I've just rebuilt an engine that was fitted with +50 thou pistons. They were JP from Australia and were able to supply new +50 thou rings for the same price as any other size available in the UK (although import duty bumped it up). I couldn't source +50 thou rings from the UK.
I understand boring out to +60 thou can be leaving the liners too thin and so was happy to be able to just fit new rings.
Dec 29, 2016 - 8:11PM
Re: Special Engine
I would like to use renault parts because I have a stock of Renault 4 pistons and conrod.
They are compliant with phoenix crankshaft 1"5/16.
And the conrod from phoenix are really to expensive.
Hi Alex. I thought the R4 pistons were either 56mm (Early) or 58mm.
Many over here used to use R4 pistons and rods.The earlier R4 rods had a 38mm journal size which is compatible with the 1 1/2" pheonix crank (which uses R4 shells)
Liners, Westwood liners list WCL 128 as 55,88 bore and 58.98 outside.
or WCL2 57 bore and 61 outside.
Many here have used the 58mm Renault pistons in a 7 block without problems,I have used a linered block bored to +060 but normally +040 is the recommended limit.
I wouldn't use the larger liners at 61mm they weaken the base of the block and the top face too much.
Currently, my block have got piston +040 but I have to bore more (+060).
Instead of bore again, I can bore to adapt cylinder liner from Westwook.
After that I bore the cylinder liner to adapt Renault 4 pistons in size 58mm (????? the liner is now really "thin" no ?).
For con-rod, I can use Renault 4 rods with size 38mm
For the crank, a phoenix crank in size 1"1/2.
Use the R4 rods 38mm and 1 1/2" phoenix crank yes.
I thought there was a 56mm piston made for export market R4's,maybe someone can confirm this?
I would have the block bored to suit the 58mm pistons,If it is ok,no porosity use it.If you need to liner it you may need to consider using Austin or rosengart rods and readily available smaller pistons if the 56mm R4 pistons are unavailable.
There is not enough metal in a standard block to reliably use the oversized liners in my opinion.
I wonder if your recommendation isn't this configuration :
Bore my block to use Renault 4 piston without (!!) liner.
Use Renault Piston in size 58mm and Renault rod size 38mm and a phoenix crank 1"1/2.
My aim is to use my car only on the road but with honorable performances. In add to this configuration I plan to use a specific head cylinder, camshaft, sump and oil pump.
Thank again you for your help
That, Alexandre, is exactly the configuration of the engine currently in my 1929 Chummy. It has done over 10,000 trouble free miles since being built from a collection of parts. (should point out, splash lubricated 11/2" Phoenix crank.)