[Healeys] Healey 100 4 cyl (A90 actually but same) Engine Bore Q

John Harper ah at jharper.demon.co.uk
Sat Dec 22 07:48:05 MST 2007


I believe that you would be disappointed with the result if you did not 
make a proper job of this. If the engine were mine I would bite the 
bullet and get the engine out. You might unfortunately find more that is 
wrong such as a cracked crank but is better to discover the whole story 
now than wonder how your engine might stand up to continued use.
There must have been a reason for a bent pushrod !


>We pulled the pistons to check the bore and all looks pretty good except #4
>had a broken compression ring (no scoring on the cylinder).  The cylinder
>bores all look very good with no scratches or scoring.  The bore
>measurements appear pretty much standard except for #4 which is about 15
>thou over.  See the table below.  The Standard bore measurment for the motor
>is 3.4375".   All the pistons weigh and measure well so I will reuse them.
>My question is with #4 a little over, can I just hone the cylinders and buy
>a set of standard rings and put them on?  I also assume I want to hone the
>The compression on this engine is only 6.9:1 (standard for the A90) and I
>really don't want to bother replacing a bunch of stuff.  The old lady just
>toodles about town so a very soft rebuild is all that is necessary.
>I don't want to rebore the cylinders as it will be a huge pain for me to
>pull the block, and even bigger pain for me to find someone in Hong Kong
>that can bore the motor properly.

John Harper

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