Replace stock O235 engine with O320-E2G AirModsNW STC

Bob Steward suggested I create a page here in an attempt to describe the process of performing the engine upgrade from the O235-C2C that our AA1x models came with to the more appropriate O320 engine. I started with a core that I purchased from Gil Alexander. I'm told Gil did me very well in selling me this core. It's an O320-E2G, which is the stock engine for the Cheetah. This worked out best for me as I wanted to use the STC available from Ken Blackman AKA AirModsNW. There are three STCs available to choose from to perform this modification. If you are considering the upgrade gather as much info as possible on all three before making your decision. Each has its positive and negative sides. Each owner needs to weigh the pro and con of each for them-self. My decision was made on recommendations of others who had used Ken's STC and by my A&P after describing the process involved and each of the STCs. Since my particular A&P/IA had never performed an O320 conversion on a Grumman AA1x before (C&P brand yes, just never an AA1x) I wanted to go with the one that had the most documentation provided with the STC.

For the engine I chose new ECI Cerminil cylinders. I picked Winchester-Aero Services for the overhaul of the engine. This STC limits the HP to the stock 150HP pistons and since the crank did not pass the AD inspection, it's my understanding I would not have been allowed to use it in my engine with the 160HP pistons. I was told by several reliable source gurus on the GG that I'd never miss the 10HP. They were right; going from 108HP to 150HP has been such a dramatic increase in power it's like I'm flying and entirely new airplane. I intend on uploading photos of the project as I put this article together. So keep an eye out for updates.

Day 1: Removal of the old O235 engine. Removal was a fairly simple process. It is a REAL good idea to keep track of every nut bolt and screw as well as making GOOD documentations of what wire came from where. If not just be sure to label every wire indicating what terminal it goes to. A good digital camera helps here too showing routing locations etc.

Day 2: Firewall prep & engine mount repair. I ran into a snag with the lower right engine mount extrusion. Fortunately I was not in excess of the allowable limit on this and after a day or research and sweating was able to save a ton of $$$ and at least 3 days of work. A separate article should be written on this repair and a good procedure for inspection for this. I stripped the firewall down of dirt and paint. Since I've never been real great with a spray can I elected to have Jeff paint my firewall. Before and after photos of this will appear here shortly.

Day 3: Hanging the engine (AKA how many washers & where do those spacers go?).