Question for our engine specialists.

[Ron LaDow]

"We might be talking about the .5mm Greg mentioned."
Vic, .02" looks pretty easy to determine.

"Ron, I'm now running a wide lobe cam with no taper and flat tappets, wonder how much rotation is going on?"
Don, you can pull the sump and see how much the tappet face overhangs the lobe. From that you could get an approximation of the delta torque acting on the face. Getting from there to actual torque, drag and resulting RPM is a bit beyond my pay grade.

Added by edit: Anyone have the cam bearing bore dim handy? Not in the spec book.

[Greg Bryan]

Here's how I measured the offset

I inserted two lifters in their bores
I put a straight-edge against the lifters and measured to the far side of the cam bore - first measurement 18.23mm
I moved the straight-edge to the other side and measured to opposite cam bore edge - second measurement 17.75
I measured the lifter shaft - 11.97mm - and divided that by 2 and got 5.985mm (which is the measurement from the lifter shaft edge to the center
I subtracted the 5.985 from both of the measurements and got 12.245 and 11.765, which should be the measurement from the center of the lifter to each edge of the cam bore.
I subtracted 11.765 from 12.245 and got 0.48mm, or approx. 0.5 mm offset.
Do you buy that? Not super precise as I was kind of estimating where the edge of the cam bore was, but pretty close.

[Greg Bryan]

Ron - adding 12.245 and 11.765 equals 24.01 - the cam bearing bore ...

[Ron LaDow]

Greg, that may well be good enough, since Don really hasn't stated a tolerance. But as you mention, measuring to the edge of a half-bore or the edge of a conical cut (in the heads) is one of the least accurate techniques.
I'll do the rods-with-cones measurement since it sounds kinda fun, and if it yields numbers close to what you found, we can pat each other on the back.

[Ron LaDow]

Ron - adding 12.245 and 11.765 equals 24.01 - the cam bearing bore ...

So prolly 24mm nomimal.
Thanks. Wife's pulling for some help in a charity event on Sat; may be Sunday before I get to it.

[Martin Benade]

Ron, you are more high tech than me. When I do a rods-and-cones measurement, that refers to me using the light sensing elements in my retina. Accurate to within 10mm.

[DonCichocki]

Thanks for all your efforts guys! I was just curious about the number, now we have some more data to put in the "useless knowledge" bin. .5mm is certainly close enough.

[Ron LaDow]

Let's see if the images are small enough to load:

I only made tooling for the intake lifters, since that allowed the the cam-tool to fit into two bores for accuracy. Pretty sure it's visible; the lifter and cam bores are not perfectly normal; the lifter bores are a small amount higher. I could do more tooling and find out within a couple of thou, but by eye they are ~.01"-.015" higher than the cam bore.
I'm gonna guess they were designed to be normal, but the difference came from variance in jigs/set-ups and the fact that misalignment in that amount has no effect on function.
Oh, and I rotated both rods/cones to confirm concentricity; they should have been concentric and are.

[Vic Skirmants]

Greg; thanks for discovering that,
Ron; thanks for verifying it.

[Ron LaDow]

Vic,
I want to try them in the right hand case half, but that's the only case I have 'loose'. I could easily get them back to you if you would be willing to increase the data points.

[DonCichocki]

Ron fantastic!
The dimension I was wondering about is the C/L of the lifter to the C/L of the "cam lobe" in the forward/back plane. If you have a cam on hand, Dykem the lobe, lay the cam in place, use your conical tappet blank to scribe a line around the lobe. Remove the cam and measure the C/L of the lobe to the scribe line ... does that make sense?
DC

[Ron LaDow]

Don,
I don't have a cam handy, and per above, the C/L of the lobe won't tell you much. If you're wondering about spinning the lifter, the amount of overhang is what will give you the best info.
But it dawned on me that just milling the cones to 1/2 'thickness' would give me flat surfaces for really good measurements. That .01" eye ball was fat; .006" is good on the right, the left hand case was .005"

[DonCichocki]

Thanks for the effort Ron!
I'll be pulling my engine sometime this winter/spring and I'll use your idea to see what the overhang is.
This community is great!

[Jacques Lefriant]

Hi
I don't think when these engines were designed they incorporated a significant amount of overhang. the use of taper and big offset were responses necessitated by higher spring pressures to keep the lifter rotating.
j

[DonCichocki]

Jacques,
As a side note, when I pulled the stock/worn #15 cam out of my '65 "C" the lobes were flat, but it had narrow lobes.
That's how I got on this "offset" post, wondering how much rotation was generated. I can see tapered lobes and radius faced lifters would work better.
DC