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Paul Coleman

Cam carrier markings

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I've just acquired a couple of 907 engines. One's from an S1 I recently bought and the other is from a Jensen Healey. I plan on making one good one from both and then selling off any unwanted stuff like the JH block. (if it's any good). However, looking through my boxes of bits I noticed one of the S1 cam carriers has a marking on the side of it which says ML TO +0005 the square bits on each corner have an 'x' stamped on them all. Does anybody know what this means?

 

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My guess is that the cam followers have been machined 5 thousands over.  Put a inside micrometer to them to check all.

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Thats half a thou isnt it?

I would have thought an instruction to the machinist to mill the face to a flatness of half a thou. Maybe on an early engine when they were stil getting things right.

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I used to machine these, albeit the later flat cam cover ones.

I am pretty sure it's oversized cam bores. Cam bores were line bored using adjustable inserts, tappet bores were machined using fixed blade Mapal guided reamers, any over size tappet bores meant the casting was scrapped.

The letters are probably the initials of the person who did the machining then the line boring, doing this was a requirement after every big fuck up but would only last a few months.

Out of interest, up until about 1990 the machining was done on Moog tape controlled vertical milling machines, after that on Mazak 3 axis vertical machines. If you have flat cam cover carriers with the I and E letters stamped on they were done on the Moog, if it is machined on it was done in the Mazak. I wrote the CNC code for the Mazak machine to machine these.

Steve

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Steve, that makes sense - thanks for the first-hand insight.  I'm curious... If the cam bores were over sized, how is the additional bore width accommodated without the use of cam bearings? 

Matt      

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7 hours ago, mswest68 said:

Steve, that makes sense - thanks for the first-hand insight.  I'm curious... If the cam bores were over sized, how is the additional bore width accommodated without the use of cam bearings? 

Matt      

Good question, I don't know! Maybe cams with oversize journals, although my parts list only lists one cam type. I remember them being stamped by Dave Simmonds who only did the line boring and the diagonal oil drilling in the cam seal bore. 

Its definitely not oversize tappets though! 

 

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