Big end bearing & piston ring sizes?

[IanMW]

Hello All,

I'm going to replace the con rods on my BAM engine with some uprated ones, at the same time I'm going to re-hone the cylinders and replace the piston rings and con rod big end bearings.

Looking at the photos of when I last had the engine apart the cylinders are glazed, so really need the glaze taken off nothing more.

Looking at the available rings & bearings they come standard or different over sizes, bearings 0.25 – 0.50 mm and rings 0.01 – 1.00 mm.

There is nothing wrong with the engine with 122K miles on it; any ideas if I should buy the standard size or oversized?

I’m thinking the re-honing might require a slightly bigger piston ring and the con rod big end bearings leave as standard as I have no plans to regrind the crank as the job will be done with the engine in situ?

Thanks

 

[Brad1011]

Should be standard surely the rings will need grinding back for the correct gap honings only scratching the bores ? Check top middle and bottom of the bores that they’re still the correct measurements this is something I want to do myself I bought the Emanual for mk4 golf gti Bentley manual as the tt doesn’t cover cylinder and crank only head for some reason ?? It’s brilliant the mk4 golf version worth getting for 17 quid, I’m sure someone with knowledge will know the ins and outs also the manual tells you Piston ring gap sizes and tolerance etc worth having


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[superkarl]

Standard bearings.
Piston rings come how they are to a standard gap on a standard bore. You can then gap them further (by delicately filling them) to a desired ring gap

Top two compression rings have a tolerance of 0.2 -0.4mm


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[danny_dj3]

If your going to rehone the bores with the block in situ then make sure you protect the oil squirters, I used a plastic top off a can of brake cleaner and trimmed it so it sat literally right to the nozzle, that way you can go low without hitting them. I'm no pro at this, but it worked well enough for me to get my compression back up to the higher end of things. What honing tool are you using outta curiosity as theres a few different ones out there. slow and steady and roughly a 45degree crosshatching is right if i remember correctly.