Heater Mod Questions

[bagarre]

I'm going to convert the cabin heat system on my 52 170 to the 53 and up design and a few questions have come up.

1. What's the size / tension of the spring on the valve cutoff door? Figure 55 #23 PN 0713019-37

2. Has anyone installed the long duct across the firewall without removing the control column? I havent tried yet but it doesnt really look possible since the duct is the same width as the plane.

3. Has anyone installed the new style heater valve on the left side of the firewall? I'm curious how the cables were routed as the wire bundle exits the firewall right where I think the cables should go.

4 Lastly, could someone give me a good reference for placement of the duct across the firewall? I could guess at the middle of my existing heat valve hole but the actual location would be better. (bottom rivet line is x inches from blah)

Thanks in advance for any help.
-David

[GAHorn]

That spring is remarkably "light" duty. It is about 3/8" coils, of approximately 22 ga steel. It's primary purpose is not to actually "pull" the valve closed....as it is to remove any resistance-to-movement issued by the bowden-wire-control.
I am not near my airplane, but I believe I can provide a source for that spring if you're willing to await my return this next weekend.

[bagarre]

Yes I can wait. I still need to order the cables and schedule some time in the hanger.
Thanks!

Could you also take a few photos of the rivet line for the duct? I'd like to put it exactly in the right spot vs plus or minus an inch or two.

[hilltop170]

David-
Like George, I am out of town and won't be home for several more days but I have pictures of my 1951 170A converted to the late style heater with the heat valve on the left side.

The control column was not removed but the battery box was and it was converted while the engine was off. That made it easier but hopefully should not be too difficult with the engine in place. If your engine/mount has not been off in awhile, that would be a good time to remove it and the engine mount and replace the mount/firewall bushings and clean and re-coat the firewall with cold galvanize spray available from Home Depot in spray cans. It is really good stuff.

You might search the Forum as I have previously posted pictures of the conversion.

[GAHorn]

Yes I can wait. I still need to order the cables and schedule some time in the hanger.
Thanks!

Could you also take a few photos of the rivet line for the duct? I'd like to put it exactly in the right spot vs plus or minus an inch or two.

I URGE you to choose the ACS A-740 "ratchet" type of control cables for the system, as that type will be very helpful and convenient in selecting heat and avoiding un-requested heater-valve movement due to vibration. (Spruce handles them.)

[hilltop170]

George, that is the exact heater cable I used, thanks to your recommendation, and it is working perfectly.

[blueldr]

I've seen that mod where the cross firewall duct was made in two pieces for easier installation with a loggled lap joint in the middle. If I was doing it, I would forego the joggle and seal the joint with a piece of heavy alunimum duct tape. (Easier than joggling the square duct.)

[bagarre]

The ratchet cables are a great idea. I might even put one on my mixture while I'm I there.

Cutting the duct in half is another good idea that a friend on the field mentioned. It's probably the route we'll take. I just hate to cut up NOS parts if I can help it.

I wasn't planning to pull the motor or mount forth is job. I'll save that for the motor swap in a few years

[GAHorn]

The ratchet cables are a great idea. I might even put one on my mixture while I'm I there. ...

I've got one in that position as well, and its adjustment-increments are quite good for the job. I usually "count" the clicks and quickly match previously-proven settings.