Piston and rod recommendations. e30 S52 GT35R

[MacBudd541]

So my build was moving along nicely until I pulled the head off and saw I had some surprises. I had no intentions of digging into the bottom end but it looks like this engine has been rebuilt before and now that I am this far in I figured I might as well go all the way. The pistons all have the same markings on them but I has not able to find any information during my google searching. My worry is that they are already oversize. I bought some Harbor Freight T bore gauges and used an equally cheap micrometer just to give myself an idea but it didnt really answer any questions. My thought is to take it to the machine shop and have them properly measured but I also need to get some parts ordered if I am going to enjoy the car the summer. I bought a CES cutring HG/copper spacer combo for an s52 already, I imagine going with new pistons means I have no use for the copper spacer but the headgasket and rings are still good to 87mm right? Should I just order 87mm pistons? What is the preferred brand and/or vendor for pistons and rods? What compression ratio should I shoot for? We have 92 octane here and e85 is not close enough so I am sticking with the pump gas. Thanks in advance bfc turbo team.

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S52_BORE_SIZE.jpg




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[m3boost]

https://www.ebay.com/itm/JE-Pistons-...item2cd2038941



https://www.cnc-motorsports.com/je-p...1-pistons.html

I bought my set from cnc.. 86.5

[someguy2800]

^^^ That is a really good deal.

OP, the pistons you have are not that bad so don't throw them away. They are serviceable to someone. Its very likely the block is still within spec to just put a new set of pistons in it. If I were you I would buy a dial bore gauge and 4" micrometer on ebay and spend a couple hours learning to use it. Tear it down at home, hone it with a 240 grit ball hone soaked in ATF on an engine stand in the driveway, about 10 seconds in each cylinder, clean it up with soap and water, and put it back together with your choice of rods and pistons. If the rod bearings that are in it do not show wear there is no reason to replace them.

[MacBudd541]

Wow, that is a good deal. I had not seen those 'kits' before, looks like they ship pretty quick too.

Hmm.. interesting about my pistons, I thought that one looked pretty bad and all of them have some of that damage to a degree. Does that look like detonation? And for some engine building newb questions: Are the sizes I see advertised the measurement of the piston or the bore? If I measure the bore of my block and it comes out 86.5, then am I to buy 86.5 pistons?

[someguy2800]

Its from detonation. It can get much worse than that. Its not a good thing but with alittle cleanup they are still serviceable at least in an NA motor. Somebody might give you a couple hundred bucks for them. Check the chambers on the head for matching damage. The sizes listed will be the bore size. The clearance is built into the pistons.