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O360-A2A, high compression

pilotea

I'm New Here
Hi

This is my first post, been reading the forum for years, and now it's my turn to ask a question :)

The O360-A2A has a solid crank, if changing to a higher compression, let's say 10:1, is the weakest link the crankshaft, rods or the wrist pins? As far as I understand the solid 360 crank is "beefier" and shouldn't have a problem running with higher compression? I found a source for higher compression pistons (can't remember the link), they recommended other wrist pins if the stock lycomings were used, but what about ECI wrist pins, are they better than the stock lycomings?

For those running 10:1, do you have any issues with detonation and what kind of performance (seat of the pants experience) did you have when you changed to higher compression?

Rgds
 
Contact ECI (now owned by Continental) regarding the wrist pins, but I think they are a copy of the Lycoming pins because they are interchangeable.

We have done a lot of research regarding knocking on Lycoming engines and found the worst case scenario to be high powered settings and low RPM, such as during takeoff with a fixed pitch prop from sea level with "high" compression pistons. I'm not saying you will have an issue, just that you should do your own research.

NASA and the FAA have published some papers on the subject. ECI may also be able to answer your questions.

Engine timing will also need to be adjusted to match your engine.

Welcome!
 
Lycoming

A long time ago some of the specialty shops were using the heavier IO 360 connection rods. I think that is no longer common. 10-1 is a non issue with 0 360. Reno people are running as high as 13-1. Lycon uses the lightest piston pins with 10-1 to save a bit of weight. I don't know what their reliability is with light pins.
In my long ago conversations with Monty Barrett the only issues with the hot rod engines was bearing wear when run hard for aerobatics with 10-1 compression. Bearings would be worn out in as little as 800 hours.
I may be able to recommend a source for quality 10-1 forged pistons, parallel valve 360's are same as 320.
 
I may be able to recommend a source for quality 10-1 forged pistons, parallel valve 360's are same as 320.

Looks like combustech's pistons are very good value, around 800 usd for 4 with piston rings.

http://combustech.com/Products/Lycoming Pistons.html

ASC1021FL

is the 10:1. The engine in question is a low time engine with ECI cylinders, around 180 hours. Engine is a narrow deck, I have no idea if that is a weaker block than the wide deck, can't find anything conclusive online.
 
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Engine timing will also need to be adjusted to match your engine.

Welcome!

Thank you very much.

I see you run dual p-mags, I currently run with one slick and one lightspeed (the version 1, about 18 years old, Plasma CDI). I have the timing set at 25 btc on the slick and 20 on the Lightspeed. I have a slight RPM drop if I turn the slick off in flight which makes sense considering the burn starts later in the cycle. Never figured out why the lightspeed has to be 20 when the slick is 25, if anyone can explain I would be gratefull :)
 
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Thank you very much.

I see you run dual p-mags, I currently run with one slick and one lightspeed (the version 1, about 18 years old, Plasma CDI). I have the timing set at 25 btc on the slick and 20 on the Lightspeed. I have a slight RPM drop if I turn the slick off in flight which makes sense considering the burn starts later in the cycle. Never figured out why the lightspeed has to be 20 when the slick is 25, if anyone can explain I would be gratefull :)

Have you checked the "real" timing on the LSE with an old school automotive timing light per Klaus' instructions?
 
I have a narrow deck O-320A with 10:1's and around 1000 hours on it.
I don't have a pic to post but have experienced one broken cylinder to case stud, and was told this is an issue with the narrow deck and 10:1's. The other issue I have had is the higher compression makes it more difficult to crank. Starting when below 40 degrees f starts to become difficult without preheating.
 
Be sure to check it with the MP line connected & disconnected at the RPM Klaus specifies. I've set up quite a few LSE ignitions, and often have to adjust the static timing to obtain the desired dynamic timing. It's also interesting to do the same on the mag timing.

The good thing about the LSE is once it's verified with the timing light you can forget about it; I checked mine last month and it's set exactly where it was in 1993.
 
Be sure to check it with the MP line connected & disconnected at the RPM Klaus specifies. I've set up quite a few LSE ignitions, and often have to adjust the static timing to obtain the desired dynamic timing. It's also interesting to do the same on the mag timing.

The good thing about the LSE is once it's verified with the timing light you can forget about it; I checked mine last month and it's set exactly where it was in 1993.

Still haven't worked out why the LSE must have a 20 degree timing when the mag has 25, if I turn my slick off in flight, I have an RPM drop , the idea of firing two spark plugs at the same time (as with two mags) must give a power advantage, I don't have that advantage at the moment., even in idle the RPM's goes down when on the LSE only, and according to the LSE instructions, I should have a higher RPM with the LSE. It runs smooth though.
 
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Still haven't worked out why the LSE must have a 20 degree timing when the mag has 25, if I turn my slick off in flight, I have an RPM drop , the idea of firing two spark plugs at the same time (as with two mags) must give a power advantage, I don't have that advantage at the moment., even in idle the RPM's goes down when on the LSE only, and according to the LSE instructions, I should have a higher RPM with the LSE. It runs smooth though.

With 10:1 you might want to retard the mag a few degrees and realize lower CHT's. A lot depends on how you fly it: high with low MP, low at high RPM and high MP, etc.

There are several Lyc models that were originally certified at 25*BTDC but later "suggested" the timing be retarded back to 20* BTDC. Someone more knowledgeable than me can advise if the 5* timing retard was a requirement via SB, or simply a bulletin or SI. Klaus is quite approachable on the timing topic if you e-mail or call him, but be prepared by carefully reading his instructions first and expect a pitch to dump the mag for a second LSE :)
 
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My 0360 in my 7 has 10.5 to one. According to Penn it has a beefier crank. I have e mag and p mag ignition along with fuel injection. It pulls HARD on take off especially at sea level. I have zero detonation issues and love the set up. Typical speed I see is 168knots tas at 9gph
 
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