Well, okay then – the cam is back in.
After a thorough cleaning with hot soapy water, brake cleaner, compressed air and WD40, the cam and the lifters are clean and installed. I haven’t tightened everything down – waiting for the head to show so I can apply some spring pressure to check the timing, but when I took the timing chain and sprockets off, I was able to take them all off as a unit. I just hung them from a nail on the wall through the cam sprocket. They are indexed as they came off, so timing should be close. I’ll be able to tweak it with the vernier, if necessary.
Midget,
You don't need the head and/or spring pressure to check the cam timing. Just use your analog dial indicator (more tension than the digital indicator.....) and the setup we used when we checked it together back on 9/15. (reference reply #1510 photos & 1509 photos, for anybody following along.)
The negative acceleration is -.00020.
Thinly, thinly, cheezy, slicey . . .
A "peak" value of -.00020 in/degree squared is at the low end of the range I was expecting. (-.00020 to -.00025 ish) It is also consistent with other BMC 'race' cams (ground by Elgin & others) in my computerized (386) records.
Engines of this type, tappet diameter, cam lobe "packaging" dimensions (this is critical because the small dimensions available
dictate nose radius for a given lift value and therefore:
contact pressure....), valve train mass, valve spring packaging dimensions (this is also critical), engine operating rpm band, etc, etc; are consistently in this "range", because this range of results is what can be achieved while keeping the valve train intact........
Uhhhhmmm....... have I mentioned "It's complicated"? (I think I have, but my memory isn't what it used to be.........I blame the suds........)
... The negative acceleration is -.00020...
I'm guessing that's the maximum value of negative acceleration? And also assuming that's inches per degree-squared of cam rotation? If 'yes', then 2 x 10^(-4) will be quite "gentle".
Yes, that is a gentle value compared to a GM/Ford/etc V-8 or an OHC bike engine or even a Flathead with a large tappet diameter, but it is also a subjective comparison of apples to oranges. On the larger engines, with more "packaging" space available, the nose radius can be larger for a given/desired cam/valve lift. Small nose radius dimensions, dictated by a lack of adequate "packaging" space, result in very high contact pressures between the cam nose & the tappet. Once the contact pressure exceeds the strength of the materials or the lubricant film strength, etc; the materials are going to spall, the end result being a cam lobe failure. I suspect that when the contact pressure for Midget's jewel is calculated, that it will be higher than the above examples. Because of the previous spalling that was encountered, this is a cause for concern.
This is why it is difficult to make equal comparisons between varous engine styles, types, and makes. The compromises engine designers make at the manufacturing level, determine the strengths and weaknesses of an engine design. And it ends up impacting what race engine builders can accomplish..........
With Midget's permission, I'll spend some more time explaining my thoughts on some of these cam train/valve train issues in the future. I don't expect everybody to agree on anything except the depth of my ignorance.............
Fordboy
(edit) for anybody out there who is interested, add this to the reading list:
http://www.amazon.com/Cam-Design-Manufacturing-Handbook-2nd/dp/0831133678
http://www.amazon.com/Design-Manufacture-Edition-Mechanical-Engineering/dp/0824775120/ref=pd_sim_b_5
Oh, the price of knowledge is not cheap........
Fordboy