'82 Shovel Valve lift
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Evo rocker arms have a different geometry than shovel rocker arms, so you cannot judge where they might hit the rocker box based on a shovel rocker arm.
When cutting the rocker shaft spacers instead of the evo rocker arms, you create a step in the spacer that fits into the end of the rocker arm. The location of the shaft cannot change, as you have correctly surmised. The step just allows for the extra length of the evo rocker arm.
Fortunately, shovel heads are very forgiving of greater installed valve heights, up to .100 extra or more. It does not change the rocker arm geometry enough to be a problem. In your case, your low mileage heads should not have sunk seats.
I would not try to set up the heads for more lift than you are going to use. That is extra work, and only results in lower seat and open pressures for a given set of springs. It's a different story if you are planning to experiment with different lift cams. Your valve float limit will be less with the lower lift cams if this is the approach you take. On the contrary, if you use a heavy spring pack for the really high lifts, that is extra money you don't need to spend when using a lower lift cam. Long way of saying, set the heads up for the cam you are going to use. If you change cams later, change the head set-up at that time. Trust me on this point, it will save you headaches and $$$.
JimComment
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JimComment
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Evo rocker arms have a different geometry than shovel rocker arms, so you cannot judge where they might hit the rocker box based on a shovel rocker arm.
When cutting the rocker shaft spacers instead of the evo rocker arms, you create a step in the spacer that fits into the end of the rocker arm. The location of the shaft cannot change, as you have correctly surmised. The step just allows for the extra length of the evo rocker arm.
Fortunately, shovel heads are very forgiving of greater installed valve heights, up to .100 extra or more. It does not change the rocker arm geometry enough to be a problem. In your case, your low mileage heads should not have sunk seats.
I would not try to set up the heads for more lift than you are going to use. That is extra work, and only results in lower seat and open pressures for a given set of springs. It's a different story if you are planning to experiment with different lift cams. Your valve float limit will be less with the lower lift cams if this is the approach you take. On the contrary, if you use a heavy spring pack for the really high lifts, that is extra money you don't need to spend when using a lower lift cam. Long way of saying, set the heads up for the cam you are going to use. If you change cams later, change the head set-up at that time. Trust me on this point, it will save you headaches and $$$.
Jim
Thanks for all info.
I may misunderstand you, but instead of lowering the bottom collars, do I have to lower the seat collar on the head? But I can't lower the guide anymore, I must keep his seat.
I don't need more than .485 or .495 lift, I don't want a dragster, just use a moderate EVO tree.
I will buy the high lift springs, and the top collars, but I don't find in medium lift w & w collars, only the high lift.
Thank you.Comment
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Thanks for all info.
I may misunderstand you, but instead of lowering the bottom collars, do I have to lower the seat collar on the head? But I can't lower the guide anymore, I must keep his seat.
I don't need more than .485 or .495 lift, I don't want a dragster, just use a moderate EVO tree.
I will buy the high lift springs, and the top collars, but I don't find in medium lift w & w collars, only the high lift.
Thank you.
JimComment
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I like the KPMI springs ...
This spring kit I could had set the installed height at 1.450"- 1.470" and have 171 lbs of closed seat pressure and at 0.0550" lift 385 lbs at open ..
But I choose to set up the installed height up at 1.500"- 1.520"
Seat pressure closed is at 150 lbs and open at .600" valve lift is 385 lbs
In order to see the 1.500" had to remove 0.020" from the head spring pocket ...
All four valves are set at this height ...
Take my 45 and outrun em all ..Comment
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I like the KPMI springs ...
This spring kit I could had set the installed height at 1.450"- 1.470" and have 171 lbs of closed seat pressure and at 0.0550" lift 385 lbs at open ..
But I choose to set up the installed height up at 1.500"- 1.520"
Seat pressure closed is at 150 lbs and open at .600" valve lift is 385 lbs
In order to see the 1.500" had to remove 0.020" from the head spring pocket ...
All four valves are set at this height ...
Comment
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