I reset my valvetrain using the mid lift method. Now I'm in a predicament where there's no conceivable 3/8 rocker stud setup available to me. With 7.375 pushrods I require a rocker stud that does not exist. As it is my rocker trunnion on my Scorpion 1.6 sits completely on the threaded area, well above the shank. There are longer studs available however all of them have a short shank area. I don't get it. Certainly I'm not the only one with a 3/8 rocker and given the amount of them that are available, WTF is going on?

Ideally I need a 1.895, 1.900 or 2.00 stud. They all work. But those longer studs have a threaded portion 1.00 long. The shanks are all the same. If that was .700 with more shank I'd be good. Right now I have a 1.750 stud and I'm only getting 4.5 turns of the Poly to the trunnion. The studs that would work require a 7/16 rocker which opens a new can of worms with regards to center bolt valve cover clearance not to mention the expense all for a damn stud. My other option was to use a .120 washer under the stud and lift the trunnion higher. Every single stud has a .700 to .710 base thread depth into the head. If I add .120 there I'll be shallow on head penetration and I'm running an aluminum head. I cant' make this nonsense up. I can't possibly be the first person to have this problem on what is probably to most popular engine setup in history. I'm open to suggestions...please.

 

What are the dimensions of the stud you currently have?
Effective stud length (under the hex to the tip)?
Overall threaded length?

 

The ones I just installed today are the longest 3/8 ones available. ARP 134-7104. The effective length is 1.895 with a 1.000 thread. They are working much better. The set screw in the poly is 2.5 turns below the surface of the poly vs 7 turns before. I think the bottom of the trunnion is just touching the shank section when the valve is set with the preload. The former ones were 1.750

 

This is an odd as I can't recall having come across it.
That said, long ago I made the switch to 7/16ths studs and there's a greater variety of those.
Your pushrod length doesn't appear to be anything out of the ordinary (mine are 7.4").
And one has to assume you performed the geometry check properly. A quick question in that regard. Did you use the roller tip axis as one of your references? One builder I spoke with was adamant about using the roller to valve tip contact as the point to measure to but that's against the prescribed method as set out by Jim Miller.
Check to be certain how much of the shank is supporting the rocker. You may have solved the issue with the new studa.
As for the polylocks, as long as there's at least 3/8ths of thread engagement your in good shape.

 

Does it have longer valves? Whats the cam lift? Also not all rockers are designed around midlift geometry. Most arent probably. You might have bad angle on pushrod side to get good angle on valve side. Then might be positioned on far edge of the stem. Might need to compromise. Check sweep width while you are at it to see. If its got any kind of cam and spring on it, 7/16 studs are probably a better idea.

 

That in itself opened up a whole other can of worms for me.

 

I think the total length of the valve is 5.00. My lift is .565. These are from the head data card

1.740" Install Ht. → Installed spring height (distance from spring seat to retainer at rest).

135 lbs @ 1.740" → Seat pressure: 135 lb when the valve is closed.

305 lbs @ .565" lift → Open pressure: 305 lb at full cam lift.

It's sure running better and sounds better. This all started after chasing a cold tick. I had 7.200 pushrods before and they were sweeping.104 wide across the valve tip. After the mid lift I came up with 7.375 exhaust and 7.400 intake. There's a noticeable lope at idle now and it's a Smoother idle. Cams a lingenfelter 74211. That's the new sweep. I used Prussian blue. Didn't leave the greatest impression but that's around .050 wide