Andy -
I've never been a fan of boosting compression on a Healey. I know
you've already decked the block so there's not much going back, but
pushing compression over 9 to 1 just really isn't all that needed in
modern times without high test fuel. 9.5 to 1 should be ok, however,
but it is at the limit of being acceptable for normal use.
With respect to the rings, I firmly believe that if you are not
racing, there is no significant value to removing rings from a 4 or 5
ring piston. I've had 5 ring pistons in my BJ8 for almost 100 K miles
and compression is still as good as the first day I put them in. You
get more problems for wear from using OEM Coopers air filters. Well
in your case you are using Burgess filters so that's a good thing.
The nice thing about using the full complement of rings is I believe
it really helps reduce oil blow-by over time and helps maintain even
compression. It shouldn't wear your cylinders any more or less than
having three rings; once the rings have set they really don't wear at
all so one or two more rings is perfectly fine. I do like like having
the oil control ring on the lower skirt, I believe it really works
down there. If you don't put the ring down there you should go full
monty and get proper short skirt pistons....
Hope that helps.
Alan
On Tue, May 3, 2011 at 7:21 PM, Andrew Thorp <bce257@yahoo.co.nz> wrote:
> Hello Everyone,
>
> I'm part way through reassembling my BN4 engine and have a couple of
questions
> that somebody may be able to help with.
>
> Firstly, I have aftermarket pistons with a second oil control ring below
the
> gudgeon and would like to leave it out and change to using a three-piece
upper
> oil ring instead of the original single piece cast iron oil rings. Has
anyone
> had good/bad experience running without the lower oil ring?
>
> And secondly, I have read a few comments that 9.5:1 is a good c/r for a
road
> Healey on premium pump gas. I also read up a lot on 'squish' and quench and
> their importance in preventing detonation. After finding my squish
clearance
> was very big at 0.106" I decked the block 0.067" to get the generally
> recommended ~0.035" clearance. Is anyone successfully running a Healey
engine
> with higher than 9.5:1 c/r on pump gas? What squish clearance does your
engine
> have? I am mainly interested in making it more efficient rather than go
> faster, it is after all a two-port head engine.
>
> Regards,
> Andy.
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