Add shuffle bushings in a 616/12 case or not?

[Juha Vane]

Sent my case to Ahnendorp in Germany for line boring. Also they will modify the 3rd piece
for full flow oil filter.

https://www.ahnendorp.com/?language=en

Now I wonder should I ask them also to install shuffle bushings in main #2?
The engine is a street one, 86mm big bore kit, Elgin 7008 cam, Webers.

[Greg Bryan]

Juha - I don't honestly know if a 616/12 engine has the shuffle bushings around the center main thru-bolt and stud, but later engines certainly did have them. I would be a good upgrade if done correctly, and it appears to be a high capability shop from the link images.

[Jacques Lefriant]

Hi Juha
I don't think it is necessary but now would be the time to do it especially if you are going to a late C?912 crank.
j

[Juha Vane]

Thank you.
At least my 616/12 don't yet have these shuffle bushings and the center bearing
bore was 60.30 and clear bearing "walk" visible. Here I plan to re-use the original
non-counterweight crankshaft. If the shop don't find any cracks in it. There are
some weight difference in connecting rods and pistons that perhaps has contributed
to this bearing walk? Have no idea if the engine was balanced.
To do the shuffle bushings is not overly expensive so probably best to do it now.

Connecting rod weight with bearing are 551 / 553 / 555 / 556 gram.
Have not the stand yet to weight big end and wrist pin end weight.
Piston weight 356 / 360 / 360 / 360 gram.

[Jacques Lefriant]

Hi Juha
you are your way of being a true "engine builder" congrats
j

[Al Zim]

You can balance the pistons by removing a small amount of material from the inside of the piston pin. it is best to do this on the outer edges of the pin. You can also slightly shorten the end of the pin. The rods should be rebuilt since the big end has stretched they will need new pin bushings and the rebuilder should be able to balance the rods end for end. al zim

[Jacques Lefriant]

Hi Al
By carefully weighing the pins and swapping parts he may be able to get a better result. Current practice on floating pins is to have a champher on the outside edges to prevent the pin from pushing out the clip. you are correct in that the pin should not be bored since the ID should have no stress risers it should be a fine hone finish or better. As you are well aware specialty automotive machine shops are not around every corner and sometimes you have to address issues as best you can.
j

[Juha Vane]

Thanks Jacques for your encouraging words.
Perhaps I'm weird, but I really like to work in the garage. One problem is that
it's sometimes hard to know what is really important and what is not.
To some "issues" there are a myriad of different opinions, some conflicting.
Like the case sealing product to use. This issue is really confusing and I wonder
how much the occasional sealing failures are becase of some way or other,
"operator" fault. Also probably some difference of sealant choice if a racing engine
is assembled that will be re-opened after a short time compared to a street engine.
I'm still trying to sort out what to use when I assemble the engine.

I will measure the big ends with bore gauge when I get back home.
The pin bushing felt OK. Perhaps I need to get a smaller bore gauge and measure it also.
There are some visible marks on the pins, but the surface feel very smooth.

Piston balancing, make me wonder because I don't know, why should the pistons
be balanced by remowing material from pin? Wouldn't it be safer and easier to remove
from piston skirt below wrist pin? My more precise scale is on the way to me, but all
pins was same weight when weighted repeatedly. Existing scale measure only 1g.

[Vic Skirmants]

You need to remove a lot of aluminum from the piston to change the weight; removing it from the pin is easier.

[Juha Vane]

OK, there is a 4g weight difference in pistons,
I have not calculated how big chunk it is in alloy.

[Jacques Lefriant]

Hi Juha
i would only remove weight from 1 piston/pin assy just install the 2 light pistons either in the 1-3 or 2-4 position.
j

[Jacques Lefriant]

Hi Juha
from what i can see the shop in Germany offers services that are not available in the US. one such specifically the boring of the 3rd piece for oversize oil pump gears. your potential engine part balancing is overkill and better than the majority of professional builders. the trick to sealing a case is more in cleanliness and care. my preference is Locktite 574. you have the enviable task of doing the job better than a professional since you can take the time to do it almost perfect. try to digest the the opinions here and in publications. there are many right ways to build an engine. enjoy.
cheers
jacques

[Mike Horton]

Juha, Lycoming aircraft engine company added the same design "shuffle bushings" you describe, in about the same time frame as Porsche added them for the 1960 MY S90, and for the same reason. The larger bushing OD affords more surface area, to support the case halves from moving under stresses, and fretting. Enough fretting can erode the halves mating surfaces, and when retorqued can lead to cracking, in high stress conditions, and aggravated by imbalance in the rotating assembly. I'd have them added. S90s, Cs, SCs, and 912s had them from the factory. Just my $.02

[Jacques Lefriant]

you only need the sleeves where you have a split bearing. BTW when you measure the ends of the rods on your fixture you can use use the little end and as piston weight for your balance.
j

[Mike Horton]

"you only need the sleeves where you have a split bearing. " +1

This location, is the same location, which Lycoming used, #2 main on 4 cylinder engines...