cam followers

[edboy]

hello, has anyone tried modifying their cam followers to increase lubrication. triumph have a tiny bore hole through the centre of the cam follower but what cutting tool is used ? as they are hard stellite and a normal drill is too thin and easy to snap. i might try welding up the drain from the camshaft tunnel so increasing oil there but am interested in any other improvements for lubrication other enthusiasts may have tried to prevent cam and follower wear.

[Greybeard]

Soon after I left school I worked at an engineering shop that used spark erosion to bore tiny holes through tungsten carbide billets.

[Briz]

A10 ones are chilled iron, not stellited. But reconditioned ones usually are.
You're not going to be drilling thru them either way. Triumph ones would be done during the manufacturing process before treatment.
Laser drilling would do it, but without a pressure feed it wont help much.
Best thing is to add some good flat-tappet-cam oil additive to the oil. Comp Cams do some, among others. Replaces the ZDDP lacking in modern oils.

BTW: what drain in the cam tunnel? There shouldn't be one.

[bsa-bill]

Yes - just a guess edboy's referring to the PRV's escape route through the timing side case ending up in the cam trough, or he has a genuine drain same as I had due to the afore mention oil route being minus it's endplug so it found a new route to the outside world via the crankcase joint - took some finding though

[trevinoz]

Funny thing about those plugs, Bill.
Some cases have them and some don't. I don't know whether they all had them ex factory.
Trev.

[duTch]

 Unless I've missed something, those holes and the ones at the front are the only usual way for oil (and pressure) to drain from rocker box- could have a flood if you block them.
  Briz, maybe your custom alloy race barrels don't have them...?
 I have four sets (3 stuffed ) and they do have.... in front of the tunnel in photo

 Bill- am not sure where you mean..?

[Briz]

Ah! you mean the pushrod tunnel, not the cam tunnel (trough).
Yeah I did drill those drain holes in the ally barrels.
Blocking them would supply oil to such holes, but it will cause oil retention in the top end. The pushrod tunnel would fill up & it'd puddle in the back of the rocker box. Possible breathing problems and if inlet guides aren't in top condition, oil being sucked thru into the inlet tract.
Tiny holes in the faces of the followers wont allow enough drainback.
I did consider putting the holes behind the tappet block rather than in front so the oil would go into the cam trough, but there isn't really enough room.
As long as the cam trough is full of oil, which it should be most of the time, then there should be adequate lubrication.
Cam & follower wear is always a bit of a problem on A10s. The cams & followers are too soft. stellited followers and nitrided cams would fare much better, but radiused followers that cant rotate are not the best design.

[bsa-bill]

Sorry guys maybe didn't explain very well, I was referring to the hole that can be seen in the rear of the camshaft through, it goes through to the oil gallery at the rear of the case,
of course depending on the feed to this gallery (up the timing side, squirts oil onto the idler gear and elswhere) the hole will also drain the camshaft through when the engine stops or the PRV is closed for instance.
Camshaft should in theory sit in oil but guess a lot gets chucked out by it.
Should say this was just a guess as to what edboy is referring to

Trev I blocked the end of mine with a bit cut from one of my better half's knitting needles - haven't had a woolly pully made since

[edboy]

thanks for very interesting replys. i bought a second hand a10 camshaft off some chap at kempton park autojumble a few years ago who mentioned the lubrication mod for cams recommended by srm.[ come here sucker. listen to my sales talk?]  i just nodded in agreement as i didnt want to show total ignorance but i think it meant blocking any drain for the oil and somehow increasing the height of the cam tunnel. bsa bill seems to be barking up the right tree as oil drains out the dreaded wear at startup could be the main cause of those thrupenny bits . i didnt know new cam followers were chilled iron rather than stellite pads. norton  twins have a drain through the front of the tappet which i might try, hence they are handed. interestingly i have an old a10 cam follower with a centre hole that has worn on the flanks but not the middle so i think that mod may help follower wear.i will take a photo today and try an upload.  i am up for experimenting.

[shuswapkev]

a bit off the thread but hardened steel can be drilled quite easily (and cheap) by sharpening up a carbide masonry bit
I drilled the primary chain shoe to rivet some nylon type wear material on...  the only problem with the masonry bits is the drill dia is a bit of a lucky dip..
 sharpened up the first one and neatly drilled a 3/8 hole thru a file...no fuss at all  $2.00 drill bit.....and well used before...

[Rocket Racer]

There is an article written by Cake Street Classics about a mod to cam followers they do, have a copy somewhere...

[KiwiGF]

one mod i have heard of is to make a groove down the side of the followers and block the followers drain hole so oil goes to the cam instead , down the grooves.

the groove can be made by careful use of an angle grinder fitted with a thin cutting disc.

[edboy]

hi kiwi, i m going to try the norton way which is a chamfered edge towards the opening flank of the camshaft. why block off the oil holes in the barrels as they look like they are for overflow only and with an opening through each camfollower the oil would drain through those first . this mod i hope would  keep the camshaft trougth full always and i m going to try the mod with those cams and followers which we are usually in two mind about refitting. so nothing lost. however still on the subject of camfollowers ; why are bsa followers still radiused when norton went to flat followers to improve performance? has anyone experiamented with that idea?

[trevinoz]

Maybe the engine designer, one Mr. Hopwood, knew what he was doing, Ed.
He also designed the Norton twin engine.

Trev.

[Briz]

The advantage of flat tappets is that they can be made to rotate and even out wear.
The Norton ones dont rotate. No benefit there.