Don Terrill’s Speed-Talk

A similar 355 engine I had built was equipped with self aligning roller rockers and guide plates- guides were taken out in short order. I put this engine together from spares with the intention of selling. I take off the valve cover to check something and I see this- self aligning stamped rockers and AFR guide plates. Why would the machine shop do this?

I'm thinking that the width between the self aligning "nubs" is much wider than the valve stem. If that's the case, the guide plates are likely a better way to go. Just a guess without seeing them in person.

as far as i know and understand, you run either guide plates or self aligning rockers, not both. both can cause binding.

I have a couple questions regarding the heads.
Are these genuine GM 906 vortec heads or an aftermarket copy??
I have seen a similar looking head but with what appears to be a baked on black coating on the inside of the V/cover area and the underside of the non critical areas.
When you used the guide plates and guided rockers did it wipe out the push rod or guide plates??

Did the shop give you back the other rockers?? If not I would be having a chat with them as that is BS.

I have seen many guys try to use guide plates with either stamped or roller rockers with the end result of ruined push rods and guide plates. It seems the push rod guide to stud to valve tip center line is way off enough that when both guided rockers and push rods are used they destroy themselves so you must not use both 99% of the time. Some say that they have had no issues but I have seen too many that have had issues.

The reason I ask about the heads is it looks like they were machined for a larger spring thus the spring cup and I recently have seen 7 failed 383 stroker marine engines with valve train issues that have the above described appearance but came with threaded stud boss's and machined for single or a dual spring.

lefty o wrote:as far as i know and understand, you run either guide plates or self aligning rockers, not both. both can cause binding.

There were many late swirl port head factory built engines that came this way. They had the self aligning rockers and a slot guided pushrod. I assume that there is enough slop in the system or the factory alignment is good enough that it never caused a problem.

Per Dave, I see this quite often. We remove the rocker arms and go to older version. Why risk it. Just cause its there doesnt means it is the best solution
reed

Take off the guided rocker arms and install a nice inexpensive set of Comp roller tip stamped rockers and be done with it. You should never run both guided rockers and guide plates on Vortec heads.

In the previous incarnation- I wish the push rods or plates were ruined, the guides were all worn out and one valve needed replacing. The heads are the old RHS vortec version. The engine was rebuilt because after that I replaced the heads with AFR vortec and measured the '0' decks and they didn't match, just poor workmanship all around. I guess I'll replace the rockers.

Come to think of it- this is the second motor he built for me, the first had the same issue and I had to buy Comp steel roller rocker- old styl. Any body care to take an educated guess on what this engine would make? See attachments.

Heads- some info anyway.
viewtopic.php?t=24652

Compression: 9.5:1

Intake: Eddy marine highrise.

need to know alot more than just what the cam specs are before we can all start making wild azzed guesses about what it might make.