Tappet sleeves

k. rogers · Post by **k. rogers** » Tue Jun 03, 2008 8:25 pm

I'm hoping someone might be able to solve the puzzle I have with the engine I am slowly rebuilding. I think the situation is the same with both 7's and Bradfords. Two out of the four tappet sleeves which bolt into the crank case have a flat cutout in them at the cam end in the case of the Bradford or a shoulder where the diameter of the sleeve reduces in the case of the 7. In both cases I would imagine this is to avoid some part of the internals of the engine making contact with the sleeves. Would anybody know the correct positions of the two sleeves in question, eg are they supposed to correspond with the inlet or exhaust valves or even both go one side or the other?

k. rogers · Post by **k. rogers** » Tue Jun 10, 2008 8:22 am

Alan Bartlett cleverly pointed me towards the parts manual where there is a picture of one of the tappet guides in question and it is referred to as the inlet guide, so problem solved - looking at the line diagram of the cam, etc, it would appear the reduced diameter is designed to clear one of the adjacent cam lobes, therefore its position in the crankcase is important. Well done Alan for having the gumption to look where I didn't think of looking!

k. rogers · Post by **k. rogers** » Sun Jun 22, 2008 10:20 pm

Having now trial fitted the tappet guides into the crankcase, it would appear that the 'chamfers' at the cam end of the guides are situated either at the top or the bottom of the guides depending where fitted, ie inlet or exhaust. The pre-war guides had a corresponding reduced diameter which may have been designed to avoid contact with the lobes either side, whereas these CC (?) Bradford ones do not appear to do this. Would anyone know if there is a reason I shouldn't use the originals with the CC cam - surely they are all interchangeable? Or perhaps they could explain exactly the position and reason for the chamferred guides.

PAUL BEAUMONT · Post by **PAUL BEAUMONT** » Mon Jun 23, 2008 12:56 pm

Ken, it is a good while since I pulled a CC to bits, but take care here! Jowett made radical changes to the cam followers on the CC. Early models had a totally different arrangement, that they eventually reverted back to something more reminiscent of the pre-war design. But the CC uses conventional collet retained valve springs with the adjustment arrangement on the tappet not the valve. I suspect, but am not 100% sure, that they are not interchangeable with a Pre-war crankcase. I would be delighted to be educated further.

k. rogers · Post by **k. rogers** » Mon Jun 23, 2008 5:23 pm

Thanks Paul, therefore can the old pre-war design followers be used with the newer CC cam, as I feel this would be the easiest way!

k. rogers · Post by **k. rogers** » Mon Jun 23, 2008 9:20 pm

Just spoken to Geoff Wills to see if he could shed any light on the subject -good news is that my cam and followers are not CC Bradford as they were very different as Paul's concerns would indicate. From the CB parts manual the two inlet tappet guides are handed, determining the postion of the before mentioned 'flats'. Unfortunately, the manual does not show clearly where the flats were intended to go but our guess would be either that a) on Bradfords the cam is closer to the crank so the flats would avoid contact between the two or that b) they were simply there to avoid something in the crankcase moulding. Anyway, I feel happier to now go ahead and fit the whole assembly into the crankcase.

PAUL BEAUMONT · Post by **PAUL BEAUMONT** » Tue Jun 24, 2008 12:41 pm

Ken, I am finally intrigued. I have a CB engine in bits I will pull it out tonight and see if I can make sense of the jigsaw!

k. rogers · Post by **k. rogers** » Tue Jun 24, 2008 4:37 pm

Paul, I have since found the CB parts manual on the JCC website (what a brilliant club this is!) and It quite clearly shows the guides in question so that I can now get the correct position of the guides in the crankcase. Also looking at the diagram of the engine it does look as though the cam is may be closer to the crank than in the pre-war, which may account for the flats on the bottom of the two inlet guides.

PAUL BEAUMONT · Post by **PAUL BEAUMONT** » Tue Jun 24, 2008 11:38 pm

Its more subtle than that! The tappet sleeves are entirely enveloped within the crankcase, except for the extension that prevents the tappet turning. So the flat does not clear anything! If you remove the exhaust tappet from its sleeve you discover that the bores are plain. (exhausts are not handed). If you do the same for the inlets you discover an oill gallery machined into the bore towards the cam shaft end. If you look even more closely you find that there is a small drilling from the end of the flat into the counterbore. Conclusion the flat is a crude oil transfer gallery. Which leaves the question does it go at the top or the bottom. Logic (at least mine) says that it should go at the top or you will never get any oil down it, but I do take your point, that if you consider the parts book and "Right hand" is off side then at the bottom is more logical.
Does anyone else follow this ramble?? can you educate us??