The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: bl**dydrivers on 31.05. 2020 02:11
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I have a NOS set of BSA .040 Pistons (believe they are 8.25:1 ratio) for 1962 A10 Super Rocket. The pistons are in good shape as they were still packed well but the rings are corroded and lock up inside the grooves when pressed in.
I’ve read up to avoid Hepolite rings from Asia and unable to locate NOS Hepolites.
Know to avoid JP rings and being in USA I’ve come across Hastings, but don’t know about them and want to hear opinions first before making the purchase or which ones I should use.
Thanks!
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b**d. If the rings came with the pistons (in other words they are the correct rings) you have nothing to loose by"polishing" the rings carefully with a Dremel to remove surface corrosion. The piston grooves also need a clear out, and everything should fit. The clincher is how much material has to be removed to restore a working ring without up and down movement in the groove greater than the allowed limit. Original A10 rings are 1/16" thick Compression, 1/8" thick Oil Ring.
Hastings have a good reputation, and are a serious player with an extensive range. Your other alternative is NOS original Hepolite, eBay (and its attendant risk as to what you actually get) would be a potential source. There are presently a fair number of eBay sellers offering Original NOS Hepolite rings here in the UK.
Swarfy
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Don't even think about using a ring with rust on it.
Throw them away.
Better than average chance they will break from a crack originating at the rust pit.
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Sure, if the rings have deep pits, not worth the risk. But if its just a light film of discoloration, that comes off with a light scrape with a fingernail, well worth a lick with a Dremel brass brush. The ring, as regards the metallurgy, is the OE Spec so worth keeping if possible in preference to an unknown (Asian) modern repro.
Swarfy.
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To be honest for what it costs I would but a new set of pistons complete with rings personally. I had a problem when I built my Super Rocket using old pistons and new rings. The article is on here and despite everything being supposedly "perfect" size wise rebored etc etc it burned oil so bad it was ridiculous. A few quid on a new set of pistons and it has done over 10'000 miles since no problem.
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As mentioned these are New Old Stock and never used.
Attached are a couple of photos of them.
The rings aren’t rusty, but rough to the touch (presume oxidation).
Can I use the rings? Or do I need to get new ones?
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I'd go with Swarfy on this one. Clean the rings with a brillo pad or similar. If only discolouration is left, I'd be fine fitting them. At least they're known good quality and fit to the pistons.
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RD Yes, those ring look a lot better than I thought they would be, and will be fine.
B***D Rebore will come back with a nicely honed cross hatch finish. If fitting to an existing bore, break the glaze, and aim for the same pattern. Run in with a cheap oil with non of the modern anti wear additives. Don't allow prolonged idling, but don't hammer it too much to start with, just treat with a bit of care and respect. Being a little too gentle to start with will result in poor bore sealing as the rings won't bed in due to insufficient surface loading in the running in period.
Swarfy