Our '52 170b with the 180hp Avcon conversion is eating through the lower section of the nose bowl. The spinner screws are hitting the nose bowl in flight occasionally, and the lip that re-enforces the lower bowl just below the spinner is slowly disintegrating. First of all, what would cause that? I suspect sagging motor mounts, but they "look" ok to me. It can't possibly be my piloting skills, as they are impeccable. Secondly, if I needed to get a new bowl, where would I go? I can repair it as it's made of fiberglass, but it has a few other problems that might be best solved by replacement. Any ideas?



And as long as I'm talking about maintenance issues, anyone else with this conversion have the #2 cylinder that runs hotter than the rest? In climb, even shallow climb, it consistently runs 20-30° hotter than 1 and 4, and 10-20° hotter than #3. In level flight it's better, but usually still hotter than the rest. If so, what are things that people have done to alleviate or at least knock it down a bit?

Thanks.

I also have a 52 170B with Avcon 180hp conversion.
Regarding the nosebowl, I've noticed the same thing after a particularly rough field landing - must be the motor bouncing on the mounts inside the cowling. Put some fiberglass reinforcement on the inside of the nosebowl lip and just needs some paint now.
#3 cylinder is the hottest on mine, though. I'm surprised #2 is hottest as it's in the front and it's the #3 followed by #4 that are hottest on mine and also the ones in the back.

I will probably end up doing the same thing, just putting the lip back on in fiberglass. Any benefit in trimming the bowl a bit? Or is that just putting a band-aid on the problem? How do you check to see if the mounts are still good?

I'm surprised that it's the #2 cylinder too. I'll have to double check to make sure the edm 700 is wired to the correct cylinders.

AKclimber wrote: I've noticed the same thing after a particularly rough ___ landing - must be the motor bouncing on the mounts inside the cowling.

Alan's landings look pretty smooth, although I don't know what post shoot editing occurs
Maybe it's time for sponsorship from AK Bushwheels to smooth out those rough landing spots?...
When I changed out engine mounts, I think I expected everything to stiffen up. Even when bushings are new, there's still a lot of weight hanging out there. Unless you are currently seeing significant sag, I wouldn't think changing the mount bushings will inhibit the amount of movement needed to scrap your closely cowled spinner and which you are going to get in turbulence or with a rough field landing. My 0.02.

Alan,
Our 170 kinda suffered the same thing. When I was 15 my instructor was putting me through the paces in preparation for my solo. When we were tying down the airplane after performing accelerated stalls we noticed that we laid a nice groove in the bottom lip with the spinner screws.
25 yrs. and a few extra cowling issues later, I thought I would try my hand at fiberglass work. I built up the back side of the nose bowl below the lip with glass, enough to be able to sand down the lip to give a little more clearance.

While I was at it, and because I had replaced the starter with a Skytech, I didn't see the need to leave the bendix notch in the bottom lip. As a matter of fact the Avcon nose bowl didn't follow the arch of the spinner along the bottom very well at all, so in the process of glassing and sanding, I did my best to clean that up.

As luck would have it, when I was prepping my son for his solo, I let him drop it in from a X-wind landing bounce and well, we found out that I glassed her in a little too tight to the spinner, so if you look at my bowl today you'll see that I took the round side of the sanding block to the bottom lip again to give it another 1/4" or so of clearance. Problem is I'm too busy to take the time to paint it right now.
From the picture you can also see that I tried my hand at flush patching around the exhaust pipe. Not the best work, but I got a contact that I'm gunna take advantage of next time that has an english wheel for that compound bend.
Don't know if this helps, but maybe it will give you the confidence to go for it. This was my first time glassing and I did it without removing the bowl from the cowling.
Good Luck,
Tom

Alan check your motor mount bolts and rubbers both MM to engine but also MM to firewall, dont want Chuck getting hurt.

I had this with the Mooney. I needed new engine mounts. Not too expensive but a bit of work! If not new ones washers on the bottom ones!

Sounds like your engine mount rubbers are sagging- not uncommon, esp if it's a dynafocal. If so, replacing them should solve the problem or at least help. You might also think about shimming the engine mount at the firewall, but this willl have an effect on how the airplane behaves when you put the wood to it-- think "thrustline". If you're not well-versed in that stuff, talk to someone who is before doing this.
I had a similar issue with my C150/150, but it was the teeth on the starter ring that were eating away at the nose bowl. I was gonna build it up etc with fiberglas but that would just start the whole thing over again- actually making it worse since there'd be more material in the way. I decided instead to get out the dremel and relieve the area that was getting chewed up back to where there'd be no interference.

Yep, you need new motor mount bushings. Not a big deal, either in effort or cost, just a bit of a PITA.

I too find #2 to consistently run hottest. No idea why, except that the Avcon nose cowl is a pretty bad design. I've thought about replacing mine with Del-Air's nose bowl, but the price is a "little" steep.

Mine is starting to have the gel coat de laminate. Any ideas on how to fix that?

MTV

mtv wrote:Yep, you need new motor mount bushings. Not a big deal, either in effort or cost, just a bit of a PITA.

I too find #2 to consistently run hottest. No idea why, except that the Avcon nose cowl is a pretty bad design. I've thought about replacing mine with Del-Air's nose bowl, but the price is a "little" steep.

Mine is starting to have the gel coat de laminate. Any ideas on how to fix that?

MTV

I bet you have a shop around that fixes fiberglass boats. A good fiberglass repairman can make that stuff like new in a flash.

I'll order the new bushings/ motor mounts today. I have to go down to the airport to get the part #'s. My dad is pretty good with fiberglass, so we'll do the repair of the nose bowl ourselves for now. How much are the Del Air nose bowls?
I like the work you did on yours, TomW. We have the notch for the old starter as well, so we'll take that out when we do the repair.

gbflyer wrote:

mtv wrote:Yep, you need new motor mount bushings. Not a big deal, either in effort or cost, just a bit of a PITA.

I too find #2 to consistently run hottest. No idea why, except that the Avcon nose cowl is a pretty bad design. I've thought about replacing mine with Del-Air's nose bowl, but the price is a "little" steep.

Mine is starting to have the gel coat de laminate. Any ideas on how to fix that?

MTV

I bet you have a shop around that fixes fiberglass boats. A good fiberglass repairman can make that stuff like new in a flash.

Actually, that was my first move. BIG boat builder/ repair outfit just down theroad. They said fixing gel coat is impossible. They recommended new.

I am not a fiberglass type, so. Dunno what to. Think. Got same answer from local body shop that does some glass.

MTV

"Gel coat" is used to hide the the cloth and make a boat look smooth. My opinion it's worthless.

I think they grind it down and resurface but I don't know much about it either. I believe the statement that it can't be repaired effectively as - is is probably correct.

What a brilliant picture for explaining the problem - if only we were all so organised!

I have been thinking about cowl interference, my theory is the increased weight of the engine in high G maneuverers causes the engine to sag in it's mounts and make contact with the cowling even though it doesn't touch when sitting on the ground... In which case, new mounts 'might' help, but there's no guarantee I can offer (beyond my experience) - it would depend how much sag the mounts have accumulated. I think they are supposed to be replaced every decade or something like that. It's on the paperwork.

If it were experimental is would be easily fixed. I don't know what kind of limits certification creates, but you could easily lay up some more glass.

mtv wrote:

gbflyer wrote:

mtv wrote:Yep, you need new motor mount bushings. Not a big deal, either in effort or cost, just a bit of a PITA.

I too find #2 to consistently run hottest. No idea why, except that the Avcon nose cowl is a pretty bad design. I've thought about replacing mine with Del-Air's nose bowl, but the price is a "little" steep.

Mine is starting to have the gel coat de laminate. Any ideas on how to fix that?

MTV

I bet you have a shop around that fixes fiberglass boats. A good fiberglass repairman can make that stuff like new in a flash.

Actually, that was my first move. BIG boat builder/ repair outfit just down theroad. They said fixing gel coat is impossible. They recommended new.

I am not a fiberglass type, so. Dunno what to. Think. Got same answer from local body shop that does some glass.

MTV

trying to fix up old gelcoat is not much fun! and usually looks pretty bad, especially if the old gelcoat has been subject to the UV's for a while...you never get a nice match and it just doesn't work easily. spot filling with gelcoat is fine but anything reasonable in area will be tough going.
If it was me i would opt for sanding the old gelcoat back carefully to the glass and then prime and paint the whole piece. Alot more work and time i admit, but unless the bit your repairing is hidden and not at eye level (which EVERYONE see's, including yourself everytime you pull her out!) i'd go for the total refurb!
my 2 and a half!

Can someone post a photo of a Del-Air nosebowl? I'm not sure what they look like & tried to google up an image. It didn't work, but I did see that Harry Dellicker passed away early this month at age 82. Too bad-- I never met him in person but I did have a (long) phone conversation with him years ago and he really knew his stuff.
I don't think you need g forces to get those engine mount rubbers to deflect. I watched a 180-horse Supercub fire up with the cowl removed once, and I thought the engine was gonna jump right off the airplane before it settled into an idle.

Does anyone have the part # for the engine mount bushings on the Avcon 180hp conversion in the 170? Our is the 0-360 A1A engine. I can't seem to find the numbers in the paperwork, and I can't see a number stamped on the bushings themselves. It's probably on the side that is to the engine and I would have to pull one of them to look at it. Here is a great cell phone photo of one of the top bushings for reference:

I would think that the p/n for the rubbers would be in the Lycoming parts manual.

Allan look at the motor mount where it bolts to the firewall, if the lower bolts are loose under power the motor could lift.