I had an engine build sitting for over a year while I took care of some other things.
I'm finally back on it and trying to measure for pushrod length.

I'm using Flotek heads:
https://www.summitracing.com/parts/FLK-101-505FT

and Scorpian rockers:
https://www.summitracing.com/parts/SCC-SCP1002

The heads came with rocker studs with an effective length of 1.75"
I'm attempting to follow the Straub Technologies video to set the rocker arm so I can measure for new pushrods.

The studs are too short, the rocker trunnion is about even with the top of the stud. I believe I need studs with an effective length of 2.3125.

Unless I use different rockers, or I'm looking at things wrong, which is entirely possible.
This is my first performance build and I'm learning as I go.

 

Akjeff,

Were there no guide plates involved before and now they are installed?

 

These are new heads and rockers on a rebuilt short block.
I did install the guide plates.

 

I guess I didn't clearly state a question.

That length rocker stud seems excessive, am I doing something wrong?
Has anyone else used these parts together before?

I've read that these rockers have large trunnions, if that's the case I can see that creating what I'm seeing, but I have no experience to know what's normal.

 

Obviously you have to have enough threads above the fulcrum for the rocker locking nut to be affective.
Also keep in mind the higher the rocker stud, the less likely your valve covers will fit.

At this point, which part is to blame? Wrong rockers or wrong studs?
I'm thinking somebody installed the incorrect studs.

If you need to swap them out, Summit sells ARP ones. You already know diameter for both ends of the stud and thread pitch, what's missing is length above the guide plate. How did you come up with your measurement (2.31) you need?

 

The stud threads are even with the top of the trunnion, I added .5625 (recommended thread engagement) to 1.75 (the current effective stud length).

 

I don't remember anymore why I selected these rockers, they were on my "to buy" list for over a year.
I may go with a roller tip rocker, I think it will fit further down on the stud.

 

Got it.

Wait a couple days before ordering any new studs.
Let's see what others suggest for length.

I too, have those same heads, but never went with the full roller rockers.
So, I can't relate.

I just don't see the need for those on street use. However, I do see the need to reduce friction and 90% of the friction is the rubbing on the valve-stem.
So, I found some used Comp Roller-Tip. 1.52 ratio.

 

Street motor right?

Let's see a picture of your problem.

I'd guess shorter pushrods.

That whole mid-lift geometry theory thing might be needed when when you have .750" lift, and 8500 RPM, and longer valve stems, deeper spring pockets, and Jesel rockers, stud girdles, etc. etc. When you change the stock geometry that much, you need to correct it, a lot. And there is zero room for error at 8600 rpm in a BBC. (Notice the high end Brodix heads and .750" lift cam on Jeff Foxwell's engine?) Leave this for the real race engines.

But on a street engine? When you are close to stock? I just do not see the need for it. It is just going to cause you height issues with pushrods, studs, valve covers, etc. It might require raising the rocker arm a lot vs stock. Stock heads are just not built for that, nor is it needed. You might even need custom length rockers, custom guide plates, taller valve covers, longer studs, stud girdle, etc. It opens a can of worms.

On a SBC just check with a sharpie and make sure your roller is close to the middle of the valve tip, and absolutely not near the edge, now that would be a problem. Ideal is dead center, a little on both sides. Make sure the width of the roll mark is like .050", not .120" As long as it goes past center once, and is not near the edge, you are OK. Make sure the rocker does not contact the spring retainer, or bottom out on the stud in it's slot. Those are real important. Some of the aluminum ones have issues here.

There is no HP to be found here, no valve lift, no reliability. It is a solution for a problem that does not exist, at least on a street engine. But it really won't hurt anything, either, if you want to go thru the exercise. But SBCs are dead reliable with stock geometry to 7000 rpm.

My stock BBC would have needed ~.250" longer pushrods than stone stock to get close to mid lift geometry. I guess the factory geometry did not work eh? For 50 years?

 

leigh1322,

You are not comprehending the problem.

Aftermarket heads. He is getting ready to check pushrod length.
Installs a roller rocker arm. Hardly any threads show through the fulcrum for a rocker nut to adjust.
Has absolutely nothing to do with pushrods at this time. It's about the stud height right now.

He wants to know if using Scorpion Arms requires a special, longer / higher than stock, rocker arm stud.

 

Anybody ask about a roller cam yet? That would explain it. Roller lifters are much taller and require much shorter pushrods.

 

Oh I absolutely am. He is trying to raise the roller rocker to Jeff Foxwell's mid lift geometry theory.
Everyone else missed that. 1/4" higher = less stud available
He just does not need to worry about that.
But I whole heartedly agree, that should not cause him to run out of stud.
Something else is going on.

I assumed he has adjustable pushrods already. Maybe he does not.
Maybe he went hydraulic roller and still has the stock pushrods.
He hasn't said yet.

 

You are missing the question too. Has nothing to do with type of cam, lifters or pushrods at this point.
Over thinking this.

Anybody out there using Scorpion full Roller Rocker Arms?????

If so, did you have to order different (taller) rocker studs to compensate for a different style trunnion?

 

The mid lift concept is good for any engine and will minimize sweep across the tip. It will maximize lift also and reduce wear.

Many aftermarket heads have longer valves to allow for bigger springs and give clearance for lift. So right off the bat the rocker must come higher...and you have to get the pushrod right during that process.

The main thing you want is for the rocker to pivot on the SHANK area of the stud...not up on the threads...so that's a key measurement and lots of studs are available. Also if using a roller cam I always recommend going to 7/16" studs vs 3/8". Might be overkill for a mild Hyd roller...but definitely good on a solid roller anything.

On my heads when I used non shaft rockers....I ended up using a set of extra length ARP studs designed for a Ford 351C arrangement where the studs extended up through the valve cover and used the valve cover as a stud girdle. I had to shorten the end of them .300" to make them perfect....but they put the rocker in the shank, gave plenty of thread engagement.(almost the full length of the adjuster nut). Never an issue even at 8000+ RPM and stupid stout valve springs and crazy cam. Those heads ran 20+ years and still have original guides.

JIM

 

This is a street motor w. a flat tappet cam and hydraulic lifters.

I do not have the adjustable pushrods yet, the ones I was looking at come in two lengths (I don't recall which they are ATM, as I mentioned it's been over a year).
My plan was to get the rocker set and attempt to get a rough measurement, so I know which pushrod to buy. From past experience, I know I'll buy the wrong one if I guess.

My first attempt at this I tried the stock rocker arms, they wouldn't fit due to the valve spring dia.

I can get pictures a bit later, if they are still necessary.
My current plan is to return these and go with Comp roller tip rockers. I believe, due to the rocker ball vs. trunnion, they will work with these studs.

Mixing and matching parts and finding what will or won't work together has been a learning experience, I appreciate the input and questions.
I have stock motor building and tuning experience, as I mentioned, this is my first attempt at a performance build.

I went back to the video and read the comments and questions there, I seem to be following the instructions.
That was my main concern when things weren't working. It seems simple enough I couldn't figure out where I was going wrong.

 

Would get a pushrod length checker and the light weight spring for checking it and do it correctly the first time. Getting the rod length correct to keep the tip centered is all you need to do.....no fancy made up equation necessary. I never had to buy extra long studs. I even bought short posi locks to fit under old school rocker covers
Most folks buy rockers and dont account for the spring diameter and that tends to be the issue i see the most

 

Thanks for the update.

If it is a flat tappet, the cam might not be on the base circle when you tried to put it together. Lifter needs to be all the way down in the bore first.

 

I had forgotten I had this pushrod length checker:
https://www.summitracing.com/parts/pro-66789

At least I remembered where I put it.

It looks good with the factory length pushrods, I'm going to try these rockers with the factory pushrods and see how it looks.

And now it occurres to me, the geometry may be "close enough".
With the valve fully closed I'm actually lifting the rocker above it's normal position in order to check it by using the method in the Straub Technologies video.

 

Sounds like you found the issue. The Scorpion rockers are too fat for the springs.
I have seen this before also. Aluminum rockers are very fat.
With a mild street motor, the Comp roller tip ones are a reasonable choice.
So are the Liberty Performance Stainless roller rockers, that are about the same $ as the Comps, full roller, much smaller than aluminum, and my buddies run them on their race engines.
For you stock length pushrods will be fine.
Just check and make sure they sweep over the center of the valve tip.