SBC valve geometry.

[Walter R. Malik]

That's a new one on me.
Does this include the typical stud mounted rocker as in a traditional SBC?

YES ... especially stud mounted or bolt down ROLLER TIP rockers.

[skinny z]

Interesting read on the two methods.

viewtopic.php?t=56596

[Lizardracing]

No one ever updates these things but here I go anyway.

I tried a 8.000, 8.050 and 8.100 pushrod using the sharpie mark on the stem and cranking the engine over 3 cycles.
The 8.000 shows about .80 wide and mostly centered.
The 8.050 shows about 40 wide and maybe very slightly to the inside.
The 8.100 looks the best to me at a little less than .040 wide and centered.
All testing was done with .012 lash cold. That works out to .016 at 200’ water.
I’m happy with that.
On a separate note, the contact pattern show the studs aren’t on quite the same axis as the valve guides. There’s not a lot I can do about that at this point. Some of this could also be the stud to rocker trunnion lash in the hole the stud goes through. The girdles may help with that.
I made the girdles several years ago so I know for sure the stud spacing is right to +/- .002.

[FloydODB]

Studs are cheap. Put a nut on it and smack it with a hammer. Just dont tell the stud.

[Walter R. Malik]

No one ever updates these things but here I go anyway.

I tried a 8.000, 8.050 and 8.100 pushrod using the sharpie mark on the stem and cranking the engine over 3 cycles.
The 8.000 shows about .80 wide and mostly centered.
The 8.050 shows about 40 wide and maybe very slightly to the inside.
The 8.100 looks the best to me at a little less than .040 wide and centered.
All testing was done with .012 lash cold. That works out to .016 at 200’ water.
I’m happy with that.
On a separate note, the contact pattern show the studs aren’t on quite the same axis as the valve guides. There’s not a lot I can do about that at this point. Some of this could also be the stud to rocker trunnion lash in the hole the stud goes through. The girdles may help with that.
I made the girdles several years ago so I know for sure the stud spacing is right to +/- .002.

Seems like you are just to worried about the contact wipe pattern to recognize anything else even exists in the geometry.

On a 23 degree Chevrolet head the studs are on a 12.2 degree angle; not the same as the valve but, somewhere between the valve angle and pushrod angle.

[billet]

Walter I think he means looking at 90 degree from the way you are looking at it. (looking from intake side to exhaust side not length wise of the head). Like the roller tip isn't leaving the laying flat on the valve stem.

[Lizardracing]

Both of you are correct.
I don't care as much about the "proper geometry", (what ever that is depends on the theory you like) On this engine I'm looking for Min sweep for guide life and not maximum power. It already has more power than I can use on any given night so endurance/reliability is what I'm after.

The pattern is showing more contact area on the valve stem, nearest the rear of the engine. Why I don't know but it's not enough I'm going to worry about it right now. The girdles fit well, the locks fit well so it's most likely the hole in the rocker trunnion is a bit bigger than it really needs to be by .005 or so coupled with tolerance stack ups on the stud and stud mounting boss. Hell, it might get better when the heads are 220' instead if 40 degree's in the shop.

[skinny z]

What spring did you use for your sweep pattern?

[Lizardracing]

The spring I'll be using.
130@1.900/420@.600