How Robust is the 318 block?

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MonkeyMadness

MonkeyMadness

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I picked up a fresh rebuilt 72 318LA (hasn't been run since the build) from an estate sale. Pulled it apart and found the block had been bored .060 over 3.970"
Block looks really good and seems to have been prepped well.
I was planning on dropping a 390 stroker kit in this block and just wounding if these 318 blocks can take a .060+/- over bore?
 
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MonkeyMadness said:
I picked up a fresh rebuilt 72 318LA (hasn't been run since the build) from an estate. Pulled it apart and found the block had been bored .060 over 3.970"
Block looks really good and seems to have been prepped well.
I was planning on dropping a 390 stroker kit in this block and just wounding if these 318 blocks can take a .060+/- over bore?
Click to expand...
Have it sonic checked is the way to find out.
 
All the rest can stand 600-650 HP. SO I imagine the 318 can too.
 
I think the concern might be the combination of +.060 and the extra stroke that can load the cylinder walls more. As most have said, check for thickness as well as core shift.

Bottom end would tend to be a little weaker than a 340/360 because of less material in the main caps.
 
Hensley Motorsports has been building 4" plus bore 318s for over thirty years. I've spoken with them on the phone about it before. While they say they sonic test them all, what I gathered was that most all they sonic tested were plenty thick enough and plenty evenly poured. Even still, they said they'd not skip the sonic test. But they said the "reject" pile was far smaller than the "accept" pile, for whatever that's worth.
 
Thanks for the input everyone, the block was dropped off at the local machine shop for a once over and sonic testing..
I was just wondering if the 318 was known for thicker castings and/or will they take such a big oversize with out issues.
 
RustyRatRod said:
Hensley Motorsports has been building 4" plus bore 318s for over thirty years. I've spoken with them on the phone about it before. While they say they sonic test them all, what I gathered was that most all they sonic tested were plenty thick enough and plenty evenly poured. Even still, they said they'd not skip the sonic test. But they said the "reject" pile was far smaller than the "accept" pile, for whatever that's worth.
Click to expand...
Were those pre 1969 blocks?
 
toolmanmike said:
Have it sonic checked is the way to find out.
Click to expand...
Having it sonic checked is a good idea even though it's late in the game since the block is already bored 0.060" over. Myself, if I was to build a stroker motor I'd bore the block only enough to clean up the bore. To much overbore can cause the cylinder walls to flex. Just because a block can be bored over a certain amount doesn't mean it's a good thing to do.
 
Locomotion said:
I think the concern might be the combination of +.060 and the extra stroke that can load the cylinder walls more. As most have said, check for thickness as well as core shift.

Bottom end would tend to be a little weaker than a 340/360 because of less material in the main caps.
Click to expand...
can 340 main caps be used on a 318 after a line hone? any aftermarket caps for 318??
 
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MonkeyMadness said:
I picked up a fresh rebuilt 72 318LA (hasn't been run since the build) from an estate sale. Pulled it apart and found the block had been bored .060 over 3.970"
Block looks really good and seems to have been prepped well.
I was planning on dropping a 390 stroker kit in this block and just wounding if these 318 blocks can take a .060+/- over bore?
Click to expand...
Depends on the block, seen a few with a 4" bore.
Mine is .060" over but was sonic tested first - thinnest cylinder is .167" on the thrust side (73 block). With a 4" stroke I would stick with smaller bore if possible but have it checked - you might get away with it.
dirty white boy said:
can 340 main caps be used on a 318 after a line hone?
Click to expand...
I would think so if you are getting the main tunnel align bored - but I could be wrong.
 
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