Header bolts - Team Camaro Tech
Exhaust and Headers Discussion related to Exhaust systems and headers.
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post #1 of 16 (permalink) Old Apr 13th, 19, 01:23 PM Thread Starter
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Randy Brutout
 
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Header bolts

Gentlemen,


I am having problems with loose header bolts. I have got my engine hot then tightened the bolts as tight as possible and within a few weeks they are loose again. What gives???


Thanks ahead of time for your help.


Randy

1968 Camaro Super Sport, 396ci, Edelbrock carburetor & intake, Muncie 4-speed, Hurst, 12-bolt posi, Flow Master.
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post #2 of 16 (permalink) Old Apr 13th, 19, 01:57 PM
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Re: Header bolts

What type of washers are you using? I use SS bolts and star washers and they don't loose up.
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post #3 of 16 (permalink) Old Apr 13th, 19, 02:11 PM
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Re: Header bolts

I use the cheap ARP bolts never had a problem
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post #4 of 16 (permalink) Old Apr 13th, 19, 02:17 PM
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Re: Header bolts

Quote:
Originally Posted by Randy Brutout View Post
Gentlemen,


I am having problems with loose header bolts. I have got my engine hot then tightened the bolts as tight as possible and within a few weeks they are loose again. What gives???

Randy
What is happening is called heat cycling. As you heat metal up it expands. If you have a bolt trying to hold that expanding metal in place it will stretch unless it expands at the same exact rate. When it cools that bolt is now loosened from it's previous torque setting. Within a few hundred heat cycles the bolt will actually fall out as it is loosened until vibration takes it the rest of the way out of the bolt hole.

A bolt that is constantly being stretched is loosing torque. We rely upon torque to hold a fastener in place most of the time (the stretch imparted to the bolt pulls the threads tight so that the bolt can not slide down the inclined plane of a ramp wrapped around a cylinder).

Instead of relying upon torque to hold the factory bolts in place they staked the bolts with a stamped steel part that allowed you to bend a tab up against a face of the hex head on the bolt. This prevents the bolt from moving which holds it in place (maintains the torque).

If you run headers you do not tighten the bolt as much as you can (torque is only 20 ft/lbs). Instead yo have to stake the bolt so that it can not move. That is why I use and recommend Stage Eight Exhaust fasteners to hold a bolt in place and preventing it from rotating.

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post #5 of 16 (permalink) Old Apr 13th, 19, 03:57 PM
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Re: Header bolts


Chick
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post #6 of 16 (permalink) Old Apr 13th, 19, 06:31 PM
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Re: Header bolts

I've had good luck with these:

https://www.summitracing.com/parts/p...make/chevrolet

'69 Z/28, Lemans Blue/White Stripes, DZ302, Tremec Magnum, 4.10, Procar Elite Seats,
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post #7 of 16 (permalink) Old Apr 14th, 19, 04:16 AM
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Re: Header bolts

Heat-treated studs and small pattern nuts and small pattern washers and get used to it, weekly ritual.

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post #8 of 16 (permalink) Old Apr 14th, 19, 05:38 AM
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Re: Header bolts

One thing that could be happening is this; If the fastener is not designed for the use, it could stretch while hot and stay where it is. This is in fact annealing it (softening it). Another issue to keep in mind is trying to use an old, used fastener. Bolts that have been stretched from prior use. This is why in many cases head bolts/studs are not re-usable. Once they have been stretched, they have lost, or used up their "memory".

The tensile strength varies depending on the steel. 8740, 4140, 4340 alloys, 9CRMO Chrome Molly, 625 & 718 Inconel Nickel-Based Alloys and 304, 316, 17-4PH & 15-5PH Stainless's are all chosen based on their use and requirements. "Tensile" is pull strength, or stretch and "memory" (will it return (or not) to it's original state after heat has dissipated). The more torque applied to the fastener, the more it will "stretch" to a lesser torque when heat is applied. It is at this time that the fastener can move radially and loosen. This is why rotor bolts get "Wired", so they don't rotate loose.

Bolts that are designed for heat cycling contain the specs that should withstand the application. But here's the thing; If the wrong fastener material is used for the application, even if you have it locked so it will not rotate loose, it could still stretch and stay, basically loosening even though it did not rotate loose.

IMO, three things need to be followed;
Make sure the correct material fastener is chosen for the application
Do not over-tighten
Lock it in place so it cannot rotate loose (I would not use Locktite).


And........On my car, I will look to ARP first. I do like the Stage 8 system as well. I was unaware of the Taylor Vibe-Lock so it's good to get positive feedback on them.
Brett.....

1969 SS 396 X66 - RS Conversion - TKO600 - 3.73 Posi - Paint Code 71-LeMans Blue

Last edited by Brettallen59; Apr 14th, 19 at 05:42 AM. Reason: typo
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post #9 of 16 (permalink) Old Apr 14th, 19, 09:05 AM
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Re: Header bolts

To add to Brett's info above you do not need a grade eight fastener. Header flanges are not subject to shear (side ways motion).

Grade eight gets to be hardened (to resist shear) by heat treating the part. Guess what happens on an exhaust system? As such a standard Grade Five bolt will work.

I do not recommend stainless for this application as the metal will quickly anneal, and they will blue instead of staying all shinny and polished like new.

Big Dave
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post #10 of 16 (permalink) Old Apr 14th, 19, 10:57 AM
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Re: Header bolts

guess I been lucky. I been dirt racing in the past (68-70)and never used an ARP bolt
that includes all the engines I built back in the day. i had several that twisted to 7400 Rs with a stock bottom end using stock bolts . NEVER LOST AN ENGINE
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post #11 of 16 (permalink) Old Apr 14th, 19, 11:52 AM
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Re: Header bolts

I used to shift my L-88 427 at 7,600 and crossed the finish line bouncing the needle off my eight grand tach's peg, and I never lost a bottom end. But I have scattered many a 283 or 327 pegging a ten grand Sun tach. I also blew up a lot of 409's because they used the same tiny SBC rod bolt that had no chance against a HEAVY 409 piston. Never figured out the sweet spot between power and reliability with 409 parts.

So Kevin you just weren't trying hard enough!

I only use ARP fasteners and studs today in all of my engine builds because people hate you if you oil down the track. I buy all new ARP studs because I have no idea who put together a motor I am rebuilding. Don't know if they used a torque wrench or an impact to assemble the motor. Buying new ARP fasteners means I don't have to care.

Big Dave
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post #12 of 16 (permalink) Old Apr 14th, 19, 11:57 AM
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Re: Header bolts

Quote:
Originally Posted by flat tire View Post
guess I been lucky. I been dirt racing in the past (68-70)and never used an ARP bolt
that includes all the engines I built back in the day. i had several that twisted to 7400 Rs with a stock bottom end using stock bolts . NEVER LOST AN ENGINE
I'm not saying no other fastener will work. ARP is just my personal preference. I make and handle machined threaded parts all day long so I feel like I can detect quality as soon as I pick up a part. ARP is a quality fastener. We use ARP fasteners in the assembly of our Rocket Engines, and our Reaver thrust chamber puts out 400,000 HP. Just my opinion.

Brett.....

1969 SS 396 X66 - RS Conversion - TKO600 - 3.73 Posi - Paint Code 71-LeMans Blue

Last edited by Brettallen59; Apr 14th, 19 at 12:03 PM. Reason: typo
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post #13 of 16 (permalink) Old Apr 14th, 19, 12:07 PM
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Re: Header bolts

Quote:
Originally Posted by Larger Dave View Post
I do not recommend stainless for this application as the metal will quickly anneal, and they will blue instead of staying all shinny and polished like new.

Big Dave

I beg to differ on SS bolts turning blue. Not sure what SS bolts you used that turned blue.



The bolts in my pictures are pushing 30 years on these headers/engine. No blue or discoloration. The washers are black and brand new only because I had the headers re-coated after removing the header wrap over Christmas shut-down and preferred to put new washers on, but the bolts look the same as when I installed them.








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post #14 of 16 (permalink) Old Apr 14th, 19, 12:38 PM
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kevin
 
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Re: Header bolts

Quote:
Originally Posted by Brettallen59 View Post
I'm not saying no other fastener will work. ARP is just my personal preference. I make and handle machined threaded parts all day long so I feel like I can detect quality as soon as I pick up a part. ARP is a quality fastener. We use ARP fasteners in the assembly of our Rocket Engines, and our Reaver thrust chamber puts out 400,000 HP. Just my opinion.

Brett.....
no problem
my Dad was a tool and die maker from the 60s till he died (am sure you know what that is ). just saying, what he has taught me has worked for me through out my life. closer to 70 than 50.
I mean no disrespect to you of your profession or what you use.
I am just stating my personal use with bolts that my dad taught me .
just for the heck of it google ABL , Hercules Power company, now Northrop Grumman which back in the time made parts for the Polaris missle and many other outer space projects. that is where dad worked. just to confirm he wasn't a self proclaimed machinist/tool maker
you are my friend (I hope) I don't mean no disrespect
this is just my opinion what has worked for me
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post #15 of 16 (permalink) Old Apr 14th, 19, 04:34 PM
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Re: Header bolts

For header bolts, I use Stage 8 locking header bolts. https://www.stage8.com/

Summit, etc. carry them

I use ARP fasteners on all "engine" assembly. Nothing wrong with their header bolts but the Stage8 are a locking type, great for headers
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