Exhaust valve rotators for Panheads

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knuckgush
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Exhaust valve rotators for Panheads

#1

Post by knuckgush » Tue Apr 27, 2010 4:37 am

Hi everyone. I'm at a point in assembling my 1951 Panhead engine, and was wondering what is the consensus about putting the Exhaust Valve Rotator Mechanism (PN 18234-52) on a Panhead as explained on page 81 of the Panhead Service manual. I have a set of them, and before I install them, I'd like to hear any comments - pro or con. Thanks!



RUBONE
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Re: Exhaust valve rotators for Panheads

#2

Post by RUBONE » Tue Apr 27, 2010 6:33 am

Just look at the short time period the factory used them before returning to the previous style and your question will be answered!
Robbie

knuckgush
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Re: Exhaust valve rotators for Panheads

#3

Post by knuckgush » Thu Apr 29, 2010 8:17 pm

Thanks Robbie. How long did the factory offer these exhaust valve rotators? My info tells me 1952 to 1958. That's 7 years. What really is the downside, besides the stated precaution of not dropping them off the valve stems during assembly and blocking the return flow of oil and possibly getting caught in the springs & moving mechanisms...? If they stay put, would it really reduce head warpage and burned exhaust valves since the ex valves would move in a circular motion slightly all the time, and not always hit the same spot? Just some food for thought I'm chewing on...

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Re: Exhaust valve rotators for Panheads

#4

Post by LittleAl » Thu Apr 29, 2010 9:55 pm

I'll admit I have no answer at all here, just a related question.

don't valves, in just about any motor, rotate to some degree on their own? There's nothing that I remember seeing that would hold a valve in an exact position. sorta makes me believe that it wouldn't be possible for a valve to hit the valve seat in exactly the same spot each time even if you wanted that to happen.

where might I be going wrong in my thinking?

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Re: Exhaust valve rotators for Panheads

#5

Post by awander » Fri Apr 30, 2010 5:21 pm

Little Al:

There is no guarantee that a standard valve set up will NOT rotate, but there is also no guarante that it will.

If you think about how the valve stem is pinched by the tapered keys at the top, inside the tapered hole in the top spring collar, and also how tightly the collars and spring are pressed together, and how the bottom collar presses against the head/valve guide, then it seems unlikey that there will be a lot of rotation. After all, what is there to cause any rotation?

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Re: Exhaust valve rotators for Panheads

#6

Post by LittleAl » Fri Apr 30, 2010 6:15 pm

ok Andy, what you say makes perfect sense, even to mentally challenged me, lol

I guess I was just thinking (especially with solid lifters) all that movement... you get my drift.

anyway, thanks for setting me straight

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Re: Exhaust valve rotators for Panheads

#7

Post by john HD » Fri Apr 30, 2010 6:22 pm

i had rotators on my '55 when i got it.

on the advice from my motor guy i removed them.

his reasons were: 1 they do not work 2 they are prone to snapping off the tip of the valve with predictable results 3 they are a pain in the butt because they can fall off if the head is flipped upside down.

john

knuckgush
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Re: Exhaust valve rotators for Panheads

#8

Post by knuckgush » Thu May 06, 2010 1:19 am

In response to Andy...The exhaust Valve rotators are what is supposed to let the valves rotate slightly, pushed by the escaping exhaust gasses. The rotators bypass the direct connection of the rocker arm to the valve stem end, and actually push down, slightly, on the keepers themselves. Thereby loosening them, just enough, to let the valve move by these turbulent exhaust gasses. At least that's what I understand the factory theory was back then. I just wonder if anyone has heard of the rotators (caps) breaking because of their thinness. (I am aware of the danger of them falling off during installation, but besides that, if that goes OK, is breakage the danger...?)

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Re: Exhaust valve rotators for Panheads

#9

Post by 58flh » Sat Aug 04, 2012 7:38 am

DONT use them!--Richie--It was a bad idea then, so dont use them now! :!: Many motors ended-up in the shop for topends. I have never put them on any pan-top I had to do. It was a idea that sounded good in theory OLNY!--Your valves will rotate on thier own!-(Thats how they keep that little clean ring on the seats when you popem apart) If they didnt We would be all kickin to death. You dont need rotators for a valve to move. 8)

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Re: Exhaust valve rotators for Panheads

#10

Post by Panacea » Sat Aug 04, 2012 2:02 pm

I think he probably has his valve job done by now...

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Re: Exhaust valve rotators for Panheads

#11

Post by kitabel » Sat Aug 04, 2012 3:17 pm

Unless the valve stem's contact surface and the rocker arm pad are exactly parallel, the rocker will tend to rotate the stem as it passes across the top by dragging 1 edge. The shovelhead rocker box has the shafts inclined 1° to the head surface to ensure this; no idea whether a similar function is incorporated in the panhead.

The entire valve assembly (valve, spring, locks, collar) is rotated by the spring as it compresses, then reverse-rotated as it relaxes. If these forces are not exactly balanced, the valve will rotate slightly in each cycle.

Don't worry about it.

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