where do Magnum heads crack?

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Dakota_Don

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If the engine ran good before being tore apart and a crack is found does that mean that the head is junk? even tho it ran great before?

Also are the crack visible and easy to see?
 
No. You almost always find cracks even in running engines. The cracks can migrate up into the coolant passages, but there's thousands that never do. If they pressure test good, it's a crapshoot if you want to use them. If it was me, I'd use the EQ heads and be done with it. They are cast thicker and use interlocking seats IIRC.
 
most of the time between the valve..... Best to magnaflux " spell ? "them....
 
Usually visible. Magnaflux shows the crack when it's difficult to see. The way to tell if they are bad is to pressure test the head and see if it leaks.
 
I was also wondering about this infamous crack issue. I have magnum heads with no visible cracks that have 115,000 miles on them. If after I have them magnafluxed and there are no cracks, can I assume that they have passed the point of cracking because of the milage or is still a crap shoot that they could still develope cracks. Trying a buget build.
 
I went to the junk yard and pulled a set of magnum heads. went and had them checked out at a shop. Would find out they were cracked so I would take them back to the yard and exchange them for a different set. After doing this 4 times I got a good set. I am never going to use magnum heads again.
 
I think the cracking issue was solved after a certain year. 95-96 or something like that. I have a set that is not cracked. It was the first set I looked at,but I also bought them at a machine shop where they had already been inspected and rebuilt.
 
needsaresto said:
I think the cracking issue was solved after a certain year. 95-96 or something like that. I have a set that is not cracked. It was the first set I looked at,but I also bought them at a machine shop where they had already been inspected and rebuilt.
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Not quite true. I have a pair of 98 heads with 150K on them. There's cracks in at least two valveseats each.
 
thanks, the EQ heads seem nice but they are about 350 each right? or are they cheaper somewhere else..

I wanted a set to throw on a used 68 318 with intake and carb to match..
 
sharpie said:
Not quite true. I have a pair of 98 heads with 150K on them. There's cracks in at least two valveseats each.
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Hmm.Maybe certain casting #'s are better? No idea. I thought I had read here somewhere about after a particular year the heads were better...Where does one find the casting # on a Magnum?

But just to clear the air. It's not just magnums that crack. G.M heads had issues during that era as well.
 
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