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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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I'm assuming those 60cc heads are Mummert aluminum heads. If that's so, will the DCR be lower than with iron heads?
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55blacktie (2/12/2022)
I'm assuming those 60cc heads are Mummert aluminum heads. If that's so, will the DCR be lower than with iron heads?Unless you change the camshaft and/or the connecting rod length, the DCR will ramp up and down at the same rate as the SCR ramps up and down when changing pistons or heads. If going with a larger chambered head on the above combination, then both the SCR and DCR will be lower.
Lorena, Texas (South of Waco)
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55blacktie (2/12/2022)
I'm assuming those 60cc heads are Mummert aluminum heads. If that's so, will the DCR be lower than with iron heads?In rereading your question again, I’m thinking maybe you are asking if the DCR requirements are different for the aluminum heads versus the iron heads? If that’s what you are asking, then for the Ford Y I use the 8.2:1 DCR as a maximum number for the aluminum heads and 91-93 octane gasoline. In theory, the aluminum heads can get away with a more compression ratio than the iron heads simply due to the aluminum not retaining the heat so if that’s what you are asking, then the maximum DCR number for iron heads and 91-93 octane gasoline would be slightly lower than what you would see for aluminum heads. For the time being, we’ll call that number 8.0:1 for the Ford Y using iron heads and pump premium without any definitive testing and/or results to back that up. I typically do not have an issue with the DCR number for iron heads mainly due to the compression ratio on most iron head combinations being less than optimum simply due to the heads being too large to begin with.
Lorena, Texas (South of Waco)
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