Ross,
In answer to your question, if you re-read my responses, you'll find this:
My own opinion is that you should have a min wall thickness of .120 but I found some wet sleeves at .115. Those are even, all the way around and not thicker in some/most areas. But, my main interest was at what thickness do you start loosing hp. There was no answer to that! I was hoping to find a few builders that said "I freshen this engine, X number of times and dyno it, each time. When it got to .X over, it lost power and I had to replace the block".
Again, I am not advocating running under .120 walls but, I am saying that if your sonic test shows a area down to that, I wouldn't worry about it.
Don't worry about not seeing it at first, most of the guy's on ST, that couldn't answer my question with facts, did the same thing, I said it 3 or 4 times there and Brent thinks I want to run .005 thick walls. I really don't know what to think about that type reaction?
Yes, I know Blair advocates thick cylinder walls but, he bored his EMC engine .047, I think.
Brent bored JJ, .040 and the 360's aren't know for think cylinder walls. I don't know if he did a sonic map but, he says he has no faith in mapping.
At least one, maybe two, have bored their 427's .060. The 427 has a clover leaf shaped cyl core but, between cyl, at 4.234, the cyl wall is only .123 and at .030 over is .108 and at .060 over, it's .093. That is with out any core shift.
Brent brought up aluminum blocks but, my question is about production, American, cast iron blocks. I don't know the specs on the alum blocks he speaks of but, I do know about heat and expansion. I'd be interested in studying the specs on those blocks if, he can provide them to me.
One of the ST responses did offer this insight into modern high hp and extreme hp, aluminum engines:
ST response by hoffman900
Some numbers digging around:
Honda NSX. 3.5L Turbo V6. 500hp from 6500-7500rpm, 405lb-ft from 2000-6000rpm. They mention a conventional iron bore sleeve would need 2.5mm (0.098in) between it and the water jacket. A 0.2mm (0.008in) Fe spray was applied, thus closing it up some. They now have 11mm (0.43in) in the bore bridge, including water jacket. 3.6in (91.4mm) bore size.
The Ford RY45 (large displacement, aluminum block developed by Roush Yates from the NASCAR FR9 for Late Model and off road trucks) has 4.500 (114.3mm) bore spacing and a max bore of 4.250" (107.95mm). My math shows it has a bore bridge of 0.250" (6.35mm) and no cooling jackets in them. So that would be a liner thickness of 0.125in (3.175mm). This engine in development, made 901hp @ 7500rpm and 692 ft-lbs at 6200rpm. 436ci and 14.5:1 compression. They found a peak of 135 bar was too high for the short block components they designed, so they tuned for an average pressure of 105 bar (bar = 14.7 lb), noting it could be higher with more robust short block components. There was a package shared this summer of this platform that made 958hp @ 8500rpm and 657 lb-ft at 6600rpm. 438ci and 15:1 compression, so I can imagine peak cylinder pressures aren't too much higher than the test engine, just rpm has moved up.
The Audi R4 TFSI DTM engine makes > 570bhp from 6500-9000rpm, and 590bhp at peak. Boost limited to 3.5 bar and fuel flow limited to 90kg/hr. It is allowed a 100kg/hr fuel flow rate push to pass that boosts power to 644hp. The bore bridge has a distance of 9mm (0.35in) and a bore spacing of 97mm (3.89in) on a 88mm bore (3.46in). I don't believe there is a water jacket in the bridges, so this would result in a liner thickness of 4.5mm (0.177in). Because they run these engines at AFR of 16:1 to 20:1, they are built to be knock resistant. It seems they rule detonation as anything in excess of 300 bar, but looking it seems 250 bar peak, maybe higher, seems to be a more realistic design number (just my guess). These engines are designed to go 4000 miles between rebuilds, have a 40.5-42% Brake Thermal Efficiency, and can "cope with more than 5000 severe (300 bar + ?) knock events before damage becomes a limiting factor" - Race Engine Technology, January 2022 issue.
Here is the Honda F1 V6. I don't know what cylinder pressures are, but 1.6L V6 hybrid, fuel flow limited to 100kg/hr, making in excess of 1000hp peak. Likely similar afr to the Audi engine (but likely even leaner due to turbulent jet ignition / HCCI combustion concepts) and need to be just as knock resistant. Brake Thermal Efficiency approaching 50% and have to go 1500 miles plus. They are also a structural component of the chassis in these cars.
All these engine blocks are aluminum with liners + coatings. Need to be sealed really well and last for thousands of miles.
So, it appears that if a aluminum engine, is designed right, they could have .098 - .125 liners and live as well as seal.
After throwing those last two numbers out (.098 - .125), let me say, for a third time that I am not advocating running cylinder walls, under .120.
I'm adding Ford's drawing of the 427 cylinder wall so, you can all see the thin side walls. Just subtract 1/2 the bore you want to use, from 2.24 and that gives you the wall thickness. This is the nominal dimension and does not consider any core shift.