Looking back at my notes for the amounts milled off of Y decks, the average factory deck height can expected to fall in the neighborhood of 9.768 +/- 0.007” about 67% of the time.  I’ll add that it’s not unusual to find a ~0.010” difference in deck heights on a block either from side to side or end to end.
 
Using the 9.768” value for the deck height, then the factory piston below the deck figure at TDC for the 292 engines would be 0.011” using 6.324” for the rod length and 3.3” for the stroke.  For the 312 engines the ‘in the hole’ figure would be 0.014” using 3.252” for rod length number and 3.438” for the stroke.  These are all perfect world numbers and variances in the rod lengths, decks, strokes, etc. would have this number jumping around.  Hence the difference in performance of similarly equipped vehicles.

Lorena, Texas (South of Waco)

Greetings to all: Thanks Ted for the great information. That hits the nail on the head in a nutshell - is where I'm going with this.   .011 & .014 in the hole for 292 & 312 respectively is ideal world figures but I had real world .071 quench and that's what I'm trying to improve.  There is the choice of steel head gaskets and/or custom pistons that should provide a middle ground measurement, hopefully.   Very interesting deck height information though.  Makes one start thinking of a reliable way to easily measure this.   Hmmmm....      Thanks, JEFF..........


64F100 57FAIRLANE500

Very interested in the information that has come out on this thread.  Ted's adding up of ACTUAL component dimensions he's run into in a 'build' to determine ACTUAL final quench dimensions...  so as to adjust engine block machine decking requirements was an eye opener and instructive for me.  I had the false notion that I simply needed to tell the machine shop when squaring the block that I needed a finished deck height of 9.750 inches.  Probably not!

Charlie Brown (me!) is turning over in his head the information and understandings that you've shared as I close-in on turning to a machine shop with my 292 to be machined for assembly with a 312 crank turned to 292 main bearing, rear slinger, and rear seal dimensions and cylinders over-bored to 312 plus .040 dimensions.  I'm quickly realizing that believed-to-be dimensional 'build' information is likely to be significantly different from what I may actually be assembling when using reconditioned components (like connecting rods and crankshafts) and/or standard availability replacement parts (like pistons).  UGH!

Thanks to all who have participated.

NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Greetings to all: I don't want to seer this thread in another direction but a 292 bored to .040 over 312 would be .090 overbore. Some blocks are noted for having thicker cylinder walls than others. Perhaps sonic testing might not be a bad idea in this case? Just my $.02.........    


64F100 57FAIRLANE500

My thinking is the same on the importance of sonic testing the existing 292 bores, Jeff.  Unfortunately, there are no guarantees, but it will at least signal if core shift is significant.

In looking at a .090 inch overbore, one exposed inclusion in a cylinder wall casting can cause 'problems'.  John Mummert's chart of engine block casting applications indicates that ECZ-A, ECZ-B, ECZ-C, EDB-E, and B9AE-F castings were machined as either 292 or 312 bores.  The sand cores for the water jacket should therefore be the same, I would think...

Jeff with your '64 engine block, I do not know IF the same sand cores were used for forming the water jackets for the casting of  '61 to '64  C1AE-R or C2AE-C  292 engine blocks after the 312 engines were no longer used in the production of Mercs after 1960 per John Mummert's chart.  Foundry retooling to change the sand cores for 292 only engine block water jacket formation would not have been inexpensive, but less iron needed for each engine block cast for four production years could have justified it, cost-wise.  I recall reading that the iron used in the engine block main bearing web areas was increased for the later year 292 blocks even after the length of the main bearing cap bolts had been lengthened with the change to B9AE-F engine blocks for 292 / 312 applications in April of '59.  This is all info. gleaned from JM's engine block chart. 

Thanks for your thoughts.  Trying to do this once and get it right!   


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York