Sealing nuts, source Options

[930cabman]

We are building a basic 2056 with a mild cam, nothing fancy. Is there a source for the sealing nuts that tie the crankcase together?

[bkrantz]

Not to start an argument, but the original design relies on case sealant around the bolt holes where the case halves meet--no sealing nuts. Though plenty of people use sealant on the stock washers and nuts.

[930cabman]

Not to start an argument, but the original design relies on case sealant around the bolt holes where the case halves meet--no sealing nuts. Though plenty of people use sealant on the stock washers and nuts.

"Sorry Mam, just the facts", thanks Bob, a sealing nut should not be required here, I will probably use a bit of silicone under the bolt head and under the nut heads.
Information is always a good thing

[Superhawk996]

Not to start an argument, but the original design relies on case sealant around the bolt holes where the case halves meet--no sealing nuts. Though plenty of people use sealant on the stock washers and nuts.

"Sorry Mam, just the facts", thanks Bob, a sealing nut should not be required here, I will probably use a bit of silicone under the bolt head and under the nut heads.
Information is always a good thing

@930cabman

To continue the argument, bkrantz is correct.

Adding silicone under the bolt head or washer is a very bad plan with respect to proper bolted joint design and ability to hold proper torque (i.e. clamp load) over time.

One of two things happens:
1) A hydraulic film is developed that basically floats the washer. You achieve torque and then the film creeps out over time and you lose torque and respective clamp load. I.e. a soft joint.

2) No hydraulic film is developed and all the sealant is squished out and you end up with a metal to metal hard joint. In this case the sealant was simply wasted and not needed in the first place.

If I were going to use anything it would be a steel sealing washer with an embedded o-ring seal (link below). However, if this were necessary, it would have been used in the 1st place by the engine designers.

https://www.anhosefittings.com/dowty-bonded...AiABEgKw2vD_BwE

At least in this case, the o-ring crushes, you get a hard joint contact around the permimeter of the washer and less chance of clamp load loss over time. But, these sealing washers are notorious for slowly creeping too and wouldn't be ideal for case sealing where you never want to lose clamp load across the case parting line and the associated critical bearing crush and resisting "pounding" load from the crank.

A vertically split case half (914, 911, and lots of motorcycles) is bad enough from a leak failure mode perspective. The other tendency is to overuse the case sealant itself (again - don't ever use Silicone!) and have the same two problems stated above w.r.t. sealant creep. I'm not sure I want to throw down on the best sealant for the case. That is whole different debate but definately DO NOT use silicone to seal the case or put under case bolt nuts or case washers.

[Mark Henry]

Not to start an argument, but the original design relies on case sealant around the bolt holes where the case halves meet--no sealing nuts. Though plenty of people use sealant on the stock washers and nuts.

"Sorry Mam, just the facts", thanks Bob, a sealing nut should not be required here, I will probably use a bit of silicone under the bolt head and under the nut heads.
Information is always a good thing

@930cabman

To continue the argument, bkrantz is correct.

Adding silicone under the bolt head or washer is a very bad plan with respect to proper bolted joint design and ability to hold proper torque (i.e. clamp load) over time.

One of two things happens:
1) A hydraulic film is developed that basically floats the washer. You achieve torque and then the film creeps out over time and you lose torque and respective clamp load. I.e. a soft joint.

2) No hydraulic film is developed and all the sealant is squished out and you end up with a metal to metal hard joint. In this case the sealant was simply wasted and not needed in the first place.

If I were going to use anything it would be a steel sealing washer with an embedded o-ring seal (link below). However, if this were necessary, it would have been used in the 1st place by the engine designers.

https://www.anhosefittings.com/dowty-bonded...AiABEgKw2vD_BwE

At least in this case, the o-ring crushes, you get a hard joint contact around the permimeter of the washer and less chance of clamp load loss over time. But, these sealing washers are notorious for slowly creeping too and wouldn't be ideal for case sealing where you never want to lose clamp load across the case parting line and the associated critical bearing crush and resisting "pounding" load from the crank.

A vertically split case half (914, 911, and lots of motorcycles) is bad enough from a leak failure mode perspective. The other tendency is to overuse the case sealant itself (again - don't ever use Silicone!) and have the same two problems stated above w.r.t. sealant creep. I'm not sure I want to throw down on the best sealant for the case. That is whole different debate but definately DO NOT use silicone to seal the case or put under case bolt nuts or case washers.

I don't agree.
I use loctite SI 5900, which is spec. on Porsche 996/997 (etc) engines, and have had no problems with it. I've even sealed a T4 case with it and no issues so far. Where it also excels is with ease of clean up if you ever have to take things back apart. Also any squeeze out stays put as it's not affected by oil or gas, so no worms. Way easier to clean up than threebond and here Yamabond has been on BO for over a year.
BTW both threebond and Yamabond are RTV. In fact many modern case sealants are RTV based. Go ahead and name your favorite sealant, unless it's oldschool permatex avation it's likely an RTV based sealant.

Loctite SI 5900 isn't something you can get from your local FLAPs and is a lot more expensive than common RTV. Here it's about $70 for the 300ml tube. You can special order it from a loctite dealer and most WC Porsche shops carry the small 50ml tubes.