Sonic check results, need opinions

[My427stang]

In the non-FE forum, you'll see me whining about what really was my inexperience with the tool, combined with some tricks of the trade to make it go easier.

Looking for opinions on what I ended up with

These are all minimum numbers, as any direction and clock position was bigger, so rather than post everything, I am just posting the numbers I think are significant, anything not listed here was .177  to over .200

Looking at drivers side bank, outward edge toward freeze plugs, I found my thinnest cylinders about 1.5 inches from the deck, all on one bank, pass side was significantly better

5 - 0.126  6 - 0.134  7 - 0.118  8 - 0.134

If adjusted for a "worst case" torque plate hone to 4.09 (I mention that because they likely won't need the full .010 to get there).  I would end up at:

5 - 0.121 6 - 0.129  7 - 0.113  8 - 0.129

It gets thicker as you go deeper, the passenger side of the block is thicker, and all dimensions around the block are thicker than those minimums.

Game plan is max 500 hp engine cammed for 5500-ish peak.  Not a racer, in a 4x4 street truck, but planning a 4032 forged piston as tight in the bore as I can with either a 1.0/1.0/2.0 ring pack, or potentially a 1.5/1.5/3.0 and want to make sure bore is stable

Thoughts?  Specifically on the .113 number?  Also, knowing a sonic checker seems to be voodoo on a round cylinder, would you run 10% less than .113 if we added a WAG factor?

Thanks

[Stangman]

Had a .095 on 1 cylinder after boring was done on a 63 427 CO block. It’s been 2 and a half years
And about 1500 miles, 1 FE reunion, and about 25 1/8 miles passes, doesn’t burn any oil and runs
Cool, fans come on at 195 and go off at 175

[plovett]

I think I would use a little Hardblok.  It doesn't even have to be a half fill.  Maybe a "quarter fill".  Just something to shorten the unsupported length of cylinder wall.  There is no downside, in my opinion.  Only a possible upside.

JMO,

paulie

[My427stang]

I think I would use a little Hardblok.  It doesn't even have to be a half fill.  Maybe a "quarter fill".  Just something to shorten the unsupported length of cylinder wall.  There is no downside, in my opinion.  Only a possible upside.

JMO,

paulie

This is the flexi block that was noisy with the Probe pistons, although it wasn't torque plate honed, I am a little gun shy.  Ironically, the lower you go in the block, the thicker the cylinders, so although I agree it could be more stable, not sure the bottom is where it needs it, although it likely would keep the cylinders more concentric    

I agree with you, no reason not to hard block, but to be equally honest, still not sure how little cylinder wall is "too little" for stability

[Joe-JDC]

That is a major thrust side and very close to where the maximum cylinder pressures will be exerted on the walls.  Ideally, you need at least .125" or more there to keep the walls from flexing under compression.  That is probably what was the problem with the other build, and you will just make it worse with another clean-up hone.  Not what you want to hear, but sometimes you just have to cut your losses and move on.  I would build a low compression streeter out of that block, and search for another block to build.  I have gone through six blocks to get two decent ones for my current build.  Joe-JDC

[jayb]

Since that 0.113 is a thrust side I think I'd be concerned.  (By the way, if I'm reading your description correctly I think that's the minor thrust side, not the major thrust side.)  The other thing that's odd is that the block is thinnest at the top.  The ones I've checked are usually thicker at the top, which of course is where you'd want the thickness. 

I'd be doing one of two things.  Either sleeve that thin bore and run it, or if you are a tad paranoid about this phantom noise you'd have to deal with, just try to find a new block. 

[My427stang]

Thanks, the punch line is I have a very nice standard bore 428 here, but I was toying with grabbing Barry's Mahle pistons and just plate hone to fit.

I am about as confident in the .113 number as I could be, what I may do is like Joe said, build into something milder with that one.  In fact, I'll probably have my guy measure that hole and see what he comes up with and sleeve it and build a 418 out of the spare parts.

No decision required today, the truck runs great with the current 390, but it needs a little more excitement next spring.  This was as much picking a course of action as it was getting proficient with the new too.  I am going to repeat with the 428 and if it correlates to what I learned here

As far as the cylinder Jay, between #7 and #8, the drill bit is clearly looser on the top of the bore than 1/2 way down, by a single drill bit size, and the sonic numbers back up those numbers.  Odd duck to be sure