Bryan Zurlo

Alrighty, I've got my heads back from TEA with the stage 2 work done and I'm at the point now where I'm measuring for pushrods and would like some feed back on my method. Below is some info on what is going on the car that would affect pushrod length:

Tick SNS Stage 3 - Standard lobes
GM MLS head gaskets
LS7 lifters
TEA heads milled .003-.004" to clean them up, 2.04 intake valves

I set the engine to where the #1 cylinder is at TDC and from there I rotated the engine farther to where the exhaust valve was just coming off its seat with the intake valve fully closed. At that point I installed my adjustable pushrod and rocker with the bolt being threaded down until there was no longer any vertical play or ticking between the valve tip and rocker arm tip. This is zero lash, correct?

From there I had my dial indicator gauge set up so that it was reading from where the pushrod seats in the rocker arm. With the dial gauge zero'd, I started tightening the rocker arm bolt and keeping an eye on the dial indicator to see how far the rocker arm tip was pushing the pushrod into the lifter.

My question is, is this an accurate way in measuring what pushrod I'd need to choose and it's affect on lifter preload?

For grins here are the results of the measurements I took with the adjustable pushrod at various lengths:
7.286" - Too short, rocker bolt fully seated the rocker was not at zero lash
7.300" - Too short, rocker bolt fully seated the rocker was not at zero lash
7.330" - .021" preload
7.350" - .025" preload
7.370" - .038" preload
7.375" - .042" preload
7.380" - .055" preload
7.390" - .065" preload
7.395" - .082" preload
7.400" - .087" preload

vettenuts

iTrader: (4)

Your numbers aren't very consistant. I took your values and looked at how they were changing with each increment of pushrod length. I would expect a linear change but it is not.

I can see what your are trying to do, but something is amiss. Have you tried this a couple of times to ensure the lifter is fully bled out? Did the dial indicator stop moving when you took the measurement? I have found it takes several minutes to fully bleed out with the valve springs in place. A check spring likely won't bleed it out at all.

Hope this makes sense.

Here are your numbers:

7.330" - .021" preload
7.350" - .025" preload
7.370" - .038" preload
7.375" - .042" preload
7.380" - .055" preload
7.390" - .065" preload
7.395" - .082" preload
7.400" - .087" preload

Here are the changes (pushrod length change, delta change, preload change)

7.33-7.35, 0.020, .004"
7.35-7.37, 0.020, 0.013"
7.37-7.375, 0.005, 0.004"
7.375-7.38, 0.005, 0.007"
7.38-7.39, 0.010, 0.010"
7.39-7.395, 0.005, 0.017"
7.395-7.4, 0.005, 0.005"

Bryan Zurlo

Vettenuts, thank you for the feedback on my numbers so far. Thinking about this last night, the lifters had been soaked in oil, but not pumped, and noticed that as I had worked on the car yesterday I could feel that the plunger travel in the lifter became more and more forgiving making me think that the lifter had started to bleed down.

That said, this morning I took measurements again and they are a bit more consistent as I got closer to 7.400" than those I posted yesterday:

7.330" - .006" preload
7.350" - .037" preload, pushrod change - .020", preload change - .031"
7.370" - .038" preload, pushrod change - .020", preload change - .001"
7.380" - .051" preload, pushrod change - .010", preload change - .013"
7.390" - .061" preload, pushrod change - .010", preload change - .010"
7.395" - .071" preload, pushrod change - .005", preload change - .010"
7.400" - .085" preload, pushrod change - .005", preload change - .006"

All this said, am I correct in thinking that 7.400" is the pushrod length I should go with since .080 is my desired preload?