Okay fellas, needing to upgrade. I need help on deciding on the Texas skyways 0-520U/ts or the PPonk/XP. Problems I’ve already incountered are the TS, only has a 80” Mac approved for it. Can you get a Feild approval for a bigger prop? MT is off the table for me and my mission. Or should I just do PPONK. Seems like that is the gold standard in 180’s. Appreciate any thoughts and info.

J-

I don’t know what current prices are now, but in 2015 Texas Skyways was about 50% higher than a PPonk at Lawson Aviation using my core to new limits. Continental OVH was about the same. I ended up going with a C58 prop with field approval, again handled by Lawson. The C58 is on the STC for the 182 but not for the 180.

I'm in the middle of a PPonk/XP upgrade for my 182 right now. I went this route over the T/S because I thought I could reuse my prop (until the prop shop said it was toast) and it was a decent bit cheaper. I think T/S quoted an additional core exchange charge since you are trading a 470 in for a 520. Lawson is doing mine as well so I was able to drop it off which saves me shipping. I read a lot of positive reviews for them and Dustin has been great to work with so far. I dropped it off at 7pm one evening and he took the time to discuss all the details and show me around the shop. Hopefully I can let you know how the engine is in 3-4 weeks!

Looks like your in Alaska, I just looked at the approved builders list NorhtPoint emailed me and it has Custom Aircraft Inc in Palmer listed. Might be worth touching base with them on the PPonk/XP and see what they have to say. I know nothing about them so don't take that as a personal recommendation.

Check to see if you have a VAR crank before you start. Non-VAR, the 520 cylinders are off the table. The O-470U/TS gets you to 260ish HP with a non-VAR crank. You can use a C204 prop with it.

Perhaps you can explain the non-starter of 520 cylinders with a non-VAR crankshaft? VAR Crank AD 97-26-17 refers to IO-360’s and IO-520’s. There are two ways to get an O-470-50; start with an O-470 or an IO-520. My understanding is Steve Knopp lowered the RPM from 2900 to 2700 to avoid the VAR issue with the 520’s. I’m pretty sure I have my original non-VAR crankshaft in my O-470-50, that started as an O-470-K.

I know I have a non VAR crank in my just made Pponk/XP 470-50. The shop also modified my Phase 1 crankcase that was a 470K. I think I was told my Phase 1 CC could only be used for the 7.5 compression standard Pponk. Only the later, heavier O470U crankcase can be upped to the 8.5 compression ratio for more money to buy an addition Pponk STC. That combo would be about the same as a TS 520U/TS.

jrc111 wrote:Perhaps you can explain the non-starter of 520 cylinders with a non-VAR crankshaft? VAR Crank AD 97-26-17 refers to IO-360’s and IO-520’s. There are two ways to get an O-470-50; start with an O-470 or an IO-520. My understanding is Steve Knopp lowered the RPM from 2900 to 2700 to avoid the VAR issue with the 520’s. I’m pretty sure I have my original non-VAR crankshaft in my O-470-50, that started as an O-470-K.

I don't think the non-VAR crankshaft is technically illegal to use when you look the AD, but the FAA did issue an airworthiness concern with a few questions for those with PPonk upgrades after a crankshaft broke in a supercharged PPonk. Just incase that airworthiness concern becomes an AD, I chose to go with a VAR crankshaft since I had to get a different one anyways. See the thread linked below for the airworthiness concern

https://backcountrypilot.org/forum/faa- ... gine-24361

Richard's shop is indeed well regarded. I would have no qualms about their building a PPonk for our 180.
https://customaircraftak.com/

chedrick wrote:I'm in the middle of a PPonk/XP upgrade for my 182 right now. I went this route over the T/S because I thought I could reuse my prop (until the prop shop said it was toast) and it was a decent bit cheaper. I think T/S quoted an additional core exchange charge since you are trading a 470 in for a 520. Lawson is doing mine as well so I was able to drop it off which saves me shipping. I read a lot of positive reviews for them and Dustin has been great to work with so far. I dropped it off at 7pm one evening and he took the time to discuss all the details and show me around the shop. Hopefully I can let you know how the engine is in 3-4 weeks!

Looks like your in Alaska, I just looked at the approved builders list NorhtPoint emailed me and it has Custom Aircraft Inc in Palmer listed. Might be worth touching base with them on the PPonk/XP and see what they have to say. I know nothing about them so don't take that as a personal recommendation.

chedrick wrote:

jrc111 wrote:Perhaps you can explain the non-starter of 520 cylinders with a non-VAR crankshaft? VAR Crank AD 97-26-17 refers to IO-360’s and IO-520’s. There are two ways to get an O-470-50; start with an O-470 or an IO-520. My understanding is Steve Knopp lowered the RPM from 2900 to 2700 to avoid the VAR issue with the 520’s. I’m pretty sure I have my original non-VAR crankshaft in my O-470-50, that started as an O-470-K.

I don't think the non-VAR crankshaft is technically illegal to use when you look the AD, but the FAA did issue an airworthiness concern with a few questions for those with PPonk upgrades after a crankshaft broke in a supercharged PPonk. Just incase that airworthiness concern becomes an AD, I chose to go with a VAR crankshaft since I had to get a different one anyways. See the thread linked below for the airworthiness concern

https://backcountrypilot.org/forum/faa- ... gine-24361

While it may be technically legal at the moment, if you are building a new -50 up, it would be foolish to do this, because the action is already noted in process. It is almost certain that this will become a fully regulatory action soon, and would then force an overhaul at some point before you would want to. I could never in good conscience guide a customer down this road. If I already had one done, I'd probably keep flying it, but remember it's a function of the HP you are putting out, not which cylinders you have. From a common sense/safety standpoint, if you are running the High Compression pistons or otherwise putting out more than 260ish HP out of the engine, I'd probably consider trying to source a VAR crank and have it swapped in whenever it makes operational sense.

Another thought, if you have the O470-U you could rebuild without the upgrade. The -U engine (has VAR crank) is a low RPM, high compression ratio (8.6:1) engine which develops 230 HP at only 2400 RPM. This was to meet noise abatement restrictions in Europe in 1977. The IO470 is rated at 260 HP. So many owners turn up the prop governor to 2600-2650 and now you are getting 260 HP. A retired Mobile Alabama TCM engine guy told me this many years ago. Mine was already turned up higher before I knew about this. I always pull back the prop on takeoff, but if you need the extra HP on takeoff it's always there. Not FAA legal. With most PPonk upgrades you'll need a 3 blade prop and added $$$.

Correction, I just saw that you're flying a 1957. But maybe this post is helpful to others. -Bruce

Acme Cub Training on Lake Hood has a '55 Skywagon with a Texas Skyways motor, if you're looking to test-fly one. I did a flight review in it a couple years back.

-DP

limerick wrote:Another thought, if you have the O470-U you could rebuild without the upgrade. The -U engine (has VAR crank) is a low RPM, high compression ratio (8.6:1) engine which develops 230 HP at only 2400 RPM. This was to meet noise abatement restrictions in Europe in 1977. The IO470 is rated at 260 HP. So many owners turn up the prop governor to 2600-2650 and now you are getting 260 HP......

I believe this is what Texas Skyways does with it's "O-470-U/TS" engine-- a 470U turned up for more (250) horsepower.

https://www.txskyways.com/services

I believe that the Norland STC for the IO470 is about the same thing-- in this case, an IO470 converted to a carb.

Starting out with the U engine, if it's equipped with the 90" seaplane prop you might need to replace it,
or at least shorten the blades.
Ditto if you decide to just turn up the governor--
a 90" prop at 2600 would be very inefficient as well as obnoxiously loud.

Is there a weight difference between the Texas Skyways O-520 and the Northpoint (Pponk) O-470-50?

Last Oct I had Lycon build me a XP-50 on a 520 case I bought from them. I have a 55 180 and I could not be happier. It came in at 301hp and has been a great performer. I had Willie Stene install in Polson Montana and I live in Texas. It was worth it to me to have someone I trust do this work. Trues between 155 and 160mph now with 31" tires. Looked hard at all the other options and would do it again in a minute!

Stolhunter wrote:Last Oct I had Lycon build me a XP-50 on a 520 case I bought from them. I have a 55 180 and I could not be happier. It came in at 301hp and has been a great performer. I had Willie Stene install in Polson Montana and I live in Texas. It was worth it to me to have someone I trust do this work. Trues between 155 and 160mph now with 31" tires. Looked hard at all the other options and would do it again in a minute!

Did you go with the upgrade to the 8.5:1 compression pistons (DER approval) that they offer? How about the port and polish?

Yes I did on all.
Plus the new Hartzell 3 blade

NWestern180driver wrote:Okay fellas, needing to upgrade. I need help on deciding on the Texas skyways 0-520U/ts or the PPonk/XP. Problems I’ve already incountered are the TS, only has a 80” Mac approved for it. Can you get a Feild approval for a bigger prop? MT is off the table for me and my mission. Or should I just do PPONK. Seems like that is the gold standard in 180’s. Appreciate any thoughts and info.

J-

What did you end up doing? I’m going through the same process with a Texas O520 UT/S except I put a deposit down before I learned about that small detail. The STC only allows a Black Mac 80”.
I have a ‘69 180H.

Don't know about the OP but I elected to do a Northpoint XP-470-50 with high compression cylinders and an MT prop. But I still have my C90 88" black mac and hope to find a path to get it field approved once I figure out which is best for my mission. As always, the project is a can of worms but hope to be flying again in a few weeks. Hope is the operative word... February is more likely. Maybe....

Not familiar with the C90, what's the complete p/n?
I suspect there's two different issues-- crankshaft counterweight configuration and rpm / horsepower.
I'd suggest reading the prop TCDS.

For example, lots of people have wanted to put a Mac C203 on a ponk,
it's approved on the 470K which is the same crankshaft configuration.
But the C203 TCDS sez "up to 230 horsepower at 2600 rpm".
Deal killer.

2A34C203 TCDS P3EA (p.2) shows different #'s:

90DC[X]-0 to 90DC[X]-18
max continuous: 285 hp, 2700 rpm
max take-off: 300 hp, 2850 rpm