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Old 03-17-2010, 07:37 PM
Jeremy Moberg Jeremy Moberg is offline
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Default Exhaust manifold Cadillac 331

A question for the owners of this engine family (331/365/390/429). Just curious what kind of luck you've had with pulling them. I need to replace the gaskets, it's not terrible but a little annoying. I remember doing this on my 76 Cadillac 500 and most of the bolts snapped in the head. In the end, I had to pull the head off to fix the problem. Is this common with the 331 also. I've heard it is with the Cadillac 500.
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Old 03-17-2010, 09:19 PM
Paul Steinberg Paul Steinberg is offline
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It is a common problem with just about every engine. I have a friend that has his own personal technique that he uses, and he rarely ever breaks a bolt. It is like the surgeon... some are just more delicate than others, and the results show their level of perfection. Me, I just plan on pulling the heads and drilling out the bolts if they break. Not much else you can do...
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Old 03-17-2010, 10:53 PM
Scott Avnaim Scott Avnaim is offline
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My best experience was after I used a oxy/acetalene torch to heat the head where the bolts go in. Get them as red as you can. Then let them cool. The heat expands the bolts and burns off the rust. When they cool down, they shrink and many times after you first get them loose, they can be turned by hand. All the bolts came out without breaking on mine. Propane won't do. Not enough heat. As a bodyman and first class scrounger, this has been a tried and true method to avoiding a lot of extra work. Of course, this is for steel heads.
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Old 03-18-2010, 09:28 AM
Richard Vyse Richard Vyse is offline
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I've had to replace my exhaust gaskets TWICE on my Lifeliner. Each time my mechanic applied heat and only had one bolt break on the first install. The second time I replaced the gaskets I had to have the exhaust manifolds lathed to make them smooth and straight. It appears as if Cadillacs have a problem with exhaust manifolds warping and I still have a little exhaust noise on the right bank.
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Old 03-18-2010, 05:03 PM
Mike Stevens Mike Stevens is offline
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Unhappy exhuast gaskets

On the 61 (390) there is not a lot of room to get your hands into the job as needed. I think you need double jointed wrists for this job with the engine in the car. Is it the quality of the gaskets? Is it the warpped manifold. Is it not retorquing them or something else. Or all of the above. I think it may be time to get them to the machine shop and milled. Then put in the new gaskets. I hate this job and I hate doing it about every other year. I have thought about some of the gasket cement for this job but if it doesn't hold then there is the work to get it off and the new gaskets in place.
Whatever happens here it is just one of those things that we all seem to be living with. I guess we should be happy that we can still find gasket kits.
Mike
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Old 03-18-2010, 05:25 PM
Paul Steinberg Paul Steinberg is offline
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If you pull the heads, have them surfaced on the manifold side.. That way, you know that you have to perfectly flat surfaces to mate to.. I don't believe in surfacing the head to block surface unless absolutely have to. Machining heads can cause as much of a problem as the warped head can if it isn't done properly. When you machine the head to block surface, you are actually dropping the head down by the amount taken off the head, which can result in a problem getting the intake manifold to seal properly. Machining heads can change the entire geometry of the engine parts where they mate up to each other...
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Old 03-18-2010, 09:48 PM
Michael Lee Michael Lee is offline
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Default just had mine done

we pulled the right hand head and had the machine shop pull the manafold off I had one bolt broken off already and one broke even with the torch. The bill was $120.00
I could not see how you could do this with out removing the head mine was a 472 but the last bolts in the rear you can hardly get to. And both the limo and the hearse have blown gaskets the hearse will be next, Also you might want to plan to replace the lifters while you have the head off. we did not replace the lifters and now that the exshast noise is gone I have a lifter gone bad that I did not hear before so I will probley be taking the intake manafold off agion to get to the lifters
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Old 03-18-2010, 10:13 PM
Paul Steinberg Paul Steinberg is offline
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I would try some NAPA lifter cleaner before I took the engine apart. Many times, you can get the lifter freed of the varnish that is keeping it from moving smoothly in the lifter bore. If the engine is sludged, then trying to remove lifters will be an even bigger problem than doing the head. Once you start down that road, you will many times wind up rebuilding the entire engine by the time that you are done. There are ways to chemically clean the inside of the engine so you can get many more trouble free years of service out of it. I would rather spend $100 on chemical treatment first, and then if they don't resolve the problem, move on to the disassembly process. The more you know about engines, the less likely you are to want to dig into them needlessly...
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Old 03-19-2010, 03:05 AM
Jeremy Moberg Jeremy Moberg is offline
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Thanks for the replies. I have heard of torching the bolts. Funny thing with my 500 was that one cylinder head was a pain in the rear when it came to anything. It was the one that needed to be removed. Not only did the bolts break in the head where the exhaust manifold bolts on snap but I even had to use a cheater bar ( arm off a 3.5 ton hydraulic floor jack ) to get the head bolts off. The other head broke free no problem. I did have the exhaust manifold machined before I installed it.
Back to the 331. I believe it is just old gaskets falling apart. I've replaced exhaust manifold gaskets on my 94 Buick LT1 with no problem. Every time I install an exhaust manifold, I make sure to put anti-seize on the threads. Really, If I pull the heads, I'm gonna rebuild the whole engine. Doesn't make sense to rebuild just the top half on an engine that old. Didn't bother me with the 76 M+M because the engine was low mileage and looked pretty good anyways. Then the bottom half is the weak point if the top is new.
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