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Exhaust Manifold Problem - Need Help!

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Old 10-27-2010, 04:39 AM
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Default Exhaust Manifold Problem - Need Help!

1986 K5 Chevy Blazer 4x4 305

Alright, I'll try and make this make as much sense as possible. For about a month now I've had a really bad exhaust leak coming from the passenger side of the vehicle. When I'd accelerate, the truck would sound like a lawnmower. I have a friend who works as a mechanic for one of the Chevrolet dealerships out here who does jobs on the side. He took off the manifold and told me that there were bolts missing and that could be the problem with the exhaust leak. He had me go out and buy matching bolts to replace the missing ones. As he was putting everything back together he had trouble with the last bolt in the rear. He said the hole for the bolt in the manifold itself didn't match up with the bolt-hole in the block. He then went on to say that I may have the wrong exhaust manifold attached to the block. I had a look for myself and saw that the bolt-hole on the manifold was about an inch or so off from the hole in the block.

What I don't understand is that I've never had a problem with the exhaust up until now as it ran quiet and never made an irregular sound. The manifold in question is the one that came with the truck when I bought it. What I would like to know is if I maybe have a 350 exhaust manifold and need to replace it with a 305 exhaust manifold or if this is a common problem and there is a way around it?

Any help or advice would be greatly appreciated. I have a day and half to solve this problem, this vehcile is my only means of transportation. Thanks in advance!
 
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Old 10-27-2010, 07:30 AM
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Bolt patterns should be the same between a 305 & 350 as far as the exhaust manifold is concerned. Are you sure that it is an inch off? That sounds like a lot. I have seen them between 1/8" and 1/4" off that has been solved by using an exhaust manifold spreading tool to line things back up (in fact there is a thread around here somewhere discussing this very thing by chevyblazerchick).
 
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Old 10-28-2010, 06:57 PM
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Originally Posted by swartlkk View Post
Bolt patterns should be the same between a 305 & 350 as far as the exhaust manifold is concerned. Are you sure that it is an inch off? That sounds like a lot. I have seen them between 1/8" and 1/4" off that has been solved by using an exhaust manifold spreading tool to line things back up (in fact there is a thread around here somewhere discussing this very thing by chevyblazerchick).
x2

An inch is crazy. 1/16, 1/8, 1/4 ya. Exactly like swartlkk said, exhaust mainfold spreader. $10 tool. Most of your auto supply places should carry them in their special tool section. If it is an inch off, you might have to fork out the cash for a new one. That's a bit far to spread, I mean you could try but cast iron is brittle, regardless it'll either work or it'll break, either way you'd have to buy a new one.
 
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