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zav6a

Well Known Member
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?
 
Googled part number

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.
 
Some info

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
 
Manuals

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

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

Which manual are you using?

gil A
 
Rockers

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).
 
Later version

zav6a said:
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).
Click to expand...

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
 
Old Post - Same problem!

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.
 
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
 
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!
 
Riki,

You may want to exchange and have Lycoming send you P/N 17F19357 which would give you the newest rocker arms.
Ross
 
Thanks Al. I have that one. Was looking for the first version to see if there is some history there that would enlighten the subject. I've asked Lycoming for a copy and also the SB mentioned, No. 477, but haven't heard back. Will post results.
Thanks again!

Here's the AD involved but doesn't mention my part numbers:
http://www.yeeles.com/Reference/AD/Lycoming/87-10-06 R1.pdf
 
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Regardless of the part numbers. Make sure the exhaust rockers have the correct bushing with the annulus to allow oil flow to the exhaust valve. Check this by putting the rocker shaft in the rocker and blow shop air into the hole in the pushrod socket, insure that air comes out of the hole below the rocker tip. I have seen several cases where these were installed incorrectly by o/h shops, and more cases where the engine builder installed exhaust rockers on intake valves and vice versa (parallel valve engs)


Don B

RV - 9. Rebuild in Progress
 
Lycoming does it also

When I tore my 700hr lycoming re-man 0/360 apart for overhaul two of the cylinders had the rockers installed wrong, ie intakes on the exhaust.
Must have been a Friday or Monday engine! BTW the engine was torn down due to corrosion and storage time.
Tim
 
ANSWER

OK, here is the answer and it's too bad the original poster didn't figure this out a long time ago. Same question on other forums too!

It turns out the numbers that are easy to read on rocker arms are casting numbers. Since the intakes have casting numbers that closely mimic the part number it's not difficult to see how those of us that don't do this for a living get confused. Thank you Lycoming....

If you turn the rocker so that the back of it is facing you and the cup is to the left facing down, you can barely make out the part numbers hand etched (!) into the top of the radius on the half closest to you.....! Ridiculous I know but true. Sometimes it's so hard to see you have to put some dirty oil on it and wipe off excess then look through a magnifying glass but they are there.
 
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