Two Piece to One Piece Cam Shaft

[Steve Pierce]

Just put a straight O-320 together for a friend. We opted for a new cam and lifters along with new ECI cylinders. According to Lycoming service data you have to replace the accessory case when going to a single piece cam/gear because the slinger ring is different. I found that Divco who does all my crankcases can modify the accessory case from a two piece cam/gear to accept a one piece cam/gear. Cost was $160. Here are some pictures.

Original accessory case and slinger ring.
100_2484.JPG

Original two piece cam and gear.
100_2486.JPG

One piece cam not fitting original slinger ring.
100_2485.JPG

Modified accessory case.
100_2259.JPG

[Bultaco Jim]

What was the reason for going to the new style cam? Wider lobes - like the later O-235?

[Steve Pierce]

The only new cams being made are the one piece cam/gear. Too many unknowns on a recertified cam and din't want to have to do this again.

[Gilbert Pierce]

My experience working 23 years for a major diesel engine manufacturer indicates most "improvements" like these are actually cost reductions for the manufacturers. Less parts to inventory, less parts to assemble, less parts to inspect, less parts to assemble incorrectly.

The H model Lycoming engines with the intregal accessory housing is a classic exmaple of a cost reduction gone wrong. Given a choice of two independant magnetos or two magnetos being driven from one drive which would you pick?

[Bultaco Jim]

When I had to replace the O-235 cam, my IA told me about the new cams, with their integral gear and wider (better?) lobes. So I had to think about the whole acc. case change routine. I figured the original cam, with it's small lobes, lasted 40 yrs, and went bad from lack of use, so I opted to go for an Aircraft Specialties cam. I would have loved to have another option, like Steve's.
What problems have you had with rebuilt cams, Steve?

[Steve Pierce]

Myself personally none, however I know a few that have. That hardened surface is very thin. No way to know how much is gone and when it is gone you are in for a case splitting.

[mmoyle]

Just put a straight O-320 together for a friend. We opted for a new cam and lifters along with new ECI cylinders. According to Lycoming service data you have to replace the accessory case when going to a single piece cam/gear because the slinger ring is different. I found that Divco who does all my crankcases can modify the accessory case from a two piece cam/gear to accept a one piece cam/gear. Cost was $160. Here are some pictures.

Original accessory case and slinger ring.
[attachment=3:34kjzbtu]100_2484 (Medium).JPG[/attachment:34kjzbtu]

Original two piece cam and gear.
[attachment=2:34kjzbtu]100_2486 (Medium).JPG[/attachment:34kjzbtu]

One piece cam not fitting original slinger ring.
[attachment=1:34kjzbtu]100_2485 (Medium).JPG[/attachment:34kjzbtu]

Modified accessory case.
[attachment=0:34kjzbtu]100_2259 (Medium).JPG[/attachment:34kjzbtu]

Steve,
I just ordered all the parts to rebuild the O320A2B...included in that order is the one piece cam shaft. Can't see the pictures you list above...
Mark M.
Platinum, Ak.


Sent from my iPad using Tapatalk HD

[59pacer]

I'll most probably go to the new one piece cam at overhaul.
I looked at the accessory case on my O-320-B2A, and the number in the case casting at the top is 71649, whereas the Lycoming parts list says it should be 72498 (and that's been superceded through to the one piece cam). I've looked at everything I can find, and the number 71649 does not appear anywhere.
Similarly, the accessory case on the O-320 E2 in my biplane has 76096, which is different to the Lyc parts list, and I can't find any reference to 76096 anywhere either.
What am I missing here?

[Steve Pierce]

There are all kinds of configurations for the accessory case but I only know of the two different configurations for the cam shaft, the one piece integral gear and the two piece removable gear. I think you are covered but you might call Lycoming Technical support to verify.

[59pacer]

So far I've established as best I can, that the numbers on the accessory housings are casting numbers, and the castings then are machined to suit the accessories.
The O-320 parts catalog lists a series of different p/ns for the different accessory case configurations for the different engine models.
I can't find any way of establishing a part number for the one I have. That might generate an issue here during the overhaul and upgrade to the integral gear camshaft.
I'd like to be able to reference a part number during the overhaul, but I can't get anywhere on that so far.
Lycoming aren't forthcoming. Divco aren't answering my emails.
Any thoughts on how I can find out a p/n anyone? Is there in fact a p/n to be found?