Just helping a new guy to the HAMB who asked this question in the "Suggestions" section by mistake. (Welcome aboard mercurymike!) His question was, "If my machinist bores my flathead block with a machine that uses the crankshaft bore to index from, how does that work when flathead cranks are offset 3/16" I think. When boring a flathead block - or any other engine for that matter - a mandrel that is the same size as the MAIN JOURNALS is placed in the crankshaft main bearing bores, which will keep the block in alignment - at 90 deg. - with the cylinders. The offset of the crank doesn't have any effect.
That makes my head hurt, Dave. Bing is teaching me to bore flatheads with a vintage bar from the '40s that works a treat! Its reference is the deck, and it does a wonderful job of keeping the bores perpendicular with the deck and concentric in the cylinder castings. This all assumes that the original machining at Ford was correct, of course. And it takes two to three times as long to do the job that modern "bars" take. But, when we deduct the time to load a block into the truck, haul it the machine shop in town, unload it, drive home, and then repeat the process to retereve the bored block a couple of days later, it's probably only taking maybe 50-percent longer to do the job in the Prune Orchard. And of course there's the enjoyment of hanging out, bench racing, and talking about the work as the old bar does its job. BTW, you don't write anymore, you old buzzard! Mike
The offset of the crank does have an effect. The mandrel will be offset just the same amount. It is the centerline of the mains that is offset. Wayno
Damn, Wayno! Dya think they've been doing it wrong in the Prune Orchard all those years? A couple of LSR-holding motors have been done this way with this old bar. Please don't say anything to SCTA-BNI. Mike
Mike is right, the boring bar pictured will bore a block perpendicular to the deck surface. If that surface is out of square with the crank centerline the new bore will be out of square with the crank centerline by the same amount. Common practice when building a high performance engine (post "back in the day") and using a boring bar is to grind the deck surfaces parallel to the crank centerline prior to boring the block. This way you ensure a bore square to the crank centerline without having to have a boring mill and the expensive fixtures that ensure this dimension is true. When I had my shop I always sent a block out to be decked square to the crank centerline before boring it. At that time you can request the deck heights to be equalized as well ensuring a constant deck height throughout the engine. This last procedure assumes that the rod center to center distance has been equalized on all of the rods and the stroke on the crank had been standardized on all throws. Frank
Right you are, Frank, and rather than me leaving an incorrect impression of Ed Binggeli's abilities as a first-rate racemotor builder, flatheads were the first phase of his life, from the late '30s to the early '60s when he persistently built and ran his F/G Willys coupe, kicking overhead ass, at a time when he was building SBCs for circle-track clients. Bing has built hundreds of SBC race motors and is called upon today for his expertise on SBCs as well as flatheads. The beauty part about learning from Bing to bore with this old bar is in understanding the real-world conditions and parameters that were 'high-tech' so long ago. Gotta love the old guys, and those willing to take the time to share their knowledge and skills are National treasures! Mike
As an aside I'll add, DAMN YOU MIKE. You just added one more name to the list of people I'd like to meet and talk to. I've posted in the past my admiration of your writing and Fullers race car construction, now I've got to add Bing's name to the roster. I guess if I ever get to Bonneville I'll have to cater a big feed for everyone and you can invite all of these guys you keep talking about and introduce me. Only problem is I might have to feed them for the whole week so i can ask all of the questions I've got and get autographs and pictures. BTW, you aren't charging for autographs are you? If so I'll have to sell my house before coming out. Frank
Oh boy! mercury mike I don't know if you realize it, but your in the same room as a bunch of flathead guys with about 300 years of experience! (and I'm a novice!) Everybody is right! They just explained it better than me! Mike, aka av8, IS using the time tested way of boring flathead cylinders. Mike is that a Sun or a Storm Vulcan bar? (I used to work in an auto machine shop) The "mandrel" that I mentioned is used to make sure the cylinders are at right angles to the centerline of the crank as Frank aka Fab32 mentions and the deck (head surfaces) are FLAT. Then Wayno aka Elmo Rodge mentions that flatheads DO have an "offset" - one of Fords little "quirks" - which - as long as the decks are square - doesn't effect the boring of the cylinders using the "old timey" boring bar like Mike is using. Before I left the auto rebuild plant that I worked in - and I ran the cylinder boring bar - they had invested in one of the new fangled boring bars that used the mandrel on the crank center line and the cylinder cutters - could cut 4 cylinders at at a time - only aligned with the cylinder wall(s). Mike, will email soon.
Nope. Your way registers off of the deck, not the crank centerline. The offset doesn't come into play. Wayno
So ... that means; as long as the mandrel sits in/on the center line of the crank, and the decks (head surfaces) are trued and squared to the center line of the crank - or mandrel - and the same distances away; using an "old timey" boring bar - like Mike shows - will do the job perfectly. I never have understood why Ford offset the center line of the mains in/on a flathead. But after almost 25 years of production and over 60 years of existance, it STILL WORKS! mercurymike, if you were going to machine a flathead block - to "full blown" racing specs. - it would go in this order. Assume you installed a set of four bolt main caps - at least the center main; which takes the biggest "brunt" of the action - the first step would be to align bore the crankshaft main bearing bores. (openings) This would insure they are concentric AND in line with each other. (a test used for proper alignment is; when the crank is lowered - have to inject here; the crank mains MUST be in alignment - into the block, with bearings and a dab of oil, it should spin freely. Then, using a mandrel in the main bearing bores; each deck (head surface) would be machined to insure the decks are square to the crank; the same distance away - can get critical in a high performance, hi compression engine. A VERY light cut would be made; just enough to square everything and insure the decks are FLAT. (needed to insure gasket sealing against coolant leakage and possible compression leaks) NOW; with all of the above in order, a conventional boring bar - the type Mike shows in the previous picture; which is anchored to the deck surface after being centered in the cylinder - does the "cutting" (boring) - by being fed down the cylinder. This style of boring bar is very accurate; as long as the deck surface is flat and square to the center line of the crank. The bar Mike shows has three - might have four - "feet" that extend out until they contact the cylinder walls, which centers the bar, then the bar - the whole machine - is clamped to the surface using one of the head bolt locations. This might be MORE than you wanted to know; but seeing as how I just went through the whole process, I just thought you might be interested. Oh, ... one more thing; when you get the crankshaft ground; HAVE THE ROTATING ASSEMBLY BALANCED!! Then if we could have Mike post a picture of what you can do to your crankshaft ... You can see just how far some of us flathead "nuts" go!!
The offset crank (I believe the A&B blocks were offset a bit too) had the same purpose as offset pistons on a Chevy--different way to do same thing. Now, what kind of readings would a modern machinist assuming the crank was dead center get on a flathead?? And what horrors would he perpetrate on the block trying to get them "right"?? The reason I post that is a bothersome memory stuck in my cranium for the last quarter century, from a magazine flathead buildup. It might have been the Senter Ardun build in old R&C? Anyway, the article reported that the machinist found an incredibly large difference in left and right deck heights--and corrected it. Hmmmm...could he have just discovered and misunderstood the offset crank? If so, what excitement happened when he tried to install pistons? I'll have to try to find that article and see what I can figgerout...
Can we dig up this 15yo thread and give it a memorial? As far as figuring deck height, if not indexed off the crank what other datum point would be used to give a false reading? I've been warned that a block can be ruined real quick by a "non-flathead" machinist. I am about to have an 8BA block bored and want to know what the implications could be. The machinist I was going to use states he has done a few and has a good rep but what would he do differently in set up for a flathead? How can I check that he knows what to look out for? Dave