Quote:
Originally Posted by bobH
John, I'm at a loss here. I'm not real strong on flatheads, but I'm pretty strong at math. If the crank center is offset, and the same dimensions are used for rods and pistons for both sides of engine, and if the tops of the pistons travel to 'deck height' on both sides, then how can that be possible unless the deck heights are different ????
Maybe I need a definition of deck height. If it is measured from actual crank center, it's a screwball measurement that could be argued to be the same for both sides. If it's from the intersection of the right and left cylinder bores, like most engines, then the decks need to be at slightly different heights.
Of course, this leads to a series of questions. Did Ford compensate for all this with valve timing and ignition timing? Are cams ground with different timing, right and left? Theoretically, I believe they should be. How about the distributor cam lobes? Again, I believe right and left timing lobes should be slightly different.
This is more math than I want to think about. My point is, if you establish a plane at the top, 45 degrees from cylinder center-lines, perhaps the intake surface, and measure down to a common reference on the decks, then the decks have to be at slightly different heights. (Or... is the intake surface REALLY at 45 degrees to the cylinder bores? Or... are the cylinder bores REALLY at 90 degrees?)
I really wonder if Ford really worked this all out, or did they just 'shine-it-on' because the math difference is pretty small. The drawings that I've seen don't really have enough info. How about the cam grinders here - can you see a difference, right and left banks?
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One thing to consider is that the shift of the cylinder center-lines will cause the rod to not be perpendicular with the piston at TDC or BDC as it would be in a conventional layout. I think it is that affect that allows the deck heights to be equal.
From what I see on the drawing the CL's of the bores are shifted .168 to the drivers side of the block using the CL of the crank for the datum point, and further, the camshaft CL is also shifted .0242 to the drivers side. I don't know enough about flathead valve pockets but I will assume that the different angles, 49.36° pass. and 52.09° drivers side were necessitated by the .0242 cam shift so that the path to cylinders on both banks be equal.
Regardless, I do not see the reason for the .0242 shift in any case.
The cam shift leads me to a question and I apologize in advance if this hijacks the thread. With the different valve angularity from side to side in the flathead an astute cam grinder will certainly have recognized the need for adjusted timing events for right and left banks. Or did they? Is it possible some thought this through and some overlooked it? Are cams for early valve angle engines different from the later f/h engines where I believe there was symmetry in valve angles? Not to single any particular performance cam out, but is a cam ground on masters that may have been designed for the 49.39° and 52.09° angles corrected for the later flathead?