The International Cessna 170 Association

I did the DelAir conversion on mine with an O360 and Hartzel constant speed. The O360 is actually a bit lighter than the old C145. However, the Hartzel is heavier than a fixed pitch. So the cumulative effect was the same weight, but the center of weight for the engine and prop combination moves slightly forward with the conversion.

I moved the battery back behind the baggage to help compensate for this, but that really wasn't needed.

Jr.CubBuilder wrote:...I moved the battery back behind the firewall to help compensate for this, but that really wasn't needed.

Where behind the firewall? ...and how do you service it?

Oh, my bad, I was tired.

Not behind the firewall, rather behind the baggage compartment.

Servicing is one reason I'd like to move it back to the front of the firewall, and the other is that long heavy battery cable that runs all the way under the floor to the starter solenoid.

The original STC location is a bit problematic with the motor conversion. The STC blueprints locate the original box in the top center of the firewall. This looks like it would be very awkward for maintenance on oil filter and mags.
The new lower motor mount arms get in the way of the lower passenger side even though the wall space is available. Another 170 on the field did the Cont. IO360 conversion and they used the Atle Dodge battery box STC, mounting that at an angle for easy removal of the sealed battery.

I'm not in a rush so I'll keep mulling over possibilities.