entropy
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posted May 29, 2007 04:06 AM
easier to degree the cams??? hmmmmm....
I can usually get the dial indicator to behave nicely while doing the intake cam, but for some reason the exh is always problematic. It just doesn't want to return to 0 after a rotation of the cam.
Cutting a bit off the left side "roof" of the cam cover helped access alot but i still have issues with that fukken exh cam.
So, I'm gonna run this idea up the flagpole and see who salutes it.
I am planning on having the exh cam machined immediately outboard of #1 lobe where i always put the dial indicator probe. Only 1/8" off the cam diameter will give a much straighter shot for the indicator probe to hit the bucket.
Can anyone think of why I shouldn't do this???
thanks in advance for your thoughts.
Karl
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Texas12R
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posted May 29, 2007 12:08 PM
Have you considered using an offset for your indicator.....Not being able to see the problem
limits my already limited ability to visualize. Ive never been afraid to cut into anything!
BUT I have always considered the consiquences. I would be concerned about the axial
load and the "notch effect " , But if I did make a relief cut it would be as large a radius as
possible. Cutting a groove with sharp edges is always a no-no.
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tcchin
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posted May 29, 2007 04:26 PM
Have you tried rotating the engine back and forth between the valve-open point and the valve-close point with the nose of the cam lobe away from the tappet such that the tappet never depresses more than .060" ? That should reduce the scrubbing effect between the dial indicator tip and the tappet that side-loads the indicator and can foul-up your zero. All hell breaks loose when the indicator tip comes off the tappet and/or is required to translate across the face of the tappet to compensate for being non-colinearly aligned with the valve axis.
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ZXLNT
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posted May 30, 2007 04:15 AM
 Edited By: ZXLNT on 30 May 2007 05:15
I dont know if these pictures will help or not, but this is the set up I had on my 1270 when it was assembled.
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tcchin
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posted May 30, 2007 06:35 AM
As you can see in the pictures above, it's difficult to get the axis of the dial indicator parallel to the axis of the valve/tappet. This means that a displacement vector in the tappet will resolve into parallel and perpendicular vector components of travel relative to the dial indicator, so as the tappet rises in the head, the indicator tip will slide along its face toward the outer edge of the head, placing the indicator into bending. If the displacement is minimized, so is the side load.
Also note that the measurement displayed in the dial indicator will actually be the true tappet displacement divided by the cosine of the angle between the valve axis and the indicator axis. That will have an influence over the accuracy of the valve timing measurements, as the opening ramps are not symmetrical with the closing ramps.
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ZXLNT
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posted May 30, 2007 08:18 AM
Dude speak english not technical jargon doublespeak...
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tcchin
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posted May 30, 2007 09:28 AM
I believe I was answering Karl's question, and as far as I know, Karl is fluent in technical jargon doublespeak.
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ZXLNT
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posted May 30, 2007 01:22 PM
Probably so, however other people may not be, um soo talented...
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entropy
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posted May 31, 2007 02:31 PM
"technical jargon doublespeak" mixed in with a bunch of acronyms is my daily bread n' butter 
Sliding on the face of the tappet is indeed my issue.
cool pix ZXLNT!
I DO #1 lobes on the outsides to get at em easier.
But, i need all help i can get.
thanks,
Karl
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Y2KZX12R
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posted May 31, 2007 04:55 PM
Edited By: Y2KZX12R on 31 May 2007 18:14
Karl i use a 90 deg angle adaptor that reaches in and keeps the dial indicator plunger paralell with the valve centerline.
You can use a very small allen wrench zip tied to the dial indicator.
I have a chart I made years ago that shows what the effect of angling the dial indicator is, in thousandths, so you can compensate....
Let me find it... brb.
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Y2KZX12R
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Y2KZX12R
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posted May 31, 2007 05:13 PM
ok, these are lift corrections for .040" or 1mm
And are assuming zero side deflection.
10 deg angle is .0006" "fine for degreeing cams, general degreeing skills will have more error effect than the 10 deg angle"
20 deg angle is .0026" "about 1 deg on the degree wheel"
30 deg angle is .0062" "about 2 deg on the degree wheel"
40 deg angle is .0122" "deflection and inaccuracy is guaranteed"
50 deg angle is .0222" "deflection and inaccuracy is guaranteed"
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tcchin
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posted May 31, 2007 08:14 PM
Again, the opening and closing ramps are not symmetrical, so what might be 2 deg on the opening side may be 4 deg on the closing side. This will throw off any lobe center calculation you're trying to deduce.
Karl - you can try bending up some of the welding rod like you did with the KG-VTP tool. You may even need to grind the sides to make it narrow enough to clear the tappet guide and the cam lobe.
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entropy
Moderator
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posted May 31, 2007 11:01 PM
Tim & Jim,
I will try bending the the probe like the patented TCC-VTP tool, and i'll grind on it a lil also. But I am gonna grind on the cams to see if i can make the fit even better.
I just love to do experiments
I didn't realize that the angle made so much difference, and i didn't realize that opening and closing were different.
you guys are awesome!!
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