O320-A2B on PA-12

Hi, folks. I've got a dumb question. I've just brought home an A2B off a Pawnee for installation on my 12. Was planning to use a Stoddard mount even though I didn't really want to shorten the cowl, but after temporarily hanging the O320 on my 235 mount (to get the engine off the floor), I got to wondering if the 235 mount is strong enough to accept the engine if I go to 18 or Pawnee tailfeathers to cope with the extra weight on the nose. Any thoughts or input would be welcomed. I don't know much (nothing) about this subject.
Thanks,
JimC

I have installed O-320 on PA-16s that originally had the O-235. According to the Piper drawings they were basically the same mount as the PA22-150. Haven't had any problems with them yet. I'm sure Tim and some others can point you in the right direction as far as FAA approval, what works best for them.

Steve

PA-12 mount

The best set up: Crosswinds STOL conversion! Its a swing out mount just like the PA-18's and places the engine back aginst the firewall the same distance as the PA-18 mount. It uses a PA-18 top cowl, bottom cowl, round airbox, nose bowl, nose bowl channels, side cowls (except longer), and exhaust. Throw the rest of that old junk in the trash and update your plane 50 years. It won't be nose heavy either when you pull the power back. Crash

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Thanks, Guys. Crash, while I recognise that the 18 cowl is the best way to go, I really want to keep the stock look of the 12 cowl. T.J., a short mount is still available, using the PA-18 exhaust. It requires that the 12 cowl be shortened by 3 inches, and I don't want to do that, though I suppose I could use a 3" prop spacer instead. I tend to like the 14.125" diameter PA-28-150 spinners. Is anyone using one of those (dimensionally the same as some of the 235 spinners)?

I'm ahead of you on a similar project. My first question is whose STC are you using. That will determine not only the mount, eligible engine models, and most everything else as well, such as tailfeathers (usually 18 tail is required), cowl, prop, etc. Kenmore is the only STC that I found that uses the stock cowl. The STC costs $100.00 and includes instructions for modifying your long mount. I spoke to Kenmore last week, and the FAA had them revise their STC to be engine model specific, so you need to find out if you can use your motor without a deviation. (Their STC used to call out for an 0-320, but now suffixes are listed.) If you really want the stock look, call Jerry at Kenmore. He can tell you everything you need to know.

320-A2B on 12

>>I'm ahead of you on a similar project. My first question is whose STC are you using If you really want the stock look, call Jerry at Kenmore. He can tell you everything you need to know.<<

Hey, Stewart. I just brought the engine home yesterday. It's an A2B off a Pawnee, firewall forward. On free, long term loan from a good friend, so the price is right. I haven't decided on which STC yet -- that's what I'm trying to determine now, and am looking for background info and advice to help in my decision. At the moment, the A2B is sitting on the 235 mount, just to keep it off the floor. I'm supporting four planes and two daughters in college, so hope to keep the swap as inexpensive as possible. I'll call Jerry.
Thanks for the input,
Jim

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12 & O-320

What's the flattest pitch that gives acceptable 12 performance on a 74" McCauley on a 160 hp A2B? The steepest pitch? The Pawnee exhaust and muffler fit the 12 just fine -- can they be used with any of the O-320 installations?
Thanks,
Jim

JimC,

If you look at the pictures posted of my 'Freightliner"
I have an O320A2B installed with Kenmore's STC, a PA22 Exhaust (modified to use the stock 12 muffler) the installation calls out a "150hp" 0320. I have gone round and round, about the installation, my 337form was FA'd with the STC being only modified by the Hp increase of 10 using the SeaAir STC for conversion to 160hp. the 337 noted that the "Flight Manual Suppliment that is a part of the Kenmore STC was ammended to show the minimum fuel required to be 91-96 octane, IE: 100LL. It was pointed out by an IA that a flight manual was not a part of the original documents required by the CAA in 1946 when the Airplane was manufactured, so infact the "Placard" method was acceptable means of marking the operating limitations. I took the matter to the local FSDO and they just a month ago approved by FA a 337 that shows that the installation on the PA12 is approved. It also addresses the installation of the Borer prop.---

All this is to say that there are many interpretations of the regs, and paths to go to meet the goal??

To answer your question the Mount you have will work fine if the diagonal tubes are sleeved (Kenmore STC)

Note: the CG is moved forward considerably! With the plane operated with light fuel load, one pilot and no baggage you are at the forward end of the envelope! However, that is why my bird is nicknamed the Freightliner as I can and have carried a 55 gallon drum in the thing and not be aft loaded!!

(best check with your IA and make sure he can get the paperwork approved prior to doing the work)

Tim

To Stewart and PA12Driver,
Thanks, I've talked to Jerry and have received the Kenmore STC and new carb box, and have ordered the sleeving. The stock Pawnee crossover exhaust that came with the engine fits the 12 perfectly with the reversal of only one scat hose outlet on the muff, and Jerry was fine with my using that exhaust in lieu of the STC'd exhaust, as is the shop that does my work. They don't expect the 337 to be a problem. Hope it isn't. Is the cg with O-320 far enough forward to allow soloing the plane from the back seat? Will be pulling the engine back off tomorrow to have the mount welded up, to turn some long firewall bolts 180 degrees for more heat muff clearance, and to install some new isolators. Now for a dumb question. Why the need for a 22 nosebowl instead of the 12 nosebowl? The 12 bowl seems to be indentical in width to the pawnee (25) bowl that belonged with the engine.
Thanks,
Jim

P.S. to PA12 driver.
Could I get a xerox of your 337? Sounds like it might ease the road I'm traveling, since my installation is quite similar to yours and I'm hoping to up the horsepower too (would like to put 10:1 pistons in my Cherokee and place the 9:1 pistons removed from the Cherokee into the 12). Aren't STC's and 337's fun? Sort of like having a root canal done and eating worms at the same time.

Great discussion. Add my name to the list of 12's having an 0320 installed. Planned on using the Kenmore STC with 22 exhaust and 12 muffler. Exactly what needs to modified to the exhaust to do this? The cabin heat valve on my airplane is ABOVE the stock 12 muffler while the Kenmore drawings show it BELOW the muffler. I planned on using the 12 shroud around the 12 muffler to get around this "detail". Is this the modification you are refering to? Jim

So goes the battle! I just got through ordering a "stock PA22 exhaust system stacks/wo/ the heat chamber on the right stack from Knisley Exhaust to replace the cracked front cross over that is on my PA12. My O320A2B was installed using the Kenmore STC as well. I found that for what ever reason the Knisley exhaust I received put the "muffler to far forward and lower than what mine is currently? This would cause interference with the mount and oil lines etc. I have know I idea of how it would have worked according to the drawings from Kenmore. I suspect that when mine was originally installed it was determined that as you are finding out that the Heater valve would not work out very well with the 22 exhaust as the 12 valve is above the muffler. The 22 exhaust gave the carb heat from the left stack shroud, (not necessary if you use a 12 muffler as it is a split hot air chamber, one end suppling the cabin heater and the other the Carb heat. This works great! There is lots of room for the muffler and I would think it best to relocate it to make access and clearance optimum? It is my suggestion that you consider doing what I have done if you don't have any exhaust now? Buy the Kninsley or anybody elses stacks and have them extended, and made to fit the location you feel best for the muffler? This is rather simple to do for an exhaust shop if you provide the measurements, or if possible have them take measurements from your motor on the mount and firewall.

There are other options: Atlee dodge has a "bolt on" modified Supercub cross over exhaust complete with front shroud for carb heat and rear for cabin heat. I know Bob Carroll has this on his 12 and I have got pictures of his installation. I think the whole kit and cabutal is about $1400.

Be sure to check on the "Approval process" prior to doing something in difference to the STC?? If it is significant??

Send me a PM if you need more details/copies of the installation? Here is one showing the muffler/ right stack and scat hose. I am having another left stack made up out of a Supercub exhaust stack (identical except for length and location of the muffler inlet.


Tim

A stock Pawnee exhaust system fits the Kenmore installation perfectly, needing only one scat tube connection relocated on the muff.

Jim

I have both a 12 and 22 exhaust on hand and never saw the difference. The 12 exhaust puts the muffler about 10" further back and the pipes going back to the muffler are parallel to the Cylinder flanges. The 22 exhaust pipes rise in relation to the flanges on the way back to the muffler. This effectively puts the muffler higher possibly because of the nose gear on the 22. Do not want to spend $1400 yet for Atlee's system, planned on buying landing gear with that money. If I send both exhausts to a shop to have the 22 exhaust modified to put the muffler in the same spot as the 12 what other suprises in this regard do I not know about yet? Jim

You only need to see where you want to pickup the inlet air for both the cabin heat side and the carb heat side? My cooler is mounted on the left rear baffle so the inlet had to be relocated to the right rear (see photo) previous post. the other inlet comes from the scat going to the lower cowl inlet scoop right side.

I would highly suggest that you put out a search for "Pawnee exhaust system"??? Sounds like a good way to go

Tim

Jerry at Kenmore tells me that the crossover type exhaust is required, that's why he used a pa-20 exhaust for the stc. I asked about using the supercub exhaust and his answer was yes, since the crossovers are there.
SB

The Pawnee exhaust for the A2B is a cross-over system and fits the longmount 12 perfectly. One scat hose fitting has to be relocated on the heat muff.

Does the Pawnee rear stack NOT have the "can" for carb heat? If that is the case those stacks may be identical to a tri-pacer with no rear seat heat. Possibly 135hp airplanes? What do you think about trying to get a rear seat heat mod approved? Maybe send some of that heat to the windshield as a defroster? Jim

Not on the side. The Pawnee has a single long muff over the muffler, with a center divider on the muffler that splits the muff into two chambers. One side feeds carb heat, the other cabin heat.
JimC

sounds like you all are on the right track? Kenmore had no problem with slight modifications using a combination of PA18 stacks, PA12/ 20 muffler and shroud/ scat to fit the firewall heat valve of choice. All the parts are PMA and work fine. My 337 gives only reference to the Kenmore STC and included drawings. the drawings are so crude and lack detail that any approximation would most likely satisfy any IA inspecting your aircraft. The beauty of the arrangement is there is gobs of room around the muffler and mount and makes maintenance a "good experience" compared to a PA18

As for the CG, I haven't tried soloing from the rear? I am sure it would not be a problem as the nose is heavy with the long mount? the questions is why? can't reach the flaps, fuel shut off, carb heat, radio or coffee cup (in my plane from the rear)

Each to his own? Jim C. post a picture or two of your project?

Merry Christmas,

Tim

I'm an old J-3 pilot (in more than one sense of the word), so like a plane to be set up for solo from either seat. I can't reach the 12 flaps from either front or rear (doesn't have 'em). I plan to locate all other critical controls (carb heat, mag switches, etc.) so they can be reached from either location. I don't have any particular urge to solo the 12 from the back seat, but do want it to be capable of that. I will take some photos, but need to wash the plane first, so that it isn't such an embarrassment. It's supposed to be white with pale blue and pale grey trim, not dusty brown with cat track decals supplemented by bird presents.

Jim,

Hard to beat the low and slow of a J3!
My cub looks a lot better on camera then up close too!

Tim

Just one thought on soloing from the back seat: The PA-12 Type Certificate requires a placard that says "Front seat for solo flying." to be displayed on the rear seat.
I'm not sure what your 337 would have to say that would allow removal of that placard.

It would probably have to demonstrate that the cg with the heavier engine on the long mount would still be within the envelope when loaded to gross with the pilot in the back (and for all other possible cg's) and would probably have to show the old and new polar moments of inertia, and that the tail volume would still be sufficient for spin recovery. I haven't run the numbers yet, but suspect they might work out OK.

Like a lot of things, they will likely work! Getting the FAA's blessing on it is another story?

Tim

PS: perhaps you could just pull out the front seat, make the front seat into a cargo area, and think of how much easier it would be to load the moose meat! I think you are onto something!!

Now Tim,
That's an idea with some real merit! Just think how heavy you could load the old '12 if it were all going within the CG envelope. Not only that but you'd have something to rest your feet on during those long, slow trips!
KL

PA12driver said:

PS: perhaps you could just pull out the front seat, make the front seat into a cargo area,

Click to expand...

And then you would have a high wing Pawnee...

I don't know why I didn't think of that before? Most of the time when we take off loaded, we are just heading for the trees anyway, just keep her straight, If we clear all is well, and then when we land (usually at a larger strip) where you don't have to see to much in front of you anyway?

Then now that I think of it I would have to lose some weight to even sit in the back with a "Whole moose" loaded up front!

Sorry JimC. what was your original question????

Another eggnog anyone?

Tim