).

Flat tappet cams for direct rocker arm contact are ground differently.

Flat tappet cams for lifter rotation are ground with a 1-3 degree taper, the lobes are offset to the centreline of the lifter, and the base of the lifter is ground with about a 72" radius. All of that promotes rotation, if rotation stops, goodbye cam lobe.

Gary