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By FORD DEARBORN - 9 Years Ago
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Greetings to all: I'm in need of one 312 piston. Can be used but must be stock sized. I soon should be receiving my block, crank, heads etc. from the machine shop and would like to do a mock up to determine deck height before selecting the new pistons. Hopefully someone still has one they hadn't discarded. Will gladly reimburse for shipping/handling etc.. Thanks, JEFF.................
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By NoShortcuts - 9 Years Ago
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Hmmmm... Question. Usually when the measurement you are setting out to make is done, it is done at all four corners of the block. IF you are looking to do that, are you intending to use the same piston and connecting rod assembly in each cylinder to assure the accuracy of the 'in the hole' reading?
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By FORD DEARBORN - 9 Years Ago
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Greetings to all: My request for a used standard 312 piston is to eliminate any surprises after final assembly. Even though this C2AE-C 292 engine in my 64 F100 ran very well, I know it was in need of at least a boost in the compression ratio department. So, I pulled the engine and made this my winter project and in Michigan, winter sometimes can be very long. During the dis-assembly phase I discovered the deck height spread was all over the map, .010 highest to lowest. Piston compression distancce varied by .006 and rod length varied by .012. Probably got lucky but was able to match measured deck height variation to each rod/piston combination. These were the correct C2AE 292 truck rods but .012 variation in length is excessive, IMHO. Bearings were excellent both ends. A lot can happen to an engine in 50 years as it was bored .040 over. This engine will now have a new life as a 312 with machining by very competent folks. With a superbly ground 312 with std. 292 mains, -.010 crank throws, mew 312 rods purchased from John Mummert, block bored to 3.800, line honed and decked just enough to true it up. I now don't expect the piston to deck height variation to be anywhere near the .010 variation as before. So will mock up one assy. in one cylinder only Then, CR(static), quench, and head gasket choice can be considered. Balance also must be considered because this crank was balanced with ECZ rods and the new 312 rods are 45 grams heavier. I just would like to see where all this now is before ordering pistons which will probably be stock Silvolite's? Is all this necessary? Probably not, but finding one dimension all over the map, then another and another, and so hats why I decided to go the 312 route. After all, I've been saving this virgin 312 crank since I as a kid for a reason, right? There's much more to this but I'm not trying to put everyone to sleep. Hope this makes sense as I'm at ties not great at explaining things in text. Thanks, JEFF........
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By NoShortcuts - 9 Years Ago
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Jeff, THANKS for your overview and recap of what you've done and what you've seen in working through the 'build' of your previously rebuilt 292.
While I understand how you found as much as a .012 variation in center-to-center length on the previously reconditioned C2AE connecting rods, I was surprised that the compression pin height of the .040 oversize replacement 292 piston varied by .006 . I wonder what make those replacement pistons were?
My understanding is that Silvolite is considered to be a quality replacement piston. Their web site information represents them as a quality offering. I vaguely recall that their 312 piston is heavier than an original Ford unit. As has been mentioned in other threads by Ted Eaton, John Mummert, or perhaps Tim McMaster... as a replacement piston, Silvolite's piston pin height is less than FoMoCo originals.
You mentioned determining the quench dimension you'll have using composite cylinder head gaskets and replacement pistons in your build. Having had the block deck surface squared and decked for clean-up purposes should help to reduce the replacement piston 'in-the-hole' dimension, but I suspect that you're going to be close to the desired safe maximum figure of .060 with your assembly.
Between JM's Probe connecting rods weighing more that the ECZ originals, and the Silvolite pistons weighing more than the original FoMoCo units, having your rotating assembly static and dynamically rebalanced is an investment in engine operation longevity, smooth operation, and optimum power generation.
Finding a crankshaft turner who is willing to take some pains in turning the 312 mains, rear oil slinger, and the rear seal area to the 292 crank dimensions, has to be challenging. In removing that amount of journal material has to require more-than-usual periodic truing of the grinding wheel surface and care to maintain the correct journal radius-es. Question... Did you find that the main bearing oil feed hole openings moved much due to the reduction in the journal diameter?
Thanks for your reply. 
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By carl - 9 Years Ago
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FORD DEARBORN (3/20/2015)
Greetings to all: I'm in need of one 312 piston. Can be used but must be stock sized. I soon should be receiving my block, crank, heads etc. from the machine shop and would like to do a mock up to determine deck height before selecting the new pistons. Hopefully someone still has one they hadn't discarded. Will gladly reimburse for shipping/handling etc.. Thanks, JEFF................. I have a new 312 standard bore piston that I will loan you if you pay shipping both ways Carl
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By Ted - 9 Years Ago
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While I do have some ‘used’ standard bore 312 pistons laying loose, it’s recommended to always use the piston that going to be actually used for the final assembly for engine mock up. The exception to this is where a custom piston is going to be made and the wrist pin height is going to be the same as the piston that’s being used for mockup purposes. It’s rare on my end to see even as much as a 0.002” variance in piston compression heights on new and matched sets. Broken sets could pose a problem though both in wrist pin heights and weights.
Here is a case in which to illustrate how things stack up during an engine build. A recent 292 build had the original pistons at a 1.783” wrist pin height while the replacement Silv-O-Lite cast pistons had a 1.760” pin height. In this case, there is a 0.023” difference and that much had to come off of the decks to simply get the piston back to where it was originally sitting in the hole at TDC. Then there was a 0.021” difference between the original steel shim head gasket and the replacement composition head gaskets and that amount also had to come off of the decks. Then the heads were grossly large on the combustion chambers versus the published nominal value. As a result the heads were then heavily milled and to get the intake manifold to fit properly, the intake side of the heads was also heavily milled. And then in resizing the rods, another 0.002”-0.003” of length was lost which also had to be made up. All this was done to simply maintain the factory rated compression ratio.
When using the same rod and piston to check the corners of the block, then variances in strokes between the various journals must be known and then taken into consideration. I’ve seen as much as 0.008” variance in stroke on factory cranks and then that can be exasperated into even more variance depending upon what the crank grinder does. You’ve already touched upon the differences in rod lengths and that can sometimes work to your advantage if the long rods are repositioned to the short strokes and the short rods positioned to the long strokes.
The 69cc and 72cc figures for the G and 113 heads are considered nominal figures and it’s not unusual to find the G and 113 heads much larger than advertised. Very rarely are they found to be smaller than the advertised numbers unless they have been previously milled. They key here is if the combustion chambers are not cc’ed, then the engine assembler is running blind when attempting to calculate the compression ratio. Assume nothing when working on any engine.
If you’d still like one of these ‘original’ std bore 312 pistons, just let me know. My contact information is at www.eatonbalancing.com .
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By FORD DEARBORN - 9 Years Ago
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Greetings to all: Thanks very much for the posts. Excellent information was all brought out. I had prepared a reply and because some of it touched on what Ted explained I''m going to enter it in anyway. Original pistons were Silvolites dated Jan 74 with 3 from other months. Maybe QC problems then? I plan to possibly use Silvolites again because everyone agrees they are a good maker of stock pistons. It's true all aftermarket stock Y pistons have a shorter CD than what Ford used. I was told this is to allow for deck machining. The max. in the hole of the 'old" engine was .028 add to that .043 for composite gasket and that put's the quench at a whopping .071. I didn't know the exact CD of a Ford piston until Ted mentioned it in the last post. Thank you. This explains why the 57's ran so good then. The 57 manual lists in the hole distance of .010 to .026 for the 312. Now, thanks to Ted, we know it was close to the .010. Looks like there are some options here: 1.Remove metal from the deck but I only intend to remove whats necessary to square up. 2.Steel gaskets should take about .020 out. 3.Custom pistons-to be determined. Noshortcut mentioned balancing, of course. Fortunately there is a very good crank grinder in my area who prepared the 312 crank. This amazing shop produces cranks for most applications from billet. There's a page on John's site listing all the Y crank dimensions. I can't answer the question regarding displacing the main journal oil holes. Do you think this could be an issue? The 312 crank with all the other items is still in the machine shop. Otherwise, I could compare it to the 292 crank. In regards to the cylinder heads, it was noticed the 1" pads below the exhaust ports were .087 and .093 each head respectively. Two chambers each head were CC'd which showed the thicker head needed to catch up to the thinner head. I believe the shop reported aprox. 66 CC's average. These are posted G's. Thanks to all for the great input, JEFF...........
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By charliemccraney - 9 Years Ago
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Ted (3/21/2015)
When using the same rod and piston to check the corners of the block, then variances in strokes between the various journals must be known and then taken into consideration. I’ve seen as much as 0.008” variance in stroke on factory cranks and then that can be exasperated into even more variance depending upon what the crank grinder does.
Will it be accurate enough to use that rod and piston to measure the stroke of the journals before the deck measurement is made?
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By FORD DEARBORN - 9 Years Ago
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Greetings to all: What I'd like to know here is the new "in the hole" dimension. After all the machining has been done on the block, a fresh crank sitting in new bearings and a new con rod with new bearings in place and a piston of known dimensions on top of all that, there will be a in the hole distance. If the piston's wrist pin center to top of piston is known, then that distance, plus the in the hole distance should equal the deck to center of the small end of the rod distance. Bearing clearances, for example, will introduce a slight error but for my purposes, this should tell me what I want to know within a couple thousands. Hopefully with this information, I can go shopping for new pistons. Then, with the new pistons and rings, the matching process and balancing process can begin. With the old engine, even as reasonably tight as it was, had very wide variation with in the hole measurements, rod length and piston CD. Wasn't even within factory tolerances. For my build, factory tolerances would be OK and hopefully, this one will be better. Ted brought up many variables in this process. By selecting good parts, good machining and attention to detail should produce a more precision assembly than what I had, IMHO. Thanks to everyone for all the great input and as this progresses, or not, I'll provide an update. JEFF........
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By Ted - 9 Years Ago
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charliemccraney (3/21/2015)
Will it be accurate enough to use that rod and piston to measure the stroke of the journals before the deck measurement is made?
Charlie. Using a connecting rod and piston in the various cylinders to measure the stroke would be quite accurate. It wouldn’t necessarily have to be the same rod and piston as you’d simply be taking measurements at the tops and bottoms of the stroke as the crank is rotated and calculating the difference in the values. If going to the trouble of measuring the stroke of each journal, then you also need to know the lengths of the rods so those can be taken into account when preparing the engine for machining the decks. Otherwise you could very well end up with highs and lows in the deck measurements that would not make sense otherwise. If the pistons come from different sets, then the wrist pin heights also become a player.
Here are the results of stroke checks on three different 312 cranks.
Crank #1 Crank #2 Crank #3
Jrnl #1 3.438” 3.437” 3.440”
Jrnl #2 3.440 3.437 3.436
Jrnl #3 3.435 3.437 3.435
Jrnl #4 3.432 3.435 3.431
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By Ted - 9 Years Ago
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FORD DEARBORN (3/21/2015)
Greetings to all: What I'd like to know here is the new "in the hole" dimension. After all the machining has been done on the block, a fresh crank sitting in new bearings and a new con rod with new bearings in place and a piston of known dimensions on top of all that, there will be a in the hole distance. If the piston's wrist pin center to top of piston is known, then that distance, plus the in the hole distance should equal the deck to center of the small end of the rod distance. Bearing clearances, for example, will introduce a slight error but for my purposes, this should tell me what I want to know within a couple thousands. .....
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.
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By FORD DEARBORN - 9 Years Ago
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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..........
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By NoShortcuts - 9 Years Ago
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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.
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By FORD DEARBORN - 9 Years Ago
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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.........
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By NoShortcuts - 9 Years Ago
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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! 
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