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self-aligning rocker arms vs. adjustable pushrod guides?

Old 10-07-2017, 10:56 PM
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ryank9398
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Default self-aligning rocker arms vs. adjustable pushrod guides?

I'm rebuilding my motor with AFR heads and Comp 268XFI roller. The heads came with adjustable guide plates. I previously had full roller self-aligning rocker arms in 1.6 ratio, part number 555-20145 from Jegs. I saw in the instructions that the guide plates were not compatible with self-aligning rockers. Forgive my ignorance, but why not? Pictures of mockup:






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Old 10-08-2017, 12:04 AM
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383vett
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You use one or the other, not both. The guideplate might want to push the pushrod past the aligning retainer. Bad things will then happen.
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Old 10-09-2017, 10:18 PM
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Thanks 383Vett.
So I took the guide plates off and was able to get this marking on the pushrods. I didn't have the head torqued down. Never done this before, is my procedure correct and is this result ok?

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Old 10-10-2017, 05:41 AM
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Originally Posted by 383vett View Post
You use one or the other, not both. The guideplate might want to push the pushrod past the aligning retainer. Bad things will then happen.


Been there done that with a previous car, had a professional engine builder put together a high performance 351 cleveland engine.
Around a week later clanking noises......... turned out he forgot you need hardened push rods with guide plates ......oil was full of shiny metal flakes.

The engine spun well over 8,500 rpm .... sounded awsome ... then after 3 months BANG a valve retainer collet's failed to do with wear and roller rocker geometry ....
Yes high RPM sounds fantastic but wear is shocking, new lesson replace collets every 2 months and pushrod length is critical.

Needless to say my 383 has forged Crank Rods and forged pistons but fairly mild camshaft running standard rockers..

There is no sweeter sound than a V8 revving to 8,500 rpm....... but i am once bitten twice shy. Am happy with a blower and low rpm hp torque , should last many many years
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Old 10-10-2017, 08:13 AM
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Originally Posted by ryank9398 View Post
Thanks 383Vett.
So I took the guide plates off and was able to get this marking on the pushrods. I didn't have the head torqued down. Never done this before, is my procedure correct and is this result ok?
What procedure did you use? Did you use a solid lifter or a really weak checker spring to make sure you're not collapsing the lifter while taking measurements? Did you measure with an adjustable pushrod?

Looks like your pushrods are a tad too long.
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Old 10-10-2017, 03:03 PM
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Normally you would want to pick either SA rockers of guide plates..... but on this combo you can actually run both with no issues....

The AFR heads with the 8mm valve stems won't positively align the SA rockers because the distance between the "guide wings" on the rocker is set up for 11/32 valves (.343) the 8mm stem (.315) this will allow the rocker to slide back and forth .028" ..... this is too much play to properly align the rocker arm and the rocker arms will come off the valve stems when actually running at higher RPM.

The normal interference that occurs when trying to use both SA rockers and guide plates won't happen because as I said there is plenty of rocker arm "wiggle room" (.028') on the valve stem so the guide plate will actually do all the aligning.
Will
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Old 10-10-2017, 04:42 PM
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My 1987 GTA actually came from the factory with self aligning rockers arms and the pushrod guides in the cast iron heads. It worked fine since both of them were lined up correctly. the car had over 100,000 miles on it with no issue.
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Old 11-10-2017, 12:01 AM
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Originally Posted by rklessdriver View Post
Normally you would want to pick either SA rockers of guide plates..... but on this combo you can actually run both with no issues....

The AFR heads with the 8mm valve stems won't positively align the SA rockers because the distance between the "guide wings" on the rocker is set up for 11/32 valves (.343) the 8mm stem (.315) this will allow the rocker to slide back and forth .028" ..... this is too much play to properly align the rocker arm and the rocker arms will come off the valve stems when actually running at higher RPM.

The normal interference that occurs when trying to use both SA rockers and guide plates won't happen because as I said there is plenty of rocker arm "wiggle room" (.028') on the valve stem so the guide plate will actually do all the aligning.
Will
Thank you very much, this makes sense to me. I have been setting this up with a bunch of feeler gauges, trying to set lash with clearance between the valve stem and the pushrod guides.

By the way, what do you think of my rocker geometry/pushrod length?
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Old 11-10-2017, 07:43 PM
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Originally Posted by ryank9398 View Post
Thank you very much, this makes sense to me. I have been setting this up with a bunch of feeler gauges, trying to set lash with clearance between the valve stem and the pushrod guides.

By the way, what do you think of my rocker geometry/pushrod length?
Your pattern on the valve stem looks fine. However, the pushrod measurement you end up with will be too long because the valve springs will bottom the hyd lifter out when checking and when the engine is actually running the lifter plunger will rise and move the rocker to a point further towards the exhaust side of the valve tip as well increasing the width of the pattern.

You need to figure out how much the lifter plunger is collasping and subtract that from your pushrod measurement.

Or redo the pattern with light checker springs... or take an old lifter, dissasemble the plunger assembly and shim it upunder the cup to act as a soild lifter.

Will
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