Hi Patrick,
My BJ8 is a poofteenth over 60 thou oversize, using DW Cosworth Pistons.
It is the most conservative bore Healey I've ever owned....
I know of at least a dozen 3 litre blocks that were bored to 3.3 litres.
Usually Volvo pistons. Ask Eric Rudd, John (in Epping, Blue Bj8) or many
others...
My bugeye was 68mm bore, using Hillman Imp pistons. That's like over 180 thou.
Had an engine with a 948 crank, and an 1100 crank in that spec. With an 1100
crank, that's 1220cc.
Never had a 100/6 spec 2.6 litre engine.
But my 2.6 litre 100/4 was just over 3 litres.... That's way over the 60 thou
recommendation...
Depends on the specific block, but if you are talking say 70 or 80thou -
assuming you can buy those pistons- don't lose a minutes sleep. Just crack
test before, and check for porosity after, and locktite impregnate after if
you think you might lose another minutes sleep...
It's all cheaper in the ultimate scheme of things.
Especially to keep an original block, and hold your hand over your heart.
BMC was conservative. Factory tolerances were measured in production cars with
wooden rulers.
Ok. They probably didn't use wooden rulers. But you get my point. Decades of
men have been over boring BMC blocks by a factor or three times more than BMC
recommended...... You are probably going 10 or 20 percent more - not 3 times
more.....
Best
Chris
Sent from my iPhone
On 29/04/2013, at 9:57 PM, "Patrick & Caroline Quinn" <p_cquinn@tpg.com.au>
wrote:
> G'day
> Perhaps someone out there might be able to assist.
> The engine from the Quinn Austin-Healey (not the soft touring car with
> wind-up windows and a glove box, but the other one) is with the engine
> rebuilder.
> It is an early 2.6 litre C-series with a smooth sided crankcase. The
> standard bore of which is 79.375mm and according to a well known parts
> supplier cannot be bored out past +60 which would take it to 80.875mm.
> When I removed the cylinder head I thought the pistons looked a little big,
> and sure enough the bores were measured today and they are 3.281 or
83.34mm.
> This is standard 3000.
> Number 2 cylinder is scored and will probably need to be sleeved.
> Has anyone had an experience at taking a 2.6 engine past its 'permissable'
> limit?
> Hoo Roo
> Patrick
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