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Hi, I have my flame suit on, just in case, but I really would like to figure this one out and couldn't find anything specific online. Here it goes:

I have 2 blocks D15B1 and D15B7. From what I've read they are identical. I started working on that D15B7 until I realized that my cylinders are not cylindrical, they are bit oval in cross section and tapered... So my solution is to bore the cylinders and use oversized pistons. I wanted to keep using PM3's cause it is safe, however FJT does not sell half sized PM3's only 75mm and 76mm.

Finally the questions:
1. What are the drawbacks/benefits and additional steps required when boring cylinders above the service limit. In this case it is 75.52mm and I am looking at 76mm?

2. PM3 or P29 Pistons? Which would yield higher compression/better results.

3. Seriously, are there any benefits that D15B7 has over D15B1 except the age?

Please share your knowledge on the subject, as well as your opinions.

Here is a link to my build:
http://www.d-series.org/forums/showthread.php?t=98840

Thanks.
 

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PM3. P29 would sit very low&deep in the bore at TDC, messing the combustion. With head milling in D15, compression ratios from 9:1 to 13:1 are achievable with head milling and using PM3's. Well 13:1 is very extreme and I'm doing it LOL, need LOTS of other precautions and arrangements to make it work but it is doable. Might not yield upto 13:1, but gets very close to it.. Valve reliefs need to be huge.. Not CC'd chambers/reliefs yet.

I have 76mm, posted block. Many 76mm engines have been made with standard block without any issues, even high-power/rpm ones.
 

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Rushi (as usual) covered just about everything. Another thing to consider is that in your engines, the bigger the bore, the more you can do to unshroud the valves which will help a LOT with breathing. I was leary of 76mm bores on stock sleeves, but given the success that people are having with them, especially if you take the precaution as Rushi did and post your block.
 
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