I'm doing an informal survey regarding pushrod length and the valve train combination you're running in your Gen 1/Gen 2 SBC.
The information I'm looking for is:

Block: decked or undecked (amount).

Heads: Make/model. Milled or unmilled (amount).

Cam: Type. Lift.

Lifters: Mfr. PN

Rocker arm: Make, style and ratio.

Pushrod length:

Head Gasket: Thickness



Example.

Block: GM OEM. Decked .010"

Heads: Brodix IK 200. Unmilled.

Cam: Hydraulic roller.

Lifters: Comp 15853.

Rocker arm: Comp steel full roller. 1.6 ratio

Pushrod length: 7.450"

Head Gasket: .041"

If you care to contribute, feel free to add as much information as you'd like. Orr's example below is very thorough.

 

Not sure if this is helpful for anything but heres mine

Oem latemodel roller block, 0 decked 9.000"
Mls .041" gasket
Comp cam hyd roller 1.000" base circle. .373" lobe .603" at valve 1.6 rocker
Afr eliminator box stock 195 heads. Standard Valves with springs at 1.775-1.780" install height.
Oem gm ls7 lifters
Comp pro mag 1.6 roller rockers
Comp 7.35" pushrods


Dart shp roller block 9.000" deck
Mls .041" gasket
Comp ground custom hyd roller. Small base circle, unmeasured
Rhs 220 castings cnc port by Speier heads to 245cc, milled ~.025 4cc or so
+.100" valves, springs at 1.90" height
Lgm shaft rockers. .380" tall stand
Morel hyd roller lifters
Comp 7.35" pushrods

Vastly different setups yet same length pushrods. A stud rocker system would likely need longer rods on the second combo. When i ran it i used 7.45 but wiped guides in 400 miles so not sure what happened. I didnt follow midlift then

 

It's interesting to see all the components involved in the stack up of parts. Something as simple as going from one model of lifter to another within the same brand may change the pushrod length requirements. The Comp 853 vs their 15853 comes to mind. There's a different seat height for each.
I haven't strayed too far from the OEM standard despite my mix of parts and I'm curious to know what other's have come up with in the testing. I'm revisiting the whole testing procedure and am seeing results that differ from what I've done in the past.
I had forgotten to include the head gasket thickness in my original post. I'll edit that and add few other items.

 

Just to many variables but i guess you can summarize it by block deck height gasket thickness, length of valves and even angle of valve, lifter type, cam base circle, rocker type and design. Tall valve used in high lift applications that have high spring install heights take longer pushrods since rocker has to sit up higher on the stud.

Despite the extreme cost of shaft rockers, i find them well worth the expense and ease in installation for correct geometry and pushrod length. Especially with hyd rollers, valvetrain rigidity and stability can mean 50-100+ hp!

 

I had thought about the .100" longer valves in my heads when I considered the list above but like you say, there are almost too many variables to keep track of. Add the extra valve length and then add the roller tip on the rocker (as compared to a stamped steel unit) and pushrod length is now a quarter of an inch longer than stock. Bring a block to 9.0" deck and run a thinner head gasket and you've gained that back.
I'm pretty sure a lot of guys, especially the casual enthusiast, has sort of glossed over this check and run an arrangement that's reasonable. In all likelyhood, if it's just a weekend racer that won't see a lot of run-time, then it may last a number of seasons. When you rack up the mileage like I do, parts have got to last.
It'll be interesting to see who has come up with what. And how they got there.

 

In the past i did a narrow sweep check and if it looked narrow i used it. Worked fine in the two milder motors, my long valve, high lift motor killed guides in a few months not even 400 miles! Never changed my methods, did what i thought was right which worked 2 times. Last build as part geometry separates from factory designs with high lift cams, higher spring pressures, taller valve heights, things just become much more critical. Hence why alot of racier setups use shaft stands to correct faulty stud rocker geometry

 

I think that's the approach a lot of us use. The question is, what is narrow? Precise geometry yields a very narrow contact mark, something along the lines of .027" for a .580" cam. I've NEVER seen a contact mark that thin.
These aren't all out race setups mind you. Pedestal rockers with cams less that .600".

 

Block: decked or undecked (amount).
Dart SHP, 9.005" deck height

Heads: Make/model. Milled or unmilled (amount).
CFE 18 degree heads, been milled approx 0.020

Cam: Type. Lift.
Solid roller, 0.682" lift

Lifters: Mfr. PN
Crower hi seat offset. 66275H-16

Rocker arm: Make, style and ratio.
T&D shaft mount, 1.6/1.6 ratio, 0.450" iffset intake rocker. 0.060" shim under rocker stands

Pushrod length:
7.00" 0.135" wall 3/8" diameter

Head Gasket: Thickness
0.051 Copper

 

Serious stuff there for sure.
I can see how this can get complicated with high-end components like that.
Obviously there's no correlation between a run-of-the-mill small block like I have and the more exotic mix of parts like that bullet.
Still I find it interesting and am keeping notes.
When some of the more average builds trickle in with information, I wonder how many will have actually nailed down the correct length or are time bombs waiting for the inevitable guide destruction and rebuild?

For those of you with shaft rockers, AlkyIROC was describing how the shafts come with a measuring aid to ensure pushrod length is selected correctly (at least I think that's what he was describing). Is that the case or is it an experienced eye and rounds of testing to nail it down?

 

There are some tools for it, but i used midlift and the stands were cut and shimmed to allow roller tip to be dead center in valve stem (lash cap in my case).
I simply set valve spring mic and lifter at half lift. Drew line thru fulcrum center and tip, and used a square edge to position rocker at 90 deg to valve stem. Then simply adjust pushrod checker til it filled the gap between lifter and rocker and added abit for preload. Dead center perfect pattern and rock solid. I can go to 7500 rpm most likely without issue. Been 7200 no signs of float

 

Makes perfect sense with the mid lift procedure.
You've seen from the marked up drawings here

https://www.thirdgen.org/forums/tech...metry-now.html

that taking a few choice photographs helps in visualizing the correct relationship between all of the parts. Setting it up this way is then confirmed by running patterns on the valve tip. Unfortunately, without getting into some real modifications, getting the rocker tip centred over the valve tip on a pedestal mounted system isn't possible. You're at the mercy of the cylinder head machine work and the rocker manufacturer. Still, if the pattern is as narrow as it possibly can be, then running off the edge isn't likely unless something is seriously amiss.
Then there's the issue of twisted rockers. Adjustable guide plates are needed to bring everything more in line and hopefully pushrod holes large enough in the head to allow the necessary clearance.

 

When you say you drew a line through the fulcrum centre and tip, by tip to you mean the centre of the roller tip or the contact point on the valve.
The reason I ask is that I've found that it's the centre to centre alignment of a full roller rocker that we're concerned about and not the trunion centre to contact point on the valve as I had been experimenting with earlier. That makes a huge difference in pushrod lengths. As much a .250" if you consider what the radius of the roller tip is.
This is what's driving the next round of testing. I'm moving beyond what appears to be an acceptable contact patch with a near stock length pushrod to one that's considerably longer. My thinking is that that contact will reduce in size from around .090" now to something around .030" .

 

Center of trunion axis thru roller wheel axis. Not the point of contact with valvestem.

There was a .075" difference in stand height using roller tip contact vs roller tip axis centerline. Big difference.