Valve lash, With WEBCAM #494 |
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Valve lash, With WEBCAM #494 |
jeffdon |
Mar 13 2010, 06:09 PM
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#1
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Senior Member Group: Members Posts: 1,094 Joined: 24-October 06 From: oakland, ca Member No.: 7,087 Region Association: None |
Ran the 2056 on the stand for a last time to get the oil warm, and do the initial change, and get her ready for installation. Did another valve check. Which got me to thinking.
I am setting it to the spec that came with the cam, .006 for both exhaust and intake. Lift (.465) and duration (280 deg.) are the same for both valves. Question is, if exhaust valves expand more due to heat than intake, why does webcam recommend .006 for both? Why not .006 and .008 as is standard? It SEEMS to be running pretty well, but I know i have a good deal of fooling around with jets and such once its on the road and i can test her under load. At one point at about 3500 rpm it started firing back through No 4., but that was right about the time i was running out of gas in my temp. tank. I shut it off, and got a big pop and some flame out the tail pipe. I would really like address/double check anything now, as its way easier accesing things on the stands. |
Jake Raby |
Mar 14 2010, 07:10 PM
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#2
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
I'd expect that you didn't carry out any valvetrain geometry procedures?? I've never seen a 494 come close to optimizing with a stock length pushrod.
The 494 has a fast ramp, it must have geometry carried out to prevent valvetrain wear, especially valve guides. |
jeffdon |
Mar 16 2010, 09:53 AM
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#3
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Senior Member Group: Members Posts: 1,094 Joined: 24-October 06 From: oakland, ca Member No.: 7,087 Region Association: None |
I'd expect that you didn't carry out any valvetrain geometry procedures?? I've never seen a 494 come close to optimizing with a stock length pushrod. The 494 has a fast ramp, it must have geometry carried out to prevent valvetrain wear, especially valve guides. I did a dry assembly and did a quick and dirty visual check of the adjuster/pushrod relation, and it looked pretty well aligned throughout its cycle. Then again, i only looked at one cylinder and just assumed that it would be the same for all others. Probably hosed myself on that one, but at this point, I dont think i want to pull her apart again. |
Jake Raby |
Mar 16 2010, 07:08 PM
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#4
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
I'd expect that you didn't carry out any valvetrain geometry procedures?? I've never seen a 494 come close to optimizing with a stock length pushrod. The 494 has a fast ramp, it must have geometry carried out to prevent valvetrain wear, especially valve guides. I did a dry assembly and did a quick and dirty visual check of the adjuster/pushrod relation, and it looked pretty well aligned throughout its cycle. Then again, i only looked at one cylinder and just assumed that it would be the same for all others. Probably hosed myself on that one, but at this point, I dont think i want to pull her apart again. ....a visual? How about a measurement of actual values? You have made an alteration of the camshaft, and probably after 30+ years at least 6 more of the 11 variables that can directly impact valvetrain are present within your engine combination. So you must follow a specific procedure to MEASURE these things and then ensure that the proper set up is carried out. Otherwise you'll wonder why the engine sounds like diesel, eats valve guides and requires constant valve adjustments. The web 494 is a cam with some aggressive ramps and due to that its hard on valve train components. |
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