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292 Overbore/Rotating Assembly Questions

Posted By customline3859 Last Week
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customline3859
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Hello all,

I am new to this forum and I haven't been able to find a clear answer with my searches, so I hope someone can help. I have been putting together a 292 y block that I purchased "rebuilt" a few months ago. The engine has already been bored .060 over, but it has some rust build up in two of the cylinders where water had sat. I have already taken it to a machine shop to have main studs installed and for line honing. They told me that they ran a quick hone into the cylinders to clean up the rust, but it didn't seem to help. I don't want this engine to burn oil, so I think I'm going to have to bore it further. I haven't been able to find 292 pistons that are larger than .060 oversize, but I've read the block can be bored up to .120 over. Is this correct? I've read that I could use a 312 piston, but would I need to change the rods or crankshaft? Any advice or information would be greatly appreciated.

Thanks,
David
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You can use 312 pistons in a 292 without changing rods, the pin to top distance is the same.  Since your bores are already 3.810, you could use .030 oversize 312 pistons (3.830)by boring the block another .020.  I use 3.830 pistons in my 292 blocks for my supercharged drag car without bore problems.

John - "The Hoosier Hurricane"
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customline3859
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Awesome, thank you. I have checked John Mummert's site and I see cast pistons that look like they're intended for a train or custom forged options only? Are there any other options out there?
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Have you asked your machine shop if they have replacement pistons available through their parts sources?  Egge machine may have something available also.

John - "The Hoosier Hurricane"
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Customline3859.  Welcome to the site.  John's info  above is good.  My reply took longer to type and elaborates a little more.  Yes, your 292 engine block can be bored oversize for use of 312 oversize pistons.  IF your 292 block has already been bored .060 over, the cylinders now measure 3.810 which is the equivalent of a .010 overbore for a 312.  In using 312 pistons with a 292 engine crankshaft there is no interference issue with the crank that requires the use of 312 length connecting rods.

I've previously found oversize pistons for the 312 offered and available in .030 (3.830), .040 (3.840), and .060 (3.860) oversize from Sealed Power and Silv-O-Lite.  Both piston makes state on the shipping box that the piston pin height is .020 less than original FoMoCo dimension.  Use of these pistons will increase the 'in-the-hole' dimension of the piston in the engine block (below the block deck surface).  Because of this factor PLUS the original FoMoCo 'in the hole' production dimension of .020 - .030 AND the use of today's composite cylinder head gaskets, I would recommend having the block decked to zero deck the pistons.  This will improve engine performance, but more importantly will prevent detonation problems with a piston quench dimension that would approach the critical number of .060 IF block decking is not done.  With heat cycle factors AND original production inaccuracy, squaring the block by decking is a GooD thing to do.  I think you will be surprised by what the machine shop finds in checking the variations from square in machining your engine block.

Because of the amount of over-boring you may need to do to clean-up the rusted cylinder bores, consider having the block sonic tested first. Core shift in the engine block casting process could be a concern with how much the original 292 is being over-bored to use the larger 312 pistons.

Having the entire engine rotating assembly re-balanced after changing pistons will serve to insure an engine that runs smoothly and provides longer trouble free service than you would experience otherwise.  Original FoMoCo engine balancing was not the optimum from the mass production system of the '50s and early '60s.

Check the link below to see how much the composite cylinder head gaskets you use will increase quench area and increase effective combustion chamber volume over the original steel shim cylinder head gaskets used as FoMoCo original equipment.  Composite gaskets provide a much better assurance of a lasting seal, but they do increase quench dimension and lower the engines original static compression ratio.
http://www.eatonbalancing.com/2012/06/30/head-gasket-volume-calculation/

Some GooD tips on y-block engine rebuilding may be helpful to you from the links below
http://www.ford-y-block.com/assemblyerrors.htm
https://www.hotrod.com/articles/build-reliable-powerful-ford-y-block/

Hope this helps!  Smile


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Hitting on all eight cylinders

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So am I understanding correctly that there is a difference in wrist pin height between the 292 pistons and the 312 pistons which will prevent the pistons from contacting the valves? 
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Posted 8 days ago
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Not from what has been written.  He's simply saying that many replacement pistons will have a slightly different pin height that will position the piston a little deeper in the bore.

However, later HD 292 engines used a rod the same length as a 312, which do require different pistons.  If the current rods are C1TE, then unique pistons are required (or a different set of rods).  Otherwise, you're good.  You're probably good - check.


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When I worked in a machine shop, I was told that oversize pistons had shorter tops to try to make the compression ratio the same as a standard piston with its original top.  We didn't do high performance work, so we never worried about the deck clearance.  In my own racing engines, I had the decks squared and equalized, then used the longer 292 rods with the 312 crank and machined the piston tops for zero deck.  The 292 rods were .070 longer, and I usually had to take about .050 off the piston tops.  I use .030 pistons, so they would have been about .020 in the hole with 312 rods.

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Charlie.  THANKS for coming in on the question I caused Customline3859 to ask about a difference between 292 and 312 pistons. 

Customline3859.  As Charlie indicated, the FoMoCo piston pin height location for virtually ALL original 292 and 312 pistons is the same.  The difference I reported in piston pin height has to do with aftermarket replacement pistons from Sealed Power and Silv-O-Lite that I have worked with.

Charlie mentioned that there exists one exception regarding the 292 pistons used in Ford Heavy Duty 292 truck engines.  These HD 292 engines were used for heavy truck applications (not pick-up trucks; only dump trucks and similar big truck applications).  These engines were produced between 1961 and 1964, have the block casting I.D. from that time period of C1AE 6015-R or C2AE 6015-C, BUT are outfitted internally with heavy duty connecting rods with the forging ID of C1TE (as Charlie indicated, they are dimension-ally the same as the 1956-1960 application 312 engine ECZ rods, but are heavier), used a forged steel crankshaft (292 and 312 cranks in non-HD 292 applications are cast iron) and the pistons (because of the shorter length connecting rods used) used an entirely different piston pin height.

This piston pin height information and the connecting rod length info I'm referencing is shown on one of John Mummert's web pages.  Click the link below to view JM's web page info.  Look at the columns 'rod length' and 'comp. ht.' (piston pin height)
http://www.ford-y-block.com/dimensions.htm

As Charlie indicated, chances are you are not working with a HD 292 engine assembly.

Hope this helps.  Smile

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I had another thought about your engine.  If the pistons are OK, you could have those two rusty cylinders sleeved, probably for less money than boring all 8 cylinders and buying new pistons.  Just a thought.  Even if those two pistons are ruined, you could buy two 292 +60 pistons.

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