Making new hole in firewall for heater
 

A recent post on installing a manifold heater got me to wondering.
Putting aside the question of weather you or should or should not do this.

How would you or have you went about cutting a new hole in a firewall?

What tool to use, how to line it up etc...

Re: Making new hole in firewall for heater
 

I put a short extension tube into the rear of the manifold heater so it would hit the firewall,I then traced the circle and cut it out with a dremel,I filed out the final fit for the heater door.

Re: Making new hole in firewall for heater
 

I used a hole saw once up on a time.

Re: Making new hole in firewall for heater
 

Rocket 1's line up for the hole is the way to go! On my model A, someone had messed up the hole and it was not where it should be, and hence, I had to make a brass plate and bolt it in place then use Rocket 1's method of alignment, but I went up on Amazon and found this, which was 2 inch and the size I needed. LENOX Tools Hole Saw with Arbor, Speed Slot, 2-Inch (1772779)! So once I got my brass plate installed on the engine side of the firewall, and lined up the hole, everything fit perfect. to connect the manifold heater, I kinda cheated on vintage and used a piece of silicon hose for a supercharger sized to fit the firewall vent and the the other end sized to fit the manifold heater and held it on with some old hose clamps. Really for the fit, hose clamps were really not needed.