[Healeys] AH100 v's A90 Engines.

[John Harper]

Alan

Other than fittings, such as the oil filter extension, rocker cover and
other external items  the engines are virtually the same. As you say there
is a difference in the number of bolts holding the distributor. Austin
raised this from one to two just about the time that the first 100 was
introduced. This also applied to other large 4 cylinder engines such as the
A70 Hereford.

Very early 100 might have only one bolt but very late A90 Atlantics might
have two. There is also the possibility that a reconditioned gold seal 100
engine might be delivered with just a single bolt fixing. There is an
Austin Service Journal publication showing how to drill an extra hole in
the distributor two hole fixing plate but this also needs a small amount
cut out of the distributor casing to allow the bolt to be tightened. The
alternative for an early A90 engine is to fit the earlier Lucas distributor
but this can involve other issues.

Best regards

On 9 August 2018 at 16:39, Bluehealey <bluehealey at gmail.com> wrote:

> Team.
>
> I have both an AH100 and an A90 engine sat side by side on my garage
> floor. It is known that the AH100 was developed to take advantage of the
> A90 Atlantic mechanicals and therefore I assumed that the A90 and AH100
> engines were essentially the same.
>
> When externally comparing these two engines there is a minor difference
> between them that surprises me. The AH100 distributor mounting base on the
> block has bolt holes tapped into bosses each side of the distributor hole.
> The A90 has a single boss and a single tapped hole.
>
> This indicates to me that the AH100 engine had its own block casting at
> the very least, and perhaps other variations too.
>
> Could someone advise if there any other significant differences between
> the AH100 and A90 engines?
>
> Many thanks.
>
> AlanB
>
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-- 
Best wishes

John Harper

AHC UK 100 Register Secretary
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