I have edelbrock performer rpm heads with 1.6 adjustable rockers how should I approach the adjustment of the valves since the old heads had non adjustable rockers.
The way I adjust valves is like this: First, make sure the cam is on the base side [valve completly closed], then loosen the rocker untill there is no pressure on the valve. On hydralic lifters, then tighten the adjuster nut, while at the same time, twirl the pushrod between your fingers. When you feel the pushrod get tighter, slowly turn the adjustment nut untill you feel too much restiance to turn the push rod. Then, turn the adjustment nut 1/4 to 1/2 turn more and lock it down. On solid lifters it is better to adjust the lash between the valve and rocker with a feeler gauge, tightening the adjustment nut utill the feeler gauge will come out with a slight drag.
I prefer the EO-IC described here with one exception; rather than spinning the pushrod I lift up and down on the end of the rocker and the retainer, as I slowly tighten the adjusting nut. Right when there's no more up and down movement is "0" lash, and then go 3/8 to 1/2 turn more. http://www.cranecams.com/?show=techarticle&id=2&PHPSESSID=1c349fcc512428ef36e24a0ef0b5928a Jody
If your lifters are filled with oil from previous use you'll have to bleed them down to get proper preload adjustment.
If the lifter is pumped up with oil the plunger won't compress to properly set the preload. Evidently your lifters weren't filled with oil. If the engine sits for awhile without running the valve spring pressure can cause some of the lifters to bleed down. Sometimes they don't all bleed down and guys wonder why they have a tap after adjusting the valves.
could be, though I can't imagine that of all the engines I've done that none had the lifters pumped up. Anythings possible, just never heard of this and I've been around the block a time or two. Jody
That doesn't make sense. The minimum amount of "lash" would be when the lifter is fully pumped up. "Tap" would be caused by lash, not zero lash...
For the hydraulic lifter to operate correctly the preload generally has to be between .020" - .060". There's a reason to keep that dimension. If it's less than .020" or more than .060" the plunger may not move correctly to take up any "slack" and the pushrod can start bouncing around causing noise. There is a balancing act going on inside the lifter. Remember, a fluid (oil) is not compressible. So in normal operation what keeps the lifter from pumping up with oil, pushing the plunger against the retaining ring, and causing the pushrod/rocker arm to lift the valve off it's seat when it's not supposed to? The inside of the lifter is an oil metering device. It's correct operation has to do with the size of the oil inlet hole, internal spring pressure, plunger size, bleed hole size and, tah dah, proper preload. Change any of these parameters and you can change the characteristics of the lifter. Think about A Rhodes lifter or Crane's Variable Duration lifter. They play around with the size and shaape of the bleed hole to cause the lifter to "leak" at low rpm but "pump up" at higher rpm in an effort to make long duration cams more civil at low rpm.
this is intriguing. A question then. What would make a lifter be completely pumped up before you do an adjustment, so that you would have to bleed some off? If you adjust lifters with the engine running, and back them off till they clack, would they not be pumped up at that point? And when you turn them down you go slowly as the vacuum and rpms drop as they tend to keep the valve open a bit when you initially adjust them down while running. But they always adjust quickly to normal operation after doing that, so why wouldn't a fully pumped lifter done with the EO-IC method do the same when you fired it up after adjusting cold? Jody
His original rockers were nonadjustable. Suppose that when the rocker bolts were torqued down lifter preload ended up at .020". Now you try to adjust them down to .040". .020" deeper. Valve spring pressure is what bleeds down lifters and most of them will be bled, but sometimes there will be one or two that come to rest on the base of the cam lobe when the engine is shut off that might not bleed down. Yup, you can adjust them with the engine running. Turn 'em slowly and valve spring pressure will bleed them. Turn 'em down too quick and you can collapse the lifter.
I haven't made it around the block yet but it's it's taken me an awful long time to get this far! BTW, I love your project cars! Now, back to our regularly scheduled thread.
OK, so who's right??!!! I still do not see how a lifter pumped up before adjustment won't naturally set it self nearly immediately when the engine is fired. All I know is I've set countless valvetrains, many that were not new builds using EO-IC and I've never worried about whether the lifter was bled down or not. I find the correct "0" lash and add proper pre-load, and the engine fires and runs great. Never had any tapping or issues. I do appreciate a differing opinion though, and that on this board you can have a discussion without a fight. Jody
