Subject: Re: [Healeys] Maximum 2.6 Bore

From: Chris Dimmock <[email-masked]>
Date: Mon, 29 Apr 2013 23:24:27 +1000

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" <[email-masked]>
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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From: Alan Seigrist <[email-masked]>
Date: Mon, 29 Apr 2013 21:24:34 +0800

Patrick-

The consensus on the list over the years was there was enough meat on the
2.6 to bore out to std 3.0.  You may want to check the wall thickness, if
done well you may be able of over bore a bit to take out the score.

Alan

On Monday, April 29, 2013, Patrick & Caroline Quinn wrote:

> Patrick Quinn
> Sydney, Australia
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From: Michael Salter <[email-masked]>
Date: Mon, 29 Apr 2013 09:25:05 -0400

Hi Patrick,
I have had experience of a 2.6 liter engine having been bored to 3000 bore.
It doesn't work. In one of Geoff's books mention is made of the block
casting having been changed to produce the larger cylinder bore. The
attached photos are of the remains of a 2.6 that had been bored to 83.34mm.
It ran well....for about 20 minutes..
A customer had purchased it as a "race ready" engine...

Michael S

On Mon, Apr 29, 2013 at 7:57 AM, Patrick & Caroline Quinn <
[email-masked]> wrote:

> http://autox.team.net/mailman/options/healeys/[email-masked]
>
>

-- 
Michael Salter

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From: Michael Salter <[email-masked]>
Date: Mon, 29 Apr 2013 09:42:38 -0400

Although others may have had different experiences I can definitely say
that mine with a 100/6 block bored to 83.34mm was not good...
The "race ready" engine (100/6 block bored to 2912cc) that we purchased
"grenaded" spectacularly within the first 20 minutes of running.
In "The Story of The Big Healeys" Geoff mentions in the second paragraph of
the chapter on the development of the 3000 that "a new cylinder block
casting had to be made for the 2912 c.c. unit".
If any one would like to see some pictures of the results I would be happy
to send them!!

Michael S

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From: Michael Salter <[email-masked]>
Date: Mon, 29 Apr 2013 18:51:00 -0400

For those with further interest in this subject I have published a short
blog article here <http://www.netbug.net/blogmichael/?p=1130>.

Michael S

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From: Derek Job <[email-masked]>
Date: Tue, 30 Apr 2013 09:06:48 +0100

Great article Mike.

I'd like to provide a link to it in my 100-Six Web Site if that's Ok

Derek
www.healeysix.net

On Mon, Apr 29, 2013 at 11:51 PM, Michael Salter <[email-masked]>wrote:

> http://autox.team.net/mailman/options/healeys/[email-masked]

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From: "Patrick & Caroline Quinn" <[email-masked]>
Date: Tue, 30 Apr 2013 18:31:37 +1000

G'day

I think it's an open ended question.

The engine in the BN3/1 is exactly the same C-series engine that Geoff
Healey was provided with by BMC way back in 1954 and was initially so
disappointed in as far as power goes. It is a C26W engine which means that
it was originally built for a Wolseley car. He then undertook quite a few
experiments on the engine in the car, including fitting triple dual throat
SUs before he was satisfied with the power. Sadly today I do not have those
SUs nor can I afford to have them built.

However when I bought the car back in 1974 it was fitted with standard 3000
pistons and I have all the service records going back to 1965. So sometime
between 1954 and 1965 it was bored out to take the pistons and ran perfectly
well through to Easter 2011 when it lost part of No 2 piston which means it
was not the fault of the block.

Watch this space.

Hoo Roo

Patrick Quinn

Sydney, Australia

From: Derek Job [mailto:[email-masked]] 
Sent: Tuesday, 30 April 2013 6:07 PM
To: Michael Salter
Cc: Patrick & Caroline Quinn; [email-masked]
Subject: Re: [Healeys] Maximum 2.6 Bore

Great article Mike. 

Derek

www.healeysix.net

On Mon, Apr 29, 2013 at 11:51 PM, Michael Salter <[email-masked]>
wrote:

Michael S

[email-masked]

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From: Austin Healey <[email-masked]>
Date: Tue, 30 Apr 2013 12:19:00 +0200

I dont have a 2.6 block at hand, but I think according to my pictures, it
is possible to optimize the piston wall thickess by offset boring. Maybe
thats the trick they also used. I am sure it can make a great difference.

Gergo

2013/4/30 Austin Healey <[email-masked]>

> I dont have a 2.6 block at hand, but I think according to my pictures, it
> is possible to optimize the piston wall thickess by offset boring. Maybe
> thats the trick they also used. I am sure it can make a great difference.
>
> Gergo
>
>
> 2013/4/30 Patrick & Caroline Quinn <[email-masked]>
>
>> G'day
>>
>>
>>
>> On Mon, Apr 29, 2013 at 11:51 PM, Michael Salter <[email-masked]
>> >
>> wrote:
>>
>> http://autox.team.net/mailman/options/healeys/[email-masked]

[email-masked]

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From: Oudesluys <[email-masked]>
Date: Tue, 30 Apr 2013 12:27:32 +0200

Op 30-4-2013 10:31, Patrick & Caroline Quinn schreef:
> including fitting triple dual throat
Well, you can always fit triple Webers/Dell'Orto's to have your 6 throats.
Kees Oudesluijs
NL

-

[email-masked]

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From: Alan Seigrist <[email-masked]>
Date: Tue, 30 Apr 2013 18:32:47 +0800

Yes, I think as long as you aren't racing these cars, and the bore out is
carefully mic'd and wall thickness checked, you can bore out to 2.9L
without too much problem.  I wonder if you can simply resleave to 2.9L?

Oddly enough I have my A90 with one cylinder bored to 20 over, and the
others all at STD.  runs beautifully smooth, albeit it only produces 85HP
so I'm not worried about it.

Alan

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From: "Patrick & Caroline Quinn" <[email-masked]>
Date: Tue, 30 Apr 2013 21:38:08 +1000

G'day

I don't know why anyone would want to bastardise the very first six-cylinder
Austin-Healey built by fitting it with Webers or Dellortos.

The next thing will be that you will suggest that I straightened the concave
firewall.

Hoo Roo

Patrick Quinn
Sydney, Australia

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
On Behalf Of Oudesluys
Sent: Tuesday, 30 April 2013 8:28 PM
To: [email-masked]
Subject: Re: [Healeys] Maximum 2.6 Bore

Op 30-4-2013 10:31, Patrick & Caroline Quinn schreef:
> SUs before he was satisfied with the power. Sadly today I do not have 
> those SUs nor can I afford to have them built.

[email-masked]

---

From: Austin Healey <[email-masked]>
Date: Tue, 30 Apr 2013 22:39:36 +0200

Hi Michael,

Although again: I dont have a 100/6 engine at hand to set a clear idea, but
I would say that offset boring can make _some_ improvement. If You look at
the siamese bores (1-2, 3-4, 5-6), if You do one slightly forward and out,
and the other backwards and out, it can leave some extra wall between the
two bores. Maybe just enough to save the day. Or not... if You are unlucky
then You loose whatever You do. Sometimes this is the fact.

Gergo

PS: with Minis it is a great route to go on if a 1275 is bored over 1340.
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