[Healeys] Forged pistons

[Bob Spidell]

FWIW, I bought forged (metric) Omega pistons from DWM for my BJ8 a few 
years ago, and they came with the admonishment:

"To keep the compression ratio as high as possible they are machined in 
height to the uppermost limit and this means, if the engine block has 
been skimmed at any time, the piston top may have to be skimmed to suit. 
This is standard practice with all good engine builders and therefore 
should not pose any problem."

Why length 18 thou longer I don't know; maybe 'stock' pistons were 
purposely cut short to allow for manufacturing differences in the block 
or head?

Bob

On 8/19/2025 10:46 PM, Roger Grace wrote:
>
> Late model BJ8
>
> In the process of changing out the block (because of a porosity 
> coolant leak into the oil drain back).
>
> Managed to find a Wolseley 110 saloon block of similar vintage. I do 
> believe that it was original and had not been previously opened. 
> Everything seemed the same and interchangeable with my original bock. 
> Well almost ...
>
> While the engine is in bits decided to do some upgrades - pots re 
> bore, crank grind, balancing, new pistons etc. etc. Now discover that 
> the pots are about 25 thou shorter than the original. Any thought as 
> to reason ? I note that the Wolseley block had concave piston crowns. 
> Maybe to reduce compression for a saloon car and the block decked to 
> set the final compression ?
>
> To add to this problem decided to spring for a set of AH Spares forged 
> pistons. Surprise surprise the compression length is about 18 thou 
> longer than standard BJ8 pistons. These variances might seem trivial 
> but they are consequential. So now will likely have to machine the 
> forged piston crowns or as a last resort consider a block shim. All 
> rather painful !
>
> Any thoughts or ideas appreciated.
>
> rg
>
>
>
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