# ls3 for aircaft

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#### PIRATE

##### New Member
what are the possibilitys of an ls3 being used with direct drive?

#### don january

##### Well-Known Member
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Log Member
Pirate: for me one of the less educatued flyers what is Is3?????? and direct drive what a corvair , vw, subaru, ???

#### Toobuilder

##### Well-Known Member
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There are several threads concerning the LS series and SBC direct drive conversions.

#### leifarm

##### Well-Known Member
I thought the LS 3 was a sailplane from the seventies

#### ekimneirbo

##### Banned
what are the possibilitys of an ls3 being used with direct drive?
There isn't anything to prevent it mechanically.
Other automotive engines have been done that way. Its simply a matter of attention to details in how you make the mechanical connection. Gary
Spencers well known canard has a Ford with just a simple prop adapter. Personally I would want some type of housing with a bearing and shaft
to lessen bending moments on the crankshaft. It can be done fairly simply. A lot of Corvairs are using a direct bolt on "fifth bearing" which is a
small bolt on adapter with a housing around it. One thing to remember is that the LS engines have a thrust bearing that is in the center of the
crankshaft rather than at the back...so if you make an adapter you might want to include an additional thrust surface in it. It kind of depends on
how you design your drive setup. As mentioned earlier there are existing threads where a lot of information and opinion already exist on HBA.

Somehow or another people thought that if an auto engine could produce 400hp, then it needed to be capable of that when adapted to an airplane.
That thought of course meant that the engine had to be operated at a higher than usable rpm so a reduction drive was needed. Personally, I have
been pushing the idea that in most airplanes the higher horsepower isn't needed or even usuable. Operating at something like 3000/3200 rpms will
allow for excellent hp amounts and the propeller can be designed to still have good efficiency.

The first thing you need to consider is the actual airplane you want to use the engine in. In some cases there is enough room to move the engine rearward
or to extend the fuselage to offset the additional weight. The thing is, you have to be realistic as to whether the airplane of your dreams is capable
of using the heavier engine. I love LS engines. I have a brand new LS3 crate engine thats going in a pickup truck. I really want to use one in an airplane.
The problem is that I want STOL capabilities, and I had to finally face the fact that an LS engine was not going to produce what I want. A Rover or a Corvair
(maybe turboed) may give me a better option. Its 400+ lbs for a LS engine, about 300 for a Rover, and about 200-230 for a Corvair. When considering any
of these engines remember that its not just engine weight to compare. An aero engine may be lighter, but usually thats with a metal prop. Use a wood or
composite prop and you lessen the total weight and put less stress on the drive and engine.

http://www.summitracing.com/parts/nal-19301326?seid=srese1&gclid=CJLappzEuMkCFZAAaQodYVUH5Q

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#### Goatherder

##### Member
I did extensive research on this subject, and prevailed on the wisdom & knowledge base of those who know about it. I set out to build a canard aircraft using the Ford V8 as in the aircraft above. Had a few conversations with the owner. He installed this some 20 years ago, and has 2000ish hours on it. His engine is 270hp and 337lbs dry. Makes this hp at 3500 rpm. Very fuel efficient at cruise speeds.

What made me change direction was packaging. Crank is in the bottom of the V8, so the thrust line of the propeller will be down there as well. I decided to use a Chev V6 & a prop drive that raises the thrust line about 5" (IIRC).

I also investigated LS engines, and talked to Dave at Waterthunder Airboats. Dave builds LS engines for airboat use exclusively, and knows what it takes to make them live in this application. Which is very similar to an application in aircraft. He advised me against direct driving a prop with an LS engine due to the thrust bearing arrangement...which in his (extensive) experience was not up to the task. He has since developed a thrust bearing arrangement with which to drive a prop directly and build a direct-drive (DD) airboat with an LS engine. It's performance was apparently pretty good, and surprised many of his critics. You can find the video on YouTube. Again, w/ DD V8 there may be packaging/thrust line issues.

LS3 with starter, alternator in ready-to-run form but w/o exhaust is almost exactly 400 lbs. Airboat prop drive adds another 70, but greatly boosts hp and alleviates packaging problems.

#### Victor Bravo

##### Well-Known Member
HBA Supporter
I've brought this up before, but it bears repeating here. An Australian glider club went to the trouble to get an automotive V8 engine derivative allowed on their Pawnee towplane. They saved enough money in fuel/maintenance/operating costs/towing performance over just a couple of years... to buy a brand new European training glider.

That was a few years ago, so I will guess that the automotive V8 developments have improved since then. If I remember the story right, the Aussies' engine wasn't even the lightest or latest V8 available.

These engines are set up to use less expensive fuel as well. It seems to me that the effort and cost required for a good aviation conversion (including whatever thrust bearings, redrives, and re-programming is appropriate) is well worthwhile. I would guess that the biggest factor will be whether your airframe is appropriate for this size/weight/power of an engine.

#### ekimneirbo

##### Banned
There are several/many truths about utilizing an auto conversion and its comparison to using a used aviation engine.

The basic idea is that someone without much common familiarity with engines would be better off to purchase a readymade and proven

Charlie

#### Toobuilder

##### Well-Known Member
HBA Supporter
Log Member
I think I can do a direct drive extension system that incorporates 100% of the propeller loads AND provides an oiling system for a CS prop for less than 25#. It's a chunk of weight, yes, but a far cry from a PSRU.

#### ekimneirbo

##### Banned
I agree on the hp required issue; it's pointless to put 400+ hp on a plane designed for 200. And I know direct drive's been done, but most of the ones I've heard about that have high time on them also have basically a short drive shaft & outboard bearings to protect the crank. (I suppose Gary Spencer's might be the exception.)

The issue with direct drive on non-aviation engines is that the output end main bearing isn't long enough to keep bending loads away from the 1st crank throw. Even the VW & Corvair guys are adding an outboard bearing, and they swing really short, light weight props. Once you add enough structure & a crank extension for an outboard bearing, you're not that far away from the weight of a reduction drive which can provide bending load isolation and torsional tuning in addition to reduction. And with bolt-&-go airboat drives going for <$2500, it's difficult to develop a one-off direct drive outboard bearing setup for less$time\$ and money. And if you want STOL performance, swinging a big prop at lower rpm is another big advantage.

Charlie
I agree with you on the need for an extension shaft and bearing to isolate prop from the crank. LS has thrust bearing in center of crank rather than at the back like Spencers Ford or smallblock Chevy.

Direct drive with a bearing should weigh maybe 1/2 of a reduction drive built to handle over 200 hp. 25 maybe 30 lbs. while the old Geschwender chain drives were about 80 lbs.