Rocker Arms

[zav6a]

I took poor notes during dissasembly and am now confused.

Looking at the Lycoming parts manual, the parallel valve engines (O-320-B2A) should have identical intake and exhaust rockers. I find I have two part numbers:

69443D which have large oil discharge orifice essentially on the radius of the rocker shaft bore

and

68520 which have small oil discharge hole, lower on the arm, about half way from the shaft to the valve head.

The Lycoming O-320 parts manual lists neither of these numbers.

Anybody know which is the intake and which is the exhaust?

[zav6a]

Answered my own question. Found this:

: The question you asked is simple to answer, but could be somewhat difficult for a lay person to put his finger on, so I'm glad you asked. The part number that you found stamped on your rocker arm is a subassembly part number. In this particular case, when this part is completed, it becomes a part of finished part number 69444. The 69444 rocker arm was used as an intake rocker arm on several different models, along with the part number 74636 rocker arm, which was used as the exhaust valve rocker arm on these applications. Note: These were not interchangeable with one another.

I'd also recommend that you or your maintenance facility take a look at Lycoming Service Instruction No. 1454 dated June 5, 1991, for clarification on this issue.

[az_gila]

Duane... My parts manual shows different part numbers for inlet and exhaust rocker arms.

Intake 69444

Exhaust 74636

The manual is PC-203-2 dated Dec. 1985

This Q & A found on the web might help... credit to GANews...

QUESTION: We are working on a Lycoming IO-360b1b. The rockers are stamped 69443d. This part will not show up on our parts list. Is it the intake or the exhaust? I believe the rocker with the oil squirt hole pointed to the spring is the rotater. HELP!

Mike Habermehl
Mt. Sterling, Ky.

ANSWER: The question you asked is simple to answer, but could be somewhat difficult for a lay person to put his finger on, so I'm glad you asked. The part number that you found stamped on your rocker arm is a subassembly part number. In this particular case, when this part is completed, it becomes a part of finished part number 69444. The 69444 rocker arm was used as an intake rocker arm on several different models, along with the part number 74636 rocker arm, which was used as the exhaust valve rocker arm on these applications. Note: These were not interchangeable with one another.

I'd also recommend that you or your maintenance facility take a look at Lycoming Service Instruction No. 1454 dated June 5, 1991, for clarification on this issue.

Of course, good ol' Lycoming does not have that SI on their web site... I wish they would get into the 21st century...

hope this helps

gil in Tucson

[az_gila]

Duane.. we both found the same thing...

However, there is still a discrepancy in the parts manual callouts...

Which manual are you using?

gil A

[zav6a]

My parts book is a PC 103. The latest date I can find in it is Feb, 76.

On a second look, may parts maniual does provide a different part number for the exhaust. It does not match my part number either but I presume that the subpart/assembly part number issue explains that as well (Parts manual number is 74636 in my book).

[az_gila]

Originally Posted by zav6a

My parts book is a PC 103. The latest date I can find in it is Feb, 76.

On a second look, may parts maniual does provide a different part number for the exhaust. It does not match my part number either but I presume that the subpart/assembly part number issue explains that as well (Parts manual number is 74636 in my book).

Is that the generic O-320 one?

Mine is PC-203-2 and covers O-320 B&D hi-compression, wide flange models...

I think in 1974 it was all narrow flange....

gil A

[zav6a]

It is generic. O-320, IO-320 and LIO-320. But it does have WCF part numbers.

[flyingriki]

I have the same problem and the OP back in '06. I see Paul McBride's explanation of the intake part numbers. Has anyone ever found a comparable explanation for the exhaust?

My book calls for a 74636 for my O-320 and I got back from the overhauler 68520.

I already got back completely wrong rockers (for angle valve IO-360) from them the first time so am concerned about what they sent now. Talked to a guy at Lycoming and he doesn't know anything about the issue....

Don't forget to write down the P/Ns for everything you ever send off for inspection and overhaul. I won't make that mistake again.

[G5Driver]

Riki,

I had the exact situation and part numbers. Download Lycoming Service Instruction SI 1454A. It gives a good explanation of proper rocker arm location.
Basically the rocker with the larger hole closest to the pushrod is the intake rocker arm. The other rocker has a small oil hole located about 1/2 way down that lines up with and sprays oil on the exhaust valve for cooling.
These rocker arms are NOT interchangeable as per the Service Instruction. The newer, latest and greatest rocker arms can be interchanged however, and have identical part numbers.
Hope this helped,
Ross

[flyingriki]

Ross,
I, and the Lycoming rep, can't find part number 68520 which is what I was sent. This one isn't mentioned in the SI. Book calls for 74636 and I know it was superseded by a generic part that can be used for either location.
Thank you though!