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toon1 |
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#1
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Senior Member ![]() ![]() ![]() Group: Members Posts: 1,849 Joined: 29-October 05 From: tracy,ca Member No.: 5,022 ![]() |
so far the liift is good, cam card say's .426, I've got about .428.
Here is a pic. with the vave at half lift. Seems a little off(leaning back) to me. Attached image(s) ![]() ![]() |
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HAM Inc |
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#2
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Senior Member ![]() ![]() ![]() Group: Members Posts: 850 Joined: 24-July 06 From: Watkinsville,GA Member No.: 6,499 Region Association: None ![]() |
The geometry in the last photo looked a lot better.
Clayton is correct that the valve stems all need to be level. If they are off it will effect valve timing. The biggest impact will be on the cross-over point. This is the point during intake and exhaust valve overlap when the exhaust is closing and the intake is opening, but both are off their seat the same amount. This is an extremely critical point in the engines cycling. Sharp race engine builders will check the cross over points on each cylinder (requires a dial indicator on each valve) to ensure that they occur within a * of each other, that's + or - 0.5 *. No point spending the bucks on the cam and all of the other innerds if the valve stem ht's are all whacked. I guarantee the stem ht's on every head that leaves my shop are + or - .005" of each other. Here's a trick for setting geometry that de-confuses the relationship between pushrod length and rocker shims. Remove the valve springs. Purchase a couple of shaft collars that are the size of your valve stems. Set the head on a bench with the valve stems up. Slide the collars over the valve stems (one for intake and exhaust) and set them so they will hold the valves open at half lift. A caliper works fine for this. With the valves in the half lift position set your rocker assembly in place with the valve adjuster locked where you want it. Now just keep adding shims until you have the proper geometry, which is the adjuster in line with the valve. If the intake and exhaust have different lifts you may have to make adjustments to one of the adjusters to level them both out. You may also have to make adjustments to your screws if the first positions you try are in-between what you can level with the available shims. Once you have that worked out, set the head on the engine and bring your adjustable pushrod in, adjust it to take out the slack. Now you have the correct shims for proper geometry and pushrod length to fit the space. This works because the pushrod has nothing to do with proper geometry. The proper geometry is a function of the relationship between the rocker arm and the valve, period. This would be easier if the adjusting screw was in the pushrod side of the rocker like HP domestic rockers and some hi-lift rockers. |
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