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  #1  
Old 11-21-2019, 05:15 PM
Flash Flash is offline
 
Join Date: Sep 2018
Location: Boerne, TX
Posts: 30
Default O-320 piston upgrade help

I have an O-320 H2AD that when rebuilt had 7:1 pistons put in, instead of the stock 9:1 pistons. The engine has the original cylinders. I am wanting to put in higher compression pistons to achieve more HP. Pistons, rings, rods and gaskets, cylinders honed, what other parts/considerations should I be addressing for this engine specifically or overall? Not trying to super mod it but I have read many threads where people say not to go above 9.5:1 but others say 10:1 work just fine. Any info on this is greatly appreciated.

Scott
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  #2  
Old 11-22-2019, 09:02 AM
smokyray's Avatar
smokyray smokyray is offline
 
Join Date: Jan 2005
Location: TX32
Posts: 1,847
Default Short answer, mo HP!

Quote:
Originally Posted by Flash View Post
I have an O-320 H2AD that when rebuilt had 7:1 pistons put in, instead of the stock 9:1 pistons. The engine has the original cylinders. I am wanting to put in higher compression pistons to achieve more HP. Pistons, rings, rods and gaskets, cylinders honed, what other parts/considerations should I be addressing for this engine specifically or overall? Not trying to super mod it but I have read many threads where people say not to go above 9.5:1 but others say 10:1 work just fine. Any info on this is greatly appreciated.

Scott
Hey Scott,
The H2AD despite all it's bad press is a great bargain engine and best of all it's a Wide Deck 0-320. This means the case through bolts and cylinder base attach points are strong enough to allow up to 10:1 compression (vice a max 7:1 for an ND). The higher comp pistons rods and rings are interchangeable in stock cylinders but a noticeable difference in performance with higher comp. When my Airboat engine builder friend JR rebuilt my 0-320E2D for my RV4 I chose the 10:1 option (per his recommendation) as I like efficiency and HP, of which I got both with the higher comp pistons. I chose aftermarket Airboat racing rods, (shot peened) pistons and rings. We also matched the pistons and rods to within a half a gram and ground the crank and balanced it also. Additionally, JR flow matched the cylinders.*

The engine runs very strong, electric smooth and actually burns a bit less fuel as well as temps staying the same across the board, Electronic IGN also helps with a bit extra HP. JR recommended I start running 100LL as I was previously using 89 octane Non E Mogas. (The Airboat bros run a 75/25% Non E MoGas/100LL mix in 10;1 setups). Additionally I had to buy a new prop as the "new" 0-320 was putting out an estimated 175HP, a definite improvement.

High Comp? Good call. IMHO
V/R
Smokey

PS: *Kenny at LyCon in CA is the best flow match expert on the planet IMHO.
PSS: Non E Mogas site www.puregas.org

Last edited by smokyray : 11-22-2019 at 10:18 AM.
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  #3  
Old 11-22-2019, 11:03 AM
Flash Flash is offline
 
Join Date: Sep 2018
Location: Boerne, TX
Posts: 30
Default

Smokey,
Awesome info! I had read similar but only from me searching forums. Nothing first hand. I have already started doing research on props in case this upgrade was viable for my engine. logistically for me using anything other than 100LL is difficult right now so keeping that won't be an issue. I have electronic ignition on one mag and a slick on the other. For me, upgrading this engine seems like a no brainer to get possibly 20-25 extra hp for a very reasonable price. My engine only has about 350 hours since it was overhauled and it runs great! I may eventually hang a bigger motor on the plane but for me, it is baby steps.

You said you all ground the crank. Is that required or can a just do a plug and play with the pistons rods, rings and gaskets?

Thanks for the intel Smokey!

Cheers
Scott
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  #4  
Old 11-22-2019, 01:33 PM
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Low Pass Low Pass is offline
 
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Make sure you have the right (more robust) piston pins. Some low CR engine pins have a thinner wall.
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Last edited by Low Pass : 11-22-2019 at 01:35 PM.
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  #5  
Old 11-23-2019, 08:41 AM
Red Mtn flyer Red Mtn flyer is offline
 
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Location: Carson City, NV
Posts: 89
Default

Ly-Con has ceramic- coated pistons available in the 10:1 ratio - and others, no doubt... You'll want to do the whole assemblies from the same sourcing, to address the wrist pin strengths, etc.
A true 'top' overhaul includes everything down to the rod bearings, IMHO.
2 things: A. with 10:1, flow porting, fuel injection, EI, etc., they can get your 320 to 200 hp. [and now the flames start - well, the dyno runs don't lie. Period.] B. There is a concurrent parallel thread that points out the more experienced among us tend to stay with more 'stock' configurations, going for more cubics to get the higher hp if necessary. Why? Because that has worked, and we aren't in the business of rebuilding our engines for every race.
Having said that: there are circumstances where the higher compression choices make sense for a longevity- focused engine -- but there ARE operational trade-offs. I wouldn't consider running one without full- boat engine monitoring, including fuel flow and air-fuel ratio... and you won't operate them in exactly the same way as 'stock'. Given the cooling issues demonstrated in the RV community, you have another whole field of 'cooling dynamics' to master.
AND the real key is the 'feedback loop' end of that monitoring system: how much have you studied the subject? It takes years of focus, and learning from the real masters. Operator's choices generate the range from 0 SMOH bone- stocks that are shelled out in 7 hours, to moderately tweaked IO-540s whose major components measure within spec on tear- down after 3600 hrs.

Short version: if you want to climb in, turn the key and go [what i think of as a "consumer" approach] -- DON'T. if you are a techie/ mech type, willing to pay for your choices with pre- study and post - mistakes -- go for it, but get the stuff already proven from somebody who has already built the learning curve.
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A&P; RLSA - A,G,W/S Falco F-8L
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  #6  
Old 11-23-2019, 08:45 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Low Pass View Post
Make sure you have the right (more robust) piston pins. Some low CR engine pins have a thinner wall.
+1

I would be confident that your original pins were the thick wall variety, but the P/O could have put the thin walled versions in (they are std with teh 7.0 pistons) with the lower comp pistons. Best to confirm. I don't recall the wall thicknesses, but I suspect you can find them online.

Larry
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  #7  
Old 11-23-2019, 09:08 AM
Flash Flash is offline
 
Join Date: Sep 2018
Location: Boerne, TX
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Quote:
Originally Posted by Low Pass View Post
Make sure you have the right (more robust) piston pins. Some low CR engine pins have a thinner wall.
Brian, Thanks for the heads up.
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  #8  
Old 11-23-2019, 09:38 AM
Flash Flash is offline
 
Join Date: Sep 2018
Location: Boerne, TX
Posts: 30
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Quote:
Originally Posted by Red Mtn flyer View Post
Ly-Con has ceramic- coated pistons available in the 10:1 ratio - and others, no doubt... You'll want to do the whole assemblies from the same sourcing, to address the wrist pin strengths, etc.
A true 'top' overhaul includes everything down to the rod bearings, IMHO.
2 things: A. with 10:1, flow porting, fuel injection, EI, etc., they can get your 320 to 200 hp. [and now the flames start - well, the dyno runs don't lie. Period.] B. There is a concurrent parallel thread that points out the more experienced among us tend to stay with more 'stock' configurations, going for more cubics to get the higher hp if necessary. Why? Because that has worked, and we aren't in the business of rebuilding our engines for every race.
Having said that: there are circumstances where the higher compression choices make sense for a longevity- focused engine -- but there ARE operational trade-offs. I wouldn't consider running one without full- boat engine monitoring, including fuel flow and air-fuel ratio... and you won't operate them in exactly the same way as 'stock'. Given the cooling issues demonstrated in the RV community, you have another whole field of 'cooling dynamics' to master.
AND the real key is the 'feedback loop' end of that monitoring system: how much have you studied the subject? It takes years of focus, and learning from the real masters. Operator's choices generate the range from 0 SMOH bone- stocks that are shelled out in 7 hours, to moderately tweaked IO-540s whose major components measure within spec on tear- down after 3600 hrs.

Short version: if you want to climb in, turn the key and go [what i think of as a "consumer" approach] -- DON'T. if you are a techie/ mech type, willing to pay for your choices with pre- study and post - mistakes -- go for it, but get the stuff already proven from somebody who has already built the learning curve.
Ben,
thanks for all of the info. After Smokey's post I spoke to Ly-Con extensively on this subject. They did an excellent job on educating me on this potential upgrade. My goal isn't to get a raped ape engine but more aligned to a hp boost until such time I hang more cubes (unless this fits the bill). The main reason I am considering this is in my research, it appears I have an excellent platform for this upgrade, a wide deck, one that had 9:1s previous, EI and full engine monitoring. I am a dork and very handy but just new to this. So a hp increase for a fairly reasonable price would be a great interim. You spoke to higher temps, I specifically asked about that and was told that it would be in line with my current temps, if not slightly less due to efficiency. IT is something that will definitely be right in the middle of my radar! Thanks again for the insight!

Scott
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  #9  
Old 11-23-2019, 09:40 AM
Flash Flash is offline
 
Join Date: Sep 2018
Location: Boerne, TX
Posts: 30
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Quote:
Originally Posted by lr172 View Post
+1

I would be confident that your original pins were the thick wall variety, but the P/O could have put the thin walled versions in (they are std with teh 7.0 pistons) with the lower comp pistons. Best to confirm. I don't recall the wall thicknesses, but I suspect you can find them online.

Larry
Larry,
Thanks! I talked to my mechanic buddy and he said we should go with new just to be sure anyway. Great info! Thanks
Scott
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  #10  
Old 11-24-2019, 09:46 AM
Red Mtn flyer Red Mtn flyer is offline
 
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Location: Carson City, NV
Posts: 89
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Flash -
good on you. My point was that it requires some thinking... not to discourage:
I have a Ly-Con IO-320EXP going into my Falco; flowed, 10:1 ceramics, PMag; turned 206hp at 2760rpm in the test cell [the math says 201 at 2700 governed prop speed]. Not looking for top speed, but rather climb rate increase.
Same like you: it makes sense for where the airplane/ ownership is; but the ops directions are going to require test carding.
[Rule of thumb: top speed increase mph = square root of horsepower increase. 's why some are breaking 1000hp in the Sport Class at RARA.]
__________________
Ben K.
A&P; RLSA - A,G,W/S Falco F-8L
50 yrs of flight and counting
Dues paid 2017, 2018, 2019

Last edited by Red Mtn flyer : 11-24-2019 at 09:51 AM.
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