lost valve lift?

rod · 05-16-2015, 07:41 PM

in the process of degreeing in a cam [327 SBC}...I have a checking head with only 2 valves and a lite spring. everything was right, so I moved on the the head which I would be using with the valves and springs which would be used. I lost about .025" lift. I put the checking head back in place and the #s came right back. I changed rockers and nothing changed and changed 3 different length push rod, no change. back the the real head and the lift is gone again. did the same, changed rockers and push rods. even tried different ratio rockers and lift is just gone. the springs are only 120 lbs on the seat and 310 over the nose, so nothing mongo. I put the dial indicator on the side of the push rod to check deflection and only got.001", which could account for .0025" lost lift. then I checked the stud [7/16"] and got .001 towards to valve [which should be a + not a -, right?]. swapped in a brand new stud, no change. next I pulled the cam out and replaced it with a stock 350 hyd. cam [using a solid to check] with the lite spring and a 1.6 rocker, the lift comes out at .414" @ 0 lash, which is what the lobe lift x 1.6 is. I then put the race spring on the checking head and I get .403". so even with a low lift cam I loose .011 lift.
I have a brand new set of stainless 1.6 rockers which check the same as a 1.6 Crane gold, I have 1 Crane 1.52 rocker and 1 Harland Sharp 1.52 and all 4 rockers check out the same [of course the 1.52 have a different lift, but still short of true gross lift] with the lite spring and all test out the same with the race spring, regardless of head used.
I can understand loosing a few thou. from stack up, but not .025 or even .011 on a low lift. so where the heck is my lift? what is it that I am missing or over looking?
any ideas or help will be greatly appreciated.
Thanks Rod in AZ

05-16-2015, 07:41 PM	#1
rod Member Join Date: Dec 2009 Location: Kingman, NW AZ. in the middle of the longest stretch of Route 66 Posts: 313 Likes: 0 Liked 20 Times in 15 Posts	lost valve lift? in the process of degreeing in a cam [327 SBC}...I have a checking head with only 2 valves and a lite spring. everything was right, so I moved on the the head which I would be using with the valves and springs which would be used. I lost about .025" lift. I put the checking head back in place and the #s came right back. I changed rockers and nothing changed and changed 3 different length push rod, no change. back the the real head and the lift is gone again. did the same, changed rockers and push rods. even tried different ratio rockers and lift is just gone. the springs are only 120 lbs on the seat and 310 over the nose, so nothing mongo. I put the dial indicator on the side of the push rod to check deflection and only got.001", which could account for .0025" lost lift. then I checked the stud [7/16"] and got .001 towards to valve [which should be a + not a -, right?]. swapped in a brand new stud, no change. next I pulled the cam out and replaced it with a stock 350 hyd. cam [using a solid to check] with the lite spring and a 1.6 rocker, the lift comes out at .414" @ 0 lash, which is what the lobe lift x 1.6 is. I then put the race spring on the checking head and I get .403". so even with a low lift cam I loose .011 lift. I have a brand new set of stainless 1.6 rockers which check the same as a 1.6 Crane gold, I have 1 Crane 1.52 rocker and 1 Harland Sharp 1.52 and all 4 rockers check out the same [of course the 1.52 have a different lift, but still short of true gross lift] with the lite spring and all test out the same with the race spring, regardless of head used. I can understand loosing a few thou. from stack up, but not .025 or even .011 on a low lift. so where the heck is my lift? what is it that I am missing or over looking? any ideas or help will be greatly appreciated. Thanks Rod in AZ