I had a chance to measure up a couple of the new Ford blocks today that a friend of mine bought as he has been going through secondhand blocks at a rapid rate in the last couple of years - 9000rpm and 190 hp puts a bit of stress on these aging blocks
so with the Aussie dollar at a high level he bought a couple of new blocks from the USA to supplement his stock of spare blocks
The blocks are the standard Lotus height for use in historic racing here not the tall block. The castings have the claimed modifications around the main bearings that should help and are very much similar to 701M blocks externally including having that casting number and all the other usual Ford casting numbers present and Ford logo so no problems with "eligibility". The claimed "reinforcement" to the clutch bell house bolt location is questionable as it appears to be like the earlier 120E blocks in this location and actually thinner than the original 701M blocks. However I have never had a problem in this area so it is probably not much of an issue.
I measured the bore wall thickness on the 2 new blocks and compared it to my data on other original blocks. It is close to the average of all the blocks I have measured ( numbering 20 plus blocks in total from all casting numbers 116E,120E, 681F, 701M, 711M). This does not surprise me as the bore casting outside diameter is limited by the sand casting technology used and the OD is typically in the 90 to 91 mm range depending on casting tolerances and corrosion. These new blocks are no differrent with one averaging 90.45mm and the other 90.24 mm across the 4 bores outside diameters. An 83.5mm bore is comfortably doable but still requires offset boring to get consistent wall thickness over 3 mm. An 85 mm bore in these new blocks would have around 2.5mm minimum wall thickness which is the very bottom end of what is just tolerable in a road engine and I would expect a failure over time in a full race engine at this thickness.
The myths about L blocks and 701M blocks AX blocks and now these new blocks having thicker walls are still just that "myths". Most blocks from the earliest to these new ones can safely take beyond 83.5 mm but it needs careful offset boring to do that and still get 3 plus mm wall thickness consistently and going beyond that while possible requires careful selection of a suitable individual block. An 85 mm bore really requires a 91mm bore casting OD which is at the top end of the range i have seen which neither of these new blocks have.
cheers
Rohan