How can you tell if you have flat cam lobes?, Strange lash issue |
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How can you tell if you have flat cam lobes?, Strange lash issue |
tornik550 |
Jun 15 2012, 02:27 PM
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#1
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Senior Member Group: Members Posts: 1,248 Joined: 29-January 07 From: Ohio Member No.: 7,486 Region Association: None |
I am paranoid of developing flat can lobes on my recent engine rebuild. I am paranoid cause I have heard so much crap about the cam that I used- scat c45. I am asking this more for curiosity sake. I had a strange issue but I am certain it's unrelated. I set my valves on cyl 1 to 0 lash (chromoly pushrods). I did that at tdc for that cyl. Te intake and exhaust valves. Seem to lift normally. The issue is that at a different point in the cycle (other than tdc or full lift) the valves are very loose. The valves go back to zero lash at TDC. The compression is actually about 5 points better on that cylander. I think it's possible that the rocker shaft bolts may have loosened a bit, however I've already removed them. It doesn't sound like a flat lobe to me.
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ChrisFoley |
Jun 16 2012, 07:50 AM
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#2
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I am Tangerine Racing Group: Members Posts: 7,934 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
If you are really setting the valve lash at TDC for each cylinder, and the lash grows at another position, you may have gotten the cam index wrong during assembly.
It is better to set the lash when you see the opposite valve is open all the way, rather than using crankshaft position. (That wouldn't solve a cam index problem though.) |
tornik550 |
Jun 16 2012, 11:18 AM
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#3
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Senior Member Group: Members Posts: 1,248 Joined: 29-January 07 From: Ohio Member No.: 7,486 Region Association: None |
If you are really setting the valve lash at TDC for each cylinder, and the lash grows at another position, you may have gotten the cam index wrong during assembly. It is better to set the lash when you see the opposite valve is open all the way, rather than using crankshaft position. (That wouldn't solve a cam index problem though.) I am pretty sure that I lined up the dots on the cam and crankshaft gears. Is there a way to check to see if they are lined up without taking apart the engine? Assuming that I indexed the cam correctly- considering the issue that I am having- if I were to set the valves to zero lash when the opposite valve is fully open (this is also when the closed valve gets loose) wouldn't my valves be too tight during the compression cycle? |
ChrisFoley |
Jun 16 2012, 12:33 PM
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#4
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I am Tangerine Racing Group: Members Posts: 7,934 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
... Assuming that I indexed the cam correctly- considering the issue that I am having- if I were to set the valves to zero lash when the opposite valve is fully open (this is also when the closed valve gets loose) wouldn't my valves be too tight during the compression cycle? I don't mean the opposite valve in the same cylinder. I mean the valve on the opposite side of the engine which is moved by the same cam lobe. Using this method to determine the correct position will result in the valve lash being set optimally. Probably the easiest way to determine if the cam is indexed correctly is to see how the engine runs. |
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