Vetterman Exhaust Cowl Clearance

[22LD]

I have an IO-540 and purchased my exhaust from Vetterman. I'm working on the cowling and finding that the exhausts from cylinders #1 and #6 do not clear the bottom cowl. Has anyone else experienced this issue? If so, any suggestion for how to address it? Thanks.

Cyl 1.jpgCyl 6.jpg

[Steve W]

Call Clint. Send him the pictures. He will work with you.

[22LD]

Thanks, Steve. I already reached out to Clint, send pictures, and will be calling him. Sounds like he's suggesting a cowl mod. I'm just not understanding why I'm the only one who seems to have had this issue. He mentioned he's built a few Cub cowls, but they are open around the boot cowl.

[stinger]

Larry, from my account with Clint you might as well start modifying the cowl . He is so smart, that he knows everything about everything . He built my exhaust however would not listen and I went back in worth many times he reluctantly did it my way. I was not happy as I was the customer . Good Luck Stinger

[rodsmith]

Larry, that is perplexing. Clint built my exhaust which had to be modified to fit around my cold air plenum and long intake pipes and still fit in the cowl. I sent him dimensions and pictures and was pleasantly surprised that it fit with good clearance. With an unmodified IO-540 he shouldn't have any trouble building it to fit the cowling. I would let him know you aren't modifying your cowling, and he needs to make the exhaust system fit.

[zkelley2]

I have a vetterman exhaust and it fit perfect to my narrow deck, parallel valve o-540. No cowl clearance issues.

[22LD]

Thanks, everyone, for the posts. I've spent the day with two IA's who have also built multiple aircraft. They are genuinely perplexed. Clint at Vetterman says the exhausts are all made in a jig and they should all be pretty close one to the next. We did experiment with moving the nose bowl down considerably (way below centered behind the spinner) and that seemed to almost eliminate the clearance issue. Really not sure where to go from here. Don't know if it's an issue with the nose bowl and the exhaust. There's another AZ Bearhawk fairly recently completed that I might be able make some comparisons and take a few measurements.

[davzLSA]

I found that just quietly sitting in front of the engine and just staring at it that usually the solution comes to me, Or the engine is just so intimated from my non-blinking gaze it just gives up and tells me the answer. Your mileage may vary.

[Battson]

Yes we have seen this before, in the community.

I think this happens depending on the propeller hub you select. Hubs are different lengths

If the prop hub is short, then the cowl is closer to the firewall and the angle to the engine is tighter. My nose is just one or two inches longer than normal, and I have ample clearance between the Vetterman exhaust and cowl. Obviously the normal Hartzell prop fits with a Vetterman, so I will go out on a limb and guess you have an unusual prop.

I think I know someone who fixed this, maybe. He was talking about blisters but I don't remember if he found another way around it. EDIT: I checked it out and he does not have blisters, so I can't imagine how they fixed it. I think maybe he lowered his cowl a little, as it doesn't line up perfectly.

I suggest very shallow blisters would be the easiest solution, with basically no impact on the look of the aircraft. Getting the spinner close to centred on the cowl is important to the look of the aircraft.

The Vetterman exhaust is a great product and I am thrilled with mine, it is now 7 years old and 700hrs in service. Flawless.

[22LD]

Jonathan, I do have the Hartzell CS 84" prop and spinner purchased from Mark. The hub/spinner are in my opinion pretty close to the crankshaft flange. 1/2" MDF disc on front of starter gear gives me 3/8" clearance from back of spinner to nose bowl. I've seen that are much farther from the flange. So that might be part of the issue.

Just as an experiment, we lowered the bowl about an inch and were able to get a small amount of clearance, but obviously it was far from centered and would require major fibreglass work. It seems almost as if the bowl for longer from center to bottom that would solve the issue, but Mark has assured me that the nose bowls have not changed in a very long time.

I've considered blisters, but in my case, it would really work. The entire "U" bend in the #6 cylinder hits the cowl.

Thanks for the input. Some good food for thought and I do think it might be related to the hub even though I'm running a Hartzell typically used on the BH.

[AZBearhawk272]

Larry,
On Scott’s build we encountered similar issue.
Fixed it by modifying the nose bowl lower side cheeks.
Only had to move outward 1.5 inches to clear all
issues and no paint blistering. If you know glass work, pretty easy. Also modified top edge of lower cowl to allow removal of lower plugs without hassle of cowl
removal.

KD #272
Phoenix / CHD

[22LD]

Thanks for the info. Haven't done any major glass work, just some small stuff on my RV. Not what I wanted to hear, but sounds like that might be in store for me. I suspect the nose bowl is probably the issue. Just looking at mine, the outer circle behind the spinner is slight oval in the vertical dimension. I have about 1/4" above and below the spinner and only about 1/8th" overhang on the sides. That doesn't seem like much but may translate into quite a bit more width out on the sides.

[svyolo]

It looks like you haven't built the cowl yet. Would it be possible to bow out the lower cowl support channels very slightly and put a small amount of curvature in the lower part of the cowl?

[jaredyates]

I have had cowl clearance problems too and found that the nose bowl is a bit negotiable, and if it isn't adequately supported, can change its shape slightly over time. Things that could change the bottom cowl position include the slope of the nose bowl in the pitch axis, and the circumference of the lower cowl just in front of the air outlet. The pipes that were way too low on our plane bolted right on to another Bearhawk and fit without any trouble. Clint's not out to scam anyone, it's just that he's got a hard job with lots of variables. I've found his support to be above and beyond considering.

[svyolo]

Fiberglass parts with a large unsupported lip like the cowl probably rarely come out of the mold exactly the same. How they are stored for a long time will also affect the shape. Having 1200 degree exhaust pipes mounted inches away will also effect it over time. Lots of variables.

[Ray Strickland]

I’ve also had great support from Clint.

[Sebastian]

Larry
You have most likely resolved your issue but I had a similar with my clearance of my exhaust headers from Vetterman. I called Clint and found out that he had headers he has made to fit tighter to the 0-540s than the ones I had. He swapped them out for me with only the shipping charge. If that hadn't happened it would have forced me to modify my cowl.

[Gary Wallace]

Sounds good. i went ahead with my cowling assuming all will be fine . Exhaust should be here friday so hopefully confirm all is good!!

[22LD]

I sent my exhaust back to Clint and he "tightened" it up enough so that now it fits. Sent it back the end of September and had it back in a couple weeks.

[Nev]

My exhaust has the same issue as the others above. The pipes from #1 and #6 both touch the cowling. I’ve checked and double checked the nose bowl position. My prop hub is a Hartzell.

I’ll contact Clint, but given that I’m in NZ, the distance, time and cost would seem stacked against any idea of sending it back for modification.

[Battson]

A small modification to the nose bowl may be a more time / cost effective solution.