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?

McMaster Carr is ALWAYS a great resource for all kinds of fasteners

Can send you some for shipping IF you want nylock case nuts. Should have plenty of smaller 13 mm nuts too. Generic picture

I use them all the time, but was thinking of a 914 specific supplier.

https://www.mcmaster.com/94645A213/ This will probably work for seepage through the threaded portion, how about under the flat washer?

Is a silicone sealant recommended for under the bolt head on the other end?

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.

Been using Permatex Aviation since I built my 1st Corvair engine in the 1960's. Never had a failure.

I used it for years myself.
What I like about the SI 5900 is I can take a part off and can clean the sealing surface easily with a brass brush and a spritz of brake cleaner without having take the component right apart.

Right now I'm fighting a case with Permatex Aviation slopped all over it. It's almost like the previous wrench just poured it on.

Sounds like a no brainer, I assume NAPA has it or I am sure it is readily available.

Thanks all for the feedback

Without getting too lost in the nuanace. Time for facts and definitions.

https://www.differencebetween.com/differenc...v-and-silicone/

RTV is Room Temperature Vulcanizing is a generic term.

Key thing is that 100% Silicone and similar high Silicone content products are not a cross linked polymer. 100% Silicone is way more prone to creep vs. Engineedred RTV products like Yamabond, HondaBond, Loctite SI 5900, Permatex, or other proprietary formulations when used properly (i.e. sparsely).

As Mark Implied, there are the proper use of sealants, and then there are those that feel "more is better" which isn't the case and is basically where I was coming from with my OP against Silicone specifically.

As stated in a previous post about why there are so few engine builders around, I have nothing but respect for Mark and guys like him building engines for a living. So in no way is this response to be interpreted as a critcism of Mark.

I think the point is A that those have never been called sealing nuts but rather they are a type of lock nut.. B if you put anything on a fastener regardless of what it is this will greatly effect the TQ values. Doesn't mean it won't work but means that it will skew the values.

I use DreiBond. It is specified for the 964/993 engines, and with it I don't get leaks.

Unless you count the warped magnesium timing chain box on the 4.0L engine.

Just my $.02.

Clay

Hate to break it to ya but the factory did see fit to use a sealing fastener on the case through bolts

Been out of the loop for a while - but this thread already epitomizes the wealth of knowledge - and sometimes the spectrum of differing opinions - that we love about 914 World!



in any case it's and

and , uh, don't tell the kids this dinosaur ever used emoticons - they wouldn't believe you anyway . . .

So far as oil migrating up and out from this location, Bob K nailed it. Assuming the case surfaces are sealed properly, oil will not be able to find it's way out via the through bolts.

Does the 911 engine use O rings in this location?

And yes, the discussion here is very good. Thanks to all contributors