Author Topic: 93 SP III Rocker arm shims  (Read 553 times)

Offline 93spada

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93 SP III Rocker arm shims
« on: September 17, 2021, 06:19:01 PM »
Hi Folks
Are the bronze? rocker shims a consumable part?
When placed next to the spring, it gets gouged out by the spring tip. Some have gone more than half way thru the bronze. Is that normal? Should it be steel on either side of the spring? What is the purpose of the bronze shim?
The rocker carrier is aluminum. Should the order be, bronze, steel, spring, steel, rocker, bronze? That would put steel to steel and bronze to aluminum.

 
Thanks
Paul
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Online John A

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Re: 93 SP III Rocker arm shims
« Reply #1 on: September 17, 2021, 08:50:23 PM »
That order sounds right . I guess if the bronze has a step worn in it Iíd replace it. On my personal bikes I delete the springs and shim it , I made up some bronze spacers and use a combination of factory washer to get about .004 clearance. If you have a standard engine I doubt you could tell any difference but I notice crisper throttle response with doing that in conjunction with a sports cam.  My theory is that you get less lost motion on valve closing when the rocker doesnít slide on the pin.
John
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Online nc43bsa

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Re: 93 SP III Rocker arm shims
« Reply #2 on: September 17, 2021, 09:09:39 PM »
In general, it is better to shim the rockers in the proper location rather than relying on a spring to take up the slack.

Buy a handful of steel shims and stack them on each end of the rockers until the rocker is centered on the tip of the valve stem and the rocker has barely perceptible endplay (or about 0.005").  Throw the springs in the trash.
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Offline 93spada

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Re: 93 SP III Rocker arm shims
« Reply #3 on: September 18, 2021, 07:45:48 AM »
Thanks folks.
My brother also suggested that.
Any idea what the black coating on the steel shims from MG is?
Paul
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Re: 93 SP III Rocker arm shims
« Reply #3 on: September 18, 2021, 07:45:48 AM »

Online Chuck in Indiana

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Re: 93 SP III Rocker arm shims
« Reply #4 on: September 18, 2021, 07:47:53 AM »
From the deep dark recesses of what I have left of a memory  :rolleyes: it seems Ace Mallot uses radial bearings there. I *think* The Kid did that on his Spot.
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Online John A

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Re: 93 SP III Rocker arm shims
« Reply #5 on: September 18, 2021, 10:34:20 AM »
From the deep dark recesses of what I have left of a memory  :rolleyes: it seems Ace Mallot uses radial bearings there. I *think* The Kid did that on his Spot.



Yes he does, he uses INA thrust bearings. They also have the thin races that go with them. Iíll look for those part numbers when I get out to the shop. If I do it that way I like to true up the ends of the rockers which is time consuming for my equipment and overkill for a street engine. It is the Ďrightí way to do it though. When I was on a funny car team I talked to the engine builder at Walt Austin Racing . they use spring loaded rockers on their alcohol engines. I was surprised at the light springs so I questioned that and he said yes it would make more power if they were shimmed solid but they already had enough so they were after quick serviceability.
John
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Offline pressureangle

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Re: 93 SP III Rocker arm shims
« Reply #6 on: September 19, 2021, 12:51:19 PM »
Available from McMaster-Carr.



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Re: 93 SP III Rocker arm shims
« Reply #7 on: September 19, 2021, 12:54:27 PM »
Available from McMaster-Carr.







I didnít notice roller rockers in the McMaster catalog.
Har har :grin:
John
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Offline Matt Story

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Re: 93 SP III Rocker arm shims
« Reply #8 on: September 19, 2021, 01:09:53 PM »


Yes he does, he uses INA thrust bearings. They also have the thin races that go with them. Iíll look for those part numbers when I get out to the shop. If I do it that way I like to true up the ends of the rockers which is time consuming for my equipment and overkill for a street engine. It is the Ďrightí way to do it though. When I was on a funny car team I talked to the engine builder at Walt Austin Racing . they use spring loaded rockers on their alcohol engines. I was surprised at the light springs so I questioned that and he said yes it would make more power if they were shimmed solid but they already had enough so they were after quick serviceability.

The end faces on my 850-T rockers are crooked enough to notice at a glance.  I want to true them up as well as fit new plain bearings, thrust washers... 

I have a lathe I could true up the ends on, but I'm not sure how to chuck up the oddly shaped rockers.  I think I need some sort of expanding mandrel.  Can anyone in the know here share that?

I am also entertaining the idea of sending them out to true them up and fit new bushes.  Any recommendations on where/who to send them to?
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Offline Matt Story

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Re: 93 SP III Rocker arm shims
« Reply #9 on: September 19, 2021, 01:30:12 PM »
I guess expanding mandrels are a thing.  Amazon has a set of 5 that includes one that should work well on the 15mm ID of the bushings. $107
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Online John A

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Re: 93 SP III Rocker arm shims
« Reply #10 on: September 19, 2021, 09:48:39 PM »
Thatís what I was going to try next time if I ever do it again, expanding mandrel. Got a link to the ones Amazon has?
John
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Online Tom H

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Re: 93 SP III Rocker arm shims
« Reply #11 on: September 19, 2021, 11:19:35 PM »
Available from McMaster-Carr.





I want 3 sets of those rocker arms!!!!

Question: Do you put the thrust bearing set on BOTH sides of the rocker or just one?

I would think you want one one each side of the rocker. But...That would probably  off center the rocker on the valve. Soo...

Is it worth adding the 1 or 2 thrust bearing set??

Tom
« Last Edit: September 19, 2021, 11:19:57 PM by Tom H »
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Offline Matt Story

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Re: 93 SP III Rocker arm shims
« Reply #12 on: September 20, 2021, 02:54:10 AM »
Thatís what I was going to try next time if I ever do it again, expanding mandrel. Got a link to the ones Amazon has?

These seem to be a cheap to medium price for what they are and with positive reviews.  I can't personally vouch for the quality yet.  https://www.amazon.com/Precision-Expanding-Mandrel-Mandres-Sleeves/dp/B071D1Q3NJ/ref=sr_1_4?dchild=1&keywords=expanding+mandrel&qid=1632075946&sr=8-4
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Offline Matt Story

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Re: 93 SP III Rocker arm shims
« Reply #13 on: September 20, 2021, 02:57:48 AM »
Available from McMaster-Carr.





Ya, which models came with those and are they reverse compatible with other big blocks?
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Offline GuzziNZ

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Re: 93 SP III Rocker arm shims
« Reply #14 on: September 20, 2021, 06:34:38 AM »
These seem to be a cheap to medium price for what they are and with positive reviews.  I can't personally vouch for the quality yet.  https://www.amazon.com/Precision-Expanding-Mandrel-Mandres-Sleeves/dp/B071D1Q3NJ/ref=sr_1_4?dchild=1&keywords=expanding+mandrel&qid=1632075946&sr=8-4
[/quote

I'm cheap.
If it was me I would just machine a bar to give a very neat sliding fit through the rocker and  a very slow taper out near the chuck.
Slide the rocker on and twist while pushing it up the taper. Will hold fine if you only take light cuts at medium revs.

Offline 93spada

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Re: 93 SP III Rocker arm shims
« Reply #15 on: September 20, 2021, 03:05:46 PM »
As usual, great info!!!
For now I just left the spring. Fall is coming fast and don't want to take away from ride time yet.
I like the thrust bearing idea and will deal with that this winter.
Thanks again to all.
Paul
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Offline pressureangle

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Re: 93 SP III Rocker arm shims
« Reply #16 on: September 22, 2021, 11:54:38 AM »
These seem to be a cheap to medium price for what they are and with positive reviews.  I can't personally vouch for the quality yet.  https://www.amazon.com/Precision-Expanding-Mandrel-Mandres-Sleeves/dp/B071D1Q3NJ/ref=sr_1_4?dchild=1&keywords=expanding+mandrel&qid=1632075946&sr=8-4

I guess I missed the  atarget.
The rocker arms are from Baisley Performance.
The bearings are only on the loaded side of the rocker.

To true the ends, I might simply chuck a rocker spindle and use the arm for a dog, and reverse to dress the other side.
Something wistful and amusing, yet poignant.

Offline MattP

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Re: 93 SP III Rocker arm shims
« Reply #17 on: September 22, 2021, 12:26:32 PM »
I do not beleave  thous bearings were intended to reverce rotation 3500 times per minute. I would just shim them or leave  them stock. Matt

Online John A

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Re: 93 SP III Rocker arm shims
« Reply #18 on: September 22, 2021, 01:20:44 PM »
If one did fail those little rollers will make a mess so check the specs on the bearings if you do it.
John
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Online rodekyll

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Re: 93 SP III Rocker arm shims
« Reply #19 on: September 22, 2021, 06:31:51 PM »
How do those radial bearings oil?

Online John A

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Re: 93 SP III Rocker arm shims
« Reply #20 on: September 22, 2021, 06:49:18 PM »
Same as the shims, seems to be enough but I think I quit using the bearings because the risk outweighed the benefit
Never heard of a failure though
« Last Edit: September 22, 2021, 06:51:14 PM by John A »
John
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Offline pressureangle

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Re: 93 SP III Rocker arm shims
« Reply #21 on: September 29, 2021, 07:46:13 AM »
If one did fail those little rollers will make a mess so check the specs on the bearings if you do it.

Yes, a stock motor is probably best for you.
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Offline guzzista

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Re: 93 SP III Rocker arm shims
« Reply #22 on: September 29, 2021, 11:16:03 AM »
I tried the Oil embedded bronze  3mm  thick thrust bearings/ bushings  .(McMaster Carr  # 2011N118)  on a roundfin cast iron rocker base and , with a stock bronze shim on the opposite side as in  the original setup, it seems to work fine and have about .007 clearance .
Not tested on an engine yet, but if it works , it maybe the easiest way to do it.   No INA radial bearings or the fear that they will go swimming 
 about inside your engine .Same part ( oil embedded  bronze bearing , not INA) wont work on square fins as the OD  of the  aforementioned  bearing interferes  with the cast aluminum base and mods would be required unless you can cut your own Oilite bushings with a smaller OD to fit
« Last Edit: September 30, 2021, 12:29:40 AM by guzzista »
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Re: 93 SP III Rocker arm shims
« Reply #23 on: September 29, 2021, 11:28:50 AM »
Man, if those thrust bearings fail it looks like a lot of hard steel roller bits may end up in bad places !!
If one chooses to install them, i would be very careful, and source them from the highest quality vendor possible.

I know INA does source bearings from china, and I know Mcmaster source from multiple locations.

I can't see any real advantage in this type of bearing, except possibly in some very high long duration racing application..
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