I have my 280XFI cam now installed and I'm at the point of figuring out my pushrod length, So far I been reading up on few ways of doing it and made a few observations along the way. For one you difinitely need to shim up your hydraulic lifter to make it a solid even with using checker spring on the valves cause it will over power the spring in the lifter with ease. I was lucky enough that one nut dropped into the lifter to replace the spring and was the perfect size. Also checker springs don't really give out enough force to make a proper mark on the valve head when using a black marker to see the pattern. I ended up just using a inner spring for the extra spring tension, seems to work lot better. Now my rockers are supose to be 1.62 ratio if I remember correctly but I'm measuring .6 lift on the valve. I thought I'm suppose to only get like .570? The cam is giving the proper lift on the lobe so I ruled that out.

I done a run through of different valve stem sizes and measured the lift for each, here are the results of that relationship.

Pushrod Length - Valve lift (+or-0.002 error at the most)
7.15 - .582
7.20 - .585
7.25 - .589
7.30 - .592
7.35 - .593
7.40 - .595
7.45 - .596
7.50 - .598
7.55 - .602
7.60 - .604
7.65 - .606
7.70 - .608
7.75 - .608
7.80 - .601
7.85 - .584

The higher up I go on the pushrod the more nosed down the rocker gets, though I thought if you did the mid-lift setup it was supose to give the most lift? I'll try to look today where that point occurs but I don't think its up in the 7.7 range.

Anyways I'm a little bit lost on which way I should go, if I try to get the least amount of sweep I end up kind of low to the exhaust side which I'm not comfortable with. I might even try just getting the mark in the middle like some companies suggest, I'll have to play with it more today.

Pic of the measuring setup



Also I took apart both my stock lifter and the new LS7 lifter to show the difference, I can't see what makes the LS7 lifter any better then the stock one. Think that was money kind of wasted, there wasn't much different other then the pushrod cup.

LS7 on the right stock L98 on the left


L98 on the left and LS7 on the right, the L98 has a deeper pushrod cup