Rocker arm stud length and guide plate thoughts (BBC)

[Fred_M1010]

I have a dilemma.
I'm assembling a 454, and the rocker studs I've got seems a little short...
I'm using ARP 100-7101 which are 1.9" tall.
But I have only about 9mm (0.35") of threads for the nut to engage.


I'm using PVS Mid-lift rockers:

Next step in rocker studs seems to be the ARP 135-7202, they are 2.35" tall.
But they have a shorter thread length so I would risk bottoming it out instead...

Should I go with the ones I have, is it enough?
If not can I use a washer over the guide plate to get it slightly higher...?

 

[76zimmer]

Fred those are 7/16 studs right. I would make sure you have at least 7/16 of thread engagement. I can't think of why putting a washer (hardened ground flat type) under the stud would be a bad thing as long as you have good head thread engagement. You might also consider the longer studs and using a washer under the locknut if you might bottom out. Give Scott (4x4high) or Heath (folkenheath) a PM on this.

 

[Fred_M1010]

Yes, they are 7/16.
I just read the installation instructions for the rockers, and they recommend 1.5 times the diameter.
So I think I'll go ahead and buy the longer ones.
It sucks that they cost $71 a set though
But I have sent PMs for both Scott and Heath in case they have some better ideas.

I also noticed that the bottom of the nuts aren't threaded for the first 0.1" or so.
So I don't think the risk for them to bottom out is so big,
and in that case I could always drill out the nuts for another 0.1",
Or find a washer with the right fit.

But one thing got me thinking regarding the longer studs (135-7202),
In ARPs catalog it says "Chevrolet bigblock (Aluminum heads)"
See link: http://issuu.com/arpbolts/docs/catalog2.pdf/48?mode=a_p
Why would it say Aluminum heads?
I can't see what could be different

On the other hand, the studs I have now seems to be for a Ford Small block...?


I have some thoughts regarding guide plates as well.
I now have some 2-piece plates, that looks alot like these:

But it doesn't say comp-cams on them, so they are probably some cheap knock offs.
They don't fit very well, so I have to bend them pretty much to align the holes.
And the thought about having more things that can get loose inside the engine doesn't comfort me very much...

Do I really need to be able to adjust the guide plates?
Is it a common problem with bigblocks (cause of the splayed valves)?

I probably should add that I have iron heads (781-castings)

 

[thatK30guy]

Subscribing to watch how this one turns out. I'm gonna buy some Crane Gold Race rocker arms and had plans for ARP studs, too.

 

[nvrenuf]

I have a dilemma.
I'm assembling a 454, and the rocker studs I've got seems a little short...
I'm using ARP 100-7101 which are 1.9" tall.
But I have only about 9mm (0.35") of threads for the nut to engage.

Is this a hydraulic lifter set up? Is the amount of threads you measured with the rockers loosely resting on the stud? If so, wont the rocker go down more as the nut is tightened (and the lifter compresses) engaging more thread?

 

[Fred_M1010]

Is this a hydraulic lifter set up? Is the amount of threads you measured with the rockers loosely resting on the stud? If so, wont the rocker go down more as the nut is tightened (and the lifter compresses) engaging more thread?

Yup, I already added 1mm for that,
it was actually only 8mm sticking up through the rocker.

 

[Fred_M1010]

Subscribing to watch how this one turns out. I'm gonna buy some Crane Gold Race rocker arms and had plans for ARP studs, too.

Keep in mind you'll need pretty high valve covers,
and even then the rockers might rub against the inner sides...
ask me how I now

I I where to do this engine-build all over again,
I would probably go for steel rockers like these:

But a roller-tip rocker would probably do as well:

Aluminum full rollers are just not worth the hazzle, and really isn't necessary for a street machine.

I do like the mid-lift concept though, to bad they don't make steel rockers with that geometry.

 

[76zimmer]

The longer studs for aluminum are probably due to more thread engagement in Aluminum (my guess)
The guideplates have been on most if not all of the BBC's I've had apart.
The adjustable part is when you start messing around with longer pushrods (you) and trying to keep the roller on your rocker in the center of the valve tip, and not off to the side. just be sure the pushrod isn't contacting the side of the hole in the head.

I used the factory thick plates and had great results lining up my rockers.

From my thread:

And a little paint marker on top of the valve stem to see where the rocker rolls on the valve tip.

The resulting bare spot shows the valve/rocker contact pattern. It looks good for pushrod length, but may have to move the pushrod guideplates a bit to center the roller tip on the valve stem:

__________________

 

[thatK30guy]

Keep in mind you'll need pretty high valve covers,
and even then the rockers might rub against the inner sides...
ask me how I now

Will the Cranes clear in these covers?

 

[4X4HIGH]

Ok, I got your PM but now I need to ask why you're even having problems to begin with. Did you go with a valve with a longer stem or even a longer pushrod? If either then how much longer is either than stock? Once I have this info I can better help you.

 

[dremu]

Will the Cranes clear in these covers?

I should know this ... I had to get those to clear my valvetrain...

They sure are purty.

Scott may remember what he put on there when he built those heads...

-- A

 

[Fred_M1010]

Will the Cranes clear in these covers?

I've no idea, I'm afraid.
I tried to use Pro comp sheet metal aluminum covers (cheap chinese stuff i believe )

They are OK height wise, but the intake rockers(if I remember correctly) rubs the sides towards the intake.
So now I have to find someone who can weld aluminum

What rockers are you using now (the ones in your pics)?

Ok, I got your PM but now I need to ask why you're even having problems to begin with. Did you go with a valve with a longer stem or even a longer pushrod? If either then how much longer is either than stock? Once I have this info I can better help you.

Why I'm having problems is probably due to me choosing an over fancy rocker
I've now realized that the mid-lift design of the rocker places it higher up.
The rocker arm is supposed to be 90degrees to the valve stem at mid lift.
And regular rockers are about 90 degrees at full lift I believe.

I don't think the new valves are any longer than the stock ones, but I'll check that tonight.
I had to use lash caps though, for the rocker to clear the retainers.
And the push rods are slightly longer than stock, but that's mostly due to the mid-lift concept I believe.
I can't remember the exact numbers for them now though, but I can check that tonight as well.

What do you think about the guide plates?

 

[folkenheath]

I agree with 4x4High, something doesn't sound right with why this is happening.

My first guess would be, are you sure you don't have too long of pushrods? How is your rocker geometry? Did you check it as Zim stated?

Also, you probably are already doing this, I'll mention it just in case. Make sure you are rotating the rocker shaft with the countersink/flat up. It is very easy to install the rocker shaft with the rounded part up instead, and then the poly lock will sit higher and not engage the rocker shaft correctly, causing premature failure.

Dart was the first to make those adjustable guideplates if I recall, they are excellent quality and work great on the ones I have used, much easier to get perfect geometry. I have found it difficult to get all the rocker tips aligned without them. And if you try and bend the factory units the hardened surface will flake off, not good. The Dart units have locking nuts on the center bolts, that combined with the rocker studs, I think they are plenty secure. I don't know about the other brands though, I though Dart had them patented.

 

[Fred_M1010]

I agree with 4x4High, something doesn't sound right with why this is happening.

My first guess would be, are you sure you don't have too long of pushrods? How is your rocker geometry? Did you check it as Zim stated?

Also, you probably are already doing this, I'll mention it just in case. Make sure you are rotating the rocker shaft with the countersink/flat up. It is very easy to install the rocker shaft with the rounded part up instead, and then the poly lock will sit higher and not engage the rocker shaft correctly, causing premature failure.

Dart was the first to make those adjustable guideplates if I recall, they are excellent quality and work great on the ones I have used, much easier to get perfect geometry. I have found it difficult to get all the rocker tips aligned without them. And if you try and bend the factory units the hardened surface will flake off, not good. The Dart units have locking nuts on the center bolts, that combined with the rocker studs, I think they are plenty secure. I don't know about the other brands though, I though Dart had them patented.

Ok, hearing that makes me feel a little safer with the guide plates.
Mine came with lock nuts as well.

I'm pretty sure that I had the flat part of the rocker shaft turned up,
but I'll definately double check that, thanks!
The rocker geometry is fine I believe, but as I said it's not done the usual way with these rockers.
Here's some info:
http://en.wikipedia.org/wiki/Mid-lift
But it really doesn't describe it so well.
I think this picture describes it best:

At half lift the "back" part of the rockers should be 90* to the pushrod,
and the "front" part should be 90* to the valve stem.
This makes it slightly more efficient, or so they say.
And since I'm pretty interrested in math and geometry, I thought it sounded like a pretty neat thing.
What I didn't think about, and the shop where I bought them failed to mention to me,
is that the rocker ends up higher on the stud, I realize that now.

As a help when installing them the rockers have a machined surface on the top of them, and when that is 90* to the rocker stud, the above is also true regarding the push rod and valve stem.

So all I had to do was set the cam lobe in question at half lobe lift with an indicator dial,
and then adjust my adjustable pushrods until the machined surface and the rocker stud were square (90*) against each other at the same time as I had half valve lift on the valve measured on the retainer.

This way the roller don't travel as much back and forth on the valve stem,
At mid lift it's actually the furthest away from the rocker stud, and at full lift it's back at the place it has when the valve is closed.

I didn't have mechanical lifters for the test as recomended though.
But instead I used really soft thin wire springs instead of valve springs, so that the lifters wouldn't bleed out.

Here's a link to the instructions for the rockers if anybody's interrested:
http://www.mid-lift.com/PUB/PUB050206PA.pdf

 

[76zimmer]

After skimming through that instruction list, I guess I'm caught up in the old traditional hype of non idealistic rockers. I used the Comp Cams Ultra Pro Magnums,

and didn't have any of these setup problems Fred. I've also used Crane and CC roller tipped rockers with great success. I'm no engine guru, but keeping it simple works for me.

 

[4X4HIGH]

So all I had to do was set the cam lobe in question at half lobe lift with an indicator dial,
and then adjust my adjustable pushrods until the machined surface and the rocker stud were square (90*) against each other at the same time as I had half valve lift on the valve measured on the retainer.

I hope this was ONLY to make sure that everything works as their instructions say. You CANNOT run adjustable pushrods in an engine they are ONLY for set-up purposes.

 

[folkenheath]

I'm with Zim. The idea of it sounds pretty good to me, but I also feel like it's solving a problem that's not really a problem, while creating other problems. It says he developed them in 1973, but yet they are still not that popular, because standard roller rockers are already good. And the roller tips help prevent guide wear themselves. Also, there is arguement that with the rocker 90 degrees to the valve at full lift is best, because that's when the spring is strongest and where the max lift is anyway. Just looking at mine and guessing, I would say the rocker is probably perpendicular to the valve somewhere between mid lift and max lift, but I never measured that. I think as long as your rocker arm is pushing on the center of the valve, you should get good service life from the guides with either setup. The adjustable guideplates help accomplish that. What brand are your guideplates?

 

[Fred_M1010]

Don't know about the brand of the guide plates, it came in an unmarked box, like most stuff from the vendor I used...
Some times I had to call and ask what he really sent me.
I don't think I'll use them again anytime soon.
And now it's to late to call and ask, cause it was almost 2 yrs ago I bought the stuff, so he won't remember it.

The engine build got placed on hold while I worked on the K30

I did check the rocker shafts btw and it was flat on both sides.

I hope this was ONLY to make sure that everything works as their instructions say. You CANNOT run adjustable pushrods in an engine they are ONLY for set-up purposes.

Ah, come on, do I really give you the impression of beeing THAT stupid
Ok that my english can be flawed at times, but It's not my native language.

Anyhow I did check out the length of the valves and pushrods.
Intake valves:.020 shorter
Exh valves: .020 longer
int. push rod: .040 longer
exh. push rod: equal length

But I don't think we can read much into these numbers.
The block has been decked, and the head's been rebuilt with larger valves.
And as I said earlier I think it's just due to the design of the rockers.

And after all, it's not a big problem.
I'll just buy the longer studs, now that I know why.

 

[folkenheath]

Don't know about the brand of the guide plates, it came in an unmarked box, like most stuff from the vendor I used...

Do they look like this and have "Dart" stamped into them...?

The Dart units are actually made for Dart heads which have even more splayed angle on the valves, so they do confom to a stock head a little when you tighten them down, but that's normal.

 

[4X4HIGH]

Ah, come on, do I really give you the impression of beeing THAT stupid
Ok that my english can be flawed at times, but It's not my native language.

Anyhow I did check out the length of the valves and pushrods.
Intake valves:.020 shorter
Exh valves: .020 longer
int. push rod: .040 longer
exh. push rod: equal length

But I don't think we can read much into these numbers.
The block has been decked, and the head's been rebuilt with larger valves.
And as I said earlier I think it's just due to the design of the rockers.

And after all, it's not a big problem.
I'll just buy the longer studs, now that I know why.

You didn't give me any impression to be honest other than trying to correct a problem and I have nothing else to go on other than what you posted. I'm just stating a fact that you CANNOT use an adjustable pushrod for anything other than set-up purposes. The reason I said that is i've seen people try to use an adjustable pushrod in an engine and they cannot withstand valve spring pressures and end up looking like a pretzel the first time they see spring pressure from a normal valve spring.