Need Refresher on Valve Guideplate and Rocker Adjustment/Alignment
Working on two smallblocks, one a flat tappet cam 327, the other is the 400 SBC with roller cam I talked about in a previous thread that will eventually make it's way into my 56 Nomad.
The 327 has Edelbrock Performer Heads and guideplates. I've checked the length for the pushrod needed and it seemed to come out to the suggested 7.900 that Edelbrock has suggested. Now, while trying to set up the guideplates to maintain that .005 gap to the sides of the pushrods, it wasn't easy but seem to have gotten it done...at least on #1 cylinder. But, after torqueing the guideplate down and now putting the roller rocker into place, there is still enough play for the roller tip to move around on top of the valve stem and suspect that's unavoidable but it's been a number of years since I've done this and would appreciate some input. Sure seems like the guideplate should be used to center the roller tip rocker over the center of the valve tip but doing that might add some side contact between guideplate and pushrod.
Thanks, Mike T - Prescott AZ
3/8" studs and 7/16" studs are interchangeable as far as heads and guideplates, because even the stock 3/8" screw in studs have a 7/16"-14 thread on the head side of the stud.
I've never seen the need for an adjustable guide plate for an OEM head, but aftermarket heads could be different. It's usually only needed when offset rockers or lifters are used. But, the Q&A on the link for the Comp guide plates does mention fixing a problem on Edelbrock heads. So they may solve your problem. Don't know why, Edelbrock is usually much better about not requiring this kind of stuff than many other aftermarket heads - because they are not radical.
The pushrods I ordered, Edelbrock 7.900, are .080 wall and hardened. In the end, these were the size suggested by Edelbrock for their performer aluminum heads. The roller rockers I've got for the 327 are Howards and not offset.
I think where I might have gone astray is after watching the 3 or 4 minute Video by Edelbrock as to how to adjust the guideplates. They mainly focus on adjusting the plates to attain a .005 clearance between guideplate and pushrod. The video shows them having the rocker studs just snugged up with pushrods in place and then just laying in the roller rockers, no retention nuts included at this point. With the pushrods just barely captured by the not-secure rockers, you were supposed to use a tool to just coerce the guideplate into position again ending up with that magical .005 clearance. Did that and then added the rockers, while attempting to keep the clearance between guideplate and pushrod. I wound up with rockers that were not exactly centered on the valve tip. Did I miss something from their video, more than likely, but after reading some comments from the various Forums, I started to think the main goal should be to keep the (in this case) roller rocker tip centered as best as possible on the valve tip. If that meant that the one piece guideplate from the Edelbrock heads had the pushrod rubbing up against it, there was no other way around it. If I'm still missing something here, please chime in.
PS - The AFR heads that are on my 400 SBC, earlier thread where I was asking about compression ratios effect based on altitude, have those two-piece guideplates so I suspect I will be more likely able to get the rocker centered on the valve tip and hopefully keep some gap between pushrod and guideplate.
Mike T - Prescott AZ
Mike T - Prescott AZ
By design Chevy rockers can rotate on the stud push rod guide plates limit the horizontal movement & keep the tip centered on the valve. With a solid lifter cam & with rocker to valve clearance the rockers will "dance" side to side a bit on the valve stem.
Have never heard of adjusting guide plates for X amount of clearance to the pushrod (IMHO total BS) as soon as the valve cycles through one event the push rod to guide plate clearance will change.
Pushrods will rub on guide plates period. Use hardened pushrods.
Self aligning rockers will limit horizontal movement they have "nubs" protruding from the tip to locate them on the valve stem.
Like churchkey, I've never heard of adjusting the guide plates for "clearance". Seems like they would be quite far off to one side or the other if they caused drag due to the pushrod angle with the guide plate.
It would seem to me that if the Edelbrock heads need adjustable guide plates, they have moved the studs relative to the valve guides compared to a stock head. Maybe they have.
I've watched the Edelbrock video a couple times and maybe it's just me focusing on that .005 clearance he mentions but after watching it, I didn't come away feeling the goal was to keep the rocker as centered as possible over the valve tip. Take a look at the Edelbrock video, it's under three minutes in length. https://www.google.com/search?q=adju...ciOtQXTs5_4Dw3
Mike T - Prescott AZ
I think that this adjusting is for adjustable guideplates which are splitted plates. The video is confusing because I can't see performer heads such a radical parts that adjusting is needed with all stock dimensions.
Use hardened pushrods and that just about it.
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