0-320 Issues...

[SimonK]

Well, I was hoping I wouldn't have to write in about my engine, but I'm getting to the point where I'm stuck on how to proceed.

My PA-14 has an 0-320-A2B (150 horse) with 500 smoh. I have a McCauley 80-44 prop on there right now, and the best I can do at static is 2250. I understand that I need to be at least running 2350 to be within limits (although that is just what a mechanic friend found while researching the problem). My takeoff roll is particularly unimpressive, which leads me to believe that it is not a tach error.

I searched on the website to see if I could get past advice on what to look for, which I did. On Saturday we checked the following items:

compression (all mid-70's)
spark plugs (removed, inspected, cleaned)
mag timing (dead on)
intake leaks (found none)
mag drop was minimal
throttle cable was in adjustment
carb heat was in adjustment
drained the carb
removed gascolator (fine shape)
inspected air filter (fine shape)
exhaust (looked up with a flashlight, cage was fine- did NOT remove, but did bang around on it to listen for internal movement- none)
I also tried leaning the mixture while at full throttle (static) with no appreciable increase in RPM.

Basically, we didn't find anything wrong. A couple of questions:

Does the 2250 (which may be a bit generous) with the 80-44 prop sound low (everyone I've talked to thinks so)?
Anything else I should be checking (besides serious internal parts, which is out of my league and I imagine must get expensive really quickly)?

I've read about various options for increasing static RPM such as the K&N air filter or the Leading Edge Exhaust System on, but I am worried that doing so would simply hide whatever problem exists. Does that seem right?

I appreciate any help I can get. I also realize I may be omitting necessary information, and if so would be glad to fill in with more details if able.


Thanks much!
Simon

 

[Lonnie linderman]

Simon sounds like the same problem I chase.
I check all the same as you, but I also check my prop to see if it was pitch
the way I was told
Also ck carb heat box leaks
Primer for leaks, to rich will cause lose of rpm
Last thang I did was have my carb rebuilt.
I get needed rpm now but I need to lean befor take off
good luck
Lonnie

.

 

[Redbaron180]

I have an o-320-A2B in my PA-18 with an 82-41 prop and I get 2500 RPM static. It will redline at 65 Knots on the climb. I also have a Leading Edge exhaust system that is supposed to help. I am curious how this compares with others. It is a fresh engine. Ron

 

[kxo300]

Simon

I don't think that you are that far off on static rpm. On my 12 with a 8243 I could only get 2300- static. We did some static pull testing to test different props etc. I had mine rebuilt and twisted to a 8241 and if I remember right I could then get 2350. Went to a K & N filter and I got 2425. The foam filter is not very effecent, to test (and ask your "wrench" first), pull the foam element out and try it, "you will be suprised"

I was told for the 12, when it was stc'd for a 150hp they left the airbox/filter the same (115 hp)! DUH! the very same filter you find on a cessna 150 and we are trying to pull 50% more air threw it on a 320 lyc.

the k&n works great.

Gary

 

[Crash]

My PA-14 with an O-320B2B (160hp) will turn 2450 static with a 82/44 prop. It has the Crosswinds STOL conversion that uses PA-18 FWF with the PA-18 round airbox. Fresh engine with Millenium cylinders. Crash

 

[T.J.]

Simon:
In level flight, full throttle, what is the max RPM?

 

[T.J.]

Also:
What did your mech use to determine the static RPM for the 80" prop? Does your STC give the static RPM?

 

[Longwinglover]

Is the static RPM you quote what you see on the tach or is it from an electronic tach checker? Mechanical tachs are notoriously inaccurate.

John Scott

 

[SimonK]

Hi All,

Thanks for the quick responses.

I did pull the spinner off and checked the prop, it was stamped 8044. But I couldn't be sure until I did that!
Is it tough to check the primer for leaks? I tried leaning the engine during full throttle (static) and it didn't do much, would doing so counteract a leaking primer?

Will definitely consider the new K&N filter when I get things resolved! It'll be a bit longer before I can go with LEES


I am able to get 2700 in level flight, full throttle.

I am not sure what the mechanic used as a basis for this prop. Unfortunately, I'm back in Anchorage now and he's in Nome so I won't see him for a bit to ask him.


Gary (or others who know), do you recall what the difference in performance was with a 125 hp increase in static RPM for take-off? I am curious if I were able to step it up 1-200 rpms what I might see. I know I'm definitely not getting the performance that I've heard from other 14 owners on this site...

Thanks again to everyone for their help!
Simon

 

[cubpilot2]

Noticed that you said that you did not pull the muffler and inspect it.
I've been fooled a couple of times by just looking up through the tail pipe and guessing that everything looked OK, but after removing the pipes to comply with the ADs found the internal baffling warped severely; especially near the center of the muffler. (talking about a standard cub muffler). Both times after installing a new muffler the engine ran noticeably better. When a muffler starts to degrade, sometimes the loss of performance will come on so slow that you may not be aware.
May be worth a check
Good Luck

 

[T.J.]

Simon:
When you say you get 2250 static, is that with the tail tied down and full throttle? Something is amiss if you get 2250 static and then 2700 full throttle.

 

[SimonK]

Yep, that's the mechanical tach. As takeoff performance is pretty poor, I was inclined to believe the tach a bit more. Also, turning up to redline (2700) seems about normal. If there were a tach error, it'd run all the way up the RPMs, wouldn't it? No real experience there...

No, didn't pull the muffler off. I was under the impression that if something was wrong in there, it would be loose metal and not warped. Thanks for the heads up, something to check the next time I get access to a hangar!

The static check was not done with the tail tied down. The brakes hold me just fine at full throttle, so I guess I don't have big enough tires
When taking off, it'll get to 2350 a little over halfway through the takeoff roll, 2400 around liftoff, and around 2500 at climbout. Straight and level is 2700.

At one runup test I got close to 2300 rpm with the mixture leaned, but there was also a 20 kt direct headwind and I figured that was about equal to being halfway through the takeoff roll and felt I couldn't trust that number.

T.J., you mention that the disparity between static and takeoff RPMs spells trouble. If 2250 were normal would you expect straight and level to produce more on the order of 25-2600 RPMs? I was also surprised when I checked the straight and level RPMs, didn't expect to see it get up so high. I have no idea what this might indicate though, except that if it were something like warped muffler baffling that it would be affected all the way through the flight regimes, not just static and takeoff.

Anyway, I am new to all this and sure appreciate everyone's ideas.
Thanks,
Simon

 

[fobjob]

I felt silly doing it, but it turned out to be the problem. Pull your carb off and check to see that the intake manifold is not from an -A2A engine, to wit: a tapered riser of about 2 1/2 in. diameter instead of the 1.92" dia. for a -32 carb. If true, it will steal about 10HP....if the engine was apart and out of your sight for even an hour...........

 

[cubunltd]

The optimum prop for the 150 hp is a 82-41 for takeoff performance. If you are running a 44 pitch, your static rpm is about right. Sounds like there's nothing wrong with the engine except prop pitch. I usually run a 82-43 on 160 hp. I have a supercub right now with 160hp, K&N filter and Leading edge exhaust that Uses a 82-44 because of the added ponies from the exhaust and filter. Haven't flown it yet as I'm waiting to get it certified, but ground tests feel real good. Don't have any figures yet. Am working on a thrust gage to measure changes.
cubsunlimited@verizon.net

 

[Carey Gray]

delete

 

[moneyburner]

Simon;
I've got a photo tach that should work through the windshield - it takes a small reflective patch stuck to the prop. (you fly, let someone else play with it). Let me know when your brother or any of those guys are coming up to TNC with the mail, they can pick it up and you can borrow it for a week - It's very accurate. I'll be here until 12/15, have to have it back before then. PM for more details.

Mike

 

[Beaver Doctor]

Ignition leads

You might check your ignition leads if you feel that your cub is not preforming the way it should, your mag timing will be right on and everything else will be working as advertised but if your leads are bad those little sparkys wont be going where they need to be.
good luck

 

[Ruidoso Ron]

I have been complaining for a while that my engine seemed anemic. Too windy to fly comfortably, but I did a tach check on a static runup today at 7,000MSL. I found that my tach was reading 75-80 RPM low at 2300. Makes me feel a lot better about it.

 

[Carey Gray]

delete

 

[SimonK]

Thanks again to all who are giving me ideas on what to look for. Hadn't ever thought the intake manifold.

I was not aware that a prop will change like that over time, sounds like I need to worry about that. Does anyone know of a shop in Anchorage that will be able to check prop pitch? Does anyone know why a prop will change so much? That is interesting!

Hi Mike, thanks for the offer on the photo tach. I think the mechanic I was talking to mentioned that he had access to one as well. I appreciate the offer, and will let you know if I need it. Just need to get back to Nome now (airplane still there).

I was really hoping that I'd find something obvious with the RPMs being low and that I'd be able to increase performance through fixing that. Sounds like I need to start working on lightening up the plane by 100 lbs (120 lbs if you count the pilot).

Does anyone have an idea of what change in takeoff performance you might experience with 150 additional RPMs?

Will look at the ignition leads with a mechanic when I get the chance, that sounds like a good investment of time. Do you think I'd still be getting redline at straight and level if they were bad?

Thanks again to everyone for their suggestions,
Simon

 

[X18]

K & N Filters

Carey,
Try the Knots2U K & N filter page for the right filter for your application.

Jim

 

[Crash]

Check your spark plugs in a checker under 100 psi of air pressure. It's amazing how many will quit firing under pressure. Clean and gap them to .017 - .019, or better yet, install a set if Iridium plugs. Good for another 25 to 50 rpm. Crash

 

[SimonK]

We put the plugs under pressure, the gauge only read 50 psi though when testing. The gauge may have been broken though, as the needle stopped moving partway through rotating the dial. Not sure.
May have to look into those Iridium plugs, sounds like there are all sorts of tricks out there.

Heading out on a business trip for a few days so won't be responding for a bit, but any more advice is appreciated.

Thanks all.
Simon

 

[RMREBOB]

Does K & N make an element for the round filter?

 

[Crash]

I also agree with the other post that said a 44 pitch 80" prop is too much pitch for an O-320-150hp. If it is down to 80", I'd get a new Borer prop pitched at 41 or maybe 42 pitch. If the cost is too much then I would at least take the one you have and have it re-pitched to a 42. Take care. Crash

 

[SimonK]

Hi Crash

Do you know where I can get a prop re-pitched or checked to verify its current pitch in the Anchorage area? I am not very familiar with changing the pitch on a prop, is there any downsides to doing so (e.g. does it weaken the prop at all, etc.)?

Also, out of curiosity, how much does your 14 weigh (being fairly new to the site I am reluctant to ask, almost seems like asking a woman how much she weighs- dangerous territory)? The previous owner(s) of mine were not afraid to pack the pounds on, and I am looking to shave some weight. I am tipping the scales at a little over 1300, and was hoping to knock it (somehow) down to around 1200. Does this sound more in the realm of a reasonable weight to you?

Thanks!
Simon

 

[Cub Kid]

Simon,

Was just out at the airport this morning, planning to move my 206 in from City Field (can get out of City fine but the parking area at the airport is another story, as they haven't plowed since the last storm), happened to see your 14 there. Looks pretty spiffy, good to see a new plane come in once in a while, rather than all the local planes going the other way.

Answer to your question on repitching is that the main downside is in cruise, you will lose quite a bit, but i must agree with others on the site that with the 150 horse repitching to 41 or 42 is your best option, depending on the condition of the prop, or you might be beter off to just purchase a new 82-41 (or 42).

Bill

 

[mvivion]

Simon,

First thing I'd do is put an automotive compression checker on the engine. With these, you attach the gauge, then motor the engine through with the starter (with all ignition leads removed). You may find (as I did) that there are issues with the engine that you aren't aware of, like in my case, two burned pistons and a bad valve. All compressions were in the 70's on that engine. Lycoming recommends the automotive compression checker in such situations.

For heavens sake, find a mechanic with a tach checker. They are digital, they don't require anything except getting in the plane and pointing them forward while at RPM.

My guess is that your tach is reading 100 rpm low. This can be different at different rpms, by the way. Check it with a tach checker, then if it's that far off (and 100 rpm is within limits, legally), yank the dang tach out of the instrument panel and get a Horizon digital tach.

Mechanical tachs are pieces of sh**, in my opinion, and getting worse every year. A lot of folks hate digital tachs, but they are always accurate, and you always know exactly what's going on. That beats the hey out of having a junk mechanical tach that reads 100 rpm off, at "some" rpm's.

MTV

 

[Crash]

Hi Crash

Do you know where I can get a prop re-pitched or checked to verify its current pitch in the Anchorage area? I am not very familiar with changing the pitch on a prop, is there any downsides to doing so (e.g. does it weaken the prop at all, etc.)?

Also, out of curiosity, how much does your 14 weigh (being fairly new to the site I am reluctant to ask, almost seems like asking a woman how much she weighs- dangerous territory)? The previous owner(s) of mine were not afraid to pack the pounds on, and I am looking to shave some weight. I am tipping the scales at a little over 1300, and was hoping to knock it (somehow) down to around 1200. Does this sound more in the realm of a reasonable weight to you?

Thanks!
Simon

The best fixed pitch prop guy around is George at Merril Field Propeller. He is actually located in Eagle River but is worth the trip.

My PA-14 with 31" Bushwheels on it weighed in at 1,240 lbs. On big tires, I think 1,200 lbs would be tough to get down to with a PA-14.

http://www.supercub.org/phpBB2/viewtopic.php?t=281&highlight=pa14+cub

Half way down the page is some pictures of my 14.

Crash

 

[musket]

Mr. Vivion,

You mentioned, in your reply, above, to Mr. SimonK, that he should

yank the dang tach out of the instrument panel and get a Horizon digital tach.

Of the two or more digital tach's available, would you share your reasons for picking the HORIZON brand (presumably the Model P-1000) over the EI Model R-1?

Thanks