MAC 72 advice

[helipaddy]

Hi Guys
Ive a friend who is restoring a Bensen and is getting his 72Hp mac up and running again and am looking for advice on what to do to make the engine as reliable as it can be, also where new spark plugs can be got.

Any advice on mods to the engine to make it better after all these years would be much appreciated


Paddy

[Earthboundmisft]

Static display...

[C. Beaty]

Originally Posted by helipaddy

Hi Guys
Ive a friend who is restoring a Bensen and is getting his 72Hp mac up and running again and am looking for advice on what to do to make the engine as reliable as it can be, also where new spark plugs can be got.

Any advice on mods to the engine to make it better after all these years would be much appreciated


Paddy

Spark Plugs: Champion D9J, gapped to .012”

Remove military ignition harness and replace spark plug wiring with automotive type having solid copper conductor (don’t use carbon conductor wiring).

Retard ignition ~1/8 inch at magneto timing marks.

If 72 HP pistons, taper from crown to just below bottom ring to a depth of the labyrinth grooves (labyrinth grooves are intended to be flame traps to protect top ring but serve to trap and pack carbon, exacerbating seizure.)

Lots of other things that Pete Johnson remembers better than I.

[gyromike]

When I rebuilt mine I did away with the roller bearing cages on the rod journals and crank journals and went with a full complement of rollers. For the connecting rods there are a pair of thrust washers that are used to keep the rod centered when the cage is omitted. I can't remember which connecting rods I used, the "A" or "E" rods.

I also swapped out my original magneto with one of Rick Whittridges CDI units and eliminated ALL of my starting difficulties. I use the Champion 509 spark plugs which I believe are the modern equivelent of the D9J's Chuck mentioned.

My CDI conversion thread.

I think Rick carries all of the parts upgrades you'll need.

[helipaddy]

Thanks Guys,
Much appreciated.
Ill pass this info on, he is a long time helicopter pilot over here who flew the Bensen ages ago and wants to get it up and running as reliably as possible, he is under no illusions regarding the engine. Ill try to get pics of his restoration soon

Thanks
Paddy