Is it normal for thru bolt o-rings to get mangled?

[stownsen914]

I've only done a few engines, but I'm seeing a trend of through bolt o-rings getting kinda mangled by the process of torquing the through bolts. Recently I had to tear back into a bottom end that I'd just assembled, and the o-rings showed signs of slicing into the rubber and also squishing out along the perimeter. Is this normal? I am using the green o-rings from Wrightwood and the Dow paste to lube them.

[Flat6pac]

I use axel grease because it won’t run heated, I find as long as the washer doesn’t spin there is minimal breakdown of the seal as I have dropped the intermediate shaft bearing and had to open the case back up.
Bruce

[stownsen914]

Thanks Bruce. Should I be making any effort to somehow guide the o-rings into the through bolt holes? I've just been lubing the o-rings, putting them in place on the through bolt, and letting the washers guide the o-rings into place as I snug things down.

[Flat6pac]

I lube the outside of the washer to keep the washer from spinning as I torque. The less spin the better the compressed seal remains
Bruce

[gled49]

I assume we’re talking about pre 964 cases. If you look closely, in general, one side of the case chamfers the thru bolt holes, the other side doesn’t. Factory race cases that I’ve seen, have both sides chamfered. So that’s what I do. I don’t see anymore O ring squish out. Even though I’ve seen a lot of O ring squish out, I’ve not seen leaks there.

[dannobee]

I was gonna say the same thing as Gordon. I thought there was a service bulletin that said to add chamfers to the left side, but it might have been in one of the Porsche training classes.

[stownsen914]

Thanks for the tips, guys. I examined my case and found that indeed on one side the holes have a deeper chamfer like the washers do (but not all of them for some reason), and on the other side the holes have a slight chamfer.

[brighton911]

Like the other fellows have stated, I cut chamfers on the LH case, used a bit of silicone grease on the O rings and all is still good some 12 years later.

[DaveA]

If you hold the washer to keep it from spinning, the O rings won't tear. Use vice grips or channel locks, and silicon grease. R/Dave

[Henry Schmidt]

We machine the through bolt sealing surface and add a chamfer as needed.
We only use Viton o-rings for starters. Throw away the blue silicon o-rings.
The o-ring is slathered with Dow 55 o-ring lubricant and carefully installed over the threads with a guide tool. The threads are then coated with anti-seize to insure an accurate torque. The added benefit of the anti-seize is that the washers won't spin.
The o-ring lubricant has an added benefit of Seal Swell. At 180 degrees the o-ring expands creating an enhance seal.

[stownsen914]

Thanks guys for the responses. I managed to do a small chamfer where needed to give the orings a better shot.

Related question - is the oring dead if the washer spins? To minimize spinning, I’ve been oiling the nut contact surface and keeping the washer to case interface dry (except a light smear or Dow 55 in the oring recess). It’s mostly worked, but I just had a washer spin. Do I need to disassemble and redo with a new oring?

[Henry Schmidt]

Originally Posted by stownsen914

Thanks guys for the responses. I managed to do a small chamfer where needed to give the orings a better shot.

Related question - is the oring dead if the washer spins? To minimize spinning, I’ve been oiling the nut contact surface and keeping the washer to case interface dry (except a light smear or Dow 55 in the oring recess). It’s mostly worked, but I just had a washer spin. Do I need to disassemble and redo with a new oring?

It is impossible to know if the o-ring was significantly damaged but the Dow 55 should provide enough lubrication to prevent damage.
Keep in mind that not all case through bolts are pressurized.

[stownsen914]

Thanks Henry. Turns out the one in question is on a pressurized galley. Probably best to replace for peace of mind. Luckily the supplier sent me a couple extra orings

[proporsche]

as said above i only use viton green o rings.I also make each washer not to slip while make it tight.
I punch the nut side washer with a punch 3x .This way when it meets the case it will not spin at all..the punch is not big at all just enough to stop it from spinning.
works for me on many engines.
ivan

[buster73]

Following Henrys advice I also had good results with using Viton-rings, Dow 55 and chamfering the case. In order to avoid spinning the washers (together with the O-rings) I used a clamp and a piece of wood to apply enough pressure to „squish“ the O-rings into place. Bolt head can still be reached with a thin open-end spanner to apply enough torque until the washers will not move anymore. The opposite washer can be kept from spinning by hand. Of course the clamp will have to come off for final torquing.

[Henry Schmidt]

I'm confused.
You guys are holding the head end of the stud with a wrench...right?
If you're holding the head with a wrench, the stud won't spin and obviously neither will the washer.
The nut end is different. lube the o-ring (with your favorite o-ring lubricant), apply anti-seize to the nut/threads and engaging face, install the washer dry and the washer should nut turn.

Caveat: If you use Supertec head studs, the studs can be installed after the cylinders are in place. Without head studs, tightening the case bolts and installing the piston cylinder package becomes incredibly easy.

[proporsche]

nice engine Henry
and yes the bolt in my case is being held by wrench i only use the washer with punches on the nut side and also yes dry o ring ...
Ivan

[buster73]

[QUOTE=Henry Schmidt;12436660]I'm confused.
You guys are holding the head end of the stud with a wrench...right?
If you're holding the head with a wrench, the stud won't spin and obviously neither will the washer.
The nut end is different. lube the o-ring (with your favorite o-ring lubricant), apply anti-seize to the nut/threads and engaging face, install the washer dry and the washer should nut turn.
QUOTE]

You are right and it is probably overkill. But was reading so many stories about cutting and mangling O-rings during installation, that I wanted to make super sure O-rings are set in place correctly and to add somewhat more control into the process, with 24 chances to mess things up. If you do this job for the first time, it seems hard to keep everything under control especially as you can only keep an eye on one side of the block. By clamping one side in place you can fully focus on the nut end and make sure the washer won´t turn. With more experience and enough helping hands you can certainly speed things up.

[stownsen914]

I didn’t get the impression that centering of the orings is a problem. Hope I didnt miss a detail.
I just used a wrench on the bolt heads to keep that end from spinning. I guess the nut end is the one to watch.

[buster73]

Became alarmed to this topic when helping a friend to tear apart an engine that developed a through-bolt leak immediately after a full rebuild. We found one of the standard blue O-rings squeezed to the outside between the flat side of the washer and the block.

In general the geometry/chamfer of washer and block should keep the O-ring centered when you fasten the nut and press the O-ring into the remaining cavity, while the resulting elastic deformation of the O-ring will seal against the bolt surface. Attached two pictures where you see how the O-ring moves inwards if you clamp the washer down and the chamfer comes into play. (used the standard blue O-rings just for this exercise). When you push down on the washer you can almost feel how the O-ring “moves into position”. With the bolt in place of course there is less room for the O-ring to move and if something goes wrong it might bow out into the wrong direction ending caught-up between washer and block.





Several factors might play a role:

No or not enough lubricant on O-ring.
No or not enough chamfer on through-holes.
Washer turning while fastening nut.
O-ring material too stiff or temperature too cold.
Wrong O-ring dimensions.
Excessive play between washer and bolt allowing washer to be off-angle.
Fastening too fast e.g. by using an impact wrench.

So I guess if you follow the typical recommendations (correct O-rings, lubricants, chamfer, no spinning washers..) the risk to mangle up an O-ring are actually quite low. Just take care and no rush for each of the 24 bolts.