[Healeys] Sedan engine hp ratings

Andy Thorp bce257 at yahoo.co.nz
Fri Nov 21 02:44:04 MST 2014

Hi Guys,

I wonder if anyone could help me out with the hp rating of the 2912cc sedan

The 'mk1' engine of the 1959 A99 was rated at 103hp, an increase of only one
on the 2693cc A105 (BN4) engine and it appears to only differ in bore size to
the smaller engine. The 'Mk2' engine in the 1961 A110 sedan then produced
120hp with only a 0.1 point increase in compression and revised exhaust cam
timing per the Mk2 Healey engine. Both engines look identical to the BN4 lump
with the gallery head and twin H4s so it isn't the DMH head giving the extra
performance. The valve sizes are the same, compression almost the same, carbs
the same... Could adding 22 degrees to the exhaust timing really make 18 more


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