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Exhaust dry tappet clearance

Mlew

Member
Hi All,
I have a core 0-320 E3D from a 1978 Beech 150 that my A&P and I rebuilt.
Divco yellow tagged all the case work. Aircraft Specialties did the Crank, Cam, tappets, lifters, socket, push rods, rocker arms all yellow tagged. Purchased 4 new Lycoming cylinder assembles from Aircraft specialties.

All intake clearance are about mid .50, perfect with -13 or -14 pushrods.
All Exhaust clearance were over .150 with a correct range of .28-.80.

Sent the exhaust rocker arms back to Aircraft specialties to find 4 with a larger toe left after grinding. The exhaust arms have the oil hole in them.
Small improvement.

Bought the longest push rods the -15 and improved to about .110 clearance.
Lycoming recommended buying new rocker arms.

Aircraft specialties was nice to let me borrow a new rocker arm to check clearances. Improved to .100 clearance.

Checked with Lycoming to be sure I have the correct cylinder and I do.

Again, just the exhaust clearance. Thoughts? Had 3 A&Ps just shaking their heads.
Thanks,
Mark
 
Exhaust valves

I’ll ask, did you install the caps on the end of the exhaust valves? Without them even the longest push rods will be short. Good luck
 
Hmmm, I have asked this question before and now I am doubting myself. I see what looks like a cap under the rocker arm and its held in with keepers and does not move. Is this the end of the valve stem or the cap?>

Its part number -11 on my parts manual. So this cap would go over the end of the valve stem and its removeable, correct>?
 
http://www.aircraftspecialties.aero/cap-valve-stem-exhaust-rotator-20-per-pack-17c19386/


This is the cap / (exhaust valve rotator) As I recall if you can see the valve retainers, you are missing the cap. It fits over the end of the valve stem, the only thing holding it in is the rocker arm, they can fall off pretty easily with the rocker arm removed.

The cap just sits on top of the end of the valve stem. If you can see the the two valve retainer clips, the cap is not installed. When the cap is installed, it almost completely fills the OD of the spring retainer cap. The cap is around an 1/8" thick, so this would explain why you are consistently .100+ off. Kinda sad that 3 different A&P's couldn't figure that out. It just sits on top with no method of securing it. It is possible that Lycoming does not include these parts with their cyl kits and the installer didn't know they were required.
 
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My thanks to you all! I think this is the problem. They were not on the new cylinders nor included with the cylinder kit. I will order 4 of them and report back!
Thanks so much!!
 
Got the exhaust caps in and that was my problem!!! Dry clearance now where it needs to be. My thanks to you all!!!
 
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