.050 Over 428FE ?

[427HISS]

Even if you sonic test any FE, going over a .040 was a no no ?
I just read about a 428 build that he bored his at .080 over. Can that really be done ?

http://fepower.net/simplemachinesforum/index.php?topic=9151.0

[My427stang]

All depends on the block, but I seriously doubt a .080 over.  Now, any block CAN be bored, but whether the rings will seal and it will split is another story.  My bet is that your guy's .080 was a 390 block bored to 428 bore.  I am sure Blair checked Mike's build closely and it was a good block, he wouldn't mess around

As far as very general rules, an A scratch or CX scratch industrial block, highly unlikely, a C scratch, might go .050, might not.  I have never seen one with enough meat to go even close to .080

[Joe-JDC]

Lots of folks went +.060" over on 428 FE and were used for many years at that bore.  I have a 68.5 CJ block that I had sonic checked in 12 places in every bore, and it is safe to +.065" everywhere.  Major and minor thrusts have over .125" at +.065".  The problem is who and or how the sonic checks have been accomplished as to their accuracy.  Offset boring was common place when sonic tests were performed in real performance shops.  Joe-JDC

[Gaugster]

I'm just getting my feet wet with this stuff but the shops around here are very comfortable with 0.040" over. Anything over that needs the data. Oddly enough it was hard to find a shop to perform sonic measurements. Not a lot of faith and profit in the procedure it seems? Regardless my 0.030" over 390 D3TE came out as 0.145" min (non thrust side) and a max of 0.195". Generally consistent data. No map was made though. The minimum was found on the passenger side bank low on the cylinder.

[1968galaxie]

For a factory low power output grocery getter 428 a major thrust of only 0.125" might live - and then again might not.
Thrust wall thickness does depend somewhat on cylinder length as well.
Longer cylinder will require more thrust wall thickness.
Take out your calipers - adjust to 0.125" - not very thick is it?


When talking of racing engine building (sbf with its short wall length), many engine builders use 0.200" as minimum thrust wall thickness.

[Keith Stevens]

For a factory low power output grocery getter 428 a major thrust of only 0.125" might live - and then again might not.
Thrust wall thickness does depend somewhat on cylinder length as well.
Longer cylinder will require more thrust wall thickness.
Take out your calipers - adjust to 0.125" - not very thick is it?


When talking of racing engine building (sbf with its short wall length), many engine builders use 0.200" as minimum thrust wall thickness.

Two builders here would disagree with you. Barry R has spoken many times about being comfortable on builds with .100 on the thrust side. I have no issues with mine at .120. Would it be a problem with 12.5:1? Perhaps.   I am at 9.9:1. Previous was at 11.4.

[427HISS]

All depends on the block, but I seriously doubt a .080 over.  Now, any block CAN be bored, but whether the rings will seal and it will split is another story.  My bet is that your guy's .080 was a 390 block bored to 428 bore.  I am sure Blair checked Mike's build closely and it was a good block, he wouldn't mess around

As far as very general rules, an A scratch or CX scratch industrial block, highly unlikely, a C scratch, might go .050, might not.  I have never seen one with enough meat to go even close to .080

Sorry I said .080 in that line, I meant .040 like in the heading.

So .040 is the safe amount, after that you're stretching the limits ?
Too bad the FE can't go as big as the 460 blocks.

[427HISS]

I really want the 428 linked. Would be very happy. 😁


http://fepower.net/simplemachinesforum/index.php?topic=9151.0

[1968galaxie]

For a factory low power output grocery getter 428 a major thrust of only 0.125" might live - and then again might not.
Thrust wall thickness does depend somewhat on cylinder length as well.
Longer cylinder will require more thrust wall thickness.
Take out your calipers - adjust to 0.125" - not very thick is it?


When talking of racing engine building (sbf with its short wall length), many engine builders use 0.200" as minimum thrust wall thickness.

Two builders here would disagree with you. Barry R has spoken many times about being comfortable on builds with .100 on the thrust side. I have no issues with mine at .120. Would ir be a problem with 12.5:1? Perhaps.   I am at 9.9:1. Previous was at 11.4.

It is your money. I would not use a block with a 0.100" major thrust wall. Even for a low power application.
0.100" on non thrust? maybe.
I would rather be safe than sorry.

[427HISS]

What you just said, blew over brain,...whoosh...

I'm feeling better after a very long haul, so !I'm getting back to my build. I'm just writing here about this guys 600 HP.
Most all 428/462 are only around 550 HP. (I know,..only ?)

[My427stang]

All depends on the block, but I seriously doubt a .080 over.  Now, any block CAN be bored, but whether the rings will seal and it will split is another story.  My bet is that your guy's .080 was a 390 block bored to 428 bore.  I am sure Blair checked Mike's build closely and it was a good block, he wouldn't mess around

As far as very general rules, an A scratch or CX scratch industrial block, highly unlikely, a C scratch, might go .050, might not.  I have never seen one with enough meat to go even close to .080

Sorry I said .080 in that line, I meant .040 like in the heading.

So .040 is the safe amount, after that you're stretching the limits ?
Too bad the FE can't go as big as the 460 blocks.

To me, their is no safe amount without checking.  There may be something I would gamble with...like .020 on a block I knew was running and wasn't going to make a ton of power, but 390, 428, 427, they all get sonic checked.  I have seen standard bore 428s with so much core shift they weren't good enough for anything but a stocker.  In Nebraska, with the abundance of industrial motors, it's worse.  You see CX on the back, expect the X to mean Xtra core shift LOL

I also would like to point out, .100 is less than an 1/8 of an inch, if you are trusting 1/8th of 600 HP working that against that thrust thickness, IMO, you'd better be sure of location and the condition of the rest of the cylinder

[427HISS]

"100 is less than an 1/8 of an inch, if you are trusting 1/8th of 600 HP working that against that thrust thickness, IMO, you'd better be sure of location and the condition of the rest of the cylinder''. Wow, that tells a not so good story.

[Joe-JDC]

When doing a sonic test, usually the thinnest spot is recorded, meaning everywhere else is greater than that spot.  After you do several sonic tests, you can begin to recognize the pattern of how a cylinder is shaped.  Many have over .200" in the thrust areas, only to have a spot somewhere that is less.  Many blocks start out thick, go thin, and end up thick at the bottom.  Also, many of the blocks that used antifreeze will be thicker than those in other climates where plain water was used.  Simple logic, but if a block has had antifreeze in it since new, it can still have thick bores even after 60 years.  I do have a block that is making 600 hp with ~125" on the thrust walls at the thinnest spot, and less than .100" on a couple of inside walls.  Next time I tear it down, it will get a half fill of hard block, and a light hone with torque plate.  Joe-JDC

[Gregwill16]

If I'm not mistaken one of Jay's dyno mules had non-thrust walls in the .080 range and we all know what it was put through.

[My427stang]

It's all an acceptance of risk, can't knock Jay's success, but my guess is it wasn't a critical area where it was .080.  If it was,   I wouldn't use one for a customer, and my guess is a thicker wall would have made a little more power to boot.  FWIW I saw 1/16 rings that left shadows on the bore on my own .90-ish 445, that tells you things were moving and seal was less than perfect

I don't think of it as much a pressure or physical resistance of strength as much as a ring sealing issue and the continuing flexing over time causing a split.  Admittedly I tend to be more conservative, but when I start seeing thin ones, I save them for the stockers, or send them down the road