I’m working on an aircraft engine project, with the parameters listed below. I’d like some feedback on a SOHC modification to the LS engine. It would be quite similar to the LT6 and LT7 series of engines, with a “Finger Follower” under the cam.

The camshaft on each cylinder head would be gear driven.







This engine is for a propeller driven aircraft, with the following engine goals / aspirations:

1) 90 degree V-8 piston engine, spark ignition, 4.4” bore spacing

2) 336.7 inches3 up to 388.4 inches3 = 4.060” bore (103.57 inches2) x 3.25” up to 3.75” stroke

3) 500 hp @ 5000 RPM (or less)

4) 250 HP (50%) 325 HP (65%) @ 3800 RPM +/- 500 RPM

5) BSFC of 0.38 pounds fuel / HP / hr (about 15:1 AFR) at 50% to 65% power

6) Two turbochargers - when one turbo could seize or explode, the other can still work, plus electronic controlled wastegates

7) MAX altitude = 25,000 feet (about one third sea level ambient air pressure)

8) “Critical” altitude = 18,000 feet (one half ambient air pressure) - Maximum rated power available up to this altitude. The turbos would be at maximum “boost”

9) Intercooler(s)

10) SOHC

11) Gear driven items that “cannot fail”… cams, mechanical coolant pumps, mechanical fuel pumps, at least one small alternator for engine controls, prop govenor

12) Belt driven accessories - hydraulic pump, vacuum / air pump, air conditioning compressor, main alternators, any other accessories

13) reversible direction of output shaft (for counter-rotating propellers)

14) 2.2:1 reduction gear box with quill shaft

15) 650 pound target weight, OR LESS

16) Small, compact size

 

Number 16 is already well accounted for with the gen3 LQ9
Number 15 is your overweight solution in search of a problem.
2 valve pushrod LS motors are durable, efficient, lightweight and make plenty of power through your stated RPM range.
.
SOHC brings weight, parts count, and NO advantage to the party.

 

This sounds like a real cool thing to do with something on the ground. Like the other fellow said the engine is durable. I would think overcomplicating putting a camshaft in the head and then getting yourself in a position where literally your life depends on it would just be unnecessary. The old non dod engines are proven and they don't have timing chain problems. Good luck with your endeavor either way.

 

Hi, I created "Camless Engines for AURA/ Boeing/ Sturman.
They were made to operate UNDER 5K RPM.
I Used Electric AND Electro Hydraulic Actuators.
Would you like my help (panteraefi@gmail.com)
Lance

 

We don’t need to make “plenty of power”… we need to make 500 hp, and no more. The time limit at 500 hp is 5 minutes, or less. 95% of the time, the engine will run at 50-65% power.

I’m not sure why you think that the engine is overweight. It will be whatever a typical LS engine with an AL block and heads weighs. The target is 650 pounds (or less). You’d be surprised how quickly all the bits add up in weight.

 

I’ve had this response on other groups. Maybe my math is different than everybody else’s math, BUT, the SOHCs eliminate valve lifters and pushrods. That’s 32 parts, gone! Plus, it makes the “V” more useful for other things, like the intercooler, or maybe an air/oil separator?

The rocker arms are replaced with the finger followers, and do NOT require studs, bolts, nuts, etc to secure them. Less parts and weight.

Did Chevrolet get this wrong on the new LT5-6-7 engines, with OVH cams and finger followers?

What is added:

1) a second camshaft

2) Bolts / castings to secure both camshafts (offset by the casting that is no longer needed in the block)

3) Several gears required to operate the camshaft

 

You would be so far ahead if you just started with a LT5 engine, I cant imagine the amount of tooling and fabrication required to pull this off and it would all be for nothing like others said.
Also I dont think the V would give you enough room for what your wanting to do.

 

Stock L33 Aluminum Block and heads.
Aftermarket camshaft spec for YOUR torque curve, with valve springs to suit. Pair of small journal bearing turbochargers: Done.
Nothing to Invent, just weld up the pipes, and adjust fueling and spark table.

 

All fun and games until the Crank Sensor goes out. Have to change that on the fly, literally.

 

You're confused. The LT engines are all central cam/pushrod/rocker engines like the LS.
What you propose would add weight and complication to what is a dependable, proven engine.
Finger followers are essentially repurposed rocker arms.
The weight you think you are saving is more than made up by the second cam and a potentially very complicated gear drive as you state under #3.
An aircraft engine needs to be basically a slow turning, low power density, BUT light design in order to live the long hours under constant high power percentage levels that running an aircraft demands. Your proposal would not end up that way.

 

I didn’t spend much time looking, but I found an intercooler core size: 9.25"L x 3.5"x 3.5" in the first few minutes of looking. I could LITERALLY fit four of those in the V space.

https://www.siliconeintakes.com/fron...ler-p-209.html

 

Magnuson TVS1900 on 4.8 LS, .550" Lift 212/218 cam, LS6 valvesprings. 4.56 gears, positrac and big tires.
Simple, reliable, available off the shelf parts. Been running one since 2016. Drove through 11 states, 3 Canadian provinces- 11,000 miles Alaska to Texas ( and BACK) the long way in 3 weeks. 100 degrees F in Texas, -25 F in Canada, ran just as strong at 9200 feet southrim of Grand Canyon as it did thru death valley. Never touched a wrench to it, except to drain the oil. EASY, smooth, quiet, 500 flywheel horspower, and as reliable as an anvil. Been driving it HARD like a teenager for 8 years.
.... Going to repeat: Supercharged stock bottom end DAILY driver, thrashed like 20 year old 4x4 , and I bounce off the rev limiter every day ( In summer. I drive gentler on ice- don't usually like to spin my winter tires ): NOTHING has broken since I put it together in 2016, have not replaced a sensor, belt tensioner, idler, water pump, Only maintenance in 8 years-
R&R belt, air, fuel and oil filters. Changed the spark plugs once. There is literally not a better, long lived, efficient, durable and easily maintained engine built by any company on the planet in the last hundred years.
I have 5
LS engines in my family fleet, ALL are 20 year old STOCK BOTTOM ENDS, never had oil pans off, aftermarket cams, exhausts, Two are forced induction, and ALL had 100,000 + miles on them before I got them. . A good friend runs a set of 3 Chevy vans, all with 5.3 for a Courier/Delivery intercity Freight business, all STOCK un touched 5.3 liter, getting nothing but oil changes and filters for 15 years. He's not yet worn out an engine, has over 325,000 miles on the one he's driving this month. Year round service in Alaska, he wears out brakes, wheel bearings, ujoints, transmissions, T-cases, , but NOT LS engines..
IF you need to regularly move loads under 10,000 pounds with Gasoline power, you WILL NOT find a better prime mover than -pick your size - Gen3 or4 LS

u can go ahead and invent **** all you want, but you will NOT find a more durable, reliable longlived 500 horsepower V8 than a STOCK Pushrod gen3 LS motor.

 

I always enjoy these aircraft discussions. They bring innovation and conversation to the table. As stated, the LT6 engine is the only current GM V8 utilizing overhead cams, and would save you likely $100’s of thousands in engineering costs, in attempting your own design of a overhead cam engine, only to make you the Guinea Pig here.
The LT6 would be an expensive endeavor to make work, but I’ve always seen that when dealing with anything aircraft related, money is usually no object.
if your looking for something compact, and your willing to twin turbo this thing, I’d look a different direction and consider GM’s 2.5 liter I4 LCV aluminum inline 4. It’s durable, reliable and would respond wildly to twin turbos. You won’t need the 7k rpm in a prop aircraft, and I don’t think you’d have to spin it that high to make good power…. but then again, the LT6 will spin 8K rpm…again that won’t work with props. Its super lightweight and very compact. Just throwing you an option across the table.

 

Sure, we could start with an LT6/7, or even LT5, except that there’s no support for that. That truly would be an experiment. If I really wanted to experiment, I’d probably start with an opposed piston 2 stroke diesel. Those were used in the 1930 by the Germans and British in airplanes.

Yes, the budget for this project is probably more than you would believe.

Honestly, we need the BSFC of 0.38 or better (lower number) at 250 to 325 hp, and high RPM tends to NEVER be that. So, all the 8000 RPM engines are great for takeoff power for 5 minutes or less, when we don’t care about fuel efficiency, but not so muy bueno for best efficiency for hour after hour.

See attachment of all the metal that we don’t need with our SOHC:

 

Are you planning to make your own blocks, or plug the lifter oil passages in GM blocks?

Are you planning to make your own heads?

How will you get oil up to the cam bearings, lobes, and followers?

I really have nothing to offer, other than curiosity.

 

I guess you can see why we will likely keep much of the LS design. But, it would not be accurate to say that the valve train is the strongest part of these engines, and the LS7 is the poster child of bad valvetrain components.

This SOHC concept is intended to lower the complexity AND parts count of the original LS design. Do you know what never fails, doesn’t cost anything, and weighs nothing in an engine? Stuff that isn’t there!!!

1) No camshaft chains, nylon gears, and some of the other stuff from GM

2) No lifters, no pushrods, no lifter guides (48 missing parts)… yes, these parts BREAK… always have, always will

3) Lots of aluminum not needed for lifter control. There is a surprising amount of AL used for support the lifters.

The Cessna 421, which we hope to be the first recipient of one of these engines, weighs almost 8000 pounds. It requires two engines.

Thank you for your support.

 

I’m not sure that this has the “track record” required to have hard data on durability.

 

This is just idiotic. The OP does not want to use an lt6 as a base, because there is "no support". At the same time the plan involves completely fabricating an ls block and heads, as well as all accessory drive systems. Literally the only stock engine parts would be the crank, rods, and pistons. Since rods and pistons can be interchanged between multiple applications, the only actual ls specific part left would be the crank. What is purported to be an ls modification is actually a clean sheet brand new engine in order to do what the OP suggests.

 

I wholeheartedly agree.

 

Didn’t realize that you were working with a 8000lb twin engine aircraft. That would have been nice info for your first post.
If your going to circumvent the LT6 platform, only to try and recreate the LT6 platform…I don’t know what I can add here to this discussion.