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Making a 0-235 C2C into an L2C

M

mbarker

Registered User
Anchorage, Alaska
Hi folks
I have a Lycoming 0-235 C2C that I am rebuilding for a homebuilt, and thinking of putting L2C pistons/rings in it.
I know some folks have done this --- wondering if anyone on the forum has experience in it?
Ups or downs? ---- pitfalls?
The C2C pistons and rings are crazy expensive, plus looking for a bit more "easy" power.

Would love to hear your thoughts.
thanks
mark
 
Looked into this for a C1 conversion, no pitfalls that I found. There is an STC to do this for Grumman airplanes. The case will have to be machined for 7/16" cylinder corner studs, be sure to use the L2C wrist pins and bolt them on, Jim
 
Hi Cruiser
thanks ----
I was looking at just putting the L2C pistons and rings into my current C2C. From the TSDS and Lycoming part numbers and info, it looks like the engine cases and cylinders are the same (except of course the motor mount).

The C2C has a 6.75:1 compression ------- the L2C has a 8.5:1 compression --- and the F2A has a 9.7:1.
There is even a bit of a discussion about taking L2C pistons and "shaving" a bit off the top for a bit lower compression, or some folks limit the MP gauge.

I was just wondering what others thoughts are about it all.
thanks
mark
 
Now that I understand your question I guess I don't know if there are any pitfalls. Did the L2C cylinders have 7/16" corner studs for a good reason or not? That's what experimenting is all about.
 
I recall reading somewhere about someone using automotive pistons. I can't remember if it was a O-235, or O-290. I'm sure it was this forum where I read it, perhaps a search would help you find it. I've found several instances where automotive pistons and rings cross-reference. Maybe someone here could tell you where to start looking?
 
Howdy
I did spend some time searching the forums and found some old discussions --- most didn't have a clear resolution --- and kind of asking the same questions I asked. ie., folks looking for info and advice.
After a morning of phone calls I have now found some other stuff.
From Aircraft Specialties -
C2C --- piston, ring set --- $950 per cylinder
L2C --- piston, ring, wrist pin set --- $350 per cylinder
L2C --- complete cylinder assembly --- $1,200

Now also looking at F series 0-235 which gives 9.5:1 compression.
I also keep hearing about the automotive (usually Ford) pistons that will work, but I have no info on part numbers and ring sets, etc. I would love to hear more about that.
I am also going to post on a few other experimental forums and see what I find.
If you have info would love to hear about it.

thanks
mark
 
If you had the dimensions of the piston you decide you want, check with summit racing and they might be able to cross-reference you to an automotive piston of equal dimensions.

I found the thread I referred to earlier. Ross Racing Pistons has the forgings for 0-290 pistons. A call to them might possibly give you some info about 0-235 pistons.
 
Last edited:
And now from another forum I find that possibly the L2C did have 7/16 studs. And that there is an STC for the conversion. SA00985CH but of course I can not google up a copy. More phone calls tomorrow try and figure it all out. Unless other folks have more info.

Also found that possibly Lycoming pulled the F series due to them coming apart in the 1500 hour range ---- but again conversation from another forum.

Interesting Stuff
Mark
 
http://precisionengine.home.mindspring.com/2plstc.htm Here is a brief overview of the STC I referenced, SA00985CH. I would guess that the L2C piston and rings would go into a C cylinder with no issue but note that the STC requires modification of the C case to 7/16" thru studs and cylinder hold down corner studs, your call, after all you are experimental.
 
mbarker said:
And now from another forum I find that possibly the L2C did have 7/16 studs. And that there is an STC for the conversion. SA00985CH but of course I can not google up a copy. More phone calls tomorrow try and figure it all out. Unless other folks have more info.

Also found that possibly Lycoming pulled the F series due to them coming apart in the 1500 hour range ---- but again conversation from another forum.

Interesting Stuff
Mark
Click to expand...
Just realized that in between my starting this response (and my wife calling me to do some stuff for her...) and finishing it, someone else posted much of the information.

STC SE00988CH is held by Bill Scott (2200 Airport Rd, Owensboro, KY 42301). His website is here. He and Carol (his wife and partner) do great work - very meticulous(!), and he is one of the most knowledgeable guys around when it comes to Lycoming engines.

The website references two STCs for O-235 powered Grumman AA-1 airplanes. One is for the engine itself (SE00988CH), and the other is to use that engine in the Grumman AA-1 airplanes (the one you referenced - SA00985CH). The website seems to indicate the two STCs together cost $500 (look here), but I suspect Bill would sell you the one to upgrade your engine separately. It would probably be worth a call to discuss your plans with him.

Here's a "summary" of the info from his web site that is pertinent to the SE00988CH engine STC:

SE00988CH allows for the modification of the original O-235-C2C from 6.7/1 compression ration to 8.5/1 compression ratio. The modification of the original O-235-C2C engine requires that the crankcase be modified by the installation of 7/16" crankcase thru bolts and cylinder corner studs. Per STC minimum fuel grade is 100LL, and the fuel tanks must be placarded for its use. Auxiliary Data Plates must be installed on engine.

 
Thanks folks for all the help ----- I must need more coffee --- after chasing the issue around for a bit, I decided to look in the parts book and of course saw that the L series engines do have the 7/16 studs. And then found the other info on the STCs. I am going to call Bill Scott today, and Precision, and see if they will chat about my plan.

What I would like to do is simply put the L series pistons in the C2C and get a bit more power. But if it take modifying the case --- and if that is a big deal, I might stick with what I have. I am also going to see if it would then require different cylinders (since bigger studs) ---- and also if I can get the work on upgrading the studs done locally.
I will let folks know what I find ---- thanks for the all the help.
mark
 
Any follow up? I have an O-235C1 (experimental) and would like to use the L2C pistons as well. I might also be interested in using the higher compression pistons. I think the issue they had was detonation. If I use 100LL, a P-mag electronic ignition, and monitor engine with an EIS, I wonder if that would be "safe" to go with the higher compression pistons?
 
I'm exploring this option with the C1B in my PA-22-108 - does anyone have information regarding such a swap for this engine?

If so, are there issues with being able to continue using mogas and/or is there a requirement to swap the propeller?
 
I’m working a DER project to use Bills STC on a C1. Yes, you need to change thru studs and corner studs to use the L2C cylinders. For Experimental, it’s up to you if you want to take the chance with your existing studs, Bill is very protective of his STC, and I had to sign an NDA to get the data to use for the DER approval.

Keep in mind that the stud set will set you back over $1000, and you still need to have the case machined.

The next issue is the propeller. If you are running a 76AM-2 prop, you can’t use it on an engine with over 6.75:1 compression, so you will also be looking for a new prop and spinner.

I was going to look into this for my engine, but just found some used pistons that I can clean up and use. I really didn’t want to go with an M74DM prop given the cost and adding another 9 lbs, so I’ll stick with the 6.75:1 compression until I decide to go to an O-320.


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