Cracks - O-320 vs. O-360

[petehowell]

Hello - Alex P. and I had been discussing cracks in the baffles and FAB top plate. Looking to get a bigger sample size for FWF cracks.

I have 850 hrs on my O-320 set up on the -9a. No cracks on the FAB top plate or baffles. I know of 3 O-360 birds locally that have had cracks in the baffling and/or the FAB top metal plate, some with very low hours.

While I'd love to claim superior craftsmanship, too many people have actually seen my plane. I think it might be engine size and vibration specific, but need a bigger sample size than 4.

So how about you post your engine, hours, and if you have found cracks. For fun, toss in if you have had a prop balance.(mine has been balanced)

I had trouble with the poll feature - So if anyone can set this up as a poll - that would be great.

[Mel]

O-320, 1075 hrs on FAB, 1st 300 hrs with 7:1 compression, 775 with 9.5:1, no cracks to date!
I also would note that the prop could relate to these cracks due to "smoothness rating". I have always run wood or composite props. First with Sensenich wood and then to Catto 3-blade.
I strongly suspect that the shaking during starts and stops with the heavier metal and/or constant speed props will contribute to this cracking.

[petehowell]

Good call Mel - I have a Hartzell CS prop, but let's toss that in the data mix. Thanks.

I realize this will all still be anecdotal, but we might see some patterns.

[Greg Arehart]

at 336 hours on IO360 8.5:1 compression,
I replaced L rear baffle (#4 cyl, left side) with 0.063 piece because of cracking in the corner bend; I have also added doubler to the rear baffle on that side where it was starting to crack (both effects supposedly from the weight of the oil cooler)
Also replaced FAB plate, which was cracking.

Prop was balanced early in its life.

Note that I also had the engine failure last December. Don't know if that contributed to the FAB cracks. I was seeing cracking in the baffles before the failure and had added some doublers but replaced the assembly when the airplane was down for engine repair.

cheers,
greg

[Ironflight]

1360 hours on a mattituck TMX-360, carburated, Dynamically balanced BA hartzell...no cracks in baffles or FAB top plate.

[Vlad]

O320, carb, aftermarket larger oil cooler, FP Catto 3 blades. Prop hasn't been balanced.

[Mark Albery]

I recognise that picture above. Almost identical on RV-8 TMX-IO360 at 350 hours. Prop not balanced.
Also had #2 exhaust flange fail at about the same time.