There are other options to get more horse power for a C180. The other popular choice is with Texas Skyways O470UTS that gets you to 263hp by using 8.3:1 compression and increases the U RPM limit to 2600. Pponk uses the 520 cylinders with 7.5:1 compression with 2700 RPM limit 275hp. I personally like the lower compression with bigger cc. We also have a long relationship with Steve Knopp, he has been doing our annual for the past 12 years, unfortunately he is so busy that he doesn't do annuals anymore. Luck would have it that the first year I take on the annual with my good friend and AI, we find metal in the filter. I'll have to try and get a picture of the filter element to post.
As for the prop that we sold, it was a 90" C204.
Some more on the Pponk decision, The Texas Skyway upgrade was more expensive by about $10,000 and that is basically for the mod to the oil system that they do. Here is a statement from their quote "The O-470-U engine is very much overbuilt for 230 HP. That’s why we selected it to increase the RPM and horsepower rating and then increase the TBO to 2500 hours. And speaking of 2500 hour TBO, the exclusive Texas Skyways Total Drain™ oil sump along with the large non congealing oil cooler and oil filter have a lot to do with that."
We already have the oil filter and non-congealing oil cooler so $10,000 for a Total drain oil sump and the STC seemed excessive. Plus I'm a little skeptical about increasing the RPM and also increasing the TBO, doesn't add up. It is basically the same engine we had, but with a prop gov allowing it to spin faster and burn more fuel for an extra 20hp. We could have used our C204 prop but we would have had to cut it down from 90" to 82" and I don't think our blades allowed for that reduction so we would have had to find new blades for the hub. Plus our prop needed to be overhauled at a cost of $4K.
With the Pponk this is what they say "to convert a stock Continental O-470 to a O-470-50 SUPER EAGLE several internal changes need to be made to the engine. First, and most obvious is to exchange the O-470 cylinders for O-520 cylinders which increases engine displacement by 50 cubic inches. The cylinders are fitted with low compression pistons which are precision balanced to within .5 grams. The carburetor is also modified. All original external accessories are overhauled and used on the O-470-50. The end product is essentially a O-520 which is carbureted and derated to 265-275 hp. Recommended TBO for the O-470-50 is 2,000 hours. A derated, precision balanced engine offers several advantages including significantly improved performance, smoother operation, less maintenance, and longer TBO."
In our environment in the PNW we were strongly encouraged to go with the nickel cylinders to help with corrosion which are offered on the 520 cylinders that Pponk uses. You can also get them for the Texas Skyway mod, but it increases the price as well. The Propeller was the biggest sticking point in the decision process. Our Prop and spinner we gave a value of $7k, that is $3k in its current condition and $4k to overhaul. So if we didn't overhaul we save $4k and if we sell it we get $3k. Are you following my logic? The new McCauley C401 86" with spinner has come down drastically in price to compete with Hartzell. We got ours for just under $11K. So over all $4K more for the propeller and the engine came out to not much more than if we had Steve do a straight overhaul with the nickel cylinders. The cost of the upgrade pencils out to less than $6000. The RR is the same for all options, so not a factor and since I'm doing it with my IA we are saving about $4K there.
Overall the Pponk made the most since financially and mission specifically. Those that have done it have been very positive about the results and we are excited to experience them ourselves.
