Morris Minor Owners Club

bmcecosse wrote:Which is why it generates less power than say a Ford engine of the same capacity and era.

Why does it make a difference if you never get two cylinders using a shared port at the same time?

All done! Surprisingly I found that several valves were too tight; I would have expected the opposite (yes, the engine was cold). I wonder if that might have had anything to do with my excessive fuel consumption (23 mpg in town, mainly small trips though).

alex_holden wrote:Why does it make a difference if you never get two cylinders using a shared port at the same time?

The inlet side of things has the mix trying to change direction in the head in a hurry (3&4, then 2&1), which IIRC causes problems that 4 port heads don't have.

Pascal wrote:All done! Surprisingly I found that several valves were too tight; I would have expected the opposite (yes, the engine was cold).

Wouldn't have been the exhaust valves by any chance?

They would be tight because of slight recession setting in. There is normally v little wear in the valve train - and so the gaps rarely open up. If they do - it's usually by a LOT - indicating severe wear of a cam lobe and it's matching follower. The remedy then is obvious.
And yes - the stop-start motion of the gases in the shared inlet (and to a lesser extent in the shared exhaust port) is the basic power limiter in the A series. Especially as it pulls twice rapidly on the first port(21) then the second port(34) - the first port flow coming to a (relative) standstill while the second port runs and then vice versa.