special nuts required or not?

[gunkholer]

So recently I've had a thread posted here about my 454 crusader exhaust/heat exchanger issues. This issue is part of that but very specific. I'm curious if anyone has had to deal with it.
The nuts called for that hold the 8" elbow (cr-20-97169) ( sierra 18-1916) to the exhaust manifold are 3/8" coarse brass heavy with nyloc. Heavy meaning instead of a 9/16" socket you need a 11/16" socket. I've searched all of North America for the nuts and washer sets (sierra 18-8540) and I've only found one place on Long Island that has them, but they won't ship to Canada. But I've tracked down a brass nut with nyloc that is standard size ( 9/16" socket). I've also tracked down a "heavy" brass nut without the nyloc. I've found them both locally.
My question is, why does crusader call for this heavy nut?
I'm only applying a max of 20 ft. lbs. torque, so I don't think it is for strength. I'm guessing it's maybe to distribute more surface area of pressure on the copper washer. My guess is that the copper washer is used as a gasket to keep the salt water from escaping out along the stud and then from escaping between the casting and the under side of the washer.
I'm guessing the nyloc is needed to keep the nut from loosening off. Perhaps also to keep any salt water that would get past the inside diameter of the copper washer and the stud and try to work it's way out the end of the threads.
I could use that heavy nut without the nyloc and a brass lock washer, plus thread sealant, but maybe the copper is too soft and the lock washer would just not get a good foothold to prevent the nut from loosening.
Any thoughts or experiences with this?

 

[Mulletwagon]

Used plain old grade 18-8 stainless steel nuts and lock washers to install my elbows four years ago with no problems. Also used anti-seize on the threads. Don't see a need for exotic hardware in this application. Good LuckFL Panhandle

 

[erich]

I was told several years ago that the nylock nuts are used to prevent water from leaking down through the bolt threads, so the soft copper washers and the nuts provide the needed sealing. Neither the washers or nuts are suppose to be reused.

 

[gunkholer]

Used plain old grade 18-8 stainless steel nuts and lock washers to install my elbows four years ago with no problems. Also used anti-seize on the threads. Don't see a need for exotic hardware in this application. Good LuckFL Panhandle

Just to be clear Mulletwagon, do you have the 8" or 4" risers? Because in my research I think the 4" risers are different in that there is no salt water coming out of the stud hole opening that the stud goes in. Are your studs SS ? I was told not to put a SS nut on a SS stud or galling with happen. Also, included in the gasket set for the elbows. there was a pink card that said not to use never seize because it acts like a lubricant and the torque setting will back off and it may start to leak. So it's interesting that you've done this 4 years ago without problems.

 

[gunkholer]

I was told several years ago that the nylock nuts are used to prevent water from leaking down through the bolt threads, so the soft copper washers and the nuts provide the needed sealing. Neither the washers or nuts are suppose to be reused.

I'm inclined to agree with you erich. But I'm also inclined to try just a regular size brass nut with the nyloc instead of the original large outside diameter nut, and see what happens.

 

[Mulletwagon]

Not sure if the studs were stainless but probably are. Stainless on stainless may gaul – especially inhigh torque applications. The threat canbe minimized by using anti-seize and ensuring the threads are true and gritfree. Deformed-thread lock nuts shouldnot be used. Always some confusion onelbows verses risers. I generally thinkof a riser as a vertical component that goes between the manifold and theelbow. In this convention, I have norisers and the elbows mount directly to the manifolds. The water path betweenelbows and manifolds are blocked by a plate and two gaskets (fresh water cooledsystem). Any leaks around the studswould likely result is saltwater above the elbow/manifold juncture and coolantbelow. Gasket pressure as a result ofbolt torque would be impacted by lubed verses dry threads. Given thesubstantial bulk of the cast iron parts, not sure the additional press on thegaskets is significant, however, given written guidance and the use of brassnuts, recommend you go lubeless since gauling would not be an issue. The recommended torque is 25 ft-lbs. You must use a crow foot to torque the lowernuts. Be sure to position the crow foot90 degrees to the axis of your torque wrench on the left side or the appliedtorque will be in error. My biggestproblem when changing the elbows was just getting them off the studs. Had to use a large hammer to rock them backand forth to overcome the rust between the studs and elbow bores. Think you have enough background to decidewhich route you want to go. Hope some ofthis helps.

 

[gunkholer]

You must use a crow foot to torque the lowernuts. Be sure to position the crow foot90 degrees to the axis of your torque wrench on the left side or the appliedtorque will be in error.

I don't understand why you said I need a crows foot, Mulletwagon? When I removed the nuts I used a socket and a ratchet with a pipe over the end of the ratchet as an extension to give me more power to loosen the nuts and that worked fine. I'm just doing it all in reverse except using a torque wrench now instead of a ratchet with an extension handle. So in other words all the nuts are easily accessible.

 

[Mulletwagon]

The nuts seemed shrouded to the point you may not be able to get a torque wrench directly on them. If you can than you are good to go. I was only able to get a box wrench on mine. Are you putting sealer on your gaskets ? There is opposing advise on that and do not know what is best. I elected to use a thin coat of Permatex. Look forward to your after action report and lessons learned.

 

[diver_dave]

I have used both SS and brass for this job. IF you need to prevent a "spiral leak", then the self-locking will help that. If you do use SS lock nuts, I would put a dab of anti-seize on the threads. It will prevent galling. The lock nut will prevent both spiral leaks and keep it tight, IF the nut is new. of course, you want to retighten this nut after a few runs. The gaskets will compress.

I had to cut a box wrench to fit some places. Tighten by your calibrated 20 ft-lb hand as required.

 

[gunkholer]

Are you putting sealer on your gaskets ? There is opposing advise on that and do not know what is best. I elected to use a thin coat of Permatex.

On that pink slip of paper I mentioned that is in each package of gaskets, it also said to apply the gasket dry. I've read that if you put too much gasket goo on, some brands will get hard and small clumps can break away and then clogg the small tubes in the heat exchanger. I've also read that permatex aviation #3 gasket goo won't get hard. Also to apply a thin coat of that stuff is best. I've inspected the casting surfaces and I filled any imperfections in the surface like casting pitts and distortion due to prying the pieces apart with my slot screwdriver, with JB weld cold cure. In the past I've replaced the two thermostat housing gaskets several times thinking the thermostat might have been the problem with my overheating. Sometimes I'd use gasket goo and sometimes I'd apply the gaskets dry. Either way they didn't leak. But if they are applied dry they are much more difficult to scrape off, where the ones with gasket goo on them just peel right off. Maybe I'll do one engine with the permatex aviation#3 and the other engine dry. Hopefully my report down the road will be a simple "all good" . I'll let you know.

 

[gunkholer]

IF the nut is new. of course, you want to retighten this nut after a few runs. The gaskets will compress.

Tighten by your calibrated 20 ft-lb hand as required.

Yes I agree about checking the torque setting the first few times of firing up the engines. As for the torque setting, I've read 20 being applied more times than 25. I used 25 on the exhaust manifold bolts, just because they get hotter was my thinking. As for the stud nuts, elbow bolts, and end cap bolts, I think I'll use 20 and if I see a slight leak, I can always increase the setting to 25. I think perhaps it's not terribly important to get the right number but more importantly to be consistently the same on everything within reason.