Header to Exhaust Bolts

[Bill Bulmer]

This may seem like an odd question, but I have Backdraft 1357 (2014 build) with the 427 Iconic motor. I just noticed today that on both sides of the car, where the header collector meets the side pipe collector, one of the four bolts is missing. It is the top front bolt on the passenger side, and the top back bolt on the drivers side. Is there any reason on earth that would have been manufactured that way, or is it more likely that they just loosened up and fell out.

If I do need bolts, does anyone know the spec on that, and is it a special grade since it is in such a hot vibrating area?

Thanks, and apologies for the naivety.

[Mark IV]

We use a "stover" nut https://en.wikipedia.org/wiki/Distorted_thread_locknut

A Nylock will not work as the heat melts the nylon and split lock washers fail with the heat cycling (takes the temper out of the steel) and allow the nut to loosen with the vibration. As this is a "tension" rather than "shear" application, a grade 5 or better will work although some bolts handle the heat cycling better than others.

[olddog]

Use anti-seize (Never-seize) compound on the bolt threads in heat applications. I have used nickle everywhere without issue. Some say copper is better.

The proper amount is fully coat the threads, and fully seat the bolt/nut. Then remove and re-coat. Install and torque.

[spdbrake]

I replaced all of mine with:
SS 5/16-24 X 1.5" Allen bolts
https://www.mcmaster.com/#92196a344/=1eff006
SS 5/16-24 self locking nuts
https://www.mcmaster.com/#90045a455/=1eff1ns
SS 5/16 washers
https://www.mcmaster.com/#96659a107/=1eff1uf

[PHMCobra]

I have BDR #1360 with a Rouse 427R (550 HP) with similar flange connections as you have. After reading your Post, I inspected my flange connections and discovered that one bolt on the passenger side had lost its nut. The four bolts on the driver's side and the three bolts on the passenger side are tight. So, thanks to your post. I will replace the missing nut. Others should visually inspect their header/exhaust flange bolts. Don't want to leave an exhaust system on the roadway! Good Post!

[Jim Vander Wal]

Tightening those bolts was a regular maintenance item for me. Didn't matter if I ran 5/16-18 or 5/16-24, all Grade 8 hex head, not sockets. I'd tighten about as much as I could but they'd still loosen up.

Part of the problem is the gaskets, if used. The more typical exhaust gaskets would burn out and then the flanges would be loose. I also built .060" solid copper, these could be tightened but the bolts would still vibrate loose.

Vibration is most of the problem, or that's what I believe. Double nuts can help, split lock washers may help. I was never a fan of the distorted nuts as previously mentioned, but these should hold and are probably the best solution.

I never used Anti-Seize on the flange bolts, never had a problem getting them off. May not be the case for your install. I wanted them to stick, the Anti-Seize seemed counter productive. Did always use Anti-Seize with steel studs into the aluminum heads but didn't have as much trouble there and easier to get to.

Jim

[olddog]

My side pipes were originally a slip fit that leaked. I had 3/8" plates made and welded them on myself. I have 3 bolt on all 4 edges that makes 8 bolts total. They are 5/16" - 18 bolt. I used stainless steel bolts and nuts, which tend to seize easily. Steel bolts may not need anti-seize, I wouldn't try stainless steel without it.

I made aluminum gaskets. I think the aluminum was about 0.100" thick. I used flat washers and torqued the bolt to their torque spec. I ran it through a few heat cycles and re-torqued the bolts. Never had any problem with them coming loose.

I would think the copper gasket would be better than aluminum. Sounds like others are having problems. I cannot say why I am not having the problem. Maybe something here in my setup is different and you can spot it. Good luck.

[Bill Bulmer]

Thanks to all, I did the work my self today, the bolt on the drivers side in the top rear was really hard to get to (steering column, and more in the way), but I finally pulled it off. The car is actually much quieter now, so it must have been leaking and rattling, but I just couldn't hear with the normal exhaust sound.

Thanks again!!

[tortuga]

Originally Posted by Mark IV

We use a "stover" nut https://en.wikipedia.org/wiki/Distorted_thread_locknut

A Nylock will not work as the heat melts the nylon and split lock washers fail with the heat cycling (takes the temper out of the steel) and allow the nut to loosen with the vibration. As this is a "tension" rather than "shear" application, a grade 5 or better will work although some bolts handle the heat cycling better than others.

You have to drive the all the way on, and to remove them you will likely snap the bolt...BUT they will NOT come off.

Cheers
Steve H
SPF 1764

[sllib]

I use the distorted lock nuts on my exhaust flange, as well as the drive shaft pinion flange, but I use the ones made by ARP that they call Jet nuts. They can be removed and replaced. I have a ARP catalog so I just got their part number and ordered them from Summit.
Bill