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+--- Thread: Non Standard Piston (/showthread.php?tid=7462)
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Non Standard Piston - Adrian Payne - 02-05-2022
Evening everyone.
I was just going to replace the rings on my 28 chummy but on extracting the pistons I find they only have 3 rings.
Anyone know what they might be off so I can get new rings. The top rings are very thick. would I be better off renewing the pistons as well?
Many thanks.
Adrian.
RE: Non Standard Piston - Ian Williams - 02-05-2022
I find these type of pistons are far more prone to burning oil than the narrow ringed versions, personally I would replace them but others may disagree. Peter Woodend NZ did have rings in stock for them in the past although I am not sure if he still carries any.
RE: Non Standard Piston - Adrian Payne - 02-05-2022
Thanks Ian. Oil burning is the reason I took them out!
Adrian.
RE: Non Standard Piston - Bob Culver - 03-05-2022
The rings are the width as original. As per the photo prone to wear of the top groove, esp as many sets too stiff. Running such rings in the distant past my RP used almost no oil, but with narrow rings I could never get below 1 pt per 300 miles of hot main road running. Ring spacers now not readily available. I have seen two thin rings in widened top groove. top edge of all rings can be very slightly chamfered. 2nd and oil rings often very little worn. If you can find, may be suitable space for a wavy spacer behind the oild ring. original Solid skirt pistons are near everlasting
RE: Non Standard Piston - Ruairidh Dunford - 03-05-2022
Hi Adrian,
this is a very old type of piston/rings and will smoke - personally I never reuse such when I come across them.
The new pistons from our A7 Suppliers are all excellent.
RE: Non Standard Piston - Ian Williams - 03-05-2022
Adrian, don't be persuaded by Bobs experiences they are are as usual quite different to most of us who have run Austin sevens for decades, bite the bullet and follow the advice to replace the pistons, trust me you will thank us in the long run.
RE: Non Standard Piston - Colin Reed - 03-05-2022
Hi Adrian,
regarding the bores have you checked them for wear, no point fitting new pistons and rings the least you will get away with is honing or deglazing the bores.
No point wasting time and money fitting to warn bores.
Colin
NZ
RE: Non Standard Piston - Dave Mann - 03-05-2022
When my friend rebuilt his RP saloon in the 1970s he searched for and found a set of these 3 ring pistons, they took a lot of running in before the engine was free. The car still has these pistons, has covered at least 60,000 miles and burns very little oil.
RE: Non Standard Piston - JonE - 03-05-2022
I'd be interested to know what gap the rings are when put into the bores in a few places...? i.e. a basic assessment of the factors that may contribute.
RE: Non Standard Piston - Bob Culver - 03-05-2022
Adrian. Are you using a classic non detergent oil? it is unusaul to see thick black build up nowadays. If the oil ring is plugged consumption increases.Ffrom factory many cars had a simple stepped oil ring; the type with relieved and drilled centre was a big improvement. Original pistons had no relief and drillings below the 2nd ring. Beware the illustration in parts book which shows drillings behind 2nd ring! Top rings with large vertical clearnce are claimed to pump oil.