Hey all,

So my first build is coming along; put the heads on and went to install my rockers, only to find out that my stock pushrods are too short @6.250. After lots of reading there's lot's of debate...so lets visit the procedure again for those of us still learning...

Setup: 302 roller, stock roller lifters, comp 35-349 cam (has smaller base circle ) GT40's with 0.001 milled off, new OEM length valves, scorpion 1.6 pedestal mount RR's.

What I did: Bought an adjustable pushrod length checker, took off the heads, then removed a lifter. I took it apart and filled it with washers to keep it from collapsing. Dropped in the "solid" lifter, put the head back on, then dropped in the pushrod tool. I installed the rocker but only spun the mounting bolt finger tight. I adjusted the tool to zero lash, then torqued the rocker bolts to 20#ft with dry threads, which took 1/4 turn. I then spun it over a couple times and got the wear pattern you see below. FYI it is not feasible to prime the oil pump at this time.

What I would like to know:

1. Without going too far into whether or not the sweep pattern is centered vs. too wide/too narrow; do these wear patterns look alright?

2. Is it possible that I under-packed the lifter? it looks like it collapsed below the retainer, which might explain why the same pushrod adjustment was too short when I did the 2nd valve. Should I add another shim in the lifter for zero play in it?






Looks like I need another shim in there?








Mark is a little choppy; its just excess marker, the rocker was centered


Thanks guys!

 

If you get checking springs it will be a lot easier. You won't have to mess with trying to get the lifter together with no play. bb's might work better but the checking springs are the way to go.

 

You know what? I will. There's so much information and debate on the topic that I just want someone to instruct me either way directly from experience. I'll have to run to Summit tonight for the springs and valve spring compressor tool, and will have an update for you this weekend. I'm anxious to see what length I come up with and more importantly how consistent the actual rod measurements come out valve to valve...

Thanks Mark!

 

You may have seen this but these are great directions for pedestal mount rocker arms. However, instead of shimming the pedestal, you're measuring the right pushrod length you need so you don't have to shim. You're also not looking for a centered pattern as much as you are a narrow pattern. As long as the pattern is in the middle third of the tip. http://www.cranecams.com/uploads/instructions/453e_.pdf

 

Back to the drawing board: I'm heading to summit tonight to pick up a set of shims, checking springs, and dial calipers.

I'll drop in the check springs and follow the standard rocker install procedure, then re-check my sweep pattern. I'll play with the shims and adjustable pushrod to see with my own eyes how it affects the sweep pattern.

I'll report back this weekend on my results, bettor or worse.

Thanks guys!

 

So I called up Comp Cams the other day and they confirmed that my 35-349 has a smaller base circle. I then spoke to Gordon at Scorpion Racing Performance to ask how my rocker's geometry compared to stock. But when I explained to him I packed a lifter to check wear patern and it came out centered, he told me not to get carried away with the wear patern so long as it's centered.

So per Gordon at Scorpion, I think valve geometry and wear patern are ok for my application. Asked him about pushrod length and he told me more preload is better than to little, that the lifter will produce full lift despite preload with performance springs like I have.

To measure length at zero lash, I took a rocker, torqued to spec, then rotated the crank till opposite lifter was at top of travel. With adjustable pushrod, I twisted it and expanded to zero lash where there was little to no resistance to twist, and no play up and down, but zero deflection on the lifter plunger. I removed the rod and measured out to 6.235". Using my stock lengths of 6.250 only gives .020 preload. Next available length is 6.305, which would yield 0.07" preload.

So I realize mild performance range of preload is 0.02-0.08"

My question is which side of the range is best? Run 6.250 rods with 0.02 preload or 6.305 with 0.08 preload?

Thanks guys!