Exhaust Manifolds - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 10-09-2000, 08:22 PM
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Exhaust Manifolds

Can anyone, for the love of pete, tell me if there are any changes in the exhaust manifolds for small block chevys in the mid 80s. I cracked a manifold and was replacing it while I did the Vortec conversion, but cannot find one that fits. It is just a little too short.

I always thought they were the same. But aparently there is a change somewhere.

The ones that do fit have a solid bar that connects the runners, the ones that do not fit just have the runners with nothing connecting them.

Any clues?

Thanks again,
Shane Bevel

The Dallas Morning News Photo Department
1986 3/4 ton 4WD Chevy Suburban
1989 Honda CB-1 400

[img] http://people.unt.edu/~shaneb/front.jpg [/img]
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post #2 of (permalink) Old 10-09-2000, 11:15 PM
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Re: Exhaust Manifolds

I ran into the same thing, except it was even stranger. I took the manifolds off of my truck to replace the (leaking) gaskets, and when I went to put them on found that they didn't fit anymore! Apparantly the iron shrinks over time as it cures and is subjected to the constant hot/cold cycle of being bolted to an engine. You can buy manifold spreaders at a good auto parts store, it's basically just a turnbuckle with u-shaped attachments on the ends. You put them in between the runners then turn the turnbuckle to spread the manifold out as you bolt them on. At this point you probably realize why the manifold with the bar between the runners fit but the others don't, right[img]/wwwthreads_images/icons/wink.gif[/img]? Using studs instead of bolts helps alot too. I'm talking if they're off by like 1/8" or 1/4", not anything like a full inch or anything.

<font color=green>Evan</font color=green>[img]/wwwthreads_images/icons/crazy.gif[/img]

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post #3 of (permalink) Old 10-10-2000, 09:42 AM
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Re: Exhaust Manifolds

Yes, the SBC exhaust manifold bolt pattern was never changed from the first 265s through the last of the Vortec 5.7s. Those log style manifolds are notorious for warping as noted above.

'70 CST Blazer, 350, SM465, NP205.
'87 Suburban 4X4, 350, 700R4
'88 Chevy PU, 4X4, 350, 700R4
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post #4 of (permalink) Old 10-10-2000, 12:19 PM
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Re: Exhaust Manifolds

Beaware that there is a difference in the end port bolt configuration between the 305 and 350s. That is why there is a gasket that has two bolt holes on one side of the port. I don't think that this is what you are experiencing. But if it is, there is an adapter plate available (try Summit) that allows the use of 305 manifolds on a 350. I think most people refer to the difference as 6 bolt compared to 7 bolt pattern. However, I'm sure Shaggy has the answer for your problem.

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