Rocker Stands

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M Penta
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Re: Rocker Stands

#16 Post by M Penta »

The 912 w/S90 heads in my C has mag rocker stands which I am considering replacing as a preventative measure. This engine was installed "temporarily" while the original engine is being rebuilt (which could take me a couple of years). The 912 engine was recently rebuilt and ran well for the 100 or so miles I drove it before storing the car for the winter, so now I am thinking of replacing the mag stands with aluminum or steel simply for peace of mind.

I did not get the numbers yet, but are the C stands a direct replacement for the S90 heads? I prefer not to use the rocker stands from my original engine, but can if I have to. I'll have to see what they cost and go from there. They appear to be easy enough to change, but have never done it on these engines.

Great info here as usual, thanks.

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Ron LaDow
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Re: Rocker Stands

#17 Post by Ron LaDow »

All light alloy stands are dimensionally identical. You shouldn't have a hard time finding a set.
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M Penta
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Re: Rocker Stands

#18 Post by M Penta »

Thanks Ron,

I did a quick search and see some out there. I'll have to take a good look at the condition of rest of the assembly to determine if I can just swap the stands, if they are worn or need work I may borrow the assemblies from the original engine. I will stop there though as I really do not want to turn it into a parts unit!

I am finding a lot of good info here on inspecting/rebuilding rocker assemblies, and I want to re torque the heads and check a few things anyway.

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Ron LaDow
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Re: Rocker Stands

#19 Post by Ron LaDow »

The stands do not wear; they are good or they are broken. The shafts and the rockers wear, but you already have those from the Mg stands.
Do NOT re-torque 616 heads; that practice was aimed at re-stretching the head fasteners in engines with compressible head gaskets after initial compression.
Added by edit, from experience; Don't 'borrow' parts from a complete unit. You'll never keep track of the parts from this or from that.
Last edited by Ron LaDow on Mon Jan 02, 2017 11:50 pm, edited 1 time in total.
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Mike Wilson
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Re: Rocker Stands

#20 Post by Mike Wilson »

If you are using Super 90 valve covers, won't they have to be changed if you are changing to aluminum rocker stands?
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Ron LaDow
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Re: Rocker Stands

#21 Post by Ron LaDow »

Mike Wilson wrote:If you are using Super 90 valve covers, won't they have to be changed if you are changing to aluminum rocker stands?
Memory: I used S-90 rocker boxes on 912 heads (w/ alum stands) without problem, but I'll certainly yield to those whose knowledge is more recent than 40 years ago.
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Vic Skirmants
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Re: Rocker Stands

#22 Post by Vic Skirmants »

The only time you have to change from the S-90 valve covers, is with the later 912 heads that have the large internal boss for the intake manifold stud.

M Penta
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Re: Rocker Stands

#23 Post by M Penta »

Thanks for the advice. I knew borrowing parts from the C engine would be a bad idea, so I will avoid that.

If the rockers/shafts are in good shape on the 912 I will just replace the stands and call it a day.

Thanks for the tip on the re torque and valve covers. I'll see what is what when I get in there.

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Mike Wilson
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Re: Rocker Stands

#24 Post by Mike Wilson »

Thanks, Vic. Another chip added to my memory bank!
Mike Wilson
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Dave Erickson
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Re: Rocker Stands

#25 Post by Dave Erickson »

Mike Wilson wrote:Thanks, Vic. Another chip added to my memory bank!
Now, is that NVRAM or DRAM? In my case its DRAM. And what little SRAM I had seems to be fast disappearing ;<)

-Dave

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Mike Wilson
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Re: Rocker Stands

#26 Post by Mike Wilson »

Seems like I lose a bit in sleep mode and if the chip isn't activated with any frequency, it fails. Good one, Dave!
Mike Wilson
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M Penta
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Re: Rocker Stands

#27 Post by M Penta »

So I had a broken intake valve spring on #3 intake, which led to all new valve springs and full rocker gear replacement with that from my original C engine. Some of the valve springs had some pitting and should not have been reused. This was an opportunity to swap out the mag stands on the 912/S90 mystery motor with the alloy stands from the C.

The rocker tips looked worn and the C's are in excellent shape so I swapped the entire assembly out after cleaning/measuring/inspecting everything. I agree removing parts from the original engine is not a good idea (and was advised against it), but it was the only option I had right now. This was a major pita to do with engine in car, but got it done after a 3 day fight . I had to modify a spring compressor to work on these heads and the whole process took a very long time. I also had to make some go/no go jigs to measure installed spring height, which turned out to be correct although there like 4-5 shims under each spring. I reused the the alum push rods since engine appears to have alum cyls. Adjusters are at correct depth and have larger oil passages (which seems like a good thing?).

All went well and back on the road, running well and noticeably quieter.

Image




912/S90 rocker asm with mag stands replaced with complete C asm with alloy stands.

Image



All C rocker parts were cleaned and inspected, everything is in excellent condition. I hate to borrow these parts from the original engine, but they will go back when I rebuild it. The 912 rocker shafts are mostly OK, I plan to send the assembly out to have the rockers resurfaced (if possible).

Image






Typical worn 912 rocker compared to C rocker.

Image

Image

my son checked all the pushrods.

Image

Everything installed. Oil passages in adjusters are pretty much centered on rocker passages. Valve adjust seemed easier with the good rocker tips. Engine is noticeably quieter and oil psi same (40-50psi).

Image

Please let me know if I missed something; any concerns, questions, etc..

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Re: Rocker Stands

#28 Post by Dick Weiss »

A slight correction;

The Normal engines used the steel rocker stands to engine # 606800 to Sept. '61.

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Re: Rocker Stands

#29 Post by M Penta »

I assume the steel stands are strongest, but how do the alloy stands compare to the magnesium? Much better or still prone to failure? What do the racers like?

The rockers with worn tips in above pics; can they be resurfaced?

'EDIT' - The pictures probably do not show enough, I will take apart the assembly again to get better pics of all parts.

I would like to send them out and have them repaired if possible. The bores seem OK and shafts are usable (although two of them could stand to be flipped).





Thanks,

Mark

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Ron LaDow
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Re: Rocker Stands

#30 Post by Ron LaDow »

M Penta wrote:I assume the steel stands are strongest, but how do the alloy stands compare to the magnesium? Much better or still prone to failure? What do the racers like?
the aluminum stands are universally preferred, except for those doing a pure concourse job.
M Penta wrote:The rockers with worn tips in above pics; can they be resurfaced?
Yes.
Check with Tim Berardelli at 703-257-5100.
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