i relized the exhaust manifold bolts on my dusters sl6 head were broke off, and a few other sl6 cars i've seen are the same way why do they break off?

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Dusters Rock

Welcome!

Do you mean the cylinder head to manifold studs or the exhaust pipe flange bolts/studs?

Maybe they have been overtightened?
Steel nuts used instead of brass nuts in cylinder head connection?
Great temperature changes do no good for exhaust manifold parts.

The bolts that hold the exhaust manifold to the intake are a "steel in cast iron" interface and the factory did not use any type of "anti-seize" compound during assembly.
Combine this with many heat cycles and the threads seize together.
At the head surface, the factory used bass washers and special locking nuts on the end studs, to allow the big, long cast iron exhaust manifold to expand and contract. If the incorrect hardware is used or if the nuts are over-tightened, the studs break.
Before tring to remove any of the manifold nuts / bolts, use penitrating oil and/or heat to try to get them loose. many times the bolt / stud breaks and you have to drill-out and re-tap the hole.
DD

If you have some that are broken, it’s probably best to replace them all - though, that’s probably being debated somewhere at this very minute. Maybe here in a few minutes.

New studs (Grade-eight) - Dorman Part # 675-093

You may also want brass nuts - Dorman Part # 680-001 or 849-001 (same nut, sold to stores in different packages)

And new castellated nuts for the two end studs Part #AN310-5 (5/16-24) at this website

You can read all about manifold mounting HERE.

Danny

if you do decide to take off the manifold to fix the broken studs make sure you soak the remaining studs in penetrant of some kind (pb blaster etc) or they will for sure snap off. let us know how it goes

thanks for the info

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Dusters Rock