Don't count out the H2AD
I’ve been offered the engine of a 172N that I fly often to use it on my 9A. The engine is at TBO, but it is in good health. If I decide to go that route I’ll overhaul it before installing it. This bring two questions that I would like your help with.
1) Does Van’s offer everything needed to install it?, I know about the engine mount, but what about exhaust and all the FWF stuff?
2) I read that the mechanical fuel pump will require a bump on the cowling, does anyone have a picture to get an idea of it?
Thank you in advance for the answers!
Aitor
Altor,
As RB and others mentioned, the H2AD has alot of misnomers attached, mainly from the number of AD's (oddly enough) the engine had back in the 70's. I have flown several RV's with H2AD's that ran great and is a viable option, especially given they can usually be bought for less than a standard engine.
Differences/Concerns: Single port Dual Mag ignition. Bendix D2000
Forward engine driven fuel pump (a standard RV6 cowl will just clear without mod)
Cam AD issues. (T-Mod is one fix)
If the engine could be bought right, and I mean under $5K, I would go with a reputable shop rebuild to include: T-Mod, 9.0 compression, new cylinders (flowed and ported) balancing and use a crank trigger electronic ignition but keep one mag. A Catto prop would complement nicely.
Low budget option: rebuild as RB mentioned with new parts and aforementioned roller mod. Bolt in, go fly with
mucho denaro in your wallet comparatively speaking.
Electronic Ignition?
Several years ago
Airtractor8, a long time H2AD flyer posted this concerning Electronic Ignition on the AD:
You cannot use a p-mag on a H2AD engine. The drive dimensions and arrangement do not match up with the drive gear in the engine. As Rocket-bob suggested your only option is full dual electronic ignition via the crank trigger method or one crank triggered Electronic and one mag.
To do this you can just use the old D2000/3000 and permanently ground one side.(you may already have this setup?) OR use a single Bendix 1200 series mag in its place. The impulse coupling variety has the same drive dimensions as the old dual mag but must be setup to turn in the right hand direction.(most of them are left hand rotation but can be easily changed to Right hand). Try part# S4RN-1227 10-349365-6
You will not however be able to use an impulse coupling with this setup ( there is none available with the required amount of Lag in the right hand direction that will suit the 1200 series). You will need to use a drive coupling commonly used on 6 cylinder 1200 series setups with retard breakers. Part # AEL 73000. This coupling uses the same drive cushions and arrangement as the D2000/3000 and will work with the drive gear in the engine.
You have to use the Electronic ignition for starting and will have to setup your ignition switch(s) to ground the mag for starting or you will get kickback if the mag fires at low speed.
For the electronic I use a CPI from Ross at SDS.
If you decide to go full electronic,he also has a nice block off plate and drive gear pin setup for dual mag engines so you don't lose all your oil pressure when you remove the drive gear from the engine. A bullet proof fully user adjustable ignition with excellent after sales service.
Good Luck
Flying a H2AD in an RV 6 for 14 years..and luvn it. 
AT8
V/R
Smokey
