I've heard that the new Boss blocks are perfectly good with stock strokes but due to the shorter than stock bores you shouldn't go with more than a 3.25 stroke. The pistons come out of the bottom of the bores too much and are unsupported. I know it's weird. Why would Ford make them with shorter cylinders? They really shot themselves in the foot!
I guess that we will see. According to Ford, they are good to 3.400" of stroke and the block was built with the 347 in mind. Even though the stock blocks have that extra material at the bottom of the bore, they have to be clearanced for the additional stroke and rod clearance for the 347. I'm not the first one to do this. Either way...there is no going back now even if I wanted to.
I heard the same thing about the new boss block also. What I read was you needed a special piston and a 3.25 stroke crank with the new boss block which is why I got the Dart sportman block. My crank, rods and pistons were still good so it was cheaper to get the more expensive block in the long run
I think the Boss block is a good choice too. However, with twin turbo's and silly gas, life expectency is shortned considerably because of even the slightest of malfuntions. Ford engineer's have done the math and come up with this combination of bore, deck highth, etc. I don't think they had in mind the use of basic production pistons and related parts, to be used in it. Would be nice if you could just transfer stuff out of your stock block into it but I am not sure that is possable without some extensive calculations and further things like that, if at all, to maintain HP and reliability of the rotating mass. I am running a 347 stock block, filled with Moroso block fill(concrete) and 12.5 compression on injected methanol. Main girdle and new studs have lasted for over 350 passes and just pulled it down for a check. Bearings are like new, as is the crank journals etc. Of course my pocket's are empty of change but buying the best part's can help the life of the engine, as well as good assy. procedures and proper maintenance. If I could, I would like to buy one the good blocks too, but my remaining years are dwindling fast and guess I will stick with my present combo for awhile.
Ford has two different Boss blocks. One with the short cylinders and another with longer cylinders. It is easier to reduce cubic inches if you shorten the cylinders than if you have cylinder walls thick enough to reduce the cubic inches and still able to bore them out to have larger cubic inches. so instead of making one bklock with thick walls on the cylinders the made two. If you want larger engines then you use the deep block but if you want fewer cubic inches you have a block that weighs less and provides smaller packages.
that would probably cover all my expenses for this up comming semester at community college but then again... ya, you did the right thing
Well I've been doing some studying and I'm not convinced yet. I'm going to check my block when I get home (I'm currently on the right coast), but I will measure the length of the cylinder walls (I've heard that there is a 3/8" difference in length between stock and boss and want to confirm that first), then call Ford and my local engine guru. My only argument with the 3.25 vs 3.40 stroke is that you are only talking .150" that the piston could possibly stick out further (given the same length rods and a different compression height). Granted it is on the hairy edge with a 347 anyway. Additionally, Ford is using these blocks for their 347 crate engine, and unless they are doing something extraordinarially different with them, they are a 3.40" stroke. I'd think that they would be having a ton of warantee claims and would pull this out of production if it were the case. Anyhow, keep in miind that this block was designed in conjuction with Nascar teams that beat the heck out of their motors. Being an engineer myself I can't believe that Ford just missed this especially when they are advertising the ability to go to a 3.40" stroke. Anyhow, I'm not quite ready to throw out my reciprocating assembly just yet (Don, stay out of my trash can!), due to web chatter (I haven't heard or read of a 347 coming apart because of the new Boss block and I want to hear from someone that did it and had catastrophic failure). Until then I will be doing some more research and let you know what I end up doing. Oh and Dave, I'm with you this could be my last motor build too (due to college for the kids in my case)...you've got a great build and your theory on assy procedures/maintenance (couldn't agree more), not to mention the methanol certainly helps by keeping things cool and increasing torque (I used it back in the late 80's <injection>. Just didn't like the maintenance aspect back then). I'm hoping that you are correct Paul...because this block is HEAVY!
