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Best plan for 160hp upgrade... o-320

punkin

Well Known Member
I have an o-320 E2A with about 1950 hours total and 540 since it was majored with NuChrome cylinders and 7:1 pistons. Oil use is very low, not scary low, but pretty minimal...about a quart every 30 hours depending on how hard I run it XC. Based on the timeframe it was majored, I don?t think it was chromed due to problems, it because at that time it was the ?thing? to do.

So I could...:

1.) pull my cylinders, send to engine shop to inspect and hone, and install 8.5:1 pistons and the upgraded wrist pins (if not equipped) and reassemble. I?d get 160hp and cylinders and lower end with about 540hrs on them. This assumes nothing is wrong and the engine shop can put a surface on the Nuchrome walls. (Likely well Under $2k)

2.) pull and replace with Superior Millennium complete cylinders and pistons and have new cylinders and a lower with about 540hrs. (Around $4300?)

3.) pull and replace with Lycoming factory nitrided cylinders (a little more, maybe closer to $4800)

What would the folks who know better do?

I?m looking to eek every last bit of takeoff performance out of my airplane, and constant speed is not an option. A little more power can?t hurt, right?
 
1 quart per 30 hrs. is very low consumption. Chances are VERY good that oil consumption would be worse after an overhaul.

150-160 hp? Look at a ruler that is divided into 1/16".
Look at the 1" mark. That is 16 or 160.
Look at the 15/16". That 1/16 mark is what you would be gaining.

Not hardly worth it unless you need an overhaul anyway, which, in my opinion, you do not.
 
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No fair!

But Mel, you’re making 175! I am really enjoying offairport stuff in my -6, but lack some of the oomph that I’d like to have for getting in the air quickly. If I repitch my GA prop to super climb, I have to be super careful to throttle back and not over speed.

I know I don’t NEEEEEEED it, but I’ve pretty much made this plane into a keeper, and I will fly the value out of the change eventually.

What if I went to 9:1...? Then I’d be at what, 165? Then I’m at what, like 12% instead of 8%? :D
 
But Mel, you’re making 175! I am really enjoying offairport stuff in my -6, but lack some of the oomph that I’d like to have for getting in the air quickly. If I repitch my GA prop to super climb, I have to be super careful to throttle back and not over speed.
I know I don’t NEEEEEEED it, but I’ve pretty much made this plane into a keeper, and I will fly the value out of the change eventually.
What if I went to 9:1...? Then I’d be at what, 165? Then I’m at what, like 12% instead of 8%? :D

My point is: I was due for an overhaul anyway. My engine was at 2800 hrs. I would never had done anything on a 540 hr. OH burning a quart of oil every 30 hrs!
Of course it's your engine and your money. It's a free country. Just expressing MY opinion. Your opinion is the only one that really counts.
 
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Thanks Mel...

The problem is, I really value your opinion, and the knowledge and experience you bring to the forum...so it would be much easier if you would tell me I?d be thrilled with 10 more horsepower and how much I?d be glad I spent the time and money to change it. :D
 
Spend the money on a constant speed prop?

Just my opinion, but would certainly give you the extra push (pull) you are looking for.

Ron
 
Scott, though I see Mel’s point, I went from 8.5:1 compression pistons on my o320 with dual mags to 10:1 compression pistons with dual sds electronic ignition and noticed a good improvement. Picked up at least 300ft/minute climb and 4 knots. I did the piston swap with only 100 hours smoh on the engine. It is a fairly in depth job but is not hard just time consuming. Plan on around 30 hours from start to finish plus machining time. My current project is a rv10 and I plan on using the high compression pistons/electronic ignition/electronic fuel injection from the start.

Bill
 
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The problem is, I really value your opinion, and the knowledge and experience you bring to the forum...so it would be much easier if you would tell me I?d be thrilled with 10 more horsepower and how much I?d be glad I spent the time and money to change it. :D

The thing that Mel forgot is that rate of climb is proportional to EXCESS horsepower- not total horsepower. So if it takes (for example) 75 HP to maintain level fight, you have 75 HP that can be converted into climb. 10 added to 75 is a much bigger percentage than 10 added to 150....... feel better - 10 HP is noticeable!:D
 
I have an RV6A with a 160HP 0-320, and Sensenich fixed pitch prop that has a 2600 RPM red line (I don't remember the pitch off hand.) It has a solid crank, so no option for a hydraulic operated constant speed prop. I typically see 2250 RPM and 10.3 GPH on take off roll. I'm guessing I'm making only 130 HP or so. I am not complaining about my performance, but it sure does hurt to leave unusable horsepower under the cowling. I operate in the Midwest (500 feet elevation), so it has plenty of performance for my operations. I have only 600 hours on this fine running engine and will keep it as is, but will certainly look at a constant speed prop option with any engine replacement.
 
150-160 hp? Not hardly worth it unless you need an overhaul anyway, which, in my opinion, you do not.

While a change from 150hp to 160hp represents about 7%, the difference is not linear. Based on the performance charts, the power gain at lower RPMs is about 15%. For fixed pitch propeller configurations, the low end gains are significant at take-off RPMs.
 
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I wish!

Just my opinion, but would certainly give you the extra push (pull) you are looking for.

Ron

I would have been all over C/S, even looked at some of the electrically controlled options...my engine can?t been equipped with a hydraulic c/s. Honestly, that would be all and exactly what I need. Pitch for getting off the ground, then pitch for cruise after climb... with variable pitch, my horsepower would be adequate, as I have played with my (compromise) ground adjustable prop and it?s capable of getting off the ground quickly...unfortunately, I?m at like instant redline in cruise config, and have to back the throttle way back.

Right now, I?ve got pitch set to ?ok? for both takeoff and cruise. I figured a handful more horsepower might be just enough to make the compromise a happier one...get a little more pickup at t/o without giving up more at cruise.
 
So...

Scott, though I see Mel?s point, I went from 8.5:1 compression pistons on my o320 with dual mags to 10:1 compression pistons with dual sds electronic ignition and noticed a good improvement. Picked up at least 300ft/minute climb and 4 knots. I did the piston swap with only 100 hours smoh on the engine. It is a fairly in depth job but is not hard just time consuming. Plan on around 30 hours from start to finish plus machining time. My current project is a rv10 and I plan on using the high compression pistons/electronic ignition/electronic fuel injection from the start.

Bill

You?re saying even if I?m crazy, at least I?ll have company?
It sounds like the guys who have gone from 7:1 to 8.5:1 have seen similar improvements to what you saw. That would be a nice boost. I don?t know if I want to go to 9:1 or stay easy at 8.5:1....
 
You’re saying even if I’m crazy, at least I’ll have company?
It sounds like the guys who have gone from 7:1 to 8.5:1 have seen similar improvements to what you saw. That would be a nice boost. I don’t know if I want to go to 9:1 or stay easy at 8.5:1....

If I WERE going to do it, I would go ahead and go to 9:1. I went to 9.5:1 and if I had it to do over, I would go to 9:1.

As far as cylinder preference goes, I prefer the Lycoming nitrided ones. BUT I would stick with your cylinders unless there's another reason to change.
 
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You’re saying even if I’m crazy, at least I’ll have company?
It sounds like the guys who have gone from 7:1 to 8.5:1 have seen similar improvements to what you saw. That would be a nice boost. I don’t know if I want to go to 9:1 or stay easy at 8.5:1....

I would definitely do it again! Pulling the cylinders are not too bad but I’ve built a few of these engines in the past so I know my way around them. If you got a repair manual and cylinder wrenches I say go for it. ��
 
If I WERE going to do it, I would go ahead and go to 9:1. I went to 9.5:1 and if I had it to do over, I would go to 9:1.

As far as cylinder preference goes, I prefer the Lycoming nitrided ones. BUT I would stick with your cylinders unless there's another reason to change.

Hi Mel I?ve seen you say this in the past and I?m curious why this is? When I went from 8.5:1 compression pistons to 10:1 I did get a very slight increase in vibration but mostly at rpms below 1200. During flight I don?t notice anymore vibration then before. My cht?s didn?t go up and my oil temps went up by around 5-10 degrees but nothin that was cause for concern. My fuel burn in cruise actually went down slightly once leaned.

Bill
 
Hi Mel I?ve seen you say this in the past and I?m curious why this is? When I went from 8.5:1 compression pistons to 10:1 I did get a very slight increase in vibration but mostly at rpms below 1200. During flight I don?t notice anymore vibration then before. My cht?s didn?t go up and my oil temps went up by around 5-10 degrees but nothin that was cause for concern. My fuel burn in cruise actually went down slightly once leaned.
Bill

Just my preference. Vibrations in the lower rpm ranges. The engine just is not quite as smooth as before. I'm pretty picky about things like this. As an avionics technician, I know what vibrations do to avionics. Of course, shortly after my overhaul, I went to the 3-blase Catto prop and most all of the roughness went away. Have I ever mentioned how much I LOVE my Catto?
 
Just my preference. Vibrations in the lower rpm ranges. The engine just is not quite as smooth as before. I'm pretty picky about things like this. As an avionics technician, I know what vibrations do to avionics. Of course, shortly after my overhaul, I went to the 3-blase Catto prop and most all of the roughness went away. Have I ever mentioned how much I LOVE my Catto?


Thanks for the response Mel.

Bill
 
You?re saying even if I?m crazy, at least I?ll have company?
It sounds like the guys who have gone from 7:1 to 8.5:1 have seen similar improvements to what you saw. That would be a nice boost. I don?t know if I want to go to 9:1 or stay easy at 8.5:1....

Keep in mind that the generally accepted limit for being able to burn mogas or autofuel is 8.7:1, if that will ever be a factor.
 
There is another option.

You say you live in Colorado and it sound like you are using your RV-6 like a Super Cub.

One option is to change out your prop with a climb prop. This will let you put out more HP on takeoff and get out of some of the holes you might be landing in.

Of course, the tradeoff is that you will be on the redline doing 65% power at 8,000' DA.

This might be a simpler and better option for you, at this time.

You also might be able to climb better than if you bumped up your engine to 170 hp but bolted a cruise prop on it.
 
Which has me curious...

Keep in mind that the generally accepted limit for being able to burn mogas or autofuel is 8.7:1, if that will ever be a factor.

There are 8.5 pistons for the parallel valve engines and 8.7 for angled valve...why? Seems like a deliberate thing to do...not 8.5, not 9, but 8.7...but no 8.7 for parallel valve? Or is it some weird design consequence of the piston shape?
 
Lose some weight!

Not you, the plane... I built a 160hp RV8A that weighed 975 lbs. That's WITH all the fairings, wheel pants, and even an autopilot! By doing that I was able to pitch my prop for cruise and still saw 1700 fpm with two on board and 1/2 fuel. The plane cruised at 205 mph/10500ft/2700rpm. My HP/lb ratio is the same as an O360 powered RV8 at the factory spec weight!.
 
Not you, the plane... I built a 160hp RV8A that weighed 975 lbs. That's WITH all the fairings, wheel pants, and even an autopilot! By doing that I was able to pitch my prop for cruise and still saw 1700 fpm with two on board and 1/2 fuel. The plane cruised at 205 mph/10500ft/2700rpm. My HP/lb ratio is the same as an O360 powered RV8 at the factory spec weight!.

And probably handles better!
 
I should start with me...

Re: weight... it weighs 1094.5 lbs with 6qts of oil. (Weighed 3 times on digital scales borrowed from my EAA chapter) That?s with a 10lb landoll ring and prestolite starter, and still a 15.6lb ballast weight ?all added by me for CG purposes. Why so tail heavy? I don?t know, I didn?t build it. But it 3 points much nicer since I addressed the cg issues. I also have 23? tundra tires on 6? wheels that I think add about 10lbs over stock.

I think I may have to accept the speed ?damage? I?ve done with my big tires and no wheel pants, and pitch my prop more for climb.

I still would like the extra power. Because power. I do run Mogas as often as I can, so that is a somewhat consideration...

Also, I look a lot better at 200lbs than my current 223.5 lbs, so there IS that,
 
If you're interested in takeoff distance, power affects distance roughly linearly. 10% more power will shorten the distance by 10%.

Weight, on the other hand, affects distance much more than that. 10% less weight will shorten takeoff distance by roughly 20%

These are very approximate approximations, of course. But not bad guides.

Dave
 
What prop are you using? I am starting a major remodel of my 160hp -6 and will be using 10-1 pistons and dual pmags. I am getting 2170rpms static and 2670 rpms wot st 8000 ft now. My prop is a 3 blade 67x70 catto. Just wondering if i was going to need a repitch or new prop.

Thanks
Hank


Scott, though I see Mel?s point, I went from 8.5:1 compression pistons on my o320 with dual mags to 10:1 compression pistons with dual sds electronic ignition and noticed a good improvement. Picked up at least 300ft/minute climb and 4 knots. I did the piston swap with only 100 hours smoh on the engine. It is a fairly in depth job but is not hard just time consuming. Plan on around 30 hours from start to finish plus machining time. My current project is a rv10 and I plan on using the high compression pistons/electronic ignition/electronic fuel injection from the start.

Bill
 
What prop are you using? I am starting a major remodel of my 160hp -6 and will be using 10-1 pistons and dual pmags. I am getting 2170rpms static and 2670 rpms wot st 8000 ft now. My prop is a 3 blade 67x70 catto. Just wondering if i was going to need a repitch or new prop.

Thanks
Hank

Hi Hank

I’m using a Sensenich 70x80 metal fixed pitch prop and on takeoff roll I’m Seeing 2350rpms. At 8000feet density altitude I can turn over 2700 rpms; which I don’t recommend as the metal sensenich has a rpm limitation of 2600. The 70x80 is a cruise prop for the 160hp rv6a and by upping the compression and going to sds electronic dual ignition it’s a climb prop now. You will have to change the pitch of your prop most definitely, but it will be well worth it imho.

Bill
 
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