How far can you typically overbore a 318?

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LXguy

LXguy

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Hey All:

Curious how much you can overbore the typical 318 block?

Are newer ones better/worse/the same?

This is referring to LA blocks, not Magnum.

Thanks for any help!

Steve
 
my '77 dated LA 318 is bored .060 over.... and .060 over is the max for any LA block...
 
67 blocks seem to be thin, 68-73 or so seem to be the thickest, have seen a 70 punched to stock 340 bore.

first step to tell if you have a block that can be bored large, is to look in the four sections of the block. See if you can see the casting line, it will lok like a crack almost, running through the centerline from the center of the odd side (I thnk) all the way across the block. :) If it doesn't have this, then you might want to have it sonic tested to see how far you can punch it. I have a 74 block, that couldn't even go .040.
 
i would sonic test any old block, but for sure anything over .030, the problem sometimes isn't they way they were cast but how many miles the block has and if there is thin spots from erosion. like the grand canyon LOL
 
Seen a steel freeze plug that was punched into the jacket and left wear a hole into a bore from the back side, bored it .030 and the damn thing had a hole in the bore!
 
.........I have had 4 bored 130 thou which is stock 340 size........2 of them had heating problems, but we got her figured.......oh ya the block is approx 10 lbs lighter.........kim.............
 
oldkimmer said:
.........I have had 4 bored 130 thou which is stock 340 size........2 of them had heating problems, but we got her figured.......oh ya the block is approx 10 lbs lighter.........kim.............
Click to expand...

Yeah, I've heard that too.....I have an article somewhere where a shop was sonic checking a bunch of old 318 blocks and taking the thick ones over .100, and I think some up to 340 size.
 
Wow. OK, good to know.

I'm going to start digging out blocks and checking em.

Steve
 
Checkout this thread here. Dude bored his 318 to 4" (+.090"). Might have to read through it some but it's in there.
 
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