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Magnum exhaust manifold gaskets


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The 8940 Magnum decided to spit a piece of exhaust manifold gasket out to make a tick noise from the number six exhaust port when she is under a load, so time to replace them. They were replaced when it was nearly new and hasn't leaked since, but when looking at them, they look like they are multilayered. The parts site says it should be part #J929012 and the 8950 uses part #932063. The 8.3L was also used in truck applications and I don't know what gaskets they used. I know to check the manifold with a straightedge for flatness, but what gaskets are you guys using and having the best luck with?

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I think they have gone through a series of improvements on those gaskets. Our 7250 needs a set currently

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The gaskets have changed design several times over the years.  Used to be multi layer stamped metal.  Now they are a graphite coated gasket. 

No, there is no two piece manifold for the 8.3's.  I just looked a month or so ago for a two piece because we had to replace the manifold on a 9330.  Yes, they do exist, for the truck division.  But the turbo location is different.  Some at a 45° angle, others underslung.  None for the Ag tractor application.  However, the new manifolds will have bars between each of the ports to help keep it from warping.  Don't worry about if the old one is flat... it won't be.  Do look how far it has shrunk.  They pull together so tight after years of service that they actually bend and pull the mounting bolts toward center.  On the 9330, I pulled the head and torched the bolts off, then beat the manifold off with a hammer.  It was a far better choice than breaking and having to remove the manifold bolts.  Still had to head the port on the head to remove the bolts.  Each one.  I almost guarantee you will break at least one bolt, and they are no fun to get out.  Soak them good with Kroil, and get the torch ready.  You might be lucky.... just depends how hot the exhaust was run and how many hours it has on it.  But plan for a long job.  It isn't always that bad, but can be.  Those tractors are getting old.

As far as the gaskets.... they all pretty much look identical no matter where you get them. 

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I have had good luck with the multi-layer gaskets. #3 port on manifold has 10mm bolt holes to locate manifold on engine, using Cummins bolts start torquing here and circling out (32 ft lbs) remaining holes in manifold are 11mm to allow manifold to expand & retract under the bolts. Also would recommend the clips that hold bolts in place after torquing, that is what keeps bolts from working loose as manifold moves. 

To take bolts out, soak them good with penetrating oil, while running tractor to heat cycle, using a big punch & hammer HIT straight in on bolts to help shock the threads while at operating temperature (keep applying  penetrating oil ) most times you can take them all out without much problem.  

I always tell customer to help me help them by starting the penetrating oil application before tractor ever comes to shop. 

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