Lycoming rebuilding guidance part 2

[j-red]

I've got my parts off to Rick Romans to be inspected. Before calling the shop and looking foolish, or spending a bunch of money on replacement parts, i thought i'd run these questions by the forum for a little perspective. (o-360A1A)

Here goes:

What is the best way to clean the engine case? I'm planning on walnut blasting the outside, then dish soap and hot water for the inside. Is it mandatory that the case be painted/alodined?

I was aware that the tappets need to be reinstalled in order, but failed to anticipate that half of them would fall out all over the work bench when i split the case. So... they're all being re-polished. Anway, what i don't know is are the oil hydraulic units matched to the tappets or just flow matched as a unit? What I mean to say is that i have all the hydraulic units together as they originally were, but didn't label which tappet each one came out of.... Do i need to have them rebuilt, or am I ok just cleaning them and reinstalling them in the "new" tappets?

Similar issue with the piston pin "caps". Are the pin "caps" matched to the pins (i.e. do they need to go back on the exact same cylinders they came out of? I ask because i damaged one cap getting the pin out due to carbon buildup, and at least one other cylinder's pin caps got mixed up with this one's. I don't see the caps for sale separately, so i imagine i'm going to be buying at least one new pin, but don't know if I now need 2 because the caps are so specific...


There is quite a a bit of lead buildup on the piston tops. I'd like to clean them without having to remove and possibly destroy the rings (they only have 500 hours on them). Any suggestions?

Thanks in advance.
Jon

[mahlon_r]

Hydraulic units are not normally matched to the tappet bodies. You say the tappet bodies are being polished...be careful with that, the cam interface surface is not flat and if you "polish them" with out keeping the radius on the interface surface ....instead of saving them you are ruining them! And if you use them like that, you will definitely have a cam lobe failure down the road a piece.
Personally, I would not reuse the piston pin plugs.
You can scrape the lead and carbon off the piston domes with a gasket scraper if you want to.
Good Luck,
Mahlon

[lr172]

Originally Posted by mahlon_r

Hydraulic units are not normally matched to the tappet bodies.

The plunger assembly (i.e. hydraulic units) is actually two parts. Those two parts are a close tolerance, matched set. That might me what your thinking of. they don't come apart unless you pull them apart.

Larry

[j-red]

Originally Posted by mahlon_r

Hydraulic units are not normally matched to the tappet bodies. You say the tappet bodies are being polished...be careful with that, the cam interface surface is not flat and if you "polish them" with out keeping the radius on the interface surface ....instead of saving them you are ruining them! And if you use them like that, you will definitely have a cam lobe failure down the road a piece.
Personally, I would not reuse the piston pin plugs.
You can scrape the lead and carbon off the piston domes with a gasket scraper if you want to.
Good Luck,
Mahlon

I'm definitely not going to polish them myself. Maybe that's not even the right term. I sent them out for overhaul, but since there was no sign of pitting or corrosion, i assumed they would just get a polish similar to the crank journals.

[aerhed]

They will actually get reground. Yes, you can move lifter assemblies between tappet bodies. The pushrod sockets should stay with their respective lifter assemblies. If you look at a socket base and the top of it's lifter you can see why. Are you starting with a fresh cam? If you use a fresh cam you should always have fresh faced tappets, and if you use fresh tappets you should use a fresh cam. If you look closely at a new cam you will see the lobes have a slight slope to them. That's what rotates the tappet. Those two surfaces, tappet face and cam lobe are the whole ballgame right there.

[tim2542]

Re: cleaning the case, how many hours on it? If you are overhauling the engine the case almost certainly needs serviced. Look at the parting line between the main bearing saddles for fretting on those surfaces. If you see any fretting there the case needs to be reworked and probably should be anyway if it has any significant hours on it.
Leave the carbon on the piston tops, the engine won't care and it will run cooler. Focus on cleaning the ring lands of carbon deposits and do so without leaving any scratches. It will prove time consuming and I don't know any magic potion to make it easy.
Tim Andres

[BillL]

I would listen to Mahlon regarding - lifter bodies, and well. . . anything aviation engines.