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Broken motor mount question

Bobby Goolsby

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I removed the 400bb from my 72 charger that I just started restoring. Found both rear lugs where the motor mounts bolt to the block broken off of the block on both sides (see pic). Will a machine shop be able to weld something on that will work?

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Are you planning on rebuilding the engine?

Maybe find another running engine with no cast issues Just a thought
 
Are you planning on rebuilding the engine?

Maybe find another running engine with no cast issues Just a thought
My original plan was to rebuild the engine. Until I found this. Now idk.
 
That's an easy fix with the motor out. Find a junk block and sawzall the piece you need. Grind to fit and find a welder or weld shop to weld it.
 
That is pretty common on later blocks especially the 400
 
Thanks! I think when I take it to the machine shop, I'll see if they can fix it. If not, I guess I'll go the motor plate route. Still cheaper than buying a new block
 
I've done it.. I'm sure a machine shop can...they see all kinds of abuse and deal with it...
 
Find some high nickel rods. Certanium 889 is the best.

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I removed the 400bb from my 72 charger that I just started restoring. Found both rear lugs where the motor mounts bolt to the block broken off of the block on both sides (see pic). Will a machine shop be able to weld something on that will work?

View attachment 1297046
Though there's no accounting for casting
integraty, a straight thru bolt has a
tendency to transfer the load thru both
holes but that load is multiplied. When we
designed the placement of a 440 in a tube
frame, we ran those loads on a stress
analysis program. The stress is reduced
by half if there are two separate bolts.
I believe your block can be fixed if you can
find a shop that has an experienced cast
iron welder. Might be pricey. Compare
replace vs repair. My top rear tab was
gone, as yours. So far it's holding up.
Zoom in on the rear top mount and
you'll notice a slight stagger where the
tab was welded. It's imperative that you
install a bolt (grade 8) with a clearance
that is pretty tight. You want the mounts'
rubber taking the load, not the bolt.

Resized_20170128_150955_001.jpeg
 
Last edited:
I cant remember the exact setting, but it was around 70-80 amps
 
Be careful, the welder doing the welding needs to be pretty experienced at cast iron welding with the correct materials and welding machine.
I wonder why both ears broke off? Collision?
 
Be careful, the welder doing the welding needs to be pretty experienced at cast iron welding with the correct materials and welding machine.
I wonder why both ears broke off? Collision?
No damage. But I also don't know the history of the car. I know it had Holley carb, intake, and headers. Guess I'll find out more when it goes to the machine shop.
 
I doubt the machine shop can figure out the cause of two ears being broken. But maybe. Possibly the bolts were over torqued?
Again the person doing the welding needs to be really skilled/experienced at cast iron welding. On my staff I had several well trained machinists experienced at welding. They ALWAYS deferred to another non machinist to do the cast iron welding. Very unusual in the union environment. Cast welding takes a lot of experience.
 
I had the exact same problem with a 440 block. I found a cast iron welder and he charged me $100 to fix the broken ear. He stated the key to cast iron welding is heating the part before doing the weld and slow cool down afterwards. The block was turned into a 500 ci stroker and produced 565 hp and 605 ft-lbs on the engine dyno. The fix is 10 years old now and there have been no issues. The engine is used in a 69 Roadrunner that is driven on the street.
 
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