Cracked exhaust manifold 396
 

Over the last couple of months I have noticed an exhaust leak on my 68 C20 with a 396, turbo 400. I thought it was probably a loose manifold or a collector gasket that was loose as the noise would go away once the engine warmed up.

Today I noticed that the left manifold has a crack in it!

Can an exhaust manifold be welded? I know it is is cast and this adds difficulty, but how much difficulty?

If I go shopping for another manifold how exclusive are bbc manifolds to trucks?

Any other reasonably suggestions?

The truck is fairly original and a bit of a survivor truck so I am not looking to go to headers or swap the entire exhaust system.
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Re: Cracked exhaust manifold 396
 

Is it really this simple?

http://m.ebay.ca/itm/Exhaust-Manifol...256?nav=SEARCH
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Re: Cracked exhaust manifold 396
 

Yeah probably, I have seen s lot of repops. I think the big cars used the same ones.

Re: Cracked exhaust manifold 396
 

Wow........That looks pretty close to original. Edit, I have a spare LH side with a hairline crack. It takes up space and has no value. You need a "new" manifold.

Re: Cracked exhaust manifold 396
 

Where on the manifold should I look to find the casting number.
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Re: Cracked exhaust manifold 396
 

Blaine I have a new repro exhaust manifold that came with a 70 BB truck I bought a few years ago. I'm not sure what side but can check tonight when I get home.

Re: Cracked exhaust manifold 396
 

They can be welded, also.
There's a special "cast" welding rod. You cannot use a grinding disc to clean out the crack, you have to use a carbide bit. They also make a "gouging rod" that is used ahead of the welding, some how it prepares the surface for the cast rod.
I'm no expert at all this, my good friend has a machine shop, showed me several years ago. It does work.
Nickle rod is NOT the same thing...

Re: Cracked exhaust manifold 396
 

http://www.yenko.net/ubbthreads/pics...8-img_0286.jpg

How different are bbc exhaust manifolds. Part number on the side 3914613. This does not align with the ATP cross reference in the eBay ad I posted above.
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Re: Cracked exhaust manifold 396
 

It is not uncommon cracked manifolds were common even in to the squares and the 88-98 style as well.

Re: Cracked exhaust manifold 396
 

As luck would have it I have a right side exhaust manifold.

Re: Cracked exhaust manifold 396
 

I,m needing a left one for my 72 402, I see LMC lists them also.

Thanks for checking.

Looks like my right one has already been replaced.
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Re: Cracked exhaust manifold 396
 

The casting numbers can vary: Here's some info. most of which I lifted off SSTIM:

The following part numbers are service replacement parts.

But don't expect a number in the parts manual to match a part you pulled from your truck.

Overall its real simple, the replacement manifolds at the time of printing (5/79) were:
3994045 LH
333846 RH (3916178 to 3994046 to 333846)
with A.I.R. this is the air pump for emission reduction (Not A/C).
343787 LH
353030 RH

There is nothing on the parts manual page showing application specific parts for a 396-402 C10-30 Air Conditioned vehicle. If there were it would probably be notated w/AC, C.A.C., or C60.