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Discussion Starter #1
Back in the early 90's I built a street performance engine with these pistons. I haven't been able to find the paperwork from the build, but JE 11.25 - 1 compression ratio sticks in my head for some reason. They measure (measured at the band between the top and middle ring) 84.328 mm or 3.320." across valve relief to valve relief, and 84.277 or 3.318" along the wrist pin. This tells us that they are pistons for over bore liners because stock 2L pistons are between 83.935mm to 83.965 or, 3.304" to 3.306" The numbers are on the exhaust reliefs which are visabbly offset. Can anyone help with the identification? Thanks!
IMG_5049[1].JPG IMG_5050[1].JPG IMG_5051[1].JPG
 

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They look like Paul Spruell’s 11:1 JE’s. I’ll look on my shelf, I a a used set I can look at.
 

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Discussion Starter #3
Thanks Peter (y)
 

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Discussion Starter #5
Hmm, mine are definitely a little different. I may have purchased them through Mike Sperry. I'll post a few more images after I plow a path to the workshop. We got another 4-6" with a hard ice coating last night. Still snowing ice chunks.
 

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Discussion Starter #6
Peter, I can see that my valve reliefs are different; the exhaust side is offset on #1 and #4, the skirt is different, mine weigh 12 grams more. I don't have the exact numbers in front of me, but mine are an overbore size. The wristpins look like they have been lightened, and the rods look like they were shot-peened and modified. I'll have to post images tomorrow. IMG_5062[1].JPG IMG_5063[1].JPG IMG_5067[1].JPG IMG_5068[1].JPG
 

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Discussion Starter #7
Looking at the Alfa Factory Engine Overhaul Manual, I see that they want the piston measured at "the diameter of the piston skirt at right angles to the piston pin bore and 17mm above the bottom edge of the skirt." I have some more plowing and farm chores to do, and then I'll remeasure and post.
 

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Discussion Starter #8
Ok, I just re-measured the pistons according to the directions in the repair manual and got much larger dimensions. To begin, the skirts on these are much shorter than the stock BORGO pistons. What I found is that the fattest part of the piston is measured as described in post #7 at the bottom of the piston skirt. Mine measured 3.342" or 84.996mm. Moving from the bottom of the skirt to the bottom edge of the piston pin, at a right angle of course, (which is about 26mm from the bottom edge of the oil ring groove) the measurement changes only about .0005" to 3.3415" or 84.8741mm. At the center of the pin (about 15mm from the bottom of the oil ring groove) it doesn't lose much going to 3.3405" or 84.8487mm. From there moving up it really gets smaller fast. At the bottom of the oil ring it measures 3.337" or 84.759mm. At the top of the piston it is smallest at 3.313" or 84.150mm.
What all of this means is that these pistons are made for 1mm overbore liners. My plan is to bore a set of old, stock size liners to fit these pistons.
 
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