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Originally Posted by Bob Kontak
Hi Eric,
Machine shop says bores / pistons are ok. Big ends on con rods must be bored and rod journals on crank ground. Micro-polish on mains only. We will use the Hastings rings you recommend.
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Great! Hopefully the crank machining and bearings are inline with the estimates I gave.
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The shop has drilled additional return holes in pistons. However, I offered to get additional info if I could from you. If you have a summary of the process that would make me feel more comfortable. There are two holes on each side currently and you can see a boss in the casting where the holes go through to the center of the piston.
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They already HAVE drilled the holes?
You have the oldest pistons if you have two 1/16" holes on each side. The new-er revision had four 1/8" holes on each side. The newest (2005-up) design has seven holes on each thrust/skirt side (see photo comparing rev 2 and 3).
You should be able to make the holes bigger, 1/8" and drill two extra.
Your machine shop will know how/where to drill the holes in "safe" places... I couldn't find a write up online doing a quick search.
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I did call Toyota and they did not indicate there was an updated ring set. They definitely had updated pistons so I am assuming the oil relief is better in these.
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They may not even know they have changed over the years.
Here is Toyota of Europe's TSB.....
gen7_oil_consumption
Here is a Toyota forum post:
piston oil holes - Toyota Nation Forum : Toyota Car and Truck Forums
Good luck!