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Discussion Starter #1
I have a block in storage that I had sonic checked a few years ago. 454 most of the numbers came back around .160 some as high as .220 but two are .139 these are one on each bank at about the two o'clock position on cylinder 3 and cylinder 6. I plan to turbo this block. From what I can find these are good numbers. Do you agree? Do you think I should try to move these cylinders .005 away from the thin side? I have pistons to either go .030 over with a 4" stroke and .060 with a 4.250" stroke.

A penny for your thoughts.
 

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Long day with the grandkids, already, maybe I'm missing something.....how do you move a cylinder bore?


Anyone can pedal a bicycle, can you pedal a flat?????
 

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"Two o'clock position" relative to what?? Are the 0.139" readings on a major thrust, minor thrust, or non-thrust cylinder wall location?

Based on your noted piston options (you say you have a choice of using either 0.030" or 0.060"), I assume this is a standard bore cylinder block. If it is indeed a standard bore block and you want to turbo this engine, then my advice is to bore as little as necessary and save the cylinder wall thickness that you have, in the interest of cylinder wall strength. In other words, if this is a standard bore block, then bore only 0.030" over....regardless of which stroke you go with.

Offset boring a mere 0.005" will not gain any measurable structural integrity. (Furthermore, whether you offset bore and how much depends on the opposing cylinder wall thickness.) Very generally speaking, if your 0.139" readings are on the non-thrust sides and will become 0.124" (after boring 0.030") as your thinnest non-thrust walls, then I'd think you're okay for a typical lake boat stock-block turbo build. Of course, anything can let go at any time.

LO
 

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Discussion Starter #4
LO, how would you describe the location of the major, minor, thrust locations on the cylinders? Specifically cylinders 3 and 6.
 

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You CAN offset a bore easily. When you put the boring bar in the cylinder, and extend the fingers (to center the bar in the bore) use a shim opposite the way you want to go.
It was pretty common in the day when stock stuff was carbed. Cyl wear was much more than it is now with injection. For stock crap, it saved more than 1 block, and location is not very critical for stock crap.
Wags
 

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Maybe you have not seen a boring bar work. The "fingers" extend out at the bottom (above or below tool bit depending on manufacturer). There are 3 or 4 fingers that screw out (usually a knob on top of the bar that moves them in and out), centers the bar, clamp it down with air or manual (depending on model), screw fingers back in, and bore. Hope that makes sense.
Wags
 

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Discussion Starter #7
Thanks wags, I knew it could be done but I didn't know how. Do you think moving the bore for the cylinder wall thickness would have any value? Do you think my sonic numbers are good? Average? Poor?
 

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Do you have the option to run a tall deck aftermarket block
 

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LO, how would you describe the location of the major, minor, thrust locations on the cylinders?
The major thrust is the area of the cylinder that receives the greatest load during engine operation, specifically when the power stroke is occurring and the piston is being forced downward while the rod's angularity is pushing that piston hard against that specific side of the cylinder (hence, major thrust). The minor thrust is the opposing area of that cylinder which receives the next greatest amount of load, which occurs as the piston is forcefully squeezing the air/fuel mixture (compression) and effectively being forced against a specific side of the cylinder due to the rod angularity, and the non-thrust portions of the cylinder are the areas where there is little-to-no thrust, relatively speaking.

Therefore, as viewed from the point of a our V8 engines in a passenger car where the crankshaft rotates clockwise as viewed from the front ot the car:
  • The major thrust is the area of all the cylinders that face the passenger side.
  • The minor thrust is the area of all the cylinders that is face the driver side.
  • The non thrust is the areas where the cylinders face each other (ie, between cylinders) front-to-back.
And so obviously when sonic checking a block, it is most important to have cylinder wall thickness on the areas of the cylinder which receive the greatest amount of load. You're minimum of 0.125" on a non thrust side at 0.030" overbore is better than 0.125" on a major thrust side at 0.030" overbore.

LO
 

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Here is a sonic check sheet from a Ford 460 engine block:



Look at the driver's side cylinders 5, 6, 7, & 8. Generally, the major thrust on those cylinders are the thickest area, the minor thrust are the next thickest, and the non thrusts (bewteen cylinders) are the least thick.

But now look at cylinder number 8: it has non-thrust thicknesses of 0.141" on one side and 0.217" on the other side. Therefore, if we were to offset bore that cylinder 0.030" toward the rear we would effectively be creating a 0.171" and 0.187" non thrust thickesses prior to the overbore. Once offset bored, the overall wall thickesses of cylinder number 8 would fall into range with the rest of the driver's side cylinder bank.

Offset borig is usually done on the front-to-rear axis. Note that when you offset bore you are messing with the consistency of the bore centers. I feel that in most cases 0.030" is the most one should offset bore. Things to be taken into consideraton is head gasket bore diameter relative to the final (offset) bore size, or how this might affect valve placement in the offset cylinder (usually a non-issue because we are increasing bore size), etc.

Offset boring left-to-right ever so slightly plays with things such as piston TDC deck height (relative to the other pistons/rods on that cylinder bank), cam-to-piston timing events, etc. I'm not sure how ciritical that really is but I tend to not want to do it and only offset bore front-to-rear. Fortunately, the Ford 460 blocks were intentionally designed to have their greatest wall thicknesses on the major and minor thrust areas as cast, so it's necesary to adjust only for non-thrust uniformity.

LO
 

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Discussion Starter #11
Steve, I actually have a DART 572 turbo short ready to assemble. But I have had this block for a while with enough parts to assemble it. Either 496 or 468. I would like to put it together and run it a little in the boat then maybe put it in the car. The sonic numbers originally pushed me toward the 572. I just don't know if these numbers are good enough for a turbo setup or if I should just put it together as a fresh stocker.
 

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Discussion Starter #12
LO regarding your sheet the lowest number that I had was .155 minor thrust .195 major thrust. My sonic guy measured 8 positions on each cylinder. One of the .139 measurements is between a major thrust and a non-thrust. The other is between a minor thrust and a non-thrust.

So, would this block be a good block?

What numbers are expected when sonicing 454 blocks?
 
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