I have gathered all the information from my previous thread and am condensing here in a new thread for simplicity's sake. Much thanks to Rick Covalt, DusterIdiot, Ceej, wjajr, and others for the help thus far.

So, I do not know the origins of my engine or its camshaft. But, having been manufactured somewhere between '76 and '80, and assuming it's a factory cam, this thread states that it is highly likely a 244° / 244° / 26° / 0.414" cam. I have no cam card, but was able to find this list on which it appears to be #3, highlighted in purple below:

<img src="http://im1.shutterfly.com/media/47a3db33b3127ccef34cc1dcb0db00000030O00EYtnDls3Zswe3nww/cC/f%3D0/ls%3D00303769806120130513025814823.JPG/ps%3D50/r%3D0/rx%3D550/ry%3D400/">

This information will allow me to determine my cam timing using the intake centerline method (106 degrees at .406" maximum valve lift).

Hopefully all the information pieced together above is accurate.

The engine is (and has been) in the car with the head on. I have determined TDC and set my degree wheel accordingly. All valve lash has been zeroed and I am ready to mount my dial indicator. However, my issue is this: while Rick recommends measuring from the valve spring retainer, Ceej advises that one measure from the rocker arm where it meets the pushrod. Ceej also discussed rocker ratio which I don't know (or frankly understand).

Do I need to know the rocker ratio for either method? Any advice is appreciated. Much thanks.

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J.R.
Tucson, AZ
'68 Dart 270 with a '76-'80 engine

depending upon which method is used you will get two different sets of lift values,, and they are both right.

when measured at the retainer, you are finding the actual valve opening amount..
when measured at the push rod end,, you are finding the actual cam lift.

actual valve opening is equal to cam lift times rocker ratio...

to understand rocker ratio,, imagin a teeter totter with the pivot set in the exact middle. When one side is down the other side will go up, and both sides will achieve the same height.
now take that same teeter totter and move the pivot slightly to one end or the other. When moved to the maximum height, the side farther from the pivot will go higher than the side closer to the pivot.

slant six rocker arms are like the teeter totter with the off set pivot.
The pivot ( shaft) is set closer to the push rod end than the valve spring end... The effect is that for every fraction that the push rod end moves the valve end moves the same fraction plus another 50%. Based upon a standard 1.5 rocker ratio..

Oh. Well that makes perfect sense, actually. Thanks, DadTruck.

I think I was confused because Ceej was making reference to some other figures (.002... .006) whilst discussing rocker ratio. I think he meant something else.

I actually went ahead and took measurements off the retainer, but the highest number I got was .389". I was looking for .406" to confirm it's the cam I think it is. At 17/1000 of an inch I realize it could be variables as simple as the dial indicator plunger not being parallel to the valve stem. But am I right to think there must be some wear to the cam lobes and/or lifters over time that would affect these numbers?

How else might I verify that it's the 244° / 244° / 26° / 0.414" cam I think it is?

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J.R.
Tucson, AZ
'68 Dart 270 with a '76-'80 engine

Very few rocker arms actually have the 1.50 rocker ratio........

If you measure both ways, you can figure out what you're actually getting for each rocker arm ratio

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Advertised duration is where the .002 or .006 numbers come into play. Closing numbers should be given as .050" valve lift values. If measuring at the lifter, you have to figure out what that means without the multiplier that the rocker puts to the valve.

In order to measure the correct valve closing, the valves need to be set to zero lash. Clearly, this won't work with a running engine. Your intake closing event will happen earlier due to the running lash. .010"

That means the valve will close earlier. It shouldn't be a lot though.

Clear as mud?

Find out where you are at zero lash. If your in the ball park, +/- a degree or two of crank rotation, then leave it alone. It's probably fine.
For all the cam degreeing fuss, I've not seen anything, but the wild rumpity cams that were far enough off to worry about. My Erson RDP ran a Zero pill, so did the OCG, and the Erson 280 runs straight up as well. The 244 I ordered for Linda's '63 spec'd on the marks. I run dual roller timing sets on everything, which may explain why I haven't had a problem that others have run into. Cheap timing sets may not line up properly.

I still check every cam I install.

CJ

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Part of Tyrde-Browne Racing

Aaaaaaas mud, yes.

So might I again ask whether lifter and cam wear could add up to .017", thus affecting the reading of my dial indicator? I still can't absolutely guarantee this is the 244/244 cam, but I'm beginning to think I should just go ahead and center the cam lift (whatever it reads), make sure the degree wheel is reading 106 degrees, and call it a day, eh?

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J.R.
Tucson, AZ
'68 Dart 270 with a '76-'80 engine

It's .406 with a 1.5 rocker ratio.

This is .27066666 at the cam lobe.


If the rocker ratio isn't 1.5, but actually 1.437; you get .389

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Going with lobe center is an acceptable method. Use 0.020" or 0.050" for your centering points to stay off the lash ramps.

If you have .017" of wear, it's time for a new cam!

CJ

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Part of Tyrde-Browne Racing