The crack is straight through No 4 outer main cap stud area, goes down 2 inches then turns 90 degrees back towards the crank another 2 inches. The whole main would have seperated from the block - it's quite thin under the main area, where it attaches to the block.
We have thought long and hard about this, including going with a brace, or with the new 5.7 block, giving up and going hemi etc. Vic Donnas with the blown alky 1UZFE dragster went through all this years ago. He did all sorts of tricks to strengthen the 1UZFE with no luck. Ultimately we want reliable high horsepower, and now we feel that can only be achieved with a billet block like Donnas made. The block is not a right off - we will repair it and use it in an injected methanol combo we want to set up for my daughter to learn drag racing in.
We have to start with choosing an aluminium grade. Some use 7000 series, others 2000 series, but I think we will run with 6061 T6, and temper to T7 after rough machining. We have to get the 2UZFE measured and 3D modelled into a computer program for the CNC - then a program has to be written to program the CNC mill paths.
I dropped in to see Andrew Kostecki who manufactures CNC heads and blocks for V8 Supercars here in Oz, and we can use some of his technology and parts - like his high performance LS1 Chev main caps, and head stud kit. We will make both a toyota and chev bolt pattern for the gearbox.
We will use .080" liners from LA Sleeve, with O-ring grooves in the top. Allowing .100" between the bores between the sleeves allows us to go 3.900" in bore (LS1 chev), and with our slight offset stroke of 3.285" gives 313 cubes. Not bad at all. Kostecki reckons the 1UZFE crank is the best he has ever seen. We polished ours, so it looks pretty good - but the machine marks in the counterweights he said is very good for dispersing oil off the crank. The crank is heavier than a big block chev.
So we feel we have the crank, rods, pistons, heads, and manifold/blower right - we just need to get a strong block and we can go take on the chevs and hemi's.
Keep posted for progress.
I am not sure about the 5.7 engine - just that it is an ally block with 6 bolt mains, 4.1 stroke and 3.7 bore. Not sure what heads they use.
I am getting quotes for the block this week.
The reason the main journal area cracked in my application (high boost and horsepower) was two fold.
1. The main journal area is very weak. The area between the cap surface area, and where it attaches to the block is thin. There are two large vent holes cast into the area which takes away material. The large bore undercuts the area as well and the radius is not that supporting.
2. The four bolt conversion - machining and installing a second main cap stud - weakened the area. The crack started from the drilled hole.
The block could be modified best for street use with a one piece crank support including the main caps - all in one.
Looking at where the extra 2 bolts would be tapped on the 2UZ, you can really see why this block would crack. That area is a bit thinner than the area where the two original studs are. The 1UZ has extra "meat" where the 2 extra studs are. I personally would not convert to a 4 bolt main on a 2UZ because of this, unless you could somehow beef it up (weld on extra material?)