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1966 C Code Coupe / 1970 Mach 1 351C
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Discussion Starter · #1 ·
I purchased a T5Z from Modern Driveline, and installing it now on a 351C. I got the flywheel and clutch installed and started working on the bell housing.

I noticed some cracks in the bell housing that I wanted to address before I proceeded. It looks like some sort of stress relief was placed in two spots on the inside which caused visible cracks around it, and there is a corresponding crack on the opposite side, along with another fairly extensive set of cracks on the right.

Before I moved forward on the transmission install I wanted to know if these cracks are unusual or if the bellhousing is damaged.

Any advice would be greatly appreciated. I sent a note to Modern Driveline, so I am still waiting to hear back from them as well.
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See my 1967 parts needs in my signature below!
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Are you sure that it is not just casting flash lines you're seeing?
 

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1966 mustang convertible sprint 200, manual steering and brakes
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Those two circles your arrows are pointing to (first pic) look like casting ejection marks to me. When it’s cast, there are some spring loaded pins that help eject the casting from the mold. This assumes the supplier is using a permanent mold vs sand or lost foam. As far as those radiating lines go, they don’t look good but could just be surface defects (not cracks). Or they could be cracks, hard to tell. Weird spot for a crack unless related to ejection or thermal stresses.
 
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1966 GT 4spd
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Agree with above.

Actually caused by heat check cracks in the die used to cast the parts. Cosmetic. You could clean it up with a flap disk on an angle grinder if it bothers you.

Phil
 

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1966 C Code Coupe / 1970 Mach 1 351C
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Discussion Starter · #9 ·
Thanks everyone. I received a note back from Modern Driveline and they said the same. Since I had to drill holes in the middle of the lines to install the hydraulic slave cylinder, it was easy to see that they were all at the surface.
 

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Cracks in the dies (molds) are not uncommon, and do not typically degrade the part. Here's a famous example, The Chevy mold cracked over 50 years ago, and they have been using it ever since. Makes the earlier pre-crack valve covers quite valuable.
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