Now, first before anybody goes posting the usual reponse to this, it's not the same question. I am fully aware that when changing to roller rockers that are not self-aligning, you have to use guideplates. The question is, why? What is the difference between the heads on the older style 350's and the new ones? From visual inspection, there is no difference besides overall head height, which is very different. But the holes for the pushrods are apparently identical, and they are the same space apart, as are the studs and valve stems. So as far as head geometry, everything appears to be the same. So my question is, why do they use guideplates on many Corvettes from the factory and not the f-cars, and what makes the old style heads and/or valvetrain alignment different? They surely are, because I have seen attempted jobs done with non aligning rockers on an LT1 and it obviously would not work. The roller tips could walk off the valve stems. So what's the difference? The section in the tech articles is pretty poor.

Quote:
Q: Should I use self-aligning or non-self-aligning rockers?

A: You have to use a self-aligning type otherwise you will have to pull the heads to tap them since the studs are pressed in.

That makes little sense. If you use non-aligning rockers you have to use screw in studs? Obviously this is hinting that you also have to use guideplates.

Also, why is it recommended against using self-aligning rocker arms with pre-87 motors? Wouldn't that be extra protection?

Also, everybody claims you need hardened pushrods with the guideplates. What about the Corvettes that use stock pushrods with mild steel guideplates?

Just wondering. I haven't been able to find a good answer to this yet.

Todd

 

Todd, long time no hear! Did you go to the 2000 Indy show? I had to pass this year. I hope to make it in 2002. Later
p.s. (I was you roomy, remember?)

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Rob P
89RSconvtZZ4TPI
92Z28convt5spd
71Impala convt 402BB
BETTER DRIVING THRU SUPERIOR HORSEPOWER!

 

Yeah, I was there this year. Not as good as the other one I'm afraid. It was at the brickyard track in a parking lot. Really hot and the drive-through judging was kind of a pain. There also wasn't any way to organize thirdgens together like before.

But John Moss' cars sure are cool as hell.

 

Todd....I dont understand it either Ive used the self aligning rockers on older heads with no problems. Lingenfelter says that the mild steel guideplates used on the vettes were there for help with assembly. The guide plates used on them are not hardened. Thats why they can use the non hardened pushrods. In Lingenfelters book he says that the older pushrods used on the non self aligning heads were hardened. And you can use them with hardened guide plates. You can check them by rubbing them with a file.

Ive been told that they try to index in two places when using them together. And can cause the pushrods to bind in the head. But arent the pushrod holes still the same? So I dont see how that would be a problem

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Black 90 IROC, L98, A4, 323 gear. SuperRamed 406 in the works!

[This message has been edited by MikeH (edited October 05, 2000).]

 

Self-Aligning Rocker: Used on cylinder heads that have the pushrod hole noticably larger that the pushrods and can cause slop in the geometry. You do not need guide plates.

Non Self-Aligning Rocker: Used on cylinder heads that have the pushrod hole as a slot to barely accomadate the pushrod's diameter and it's intended travel. Also can be used on aluminum cylinder heads, but with the addition of guide plates and hardened pushrods. If using these rockers on cylinder heads with large pushrod holes, you'll need guide plates.

Guide plates and hardened pushrods go hand-in-hand.

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George P. Lara
1994 Z28 LT1 T56
1984 Z28 High Output
Member: SCCA, SCFB, SC3GFB

 

Well, I don't know if I can give your questions the best answers, but I'll try.

Self aligning rockers are only found in a non-roller tip stamped rail rocker or the ford rail style rocker arm assembly (where the rockers are mounted on a shaft). The stamped rail rockers were installed in '86 or '88 (can't remember). They have raised ridges (rails) at the rocker arm tip that traps the valve stem. This keeps the rocker from moving back and forth. The rail rockers require a longer valve stem, placing the keepers a bit lower on the stem. You cannot use them on the earlier (pre '86/88) valve trains or the valve spring retainers will come off.

Non self aligning rockers on stock heads (with the exception of the aluminum vette heads) have a small hole in the head that keeps the pushrod centered under the rocker. The aluminum vette heads and many aftermarker performance heads don't have a hole. The area between the pushrods is open. Guide plates are required to keep the pushrods centered under the rockers.

The earlier model (pre rail rocker) pushrods were / are made of hardened steel. The new rods (used with rail rockers) are not and can't be used for older aplications. If standard pushrods are used, they would wear out prematurely because they would be rubbing against the head.

The corvette guide plates that you refered to of being non-hardened were used on the assembly line to position the pushrods prior to installing the rail rockers. They are not hardened because the pushrods are not hardened.

As to what rocker to use, if you have screwed in studs, the non self aligning rocker with guide plate is the best. Or you can spend about $1500-$5000 and convert to a rail (shaft) system that Winston Cup engines use.

Clear as mud? Hopfully someone with more knowledge on this subject will jump in.

Mike

 

Mike... I used the self aligning type rockers on an old set of rebuilt 882s with no problems.

Ive been told the same thing about the valve tip being taller. Maybe it was just a matter of time before something went wrong?

I did tell the guy that built them they were going in a 91. Maybe he used the later style 194/150s in the older heads. Is that possible?

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Black 90 IROC, L98, A4, 323 gear. SuperRamed 406 in the works!

[This message has been edited by MikeH (edited October 05, 2000).]

[This message has been edited by MikeH (edited October 05, 2000).]

 

Guys, that's all really helpful information. It still leaves a couple areas of confusion though. The main problem that I'm still confused about is that on many of the new style heads, the pushrod hole is the exact same size as on the older ones. Now, I can understand why guideplates are obviously needed on engines with an open cavity where the pushrod is. So with those heads, it's clear. But why did they still feel the need to require self-aligning rocker arms on the later style heads with the same small pushrod holes? Seems redundant. And I'm still not clear as to why it's not good (supposedly) to run self-aligning rocker arms on older style heads. Is the indexing them in two places the reason? If so, then that wouldn't make sense on corvettes that had both self-aligning rocker arms as well as mild steel guideplates. And it also dosen't make that much sense for them to use guideplates just to aid in assembly.

Any ideas? This is pretty informative.

Todd

 

Well, Corvettes (L98) had aluminum heads, so you must use guide plates and/or self-aligning rockers in order to reduce wear on the aluminum from the pushrod. Since the B2L was a cast iron version, I would think that GM (being "thrifty" as they are) just decided to use the same rocker arms as on the Aluminum L98s on the F-body B2L. In reality, nothing will go wrong if you use self-aligning rockers with cylinder heads that were designed with the pushrod slot, unless the heads are tweaked, which of course you wouldn't use anyway.

 

MikeH,

It could be possible that you're builder used the "new" taller valves for the self aligning rockers. This subject inspired me to look through my Lingenfelter book. That must be where I got the assembly note for using the non-hardened guide plates with self aligning rockers. It's funny how some of the little things stick in a persons memory. He also makes a point to say, in bold print, "Never use a rail rocker on an earlier valvetrain."

Todd,

The only answer I can give you that might hold water is that hardened pushrods are about twice as much as non-hardened pushrods. Rail rockers are the same cost as standard rockers. I'm sure GM continued to use the rails for cost reduction reasons.


I did find out something else as well. I was wrong in my above post in one regard (and possibly more ). Self aligning roller rockers are available without the shaft mount system. They incorporate a washer slightly larger than the roller, on both sides of the roller tip that keeps the rocker centered over the valve stem.

Mike

 

So, would it be safe to assume the World Products S/R heads (pre-1987) style could use non self-aligning type rocker arms and no guide plates?
thanks

Added: These heads have a small pushrod slot
with very little room for side to side movement of the pushrod.

[This message has been edited by Matt_Ky (edited November 09, 2000).]