Exhaust Manifold Leak (Suspected): Tips, Suggestions, Experience?

[Charlie207]

There are various grades of stainless steel; I wish Dorman would specify more specifically what they're made of.

Well I'm 99% confident it's not in the same universe as the stainless I used to mill down into landing gear. They are probably at least 5% marshmallow mixed in with the iron, cobalt,and nickel.

 

[Charlie207]

so I can't find what I'm looking for, but I also didn't realize what arp is calling stainless steel header bolts/studs is 170k psi. that's some specialty stuff, I'm not sure there's much stainless about that metal besides not rusting lol. but seem like good stuff. personally I'd like a hex tip to the stud to help install and removeal, they come in handy and a crimp style lock nut, and not huge fan of 12 point since I don't have any 12 point sockets. well a few. but they seem to be a high rated strong stud.


this more what I'm use to for stainless


"The hardest and strongest of the hex bolts

Despite the popular belief, a stainless steel bolt is actually weaker than a grade 8 bolt. In fact, according to the Society of American Engineers (SAE), grade 8 bolts are the strongest and hardest hex bolt you would want to use in constructions or the automotive industry. While the carbon alloy bolts have a proof load of over 120,000 psi, their stainless steel counterparts don't carry an indicative proof load. Moreover, the minimum strength of grade 8 bolts is around 130,000 psi, whereas stainless steel strength doesn't exceed 90,000 psi."

grade 8 being about metric grade 10.9. the dorman studs have a 10.9 grade nut on them, so I'd hope the stud is rated the same. they aren't stainless steel because a magnetic will pick them up, just plated with something so they don't rust. probably zinc.

A Mini Guide On Grade 8 Bolts — Melfast

Grade 8 bolts are specified for high strength applications and are commonly used in heavy manufacturing, such as tractor and truck fabrication for instance. The bolts are typically made of a medium carbon alloy steel that is plated in zinc for extra resilience. The grade 8 bolt can be identified via

www.melfast.com

so yeah, it seems what arp is calling ss is very strong by the psi they give out.


either way, totally your call. I'd get that stethoscope and see if you can find the leak. it could be at the collector forsure. from the video that can definitely be an exhaust leak as it seems to go away as it warms up and everything expands. I'd personally confirm before taking everything apart thou but if you don't mind the work and money, definitely can't hurt

I'm sure they want to balance out the threat of shredding the tiny threads in the cylinder head if they used super steel hardware.

 

[petethepug]

08 Yukon w/ 5.3L. I didn’t read past posts thoroughly so if somethings already covered, that’s why.

On my 08 YXL 6.2L I verified no codes present, plugs replaced with OEM. The tick was still there. Had the Mani off for the AWD 100k Maj serv when trans was pulled. Yup, two broken studs. One took 2 hours to extract.

I didn’t know about the ARP Mani studs at the time or I would of installed them. On our Alum heads Stainless probably not a good idea as it reacts with Alum to create red oxide. Salt speeds the process.

When the job was done, the tick was better. New plug wires really helped and stopped it except when it was below 50*F on start up. What I was left with was GM’s infamous “piston slap” that occurred on the Gen 4 V8’s.

Piston slap can be unnerving when it’s really cold but ultimately harmless. Carfax recently emailed me that my 08 Denali has over 240k on it with regular jiffy lube changes. I sold the truck in 2020.

I’d do the ARP standard studs for just a bit more cost. Obviously reusing the old studs is asking for trouble on Aluminum heads. One broken stud can cost you $250 in labor depending where it snaps.

 

[solli5pack]

Might be worth to take the serpentine belt off and start the truck to make sure the noise isn't coming from one of the engine accessories...