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Old 11-13-2019, 03:31 PM   #1
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1990 454 Chevy exhaust manifolds

Hey all - old problem, new situation. Our 1991 YellieBelle has ~21,000 miles on her, we got her last year with ~18,000 on her. When I got her running (hose on internal gas tank mounted fuel pump doesn't like alchohol in gas), I could hear the tale, tale, tock-tick-tick until she warmed up. Ole right side bank, #8 cylinder.
It's not really that bad - but I know leaving it alone will be cause for more extensive work later.


Like I said, it's really not that bad - so after having recently tearing the hydroboost and radiator out (installed rebuilt hydraboost, had rotted radiator recored) - I think fixing the exhaust manifold leak is next on the list.


So - looking for ideas. Should I -


1. Just (hopefully) retorque the manifold bolts, and if I break one then pull the manifold? Should I PB Blaster or Kroil the bolts first?

2. Go ahead and Kroil or PB Blaster the bolts first, then retorque, or go ahead and pull the manifold off to make sure all mating surfaces are clean, then reinstall using a high temp sealant on mating surfaces, as well as some type of thread sealant on the bolts (for easier future removal, provided I have to do this again)?
3. Just switch to tube headers? TO include or not include new muffler/cat (these were built with muffler in front of cat)?
4. Should I do the same to the left bank that I do to the right bank? (FYI- I will be fabricating the right side splash shield that helps to insure air is drawn past the right side exhaust bank before exiting the wheel well i.e GM p/n 15983041. The left bank shield is still there).



Appreciative in advance of anyone's experience!
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Old 11-13-2019, 07:02 PM   #2
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I've had success with PB Blaster on stubborn Bolts and given the year here - Be careful - Spray and re-Spay for several days- and only use a hand wrench or Ratchet-- No Air impacts. Be Gental at beginning and apply force as needed -- most of all be Patient .. Make sure the Socket fits the Bolt and begin the process of removal !!
Headers will rust out far more quickly Than your Manifolds !
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Old 11-13-2019, 07:46 PM   #3
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Victor blue gaskets were the best for me.
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Old 11-13-2019, 08:04 PM   #4
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Lay a straight edge on clean manifold gasket surface......might need to be resurfaced......and new bolts with never seize.....
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Old 11-14-2019, 07:41 AM   #5
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Try to loosen the bolts while the engines warm. I never broke any. Also if yours has a exhaust bypass valve bolted to the bottom of the manifold where the exhaust pipe attaches on the right side, that's another spot for leaking.
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Old 11-14-2019, 07:52 AM   #6
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Thanks all for your input!


So the consensus is to pull the manifold rather than attempting to just retorque (after a generous application of PB Blaster and insuring I can can get the bolts/studs to turn - in tandem with fabrication and installation of a right hand side splash shield)?


I assume the bolts/stud issue of breaking off is due to the seized threads of the bolt/stud as it threads into the head - but insuring I get penetration of the PB Blaster to those threads means having to get past the manifold (except for where there is a gap between the manifold and head, and even then I can be certain PB Blaster is reaching the threads of the bolt/studs).
I assume this is why the repeated days of applying PB Blaster?


FWIW - was hoping at 21k miles that maybe the bolts/studs wouldn't be that badly frozen in (granted that situation is probably a combination of time/miles/and environment. I'm in Texas, the motor home has always lived here so road chemicals not as much of an issue to speak of).
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Old 11-14-2019, 08:38 AM   #7
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Quote:
Originally Posted by Jyrocharlie View Post
Try to loosen the bolts while the engines warm. I never broke any. Also if yours has a exhaust bypass valve bolted to the bottom of the manifold where the exhaust pipe attaches on the right side, that's another spot for leaking.

Thanks Jyrocharlie! You make a good point about letting the engine warm up a some first. I assume after a few shots of PB Blaster.


Mine doesn't have a bypass - although until recently identifying the origination of the tick-tick-tick, I was thinking that what I was hearing might be either the donut in the joint where the manifold connected to the factory header or the heat riser valve (which as it turns out, this one doesn't have).
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Old 11-14-2019, 11:50 AM   #8
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Exhaust manifold bolts were an issue with those old throttle body injected 454. The timing was retarded to meet EPA emission rules and the fuel was still burning when the exhaust valve opened. Thus the exhaust manifolds ran very hot. If you just resurface the manifold and reinstall, the issue will return. Go with header and fix the problem permanently.
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