special nuts required or not?
Posted: Fri Oct 26, 2018 4:06 pm
I have a 37 Trojan with 454 Crusader gas engines. I'm in the process of cleaning out the exhaust/heat exchanger of all the corrosion build up.
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. Which might be the reason why they went with a special nut with nyloc
Any thoughts or experiences with this?
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. Which might be the reason why they went with a special nut with nyloc
Any thoughts or experiences with this?