I'm in the process of doing a head swap on an SBC and I ran into a problem while putting the rockers on the new heads. When I tighten the rocker until there is some resistance while spinning the pushrod, then go another 1/2 turn, the spring starts to compress a little instead of the lifter. Is this normal? I thought the lifter is supposed to compress during the additional 1/2 turn to have some preload. The cam and lifters were already in the engine and have not been touched, and the lifters are still full of oil. The engine ran great before this head swap, so I do not suspect any problems with the lifters. Rocker arm geometry looks great, the roller tip is right in the center of the top of the valve stem, so pushrod length is not an issue.
Some suggestions would be appreciated, I halted the project until I can sort this out.
Will the lifters eventually bleed out once there is some spring pressure on the pushrods? I'm not liking the idea of a rough idle with backfiring if the valves do not fully seat.
This is normal.If you let the engine sit for 10 minutes or so it will be ok... The lifters will bleed the oil out by then... If you want to go through the greif you cound put a dial indicator on the retainer when you set the valve and zero it before you adjust the rocker and then wait untill it returns to zero,then move on to the next, but it really isn't necessary...
I think there's a problem with the "some resistance while spinning the pushrod" part. I would just tighten until the lash is gone then another 1/2 turn.
I think I got the problem licked, the springs eventually settled down once the lifters bled out. I measured them with an extending caliper and they returned to the 1.75" height I set them at. As far as the "feel" for resistance on the pushrod, it's pretty obvious to me when it hits zero lash, I turn the adjusting nut very slowly to be sure I don't go too far.
I like to wiggle it side to side - and yes I'm talking about the pushrod
I find that it is a little harder (again, no pun) to set the lash with new lifters, pushrod and rocker arm because they haven't taken a set and there can sometimes be quite a bit of resistance. By taking the top of the pushrod and going sideways in line with the rocker stud (driver to passenger side) it's really easy to feel when all the clearance is taken up. But - whatever works for you since there are many ways to end up at the same place.
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