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A garage full of parts came with my cars and I am trying to sort out what is sellable and what is junk. I pulled 4 blocks out and in trying to id them noticed 3 of 4 had what appears deterioration of the metal at the back of the block towards the distributor but inside the block. Is this normal or are these junk? Thanks
Wheel Tire Automotive tire Synthetic rubber Tread

Bicycle part Bumper Automotive tire Auto part Metal
Automotive tire Wood Auto part Automotive wheel system Tire
Wheel Tire Automotive tire Synthetic rubber Tread
Bicycle part Bumper Automotive tire Auto part Metal

Automotive tire Wood Auto part Automotive wheel system Tire
 

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I've only tore down about 10 engines in my career as a enthusiast. I have never seen a lack of casting material like those. Usually it's the opposite, some extra flashing material that can be ground of to make it pretty or to help the oil flow ever so slightly better. I'm not saying they are not good cores, I'll let the more experienced chime it, but I would not consider them for souped-up build. You might ask "why" and I'd have to say because "I don't know any better". Even if they are good-to-go, perception of a problem can reduce their value.
 

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This is what I have seen on the three 400 blocks that have come through my shop (pic borrowed from the net)...

Photograph Automotive tire Tire Wheel Rim


The extra flashing is seen, above, between the opposing rear lifter holes as a lighter colored ridge. The OP's photos show holes or voids in the rear wall. After flipping through photos, on the net, of our beloved blocks, I see several with holes and voids in that area...must have been a common occurrence. I would still consider it to be a less than desirable casting. I can't begin so suggest that it won't hold up and I would certainly not throw them out.
 

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A garage full of parts came with my cars and I am trying to sort out what is sellable and what is junk. I pulled 4 blocks out and in trying to id them noticed 3 of 4 had what appears deterioration of the metal at the back of the block towards the distributor but inside the block. Is this normal or are these junk? Thanks View attachment 157399
View attachment 157400 View attachment 157398 View attachment 157399 View attachment 157400
View attachment 157398
Casting flash, not a problem unless it breaks loose on a fresh engine. Carefully remove it with a die grinder before hot tanking.
 

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That's what I'm thinking
You can deburr the casting flash using a die grinder/sanding rolls. I never did this nor even thought about doing it in the past. I did do it on my 455 block because I read it can prevent any casting flash to break off and fall into the engine and smoothing the edges out can help to prevent any stress cracks as well as help with oil return.

With the millions of engines Pontiac cast, when was the last time you hard of one going south because the casting flash broke off and damaged the engine? So it is one of those things I feel can help to make you sleep better at night, but may not make a difference one way or the other - and makes for good conversation in a group of motorheads that you deburred the lifter valley of casting flash and it cut 1/2 second off your 1/4 mile times. (y)

Auto part Gas Composite material Metal Automotive exterior
 

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Along with cleaning up the casting flash around the lifter bosses, I have been advised by a long-time Pontiac drag racer to open up all the oil return holes in the valley. I have opened them up with a die grinder by about 1/16th inch or a bit more, but try to open them up towards the slope that the oil is running down to begin with. Then I chamfer the hole opening up slightly to eliminate the sharp edge. You can see one of them in Jim's photo...dead center in the photo. It's just one of those things that sounds good to do without any study to prove it. I sleep better for it.
 

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A garage full of parts came with my cars and I am trying to sort out what is sellable and what is junk. I pulled 4 blocks out and in trying to id them noticed 3 of 4 had what appears deterioration of the metal at the back of the block towards the distributor but inside the block. Is this normal or are these junk? Thanks View attachment 157399
View attachment 157400 View attachment 157398 View attachment 157399 View attachment 157400
View attachment 157398
I would have been wondering the same thing. It amazes me that blocks are made using sand casting molds. I’ve seen the ”how it’s made videos” and know it’s been done this way for decades. It never would have occurred to me, but then I am still in awe of vinyl records (some of you may remember those) and the quality of sound picked up by a needle.
 
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