360 sonic check

[Pentroof]

Measurements are allegedly from top of bore, as he said all lower measurements were thicker. Believe it?
This is my block. My machinist dropped it off with another shop to do the measurement. Thrust numbers seem high on 5-8 bank.
Bores are currently 4.050 plus wear. Amazingly, it still measures barely above stock and almost can't feel a ridge.

[WerbyFord]

How & where was the before & after calibration done?
It was DONE, right?

Thing is, the thinnest non-thrust is .179". ok.
Let bore it .180-over for a 4.230" bore and make a 427 (yay).
Now the thinnest wall will be that .179"-.180/2=.089", still passable for a street 427, and all the other wall are thicker.

I just have trouble believing you could bore ANY 360/390/410 block to 427 bore and be okay.
Just saying I don't trust it.

What kind of drill bits fit in between the bores?
That's a double sanity-check in situations like this.

For example, between Cyl #2 and #3, the gap should be
4.630-4.050-.261-.231=.088"
So you'd figure about a 1/16 or 5/64 drill should be all that will slip thru that gap.
Is that the case? Otherwise the sonic is just wrong, the math doesn't work.

OK wait, now I'm seeing the .162" on the drivers thrust side. (And .330" on the other thrust). If true that's a LOT of core shift on that bank and awfully thin thrust. Its unusual to see a thrust wall THINNER than a non-thrust wall but if that's true I wouldn't sink much morey into that block or bore it more than needed.

Still, I don't trust those non-thrust numbers so I kinda don't trust the whole thing.

[fekbmax]

Good find, make a stout block and get a few over bores outa it.
It's a keeper.
I have 2 391 truck blocks with really nice sonic numbers and showing minimal core shift setting under my bench. Waited to long to get rid of them now with the BBM blocks out (when and if there available)..

[Joe-JDC]

It the transducer head didn't have an arc to match the cylinder curve, then the readings will be off just like that sheet.  I bought a block with supposedly thick cylinder bores like that, and when I did a sonic check, the numbers were all off nearly .070" smaller than the seller's claim.  I had a second opinion/sonic test from a reliable machinist, and his measurements were within a few thousandths of my readings.  Get another sonic test and check against those numbers before you spend money on pistons, etc.  Joe-JDC

[Katz427]

I have done sonic testing, it is easy to get inaccurate readings. I have to agree with JDC.

[wsu0702]

Measurements are allegedly from top of bore, as he said all lower measurements were thicker. Believe it?
This is my block. My machinist dropped it off with another shop to do the measurement. Thrust numbers seem high on 5-8 bank.
Bores are currently 4.050 plus wear. Amazingly, it still measures barely above stock and almost can't feel a ridge.

Quick check of the math will tell you those numbers are BS.  FE blocks have 4.63" bore centerlines.  Subtract 4.05" from that and you have .58" inches left for 2 cylinder walls plus the water jacket clearance.  A 4.05" bore block casting should have a water jacket clearance in the .26" range minumum.  So the cylinder walls should be in the .160" range with zero core shift.  Less/more with core shift.

[My427stang]

I agree, process problem somewhere.

If you measure between each cylinder at the top, you can ensure your calibration is right because the deck is solid and you can measure with calipers, once you get that repeatable across cylinders, every time, then you can start to trust other mesaurements.

Ironically, those measurements between cylinders look like they are in the ballpark, (approx. .400 combined) although just a smidge high indicating that he may be off slightly in calibration.  Those 300+ numbers though, my guess is he was too close to the deck, had a transducer issue, or something else was going on.

I would either try again, starting with the decks for verification, or try another operator (not to poke anyone in the eye, just to see differences)

FYI - I took a an afternoon with two blocks using mine before I could trust it, and found that the smallest transducer slightly shaped, combined with white grease as a medium got me there.  I was all over the map until I got the feel of the tool and a consistent procedure

[Pentroof]

OK wait, now I'm seeing the .162" on the drivers thrust side. (And .330" on the other thrust). If true that's a LOT of core shift on that bank and awfully thin thrust. Its unusual to see a thrust wall THINNER than a non-thrust wall but if that's true I wouldn't sink much morey into that block or bore it more than needed.

Still, I don't trust those non-thrust numbers so I kinda don't trust the whole thing.

Werby, to be clear, the .162" is the minor thrust side. If it is real (and I don't believe any of these numbers to be real, which is why I posted), it's not an overly thin number, in my opinion.

[WerbyFord]

OK wait, now I'm seeing the .162" on the drivers thrust side. (And .330" on the other thrust). If true that's a LOT of core shift on that bank and awfully thin thrust. Its unusual to see a thrust wall THINNER than a non-thrust wall but if that's true I wouldn't sink much morey into that block or bore it more than needed.

Still, I don't trust those non-thrust numbers so I kinda don't trust the whole thing.

Werby, to be clear, the .162" is the minor thrust side. If it is real (and I don't believe any of these numbers to be real, which is why I posted), it's not an overly thin number, in my opinion.

Oh for sure .162 is ok for minor thrust, but given that the other numbers et between #2 and #3 are almost physically impossible, I just don't trust the whole thing.

Lots of other good tips here, BTDT myself on many blocks. It IS a skill set to be learned.

Needs drill bit test all around to see what jives w sonic & what doesn't.