4-732 Firewall Baffle

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CF-KYE
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4-732 Firewall Baffle

Post by CF-KYE » Wed Dec 10, 2008 07:35

Morning all,

A friend of mine just bought a 7AC that has been re-engined with a C85, but the previous owners never did any of the mods for increasing the cooling. He's purchased a new nosebowl from Univair and now we're setting up to do the firewall mod. I have the drawing for the mod to the firewall but I need a drawing of what the baffle (part #4-732) looks like. Has anyone got one?

thanks,

Dan
warbirds@shaw.ca

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joea
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Post by joea » Wed Dec 10, 2008 08:26

Dan,

Just emailed the drawing to the email on your post.

Keep an eye on your oil temps. If they are higher with the bigger engine, you might want to put a blast tube pointing down to the oil screen area. Its been discussed on other threads on this forum and works very well to lower oil temps.

Hope it helps and let me know if you need others.

Joe A

CF-KYE
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Post by CF-KYE » Wed Dec 10, 2008 13:04

Thanks Joe,

The Aeronca clan to the rescue - as usual! I hadn't thought about that blast tube but I have one on my 7CCM now that you mention it. Thanks for the tip - we'll be adding one. I'll be posting a querry about brake parts for this "7BCM" shortly. The airplane has oddball hydraulic disc brakes. I can't think of the name of the mfg off the top of my head but they were in Harbour City, Calif and I've never heard of them before. It looks like so far we've got at least one busted brake disc to find a replacement for. She was your classic semi-abandoned, flat tired Aeronca with some pretty questionable maintenance issues, but after pulling the wings and tail and cutting the belly out her she's sitting in a warm shop undergoing a pretty heavy C check!

Dan

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Post by Holcombe » Wed Dec 10, 2008 22:02

You are worried about heat, I can't keep my 7CCM C-90 warm enough.
After all the talk, I think there may be a bunch of defference in how well the baffles seal against the cowl.
Tail winds are a "Good Thing"

CF-KYE
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Post by CF-KYE » Thu Dec 11, 2008 07:40

Hi Holcombe,

Have you ever tested your oil temp gauge with a pot of boiling water and verified it's accuracy? It is unusual for them to be too cold. Even in the winter all I've ever had to do to get good oil temps is tape off the oil cooler inlet hole and I have a C90 in mine as well.

Dan

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Post by Holcombe » Thu Dec 11, 2008 11:41

I have checked my oil temp gauge against a probe on a multimeter and it reads about 20 degrees cold. Still my oil is running about 100 degrees above the outside air temp or a little less. On a 30 to 40 degree day my oil is not getting warm enough to drive off moisture. result, frequent oil changes. Less than 25 hours.
I do cover the air vent to the bottom of the crankcase. It makes maybe 15 degrees difference.
I have a remote spin on oil filter. I tried makeing a sock for that but it didn't seem to make much difference. The oil tank sock from wag aero seemed a fire hazard as it was too close to the Hanlon Wilson exhaust.
Restricting the air out the bottom of the cowel seemed too extreme for my climate here on the coast.
Tail winds are a "Good Thing"

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Post by CF-KYE » Thu Dec 11, 2008 12:11

I have pretty much the same setup as you except I don't have the spin on filter, although that is going to get added this spring on the annual. I do have a six qt tank but can't see that making much difference. I probably run anywhere from 160-170F for an oil temp on a typical summer day, and can get almost the same thing (maybe 130-140) by just taping off the oil cooler inlet in the winter. Summer oil is Shell W100 and winter is W80. The J-3 with a C85 does about the same in the summer. The max oil temp for a C85, C90 or O-200 is 225F, but sometimes people think that you have to get it up to 212F to get rid of the moisture - and of course that's just not true.

Continental says min oil temp for take-off is 75F, and when it's cold I just keep the power on all the time and come down final on the backside of the power curve pulling something probably around 1500 rpm. When it's seriously cold I turn up the heat in the shop and twist wrenches! :D

Mnflyer
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Cont max oil Temps

Post by Mnflyer » Thu Dec 11, 2008 13:48

Hi the max inlet oil temp for the 0-200 / C90 is 240*F when using detergent oils per Cont Specs MHS-24 and per note 6 of the TCDS.
I agree 100% the oil temp does not have to reach 212*F to get rid of the oil.
My 0-200 runs cool oil temps also this time of the year its hard to get above 165*F with the oval air inlet blocked off the oil screen blast tube removed a nice wool mit on the oil filter and both nose bowl cyl openings blocked about 1/3 on the inner (next to the prop) part. Installing the cyl. covers brings the oil temp up the most on my plane, as of yet I haven't installed the lower cowl baffle. The oil tank cover helps a lot with the temps and really helps if one shuts down for a hr or so to fish etc , I/ve seen them in use here in MN for 40 years and have never heard of them catching fire (and I've seem some pretty oil soaked ones in use) they look to be made of a fire resistant material.
GB MN.Flyer
Flying a Champ 7DC and a HKS Kitfox III

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Tim Juhl
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cooling

Post by Tim Juhl » Thu Dec 11, 2008 19:19

I have a C85-12 built up with the O-200 crankshaft mod & etc. I too have a problem keeping it warm enough in winter. Summer temps may hit 190 on a warm day, but I have trouble getting 140-150 on a winter day.

My cowling does have the cooling mods and I put a lot of effort into building up silicone baffle seals that seal well. I think the baffle seals do more to promote good cooling than anything. The old felt seals let a lot of air escape.

Tim

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Post by jkvincent » Thu Dec 11, 2008 20:01

Dan,
I also have a C85-12 in my Champ which does not have a modified firewall. Is his engine presently installed
so he's certain he needs to modify the firewall?
My engine mount is slightly longer (+/- 2") so everything fits without the "dishpans".
It also meant a slightly longer top & bottom cowl.
Jim

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Post by CF-KYE » Thu Dec 11, 2008 20:42

Hi Jim,

Yes, as a matter of fact the previous owner actually cooked the new engine and then had it rebuilt again and there's very little time on it right now - less than 100 hrs - but the engine checked out perfectly with nice clean oil, nothing in the screens, and 78 was the lowest jug. It's got the short mount but has the B&C starter and 200G alternator so everything fits ok. I've got the long mount on my 7CCM but will probably go back to the short one to make her a little less nose heavy. She's perectly balanced with two of us onboard but has just abit of a heavy stick landing with just me up front.

Dan

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