A65 Cylinder experts? Rocker arm bosses.

[Robert Lees]

My new cylinder has no bushings in the rocker arm "ears" (bosses). See photo.

Is this normal? My contacts in Oregon, at the engine rebuild, say "the rocker shaft we have is far smaller than the holes in the cylinder head boss"

Harrison (who supplied the cylinder say) "Yes, it is normal that there are no rocker arm bushings. The rocker ears were not worn out, therefore they did not need bushed"

Are there two diameter rocker arms for the A65?

As an aside, I note that the 1973 Continental SB M73-13 (see attachment) addresses how to bush these.

Thanks for any help/advice.
Rob

[Edwin Otha]

Re: A65 Cylinder experts? Rocker arm bosses.

Only one size rocker arm shaft. Check the size to see if the boss' were reamed and the bushings not installed.
EO

[mikeg]

Re: A65 Cylinder experts? Rocker arm bosses.

A-65 (A series) only has one size rocker shaft. The A series cylinder is bushed only as a repair. Never seen one worn.
Mike

[mikeg]

Re: A65 Cylinder experts? Rocker arm bosses.

A-65 (A series) only has one size rocker shaft. The A series cylinder is bushed only as a repair. Never seen one worn.
Mike

IS THERE AN ECHO :-)

[astjp2]

Re: A65 Cylinder experts? Rocker arm bosses.

There should be only about .003 at the most clearance. I would have to look up the spec but its the same as the O-200 and c series engines. If you have about .050 or more, its missing a bushing and needs to go back. tim

[Guest]

Re: A65 Cylinder experts? Rocker arm bosses.

Rob,

I placed a photo of an A65 cylinder that I have.

It has no bushing. The rocker are shaft measures about .607" o.d.

When I use a caliper to measure the boss width at the center of the hole it measures about 1.28" - 1.30".

Scaling those gets; 607/1280=.474 to 607/1300=.466

Scaling your picture, hole size to boss width is 182/397=.458

Not sure that helped as much as I hoped it would but the hole does not seem to be too big based on that.

Someone needs to compare the hole i.d. to the rocker shaft o.d. of .607" or call Harrison and ask what they think the i.d. should be.

Dave

[Ragwing nut]

Re: A65 Cylinder experts? Rocker arm bosses.

Only one diameter shaft. Usually the outers are the problem. Stick the shaft in each end boss and check to see if it feels loose or tight. If it feels loose, use a bore gauge to check diameter is within limits.

[Mark Bowden]

Re: A65 Cylinder experts? Rocker arm bosses.

Yes, latest Conti overhaul manual says bushings are only for repair. Shaft in boss service limit is 0.007". New parts min. clearance is 0.0002 and max is 0.0017". Prior to inspection of rocker shaft they are to be polished with crocus cloth moist with kerosene and then polish with dry crocus.

If bushings are required for repair, line ream bosses and then line ream bushings. Bushing PN is (22949) is a replacement part only for repair of worn bosses. Boss line ream callout is 0.703" +/- 0.0005"; bushing line ream is 0.6094 +/- 0.005".

Emailed you the manual. Glad you have parts.

Mark

[astjp2]

Re: A65 Cylinder experts? Rocker arm bosses.

The big question is why is your mechanic not giving you measurements that you can call the cylinder ship with? A simple caliper will tell you what you need to know. Tim

[mikerice]

Re: A65 Cylinder experts? Rocker arm bosses.

Hi Rob,
As I recall, when we bought complete refurbed cylinders from Gibson, the rocker shaft assembly was NOT included. We had to reuse the ones from the old cylinders. I will double check though, to see if we have any extra rocker shafts.

Mike

[Robert Lees]

Re: A65 Cylinder experts? Rocker arm bosses.

Thanks for everyone's responses.

Harrison tell me that the bores for the rocker arm are OK. I am awaiting confirmation from my Oregon A&P/IA of this.

I am expecting to re-use the rocker arms and all valve train gear.

Thanks again,
Rob

[Robert Lees]

Re: A65 Cylinder experts? Rocker arm bosses.

Thanks for everyone's responses.

Harrison tell me that the bores for the rocker arm are OK. I am awaiting confirmation from my Oregon A&P/IA of this.

I am expecting to re-use the rocker arms and all valve train gear.

Thanks again,
Rob

[Guest]

Re: A65 Cylinder experts? Rocker arm bosses.

Hi Rob,

How did things work out with your cylinder?

Dave

[Robert Lees]

Re: A65 Cylinder experts? Rocker arm bosses.

Dave,
I'm awaiting confirmation that all is actually OK with the rocker arm ears, thanks for asking .

I'm in the situation of having very little control over my engine. I hope the FAA system is robust enough to improve my confidence. (This engine only had 120 hours since rebuild, albeit about 4 years ago). Also, it's been a while since I dealt with small Continentals, I tend to deal with large Lycomings and M14P's now).

To be fair, I'm in no great hurry. Hangarage is paid for (at EAA Chapter 617 at Prineville, who have been just brilliant).

Having spent all this money, I have a "Grand Plan" to do another Tour next year, from Oregon to Nevada, southern Utah, Arizona and other places. At some point nearer the time I'll be seeing if anyone wants to join me.

Rob