The International Cessna^® 170 Association

This last annual, I pulled off the old firewall pad and was amazed at the corrosion from old glue and the number of extra holes drilled from years of who knows what.
So, we cleaned it best we could (It turned out to be solid), riveted up all the holes (big steel pop-rivets) and painted the thing on the inside.

I'll never put a firewall pad in after seeing that mess.

I'm in the early stages (collecting parts) for a TCM IO-360 conversion and thought, "Why not replace the firewall when it's all apart?"

How nuts is that? It seems like a few days work to drill out and rivet in a new one. Am I missing anything obvious?

Maybe a few more days to clean up and prime internal bits that I'll never ever see again.
What else should I do if I do this?
Rudder pedals, brake cylinders/hoses?

Is this a bigger can of worms than I want to get into?

Lots or full-restorations began as small repair schemes.

Pulling off and installing a new firewall is a good days work if you know what you are doing and start at about 8 am

I'm interested in this as well. I have as much visceral hatred for patches as I do for unusable holes in a piece of material (and overspray and general griminess). I would see that as a good way to access areas of your airplane that haven't seen the light of day in over 60 years, such as your rudder pedals and associated hardware, as well as having more unrestricted access to the back side of your panel. Mike Roe posted some pictures of the new firewall that he was putting in N2475D, and it was a beautiful sight.

Hip bone, leg bone philosophy aside, I would be concerned with ensuring that the firewall didn't shrink, causing fitment issues with the cowling, making it painfully obvious to anyone that your firewall were replaced. I've seen more than a few C150s with a cowling that doesn't match up to a replacement firewall. I'm sure that has every bit to do with the competence of the person performing the repair as it does with the quality of the part, but I would hate to think that I ruined something that was functionally okay for the sake of getting rid of a few old holes.

So long as one has a concerted plan of attack instead of making new work for themselves "while I'm in there", I think that the benefits would far outweigh the costs and effort. I wouldn't set out to make a one-day job, but certainly within a week or two to make sure that everything was kosher wouldn't be bad, if I were writing the checks and making the decision to have my airplane down for a period of time.

Bushings for the rudder torque tubes are cheap and easy to replace.
The replacement Cessna bushings are plastic, not metal, but they were less than $20 for the set.
Trivial job with that kind of access.
Easy access to the brake hoses, cylinders, pedals, etc. fix it all when you have the firewall out. None of it is difficult.

Much harder to do it from the other side.

We did it on my 55 170B project. Used stainless steel replacement.
John

You might contact Dick Doll (his San Diego area address is in the 2011 TIC170A directory) for advice. I believe the replaced the firewall on the conversion of his C-170B.

Ohh, this would make it easier to put the header tank under the floor too.

bagarre wrote:Ohh, this would make it easier to put the header tank under the floor too.

David dont be a design engineer think as a mechanic for accessibility when you have to repair it. You probably dont want that under the floor . D

Very good point.
And to think I get on people's case about that very same mistake in software development.

I guess you have to follow the install per the STC but...if you could copy the 172 XP, it's header tank would fit nicely under the R/H floor with the aux pump under the L/h side and no requirement to butcher the firewall.