Push rod wear mark judgement.

[Stale Giverhaug]

Hello.
I would like some second opinions on my push rod length checknig.
Chevy small block, faktory roller block. Vortec heads with Beehvie springs, TRW roller self aligning roller rockers 1:1.5 until now.
Changing to same type, but 1: 1.6
Standard push rod length 7.2 inches until now.
amshaft:
HOWARD'S SBC 305-350 Chevy, Hydraulic Roller 183215-14
Valve Lift Intake:.495
Valve Lift Exhaust:.500
When changing rocker arms, I decided to do a proper check of the valve train geometry, and to make it short: Using the "mid lift method", 7.6 inches push rod length gives the perfect geometry.
But by using this length, the wear mark will be placed very close to the edge of the valve tip.
Because of that, I did some testing with different lengths, including the 7.2" stock length.
I tested 7.6", 7.4", 7.3" and 7.2"

Push rod holes are widened with a 13 mm drill a long time ago before I assembled the heads, so this should be ok.
The Beehive springs, retainers and locks are bought as a "Vortec high lift kit" from Alex' parts.

The shorter push rod , the wider sweep and the closer to centre of the valve tip, the wear mark ended.
What of the alternatives should I choose?
To make a visible mark in the valve tip, I rugged the push rod a bit side to side during the test. Maybe that have widened the mark a bit, I don't know.

 

[COPO]

7.2 looks the best. You may not find an off the shelf perfect length for that perfect center mark unless you have custom rods made. I would use the 7.2’s.

 

[1971Dan]

You may need rockers with a backset trunion stud location in order to achieve the correct rocker arm geometry along with a sweep pattern that is closer to the center of the valve stem.

 

[G72Zed]

What's "perfect" or "correct" valve train geometry in the SBC, Standard OEM based, Mid-Lift, Low -Pivot ??

Many ways to setup a stud mount valve train, I agree some "look" better in theory and "perfect" on paper/YT, but leave out other things that matter.

Looking at your situation and pic's, I agree with COPO, stick with what GM designed for a roller setup....7.200" and be done with it, there's more in the PR size than the scrub pattern you are looking at.

As for roller rockers with "back set" trunions to "fit the mid lift" target setup, look at Crower, they are around 485$ USD for a set of 8, be it 1.5 to 1.85 in .05 ratio increments, and do not come in "self aligning" or 3/8 stud size, and for good reasons. And when you are in for 1K in stud mounts, you may as well go shafts unless you are fitting into class rules.

Just my experience.

 

[1320feet]

Looks to me that a 7.100 or 7.000 would get you dead center.