Can someone point me to where I can find the STC instructions for a PPonk engine or have a copy they can share with me? I can find the STC record on the FAA website but that doesn't give much detail. I'll try getting in touch with Northpoint, but thought I'd try here since its a weekend and I have a little time to kill.

My 182 is flying fine with 1500 hours on the 470R but I am trying to decide what I want to do in the future. I got a quote to convert the 470R, which would require case milling and a new crankshaft. With that in mind, I'm thinking I may passively look for a 520 to covert and swap it out when the time comes. Sounds like the right engine may be a matter of pulling the fuel injection and external modifications only; Anyone know if a low time 520 could be acquired and converted without a full overhaul? Thanks

I supposed you "could" do that, but the real question is why?? If your gonna go thru the effort of an engine swap, why not start with a new motor?

The normal Ponk runs low compression pistons, so you'd would be pulling the jugs. Some want to keep the low comps because they want to run autogas, but most seek deviation to run the high (stock 520) pistons.

To answer your question, the big (although not so big) thing that gets changed for a 520 is the carb. This gets modified from the 470. You will also need to change the oil sump and the induction tube up front. You can use the three different sizes, but to avoid icing, most have been sourcing the smaller one. There are also a couple of small other things like the alt mount/engine leg etc... All of this can be either found used or taken off your 470-R.

Look for a D or an F to start with. You can also change most 520s to a D/F with a little work.

I understand why and am empathetic, but the only rub is now that Steve Knopp has sold the STC, the price has doubled. All in all, its a great way to go.

Very unlikely.....


On the surface, I might have agreed with big... and do agree with his thought process on questioning the merit. But assuming that your airplane has never had an O-520 of any flavor in it, you will have to come up with an STC to attach that engine to the airframe.

I doubt any STC holder is going to sell you the paper to hang an unknown onto your ship. When Steve owned the Pponk STC, and probably now with the new owners, there were only certain shops that were authorized to build these engines. So while it may be physically possible, it is probably not going to happen.

As has been discussed before, building a legal engine that makes 'rated' power, and building a high quality / performance engine with exceptional balancing and flow characteristics are two vastly different things. For some people 'trade standards' are ok, for my money shooting for the bare bones minimum to get by with would be a shame given the time and effort your going to spend to get there.

Done right, you will need carb work regardless of engine age, you will need an exhaust regardless of engine age, and there will be a plethora of external components that you will change because they will have wear or need fitting to the new engine. Why would the internals (arguably the more important pieces) be any different?

Lastly, all it takes to own an airplane engine is money. It takes a little education to treat one such that it provides longevity. Buying a chronologicaly low time 520 is no guarantee that the prior owner had any clue as to how it should be treated. It may only have a couple hundred hours on it, but it only takes a couple minutes to harm one for good. That is a gamble I'd not take without splitting it, and at that point your married to replacing many if not most of the consumables that you would in an overhaul, so a little machine work on the way to a '0' SMOH seems like a no brainered....


Take care, Rob

There is a Canadian stc in Ontario that allows a 520 d or other models plus any prop for 185 last time i know was 2000$ can.could get u information just private message if any one wants

Points taken....I kinda figured it may not be the best idea but thought I'd at least check into it. My best bet, when the time comes, is probably to just have the 470 I have now either overhauled stock or PPonk'd. Since the cost of a runout 520 looks to be in the 12-15k range, buying one and having it overhauled doesn't seem to make sense financially.

For me, the thought process was a derated stock 520 with low hours has to be better than the 26 year old 470 I have now. I have no doubt that a shop can make a smoother running, higher performance engine for 40-50k, but if I could be into a better engine than I have for half that, it might not be such a hard pill to swallow. I'd be comfortable doing the engine swap, externals and paperwork myself but Ill leave splitting the case to the guys who do it on the regular. I'd like to do an overhaul, but by time you add up all the mandatory replacement parts, I'd rather pay a bit more to have someone experienced do it with a warranty.

Figured this place would keep me in line. Thanks

Kenmore Air used to have a 520 conversion for the 180, which they used on all their 180s. I’m not sure what that conversion is all about, but a phone call can answer that question. At one point, I researched it and I THINK it was a converted 520.

MTV

mtv wrote:Kenmore Air used to have a 520 conversion for the 180, which they used on all their 180s. I’m not sure what that conversion is all about, but a phone call can answer that question. At one point, I researched it and I THINK it was a converted 520.

MTV

Kenmore still has that STC and they’re still using it on the base 180s. It is basically an IO-520D with injection removed and a carburetor installed. It is only available for a fairly narrow window of airframes.

I just sent $3000 for two STC's (one for airframe and one for engine) to NorthPoint and am converting my O470K with a Phase 1 crankcase. Central Cylinder in Omaha is an approved shop that can mill the crankcase for the 520 cylinders so I hauled it down in person (140 miles). I have been running an oil pump off an O470U with spin on filter so that should be good. I am going to need different connecting rods also according to Dan at Central Cyl. Pretty sure you can just pull the injection off a TSIO-520 and install without full overhaul because I remember reading that O and N that converts T210's to turbines would sell that engine for Pponk STC. I might convert the O-470U on the 180K I just got and will be interested to find out if the connecting rods in it would have to be changed.

Update on my Pponk project. Going to have to get a 520 oil pump since it has deeper gears. Also, may or may not be able to modify my connecting rods for the next size bigger rod bolts. I think mine are from 1956 when the engine was new so betting they won't work for Pponk but crossing my fingers.

Selling to an individual wasn't a probem for us, but they won't send you the instructions until you purchase the STC. Even then, the instructions are pretty vague.

We were in the similar boat. An O470R that was at 1500 hours, running fine and no problems. We knew we'd have to "ruin" a good engine with all the mods and didn't want to have any downtime so we bought an lO-520-D core with all the right stuff as the base. We also had them guarantee a yellow tagged case and crank in the event our core didn't pass recertification.

Should be built in the next month or so and I can tell you how it panned out...

mtv wrote:Kenmore Air used to have a 520 conversion for the 180, which they used on all their 180s. I’m not sure what that conversion is all about, but a phone call can answer that question. At one point, I researched it and I THINK it was a converted 520.

MTV

They have one STC that converts an O-470 to a 520, but I believe that it only applies to the O-470U, which is a slightly different animal than most of the other 470s.

Scolopax wrote:

mtv wrote:Kenmore Air used to have a 520 conversion for the 180, which they used on all their 180s. I’m not sure what that conversion is all about, but a phone call can answer that question. At one point, I researched it and I THINK it was a converted 520.

MTV

They have one STC that converts an O-470 to a 520, but I believe that it only applies to the O-470U, which is a slightly different animal than most of the other 470s.

No.

The Kenmore STC uses a converted IO-520D. I installed them when I was a line mechanic at Kenmore.


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Speaking of PPonk, can anyone shed any insight on whether 90+ Mogas Ethanol Free can be used in a PPonk with 8.5 Cylinders.

I've done some homework on Octane and Compressions and can't find a real reason [other than STC requirements and Testing] why 90+ Ethanol Free can't be run in a PPonk.

It would seem that a STC could be created if someone is willing to go through the testing. I have not done this because of course it's not authorized, but, has anyone dug any deeper into this than just "use 100ll?".

Big benefit for Seaplanes.

Update on my Pponk project. Going to have to get a 520 oil pump since it has deeper gears. Also, may or may not be able to modify my connecting rods for the next size bigger rod bolts. I think mine are from 1956 when the engine was new so betting they won't work for Pponk but crossing my fingers.

When I picked up the engine I found out the 470U oil pump with spin on filter that I had been running on the 470K is still on there. I think he said a Service Bulletin came out saying it was okay. Did have to get different connecting rods. A new 520 oil pump with spin on filter is very costly. Central Cylinder has a trailer they pull outside and run the engine for a while. Here are the numbers that show oil pressure is fine.

Flew my XP470 for an hour today since it was so nice-----60 degrees and smooth air so I could run it hard. Looks like about at the yellow for airspeed at 24 square. I had the cowl flaps closed not to long after taking off and temps seemed good. Oil pressure was just above the white line which is 50 so like that better that top of the green like before. Other than a little oil weeping from the crankshaft seal it seems like all is well. Did realize that big balance tube wasn't going to fit before too far along and put the little one from the 470U on. I had Central Cylinder reuse the bearings, cam and followers since they were still in good shape from the overhaul 11 years ago. They are able to machine the crankcase for the 520's since I started with a 470K. Sure like the 100 watt Reiff preheat on the cylinders and one pad on the oil pan(will add the second when motivated). Guess the white spinner doesn't look too bad.

nickelb wrote: Speaking of PPonk, can anyone shed any insight on whether 90+ Mogas Ethanol Free can be used in a PPonk with 8.5 Cylinders. I've done some homework on Octane and Compressions and can't find a real reason [other than STC requirements and Testing] why 90+ Ethanol Free can't be run in a PPonk....

"Other than STC requirements"....bingo.
It might work just fine-- just wouldn't be legal.

nickelb wrote:....It would seem that a STC could be created if someone is willing to go through the testing. I have not done this because of course it's not authorized, but, has anyone dug any deeper into this than just "use 100ll?". Big benefit for Seaplanes.

The standard 470XP engine is 7.5 compression, seems like 87 octane might be enough for that.
8.5 might require 91 octane.
Maybe you could contact Petersen Aviation & see if you can interest them into adding the 470-50 / 470XP engine to their mogas STC.
There seems to be enough of them around to make it worth their while.
I believe that EAA only does 87 octane mogas stc's.

Speaking of PPonk operations. Our Pponked O470R just passed the 10 hour mark. It runs very smooth. The only notable point is that with everything all in, the prop only turns 2550. Pull the throttle back a little and RPM increases to 2700.
I am guessing full rich mixture is just a little too rich and when throttle is reduced, full power is produced?
The carb was overhauled with the engine and the install shop said they did not change any settings.
Another operating question, does anyone have any performance tables? The Northpoint site just compares to a stock O470 and the STC does not have any tables. What is 75% power at sea level?

PNW Flyer wrote:The carb was overhauled with the engine and the install shop said they did not change any settings.

Experience has shown that the 0-470-50 engine requires a considerable increase of the fuel flow at full power over the stock 0-470R configuration. Have you monitored your fuel flow, EGT's and CHT's at full power?

My 0-470R conversion to 0-470-50 required a couple iterations to achieve a comfortable full power fuel flow. At near sea level my full power fuel flow is 27 to 27.5 gph.

PNW Flyer wrote: Another operating question, does anyone have any performance tables? The Northpoint site just compares to a stock O470 and the STC does not have any tables.

A few years ago, Steve Knopp told me to use the Cessna 206 performance tables for the IO-520A. My experience has been that this is reasonable.

nickelb wrote:Speaking of PPonk, can anyone shed any insight on whether 90+ Mogas Ethanol Free can be used in a PPonk with 8.5 Cylinders.

I've done some homework on Octane and Compressions and can't find a real reason [other than STC requirements and Testing] why 90+ Ethanol Free can't be run in a PPonk.

It would seem that a STC could be created if someone is willing to go through the testing. I have not done this because of course it's not authorized, but, has anyone dug any deeper into this than just "use 100ll?".

Big benefit for Seaplanes.

IDK if your homework has been automotive based or airplane based but there is a difference mostly because of ignition timing and CHTs. Cars have variable timing and the CHTs are cooler and steady because of liquid cooling. With fixed timing and hotter CHTs the detonation margins are smaller in airplane engines which is why high octane fuel is required at what most people would consider low compression ratios.

Some guys do operate their pponks on mogas and say they haven't had any trouble.

The mogas STC that Peterson developed for the IO520 (8.5:1) requires 91 octane fuel, water-methanol injection that kicks on when CHTs get to 400F and hotter or when MP is 25" and higher. This is to increase the detonation margin because during those engine conditions mogas does not have high enough octane to maintained adequate detonation margins on its own. I doubt Peterson would be interested in adding the pponk to the aml because he'd be losing money. Few people want to run mogas and even fewer would be willing to install a water-methanol system so they could run the mogas.

whee wrote:......The mogas STC that Peterson developed for the IO520 (8.5:1) requires 91 octane fuel, water-methanol injection that kicks on when CHTs get to 400F and hotter or when MP is 25" and higher. This is to increase the detonation margin because during those engine conditions mogas does not have high enough octane to maintained adequate detonation margins on its own. I doubt Peterson would be interested in adding the pponk to the aml because he'd be losing money. Few people want to run mogas and even fewer would be willing to install a water-methanol system so they could run the mogas.

FWIW the standard "ponk" / 470XP is 7.5:1,
vs the standard O470 at 7.0:1.