Question for Paul McBride, General Aviation News engines expert: With the lack of O-320 engines currently out there and officials at Lycoming Engines saying 24 weeks for a factory overhaul of the O-320-D2G for my 1979 Skyhawk, I’m digging deep to get a core I can overhaul and have ready when my high-time D2G gives out.
Can I take a 150-hp O-320-E2D, from a 172 or Cherokee, and rebuild it with D2G parts and make it a 160-hp D2G?
I know there are 160-hp STCs for this, but they all limit RPM and full power operation. It’s not really 160 hp like a D2G or D3G.
Steve
Answer: Steve, I hate to be the bearer of bad news, but what you would like to do regarding converting a Lycoming O-320-E2D to an O-320-D2G is not possible.
For one thing, the crankcases are completely different, as I’m sure other major parts are as well.
The O-320-E2D was built to meet a low cost engine requirement for certain airframe manufacturers. An increase in horsepower was never considered.
Under the present day supply chain circumstances, you may want to consider getting an engine on order even with the extremely long lead times if you can handle the financial hit.
You should also keep in mind that prices rarely go down and most certainly will increase, so this makes the decision as what to do even more challenging.
I must admit that I’m glad the decision is not one that I have to make, and can only offer my best wishes for you as you move forward.
For a Cessna weighing about 2,000 lb, the added 10 hp will result in about an increase of 160 fpm in rate of climb. It is the hp in excess of that required for level flight, at the same airspeed, that determines the roc.
So, going from about 700 fpm to 860 fpm is a nice added performance increase.
As was said, the added 10 hp will result in a small increase in cruise speed.
Penn Yan has an STC to convert the E2D into a 160hp engine. A friend had it done.
Hi Steve,
The simplest way as Paul suggests, is to place and order for an exchange overhaul or rebuilt 160HP, 0320 engine. In the past Lycoming have been very accommodating in accepting the Es in exchange for Ds. providing they were as removed and with up to date engine logs. Not sure these days as times have been tough for all, would’nt hurt to ask though?
If you really want more take off and cruise performance I would go with what Klaus suggests and install an 360 STC upgrade. This engine is heavier but you get another couple of hundred pounds on the payload with the STC. The 360s have 4 and 3/8 inch crankshaft stroke length, whereas all the 320s have a 3 and7/8 inch stroke length, the bores on both the 320 and 360 are 5 and 1/8th inches in diameter which is the same, its just that the cylinder barrels are slightly longer to allow the use of the same length connecting rods. Compression ratios are 8.5:1 on both, engines which are rated at 2700 rpm. The extra performance comes from the greater crank leverage (Torque) and thrust via the larger diameter propeller, which is required as part of the STC. Horse power is just a calculated number i.e Torque x RPM divided by a constant. A dynamometer measures torque using a load cell and RPM from the shaft rotation. Horse power is calculated from these two numbers and corrected to a standard such as SAE. The gen 2 Cessna 172R use the 360 cubic inch capacity engine. The R Model RPM takeoff limit is 2400 and 160 hp is produced at this rpm. Compression ratios are the same 8.5:1 There is an STC to fit a larger prop, a recalibrated tacho and anti ICE intake to the R model, to run it up to 2700 rpm (180 hp).
I agree with Miami Mike, cleaning up things on the airframe can be a very good way for cruise performance increase. The main thing is don’t get too hung up on the HP number, how long do you spend at full throttle anyway?
best regards Kiwi Don
LAME/IA , New Zealand
Long time engine and propeller overhauler and thanks to Paul for all his help over the years, it sure was appreciated!
I would recommend looking into replacing the exhaust system with a ‘Power Flow’ unit.
the claimed gains are 20+ HP from a tuned and much less restrictive system.
So, no need to touch a good running engine.
[ I have no connection to power flow, I just wish there was one for my Cont. GO-300 ]
Steve, why not o/haul your present engine, but have the cylinders bored .010″ over size, that alone will give you 160 h.p. total.. I did that to my 0-320 plus some other things to the heads and cylinders, plus after market exhaust and a bigger carburetor, now that 0-320 puts out 170 h.p. , it went in the RV-4 that I built. It hauls the mail, has been in the aircraft over 12 years trouble free, I love the performance, and fuel burn. Sometimes the experts on said subject cannot explain themselves, and offer more confusion than clarity.. glad to be of help.
Just get an STC from Air Planes for an O-360 180 HP engine and gross weight increase. If that is not enough then you have the wrong plane and you need to look for a Cessna 182 with 230 HP.
The O-320 150 to 160 HP is good for trainers and two place aircraft. The O-360 180 to 200 HP is good for four place aircraft that mostly fly within a two hundred mile radius. Cross country four place aircraft should have a minimum of 200 HP.
Ten horsepower will not make a noticeable difference. As a rule of thumb, we get a speed increase equal to 1/3 of the percentage of horsepower increase. Example – a 150/150 has a 50% hp increase, it picks up about 17 mph in cruise. What you’ll get from adding 10 hp likely won’t even show up an the ASI – it is within the acceptable error range of the instrument.
If you want to go faster (and who doesn’t?), by far the most cost effective way is to reduce drag. Read Kent Paser’s book, Speed With Economy, he picked up a whopping 60 mph in cruise, +800 FPM in climb and 8,000 ft increase in ceiling in his Mustang II with almost no additional horsepower. Adding higher compression pistons only got him 2 mph of that, the rest was entirely through fanatical efforts in drag reduction. Read some of the old Jim Bede material (it is online somewhere – JB was a great engineer but shall we say not exactly the best businessman),
Probably the quickest, cheapest way to pick up a (tiny) bit of speed is simply to wash and wax the airplane. Then make sure all the cowlings fit properly, doors close properly, the airplane is in rig, remove any antennas which are no longer needed, make sure the engine baffles are in good condition (cooling drag alone is something like 35% of total drag).
There’s plenty of stuff on the net about drag reduction for GA aircraft, Google is your friend.
It’s the difference between ‘can I’ and ‘May I.’ I get the proposition, and that kind of thing is done day-in, day-out in hot rod power boosts of factory stock engines. Been there, done that. However, if one’s dragster blows an engine in the quarter mile, you just push the wreckage to the side and face the anger of the strip managers for getting oil all over your lane. However, if your airplane engine blows at altitude, you have less than a minute to say your prayers and prepare for eternity. Big, big difference. Safety first. Regards/J