when did GM start slimming down on the good,thick material they used in their factory 350 blocks? is a 1979 "010" block a good one or is it one of the "diet victims"? i have another older block but it isnt an "010."

the last 79 4 bolt 350 I had was junk, major core shift as well. And an above average amount of corrosion-bad iron? I sold it for $25. I don't remember if it was a 010 casting though. The best seem to be prior to 79 from what I've seen.

So would you consider '78 and prior for a good core?

Also sorry to sound silly but what's "core shift"?

1955?
Oh, wait, that was the year I was born......

Core shift, Dawg, is what happens when the sand casting cores at GM move slightly from where they intend them to be when casting the block.
It can cause the cylinders on one side of the block to be thinner than on the other side.
It's best viewed by looking at the area around the front of the block where the camshaft goes. If the hole for the cam is smack in the middle of the boss, both front and rear on the block, the the core shift is likely to be minimal.
If the hole for the cam appears to be off to one side or the other, then core shift is a possibility.
The best way to check for this is to have the bores sonic checked for thickness. The previous description is rule of thumb only.
Remember, I was the guy who "thought" that 396 blocks could be bored to 4.25". Only if there is no core shift. I still think it's a vaible deal BTW.
Ron

what is the average cost of sonic testing the cylinders?

we get 40 dollars to sonic test the cylinders on a V-8 block

The blocks with the small vin pad have much less iron in them when comparied to the earlier ones.

Speaking of boring out blocks. What year did they "thin" out the 283 so they couldn't be as reliably bored out to a 4" bore?

Originally posted by Mike Feudo:
The blocks with the small vin pad have much less iron in them when comparied to the earlier ones. What year did this happen? My '78 350 has a smaller vin pad than my '69 350.

And so would that mean the reinforcement from the '78 350 is missing and the block is of a higher probability for core shift?

Should ones with small pads be avoided at all costs?

core shift isn't just a problem in the later blocks. i had a '70 with significant core shift. not good for high performance, but fine for low grade rebuild.

thanks for the great response! smile.gif

CNC BLOCKS N/E,i wish you were local,your price is very reasonable! graemlins/waving.gif

Personally I have had real bad luck with any of the blocks with small vin pads. If you look hard enough you can find an earlier block. A 2 bolt will work for just about anything you will build.

Does this go for all small blocks? Or just certain ones?

Jobberone, I had my '59 283 sonic tested and then bored to 4.00". I was told it could go another .030" over. Don't know about the later blocks, though.