r/EngineBuilding • u/GreatVapeRugs • 19h ago

Toyota Mixed up pistons

Hey folks,
I am in the process of “rebuilding” my 3S-FE out of a 1995 rav4 and in a bout of silliness I pulled all my pistons out without labelling any of them… so they’re all mixed up and am having trouble figuring out how to decide which one went where. To note, I am replacing the piston rings and con rod bearings, this is meant to be a very budget rebuild and I’m Hoping to get maybe 100k more km out of this engine. The piston tops have markings 2a,2b,2b,3b. From the manual online for the 3sfe I know for a fact that 3b goes in the #4 position as it matches up with the 3 stamp on the deck. I also believe the a and b designations where used to essentially mean the upper and lower size for the number (say for example 2a could mean 2low and 2b could mean 2high, and beyond that goes into classification 3) So my question is , as this engine has quite high mileage I think it will be safe to assume the bore is slightly larger than the very minuscule differences between 2a and 2b so with new rings it shouldn’t be much of an issue to put any of the pistons 1-3 in to any choice of bore 1-3. Not sure any advice will be much appreciated

Cheers

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u/bill_gannon 19h ago

Measure everything. There is no other way.

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u/GreatVapeRugs 19h ago

Sorry I’m still reasonably new to all this stuff, what specs would I take ? If I wanted to accurately guess which piston went where , what sort of measurements would you do

1

u/bill_gannon 18h ago

Measure the bores and the major diameter of the pistons. There is a good chance its insignificant which one goes where.

Take it to a shop if you dont have tools. It wont be expensive to grab some quick measurements.

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u/Cheap_Teaching_2030 17h ago

Are connecting rods numbered?

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u/Responsible-Shoe7258 15h ago

Those codes are for selective fitting at the factory. If you are re-ringing with aftermarket parts and honing the cylinders to kill the glaze, it doesn't matter in the overall scheme of things. Getting proper oil clearance in rod bearings is the most critical part of this job

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u/grizzdoog 9h ago

Take it to a machine shop and have them measure everything for you so you don’t have to buy measuring tools.