Tried installing my set of Scorpion 1.6 roller rockers today only to discover that the guide slots in my 601 heads were binding the pushrods at zero lash.

If there was even the SMALLEST bit more.of elongation towards the bottom of the guide slots they would clear.

Can the slots be clearanced with the heads on the engine or is my only option to send these back for a set of 1.5 rockers?

 

Try some longer push rods.

Cjeck your valve train geometry while you're at it... might well turn out that you need longer push rods anyway. Maybe it's a sign from Above.

 

What length would you recommend using?

I was trying the stock length hardened steel rods and at zero lash they were binding to the point where the lifter cup could not pump all the way back out after turning the engine over.

 

I had this same issue, the only thing about longer pushrods is they might scrub the head, when I tried there was about only a paper thinkness' clearance... so I didnt install them.

 

If the pushrods are hardened steel wouldn't this eventually "wear down" the holes to the needed clearance as long as everything runs OK?

 

Theoretically. But would you really want to take that chance? And do you really want little slivers of metal running through your motor, I mean they will probably just get stuck in the oil filter. But to me the less metal floating through your motor the better.

 

Not gonna argue that. What length pushrods did you use with the 1.6s?

 

I didn't. I went to the local race shop and they gave me a few different lengths (one of each) and none of them had any decent clearance. So now I am stuck with these rockers and nothing to use them on.

 

I want to make sure I'm being understood clearly.

The problem is that the pushrod is binding at the side of the guide slot towards the EXHAUST SIDE of the head. So some longer pushrods should theoretically move the pushrod slightly upwards in the guide slot towards the intake side while also taking geometry into consideration?

 

IT SHOULD, yes. But Like I said, I went and got longer ones and really didnt help much. Maybe I didnt go big enough though.

 

Then that is what I will try.

Regardless of how much clearance my eyes are content with, It's how it "feels" that matter to me. If I can properly set lash and rotate the engine completely over without binding up the lifters I'll be OK with that. Honestly a minute amount of "contact" between the pushrod and guide slots doesn't sound like a problem. There only a paper amount of thickness between the pushrod and the left/right sides of the guide slot to begin with. That's why guide slots require hardened rods.

With the stock 7.8" rods, it was binding so bad the lifter could not achieve full lift and I was unable to properly locate zero lash by spinning the pushrod.

 

Sorry, I was in a fog when I replied; I thought you were complaining about the end of the slot in the rocker hitting the stud.

Cancel and delete my earlier comment. My brain got a cramp all the sudden. Let's start over.

Think about the meaning of "ratio" for just a minute. "Ratio". Such an intriguing mathematical concept. But this is more than just math, it's rocker arms we're talking about here. So what is that, anyway?

Right: in the case of a rocker, it's the distance between the stud and the point where the tip contacts the valve stem, divided by the distance between the stud and the push rod seat. Eh??

Let that sink in for a minute. One distance, divided by another distance.

Now that your brain is all the way wrapped around it, how do you suppose a mfr can change that about a rocker, in such a way that you can just bolt it on?

Can the mfr change the distance from the stud to the valve stem? I'm kind of doubting it. At least, not by much ... although they usually do lengthen that just slightly, which moves the contact point outward on the valve stem a little. But that's really done only just a little, since that's all that's possible.

Can the mfr change the distance from the stud to the push rod seat? ABSOLUTELY!!.

And to increase the "ratio", which way would that distance have to be changed? (see definition of "ratio" above)

Right: the stud can't be moved, so the mfr would move the push rod seat closer to the stud.

Eh??

This often, usually in fact, moves the push rod so much closer to the stud, that it rubs and binds against the end of the slot.

Only cure is to lengthen the slot.

http://www.summitracing.com/parts/CCA-4710/

There is no "need" for hardened push rods in this application. This was the guide method employed in virtually ALL factory SBCs up until about 87. Now granted that was only about 30-some-odd years of production, involving .... Iunno, tens of millions or so, of these motors, every single one of which was built without aftermarket hardened push rods; but that's probably a good indication that even though harder push rods are generally "a good idea" in a hot-rod build, they're not inherently "necessary" just by reason of the guide slot.

 

Honestly I was a tad confused on how the pushrods were going to help any.

The only concern I have with lengthening the pushrod slots is how can this be done with the engine in the car? Aren't there going to be shavings going everywhere?

 

Buying a cheap 1/2" drill bit is cheaper than buying pushrods, or anything else. Or just pull the intake, pack the drill flutes with grease, put thick oiled rags over the lifters. I did this at the dirt track races one time, out of desperation. That engine looked fine on tear-down at the end of the season. This requires guide-plates or self-aligning rockers.

 

By the way, screwing up valvetrain geometry in hopes of gaining clearance is not a wise idea. Longer pushrods aren't called for unless the rockers have super-deep cups.