Waynebaby Posted March 2, 2016 Report Share Posted March 2, 2016 Hi All, I've attached a picture of one of the cam-followers from my Mk3 GT6. As you can see, there is a small chip on what is an otherwise unblemished follower. The rest of the folIowers and the camshaft are in good condition. This is possibly a daft question, but should I change the damaged follower or is the chip in a region of the follower which the cam lobe does not bear upon? I know that a new follower is relatively cheap, but I'm not keen on inflicting on my engine the "running in" procedure for a new follower (thrash the engine at 2500+ rpm for the first 20 minutes post rebuild to let the cam-lube work it's magic) unless I have to. Wayne Link to comment Share on other sites More sharing options...
dougbgt6 Posted March 2, 2016 Report Share Posted March 2, 2016 I would ask myself how has this happened? Has something wacked it? Has that weakened it? Or Is it made from a dodgy piece of metal in the first place? Is it going to loose more chunks in a spectacular fashion? I'd change it. Link to comment Share on other sites More sharing options...
Waynebaby Posted March 2, 2016 Author Report Share Posted March 2, 2016 Good points Doug - I hadn't thought of it like that. I think I'm probably going to change it and grin and bear the rather brutal start-up regime. Link to comment Share on other sites More sharing options...
dougbgt6 Posted March 2, 2016 Report Share Posted March 2, 2016 I've never run in a cam and followers, what's involved? 2500 rpm doesn't sound like too much? Link to comment Share on other sites More sharing options...
Waynebaby Posted March 2, 2016 Author Report Share Posted March 2, 2016 The cam manufacturers (e.g. Piper) give instructions for the first start-up which include dire warnings about not letting the engine idle at all for at least the first 20 minutes. It might be voodoo engineering, but supposedly the combination of heat, pressure and the high zinc content of the cam-lube has a beneficial effect on the surface finish of the cam-lobe and cam-follower thus maximising longevity. From what I've read, the reason for avoiding tick over during this period is because the cam to follower loading is higher at lower revs and you need to avoid the possibility of breaking down the oil film at this critical period. Wayne Link to comment Share on other sites More sharing options...
Clive Posted March 2, 2016 Report Share Posted March 2, 2016 Wayne is spot on. Cam "breaking in" is incredibly important and can result in poor life expectancy if not followed. All the cam makers give clear instructions on this. Link to comment Share on other sites More sharing options...
JohnD Posted March 2, 2016 Report Share Posted March 2, 2016 Ignore it. That chip has been there since the engine was first built - look at the colour inside the chip and outside. It's clearly not wearing on the bore or the follower either. Put it back and forget it. It's FINE! John Link to comment Share on other sites More sharing options...
Waynebaby Posted March 2, 2016 Author Report Share Posted March 2, 2016 John, Thanks for your advice, but a new follower and a new push rod to go with it are already winging their way from Rimmers. I won't need to fit it for a while though as I'm awaiting the return of my damaged cylinder head, which gives me the time to mull over the two options. Wayne Link to comment Share on other sites More sharing options...
John Bonnett Posted March 2, 2016 Report Share Posted March 2, 2016 Having suffered the results of soft cam followers I would urge you to take John's sound advice. Stick with what you've got. Damage to my engine included the loss of three lobes from the camshaft the swarf from which destroyed the oil pump. There are a lot of iffy cam followers out there so beware!. Link to comment Share on other sites More sharing options...
Waynebaby Posted March 2, 2016 Author Report Share Posted March 2, 2016 Thanks John, you've convinced me to leave the new follower in the bag when it arrives! Link to comment Share on other sites More sharing options...
JohnD Posted March 3, 2016 Report Share Posted March 3, 2016 No probs, Wayne, that's the power of Johns. John Link to comment Share on other sites More sharing options...
Pete Lewis Posted March 3, 2016 Report Share Posted March 3, 2016 I wonder what triumph did on production build test beds, anyone found the process sheets for production engines Ive said before many manufacturese in the day ran them on town gas and often engines back to back so the running turned the other i doubt they would have 'run in' cam followers one things certain its best to never mix new followers old cam or old followers new cam a worn follower with a slight concave base will soon pluck the edge off your new cams. going back to the years of being was it poor or tight? i had a well run Ryton built 78 Talbot Alpine with the 1442 cc a really bag of spanners valve train, I won a cam form the factory but could not afford the followers, so into a pillar drill on some fine wet dry and refaced them on a hard block, , this took a lot off and the tappet screws only just long enough, but despite all it was sold , really nice and quite...it remained quiet like that for over 100,000 miles till scrapped not something i would advise but when you had to get out and get under or starve its surprising what will work well Link to comment Share on other sites More sharing options...
Waynebaby Posted March 3, 2016 Author Report Share Posted March 3, 2016 Pete, Your observation of the inadvisability of mixing new and old components has helped to convince me that I should stick with the original cam-follower, although I imagine that an old cam with a new follower is less likely to cause problems than visa versa. Cheers Wayne Link to comment Share on other sites More sharing options...
Pete Lewis Posted March 3, 2016 Report Share Posted March 3, 2016 both can be a well founded waste of money, the followers are slightly offset to the centre line of the lobe so it makes the follower rotate as its lifted, many when new have a very shallow convex surface, when they wear they start to pluck metal off the leading edge of the lobe, so this starts to take on the shape of the worn follower , and they become a sort of matched pair put a nice new follower on a cam thats now not entirely 'flat' and the old cam minces the new follower so really its stick with what you have or change the lot .....again you pays your money and makes the choice compromise can work ..got that Tee shirt , but utopia is the way to happy motoring. with deep pockets , its all a preference theres no point in spending £££££s and only doing 500 miles a year some guys spend a fortune and never use it , whilst others spend as little as possible a drive many thousands on miles so like to poodle around others thrash the nuts off it . there's a happy in between .....somewhere Pete 1 Link to comment Share on other sites More sharing options...
JohnD Posted March 3, 2016 Report Share Posted March 3, 2016 A concave surface, Pete? I used to believe that a new follower would be slightly convex, you mention concave, but I learnt recently that OE Triumph followers are/were flat when new. Do you know what they should be? John Link to comment Share on other sites More sharing options...
Pete Lewis Posted March 3, 2016 Report Share Posted March 3, 2016 Senior moment in cons caves and vexs , good spot john i cant type on a tablet either !!! Edited the cock up. I Dont know John, maybe the designs of conVEX or flat depends on the amount of offset some marques have varying ideas on all this pete Link to comment Share on other sites More sharing options...
Waynebaby Posted March 4, 2016 Author Report Share Posted March 4, 2016 I thought I'd post some pictures of the new cam-follower (which I've decided not to use) compared to the original. The new follower is, as you'd expect, dimensionally identical to the original but the construction seems different. The business end of the original has a 4mm region which seems to be made of different darker material whereas the new follower is the same colour all over. Do you think the OEM follower is really fabricated from two separate sections or might the darkening be a phosphate coating? Wayne Link to comment Share on other sites More sharing options...
John Bonnett Posted March 4, 2016 Report Share Posted March 4, 2016 I thought I'd post some pictures of the new cam-follower (which I've decided not to use) compared to the original. The new follower is, as you'd expect, dimensionally identical to the original but the construction seems different. The business end of the original has a 4mm region which seems to be made of different darker material whereas the new follower is the same colour all over. Do you think the OEM follower is really fabricated from two separate sections or might the darkening be a phosphate coating? Wayne Case hardening? Link to comment Share on other sites More sharing options...
Waynebaby Posted March 4, 2016 Author Report Share Posted March 4, 2016 I suppose it could be nitriding or something similar John. I also noticed that the new follower has a very small chamfer machined into the tappet face, so I wasn't being accurate when I said it was dimensionally identical to the original. Link to comment Share on other sites More sharing options...
JohnD Posted March 4, 2016 Report Share Posted March 4, 2016 The dark area is just staining from exposure to hot oil and contaminants for years. Look at the top end of your valve stems for the same effect. John Link to comment Share on other sites More sharing options...
Waynebaby Posted March 4, 2016 Author Report Share Posted March 4, 2016 Ah. Of course - it's obvious now you've pointed it out. The dark portion is the part of the tappet that doesn't run in the cam-follower bore. It was the precise delineation of the colour change which fooled me into thinking it was an engineered feature. Wayne Link to comment Share on other sites More sharing options...
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