Jabiru cooling plenums ignition leads

[Paul davenport]

Not wishing to reinvent the wheel . Has anyone modified the rear of their Jabiru cooling plenums to allow the ignition leads to come out easily . If you have do you have any pictures

[Old Koreelah]

Paul there was a discussion on Jab plenums a few years back. Some preferred the older type with plug leads poking thru holes in the fibreglass. Others liked the newer ones which covered the whole lot, with all plug leads coming thru a rubber grommet at the back.

 

I built aluminium versions of the second type; they lift off vertically, leaving the plug leads in place.

[Paul davenport]

Thanks OK I was hoping to get some pictures of an original plenum modified so I don’t have to do too much R&D myself

[Kenlsa]

You need to have the rear hole as tight around the bunch of leads as possible to avoid air bleed.

Best way to remove the plenum is to cut the O ring thru on one area, so you can wrap the cables. Also place a cut from the lead entry hole down thru the rear of the plenum to the opening at the bottom.

Then you can remove the O ring from the hole, slightly manipulate the cut to offset the edges and slide the leads down and out, and then remove the plenum. Easy!

Reverse to replace the plenum.

I have seen holes made larger so the cap will come out one at a time but then there is always too much leakage thru the hole. Not so bad for a gen 4 as they run cool but not so good for Gen 1 that has fewer fins.

The old style plenum with the exterior plugs are not as efficient as they should be, that's why the move early by Jabiru to the latest style.

You can be forever chasing cooler air with the early ones, needing cross over pipes, gull wings etc.

Ken

[Old Koreelah]

Paul sorry I'm not much help, but thinking laterally, why not fit Iidium plugs so you don't have to remove the plenum so often? I just had mine out for a look for the first time in nearly a decade.

[rendrag]

Sorry to sound stupid but could someone post a couple of photos of the options my (engine2965) has fibre glass air cowls with the spark plug heads sticking out through rubber o rings and the plug Ht cap pushed through Theo ring closing up the clearance.

Here in the uk where it is not so hot I have just fitted cooling pipes for the coils!!