Pigsty Racing

[Charles P]

I'd shy away from "flat" as a target and look to re-radius to a much broader radius. Whether it's 3/4 or a little larger is a matter of choice but I'm with Dave here. It's the single best improvement to breathing, whatever the rest of the engine

Charles

[Speedex750]

I've just had a road cam done by Paul Bonewell, in conversation with him he said that 0.8" is the maximum radius that should be used otherwise the follower digs into the flank causing very high wear. I do know of an engine that does have completely flat followers, it doesn't do many miles per year and is still going, but I'm not recommending this.

Expanding the topic slightly, I also found out the hard way that re-profiled cams may need the end of the follower narrowing - tapering in the flat sides either side of the radius. I've seen followers like this before but only with the current engine and cam have I ended up with them riding on the unground part of the shank giving very odd timing and lift figures. The tappets seem to be slightly offset to the cam lobes and if the re-ground area is quite narrow the follower can ride on the shank of the camshaft. Beware!

Dave

[Ruairidh Dunford]

I also found out the hard way that re-profiled cams may need the end of the follower narrowing - tapering in the flat sides either side of the radius.

Absolutely correct and oft overlooked. Tim Myall alerted me to this many years ago, well worth bringing up.

[Nick Lettington]

I dug out a set of cam followers. One of the 8 is not countersunk for the lock nut. It came in a set of 8 s/h ones from a cherished supplier. Being English, didn't complain... Any reason why it isn't countersunk? 

Dave... Can you countersink it? If not I may dig deeper and see if I have another...

[Austin in the Shed]

No I can't countersink it but there are plenty of them about,I can find a spare if you can't.
Another thing,or two to mention is to check they are not split due to over tightening and the bronze guide will likely need shortening, (1/8" or so) even on just reprofiled followers or the locknut could rest on it(ie the follower doesn't touch the cam)
Reduce length on guide on tappet chest end.

[JonE]

I'd shy away from "flat" as a target and look to re-radius to a much broader radius. Whether it's 3/4 or a little larger is a matter of choice but I'm with Dave here. It's the single best improvement to breathing, whatever the rest of the engine

Charles

I'd be interested to know whether radiusing the followers would be a sensible adoption for even a bog standard LC engine, when renovating/maintaining? I'm conscious of Ruairidh's suggestion of any form of bhp upgrade putting extra stress onto the system which could affect longevity. (i.e. different cyclinder heads or taking metal off the cylinder head) but where is the line drawn? Would it be sensible, for instance, on engine that has the later crank rather than the spindly early one? I was also wondering different thicknesses of head gasket would just give that bit of extra help for little effort. [I've got an early engine already sporting a Ruby carb and manifold... presumably as it was what was lying around]

[Zetomagneto]

Just got my reprofiled follwers back from Dave, nice job, well pleasd.
Thanks Dave

[Nick Lettington]

Funilly enough, so did I. First class job. Thanks Dave.