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DiLL (2/2/2022)
Joe, would you mind sharing the specs on the forged pistons you ordered from JE? I'm in the process of trying to get my pistons ordered and would like a reference. If for competitive reasons you're unable to I understand. thanks! 55blacktie (2/2/2022)
Joe, does that include forged flat-tops/w no valve reliefs and metric rings for EBU and C2 rods? Thanks. Because there were some questions regarding piston ordering asked in a different and somewhat unrelated thread, I have started this post specific to ‘Custom Pistons’. When ordering custom pistons, the piston rings are the first consideration and are ordered prior to ordering the pistons. Piston rings are not available as an ‘off the shelf’ item for every possible bore size so the bore size must be determined first. Depending upon the availability, it may be necessary to juggle the bore size in order to get the ring width sizes you are looking for. Because of the many small bore metric sized pistons that are available, there are a number of cylinder bore size options but these may not fall in the normal 0.020, 0.030, 0.040” sizes that are typical to the American engines. In some cases, the final bore size may fall into ranges between those numbers. When the rings are ordered, you will need the bore size, ring thickness, and radial depth numbers for those rings so that the pistons can be machined specifically for those rings. A word of caution about ring thickness. As the rings get thinner, the cylinder wall finish gets more critical.
  Lorena, Texas (South of Waco)
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Group: Administrators
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Having received a couple of phone calls regarding how to calculate the wrist pin location in a custom piston, I’ll revisit this in slightly more detail. Besides knowing the wrist pin diameter to be used, you will need to specify where the wrist pin centerline will be as measured from the top of the piston. In piston manufacturing terminology, this is referred to the compression height (CH). The factory wrist pin diameter for the Ford Y is the same as the later produced small block Ford engines (SBF) which is 0.912”. If using aftermarket rods or retrofitting connecting rods from another engine family, then the wrist pin needs to be compatible with those rods. While the factory sized 0.912” pins work well with the factory connecting rods, both the 0.927” and 0.866” pins are popular choices when aftermarket rods are being used. Regardless of the pin diameter that is chosen, it must match the wrist pin size of the connecting rod being used. While the CH value calculation does not take into account the actual wrist pin diameter, the wrist pin diameter is a consideration in that it is a player in determining the amount of room that is available between the top of the wrist pin and the piston top in regards to piston ring placement. If going with a larger diameter wrist pin, then that area is going to decrease and in some cases, may be a tight fit for the ring package. The calculation for the CH is as follows. Deck height minus connecting rod length minus half of the crankshaft stroke. This is for a zero deck combination. If wanting to have the pistons down in the hole a given amount, then also subtract the amount that the pistons are going to be below the decks. Here’s an example of the numbers for a zero deck Y-Block combination assuming the decks are being machined for a 9.750” deck height. 9.750” – 6.125” – (3.600” / 2) = 1.825” CH If wanting the pistons 0.005” in the hole with a 9.750” deck, then the numbers look like this. 9.750” – 6.125” – (3.600” / 2) – 0.005” = 1.820” CH
Lorena, Texas (South of Waco)
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