[Healeys] BN1 Le Mans Pistons

[John Harper]

We don't often see technical tips but here is one that perhaps only a 
few people are aware of.

I am in the process of reconditioning my BN1 Le Mans engine and decided 
to keep the original pistons and just fit new rings. It is believed that 
these pistons were fitted when the car was quite young at the Donald 
Healey Motor Company.

I had great difficulty finding replacement rings and had after much 
searching to give up and have the compression ring grooves widened.

Most owners will know of Standard and so called Le Mans pistons with 
Hepolite Number 12572 (C.R. 7.5 to 1) and 12623 (C.R. 8.6 to 1) 
respectively. These have 3/32" wide compression rings.

However mine are Hepolite 14296 with a stated C.R. of 8.1 to 1. These 
appear in catalogues up until the early 1960s but then disappear.

The problem is that the compression rings fitted to these pistons are 
NARROWER at 0.070" wide.

So if you have these early pistons and need to re-ring them, be warned.

Regards
-- 
John Harper