What are these plugs for?

Mark Burns · #1 05-04-2007, 09:40 AM

I've noticed on Superior engines they have plugs where the tappets and lifters are. What are they for?

They are not on my Lycoming.

Photo from Jeffsrv-7A.com ( I added the arrow)

Jamie · #2 05-04-2007, 09:52 AM

I'm not sure but I believe those are only there on the engines with roller tappets.

My xp-360 doesn't have 'em.

Radomir · #3 05-04-2007, 09:56 AM

Only on roller tappets.. those are set screws that prevent the tappet from rotating (since orientation matters)..

Mark Burns · #4 05-04-2007, 09:57 AM

Ok, that makes sense.

Thanks guys,
Mark

az_gila · #5 05-04-2007, 10:52 AM

That's interesting...

I guess these extra plugs (set screws) are about the only way that a Roller Tappet engine can be identified easily from the exterior...

gil in Tucson

Brian Vickers · #6 05-04-2007, 11:26 AM

I noticed a number of the beautiful new engines I see posted are not painted. Only the steel cylinder barrels are painted. Is there a protective coating that is not apparent from the photographs? Maybe a light alodine dip? Just going with bare metal? Gorgeous looking new power plants you guys have on your projects by the way. Those beauties belong in a corner of your living room.

Thanks in advance for your reply.

Sincerely, Brian Vickers
RV4 finishing

scard · #7 05-04-2007, 11:35 AM

Hmm. I have a roller tappet O-320 that doesn't have those set screws.

Jamie · #8 05-04-2007, 11:51 AM

Hey Brian:

The XP-360s are alodined and according to Superior provides more than adequate corrosion prevention (here we go again with the whole primer thing.

). Paint from Superior at the time of my purchase was $500.00 so I decided against it since it's only an aesthetic thing. Personally I enjoy the look of the alodined surface as it makes the fine casting and machining work on the engine stand out.

mahlon_r · #9 05-06-2007, 10:26 AM

Quote:

Originally Posted by scard

Hmm. I have a roller tappet O-320 that doesn't have those set screws.

Only Superior uses the set screws to orientate the roller tappet. Lycoming uses the shape of the tappet body, so if your engine is a Lycoming roller tappet engine you won't have the set screws.
'The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk.?

vlittle · #10 05-06-2007, 11:33 AM

Quote:

Originally Posted by mahlon_r

Only Superior uses the set screws to orientate the roller tappet. Lycoming uses the shape of the tappet body, so if your engine is a Lycoming roller tappet engine you won't have the set screws.
'The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk.?

Yup, the Superior (Theilert) roller tappets are circular in cross-section, whereas the Lycoming ones are square in cross section (all according to HRH Bart Lalonde at AeroSport).

The set screws prevent the Thielert tappets from rotating.