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Originally Posted by DaX
Not that I'm close to buying an engine or anything, but I cannot find anywhere (already searched) a listing of what engine model stands for what. I hear lots of stuff tossed around "stay away from the H2AD", "A1A is good" - but I want to be able to decide for myself, and I can't do that unless I can see what all is available and what the differences are.
I'm sure it's out there, and I'm probably just overlooking it, but I'd appreciate a helpful nudge in the right direction. Someone please break it down for this newbie. Thanks  |
First, a publication called "Certified Aircraft Engines", SSP-204, Feb 2004.
http://www.lycoming.com/support/trou...ces/SSP204.pdf
This is lycomings Certified engine guide. It explains the difference between a A1A, D1A and H2AD (somewhat in broad terms). The guide explains their engine suffix for all their engines. The suffix indicates things like if an engine has dynafocal/conical mounts, constant speed prop capability, carb or FI, compression ratio, HP, type of: carb, mag, crank, prop flange.........
It's a good start. Most Lycs start as an A1A, call it the base line or generic engine. The other engines or suffix ID's are usually differences referenced back to previous models. All variations trace back (usually) to the base line. Some times the differences are inconsequential, like a new magneto dash number. Other times its a major differences, which can make the engine undesirable or usable for RV use. The guide is cryptic and convoluted somewhat but its a good start.
You can always search these archives with an engine suffix. I am sure people have already asked if engine 'XYZ' is OK to use in a RV and why or why not.
A select few reasons of many people prefer one engine over another:
-HP a 150 HP verse 160 HP O-320's (debate on value of 10 HP)
-Constant speed prop - Sold crank vs hallow crank, Governor accessory drive
-Fuel pump - Some Lycs don't have a mechanical fuel pump set-up (for high-wings)
-Engine mount - Dynafocal I, II and Conical. Dynafocal I is preferred (the others work)
-Wide or narrow deck - preference and not shown in SSP-204 (basically narrow=old, wide=newer)
-Sump - some carbs/TB's are bias to the rear, even side/aft mounted (may be changed out if u find a sump$$)
-Induction (I or IO prefix)- Carb v FI, fwd/horz or vertical. (Horz is FI or pressure carb - stay away from press carb)
>Converting a 320 from 150HP to 160HP - Is not recommended on some models of the 320 but its done all the time.
>Engine mount: Dynafocal I, II and Conical mounts are all supported by Van's; they require different mounts.
>Sumps - can be changed and cowl mods are done to adapt the unique engines (H2AD) to RV's for example. Search the forums.
>Fuel Pumps - Some engines don't have the drive pad for the mechanical pump. There are work arounds for that. Search the forums.
>Constant speed prop - Some engines config's that indicate fixed prop can easily be converted to CS props, some can not. It primarily has to do with the crankshaft being hallow. The SSP-204 guide is not great for determining this. In the real world there are variations within the same model number. Hallow cranks use a removable plug to adapt to fixed prop operations. That plug can be removed. A solid crank? Out of luck. The case also needs to be drilled for hyd fluid and an accessory drive pad for the gov is needed. You can always modify & switch parts, but that becomes uneconomical. General wisdom is buy what you want, unless the engine is free, conversions can cost more money and time than it's worth.
>H2AD - is unique, an engine that works; again search the forums. If found for a bargain in good condition, it can be a good value but does require "adapting" and requires a H2AD engine mount from vans. Its an OK engine w/ a bad rep from it's early years. Again long story - do an archival search here.
Some things are preference and some NO GO items. Do a search on any of the above topics and you'll find extensive debate. Bottom line there are similarities between all models.
A good conversion idea many have done, is get flying with say a used fixed pitch prop engine. When your are ready (and have the money) to go constant speed prop, fuel injected or what ever your heart desired, sell the engine and buy another that fits the bill 100%, verses converting the existing engine.
Go to lycs web site or Google Lycoming
'Key Reprints'. This is a free publication. "Key Reprints" has articles on General (info), Maintenance and Operation of Lyc engines. The info is a goldmine. I think every pilot should read the key reprints once. Also consider Sacramento Sky Ranch "Lycoming Continental Engineering Manual". Well worth buying.
http://www.sacskyranch.com/pubsem.htm
Good Luck & happy engine hunting. Of course buying a new engine solves the alphabet soup issue. It's another debate worth researching - New v Used. By the time you buy and rebuild an old engine, you may be with in $1000-$9,000 of new. One will be a used rebuilt, the other a brand new engine. You decide but in context of overall build cost, consider the new option with warranty.
Lycoming engine models - D1A? A1A? What??
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