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natural gas engine

12K views 14 replies 11 participants last post by  cougar1969 
#1 ·
I'm rebuilding a natural gas powered 460 for an irrigation well. I was thinking of using some performance modifications to increase performance and longevity. Like forged pistons, cam, maybe raise compression with a flat top. The engine runs 1800-2000 rpm 24-7 when it doesn't rain. What compression can you run with natural gas? Any suggestions?
 
#2 ·
Hi Dennis , I natural gas likes more compression (if memory serves me correct it NG has an octane rating over 100), we use to use 460's as pumping units but we switched to 3phase electric about 15 years ago,but I think a stroker 460 would work great , I know of one guy up here that use to run 2- 549 IH ans switched to 2- 440"s stroked to 572 and they use just about 1/2 the fuel that the 549's used ,I think a 545 stroker would work great .030 over bore with flat tops and a 4.5 stroke crank would be a torque monster at low rpm and I can't see why flat top hypers wouldn't work ( one of TMD's cheap $789 kits)
Frank
 
#3 ·
I'm not really sure about how high you could go with the compression ratio because the rpm is very low and it's quite easy to make the engine detonate at below about 3000rpm.

With that said, if you stay at or near the stock compression ratio and run a camshaft that's more aggressive dynamically than the stocker(more lift with the same or less duration) and a more optimum lobe separation and intake lobe centers I see no reason why it wouldn't pick up some over the stock engine.

What's the compression ratio on an engine like that? It seems to me that 330 Oldsmobiles which were often used for similar duty ran around 10:1 compression ratio. What it was actually I don't know.

I doubt that a forged piston is needed and I think that a cast piston will provide longer engine life with less wear on the bores which I doubt will show any wear to begin with....
 
#4 ·
Load?

What kind of power/torque does the pump require at the rpm you need to run it at?

Building a 500ft-lb engine to drive a pump that requires 100ft-lbs at its peak operating rpm won't do much except waste fuel.

I'd be tempted to simply take boneyard EFI motors, top them with a gas mixer on an adapter plate, cork the injector holes, lock the spark 3-4 degrees below the edge of knock (turn the distributor and listen while pumping...), and let it run until it dies. Price is right, disposable. Cam is about right for the job too. Hypers and that ring package is right for the job. Intake/exhaust is right as well. If it provides enough torque, why not just do that? If you need more torque, then I can see building something stronger perhaps. If I built a nice motor for my pump station, I'd be worried about it disappearing late one night.
 
#5 ·
460 NG build.

I agree with ByronRACE about using a 460 EFI engine or at least the heads and manifold using a PME 4V carb adapter.

The intake ports on the EFI versions are great for building low end torque. The exhaust ports are raised for better flow than earlier versions. With a good RV style camshaft it should produce some awesome low end grunt.

I have used RV cams in big blocks before and they produce incredible low to mid range pull but usually sign off at 4500 RPM. That should be perfect for the RPM range your looking at.

The EFI intake manifold is also better suited for low end torque production than the 460 NG intake. Most 460 NG and industrial engines I have seen use a cast iron version of the SCJ intake manifold.

If you use a hydraulic flat tappet RV cam then be sure use oils or additives with a high zinc content. Crane has a hydraulic roller cam #359331 that has the right specs.
 
#6 ·
This information is from a Impco carburation manual dated 1988.
COMPRESSION RATIOS. 1. Since natural gas has favorable anti-knock qualities, high compression ratios are practical within limits imposed by electrical ignition systems and compression heated ignition. a. Gasoline (except premium grade) is limited to about 7 to 1 compression ratio. b. Propane, grade HD-5, is commonly used in engines with 10 to 1 compression ratio. c. Natural gas is capable of trouble free operation in engines with 10 to 1 compression ratio plus a turbo-charged air intake pressure of 6# per square inch or more. Hope this helps, John.
 
G
#7 ·
I woudn't worry about increasing performance, Concentrate on good machine work and quality parts.

Typical constant RPM pumps only have so much capacity and only require so much hp to operate, increasing performance or the motor will probably decrease fuel efficiency and be useless anyway.
 
#8 ·
My neighbor uses TRW 2443 forged pistons in his 460 natural gas irrigation pumping unit. Reasoning of his engine builder was that it was better to burn the fuel in the cylinder than in the exhaust port. With the D3 heads, it's probably around 11.5 to 1, but since these things run at constant rpm, detonation isn't an issue. When you can get relatively "free' power like when raising the compression ratio, I would think it's going to help fuel consumption because the throttle isn't going to be open as far to achieve the rpm desired.
And they are tough pieces - his Murphy guage was plugged on his water pressure, and he ran out of water in the night( for the pump), and the 460 reved mental until it blew up. It broke the head off of the stellite valve, and the piston punched it right through the haed, and the cylinder split so bad you could easily see the inside of the block through it, and the piston was still in one piece. :shock:
 
#9 ·
Ford had some HiPo LPG/NG engines that you could buy as industrial units. They came factory with forged flat tops and a type of marine cam. Neighbor has a couple of them. I was running a high comp propane motor in my 79 with hyper pistons, they went bye bye in a hurry. I don't think they liked the cylinder pressure. Cranking psi was close to 190 psi. If a little more hp is needed can they lower the ratio on the gearhead? Let the motor rev a little higher and not lug as much. Almost all of my gearheads are 5:4 and motors run about 2200. I have had good luck with durability. What carb is on it now? Another easy way to get just a little more hp is a 425 Impco on a DOOE intake, good for an instant 7 to 12 hp.
 
#10 ·
RE: Natural Gas

I work for a natural gas utility company and have a lot of experiance with this fuel. If you convert an engine to natural gas without increasing the compression ratio you will loose some power. The Ford 5.4 dedicated CNG trucks had around 13-1. You also need to run more timing. Natural gas has an efective octane of about 130. It is a pretty good fuel for stationary engines, not so great for cars and trucks. All of the OEM,s have stopped offering CNG vehicles except Honda, they still sell cng civic's.
 
G
#14 ·
Post Whore!

The block is a D1 so I figure the pistons in the hole by .010 if not .020.

It had D3 heads and a peek in the Spark plug hole shows a flat top piston with two eyebrow valve reliefs..

Pull the valve cover and nothing special there.. just clean! STD non adj valvetrain
 
#15 ·
Re: RE: Natural Gas

66 ragtop said:
I work for a natural gas utility company and have a lot of experiance with this fuel. If you convert an engine to natural gas without increasing the compression ratio you will loose some power. The Ford 5.4 dedicated CNG trucks had around 13-1. You also need to run more timing. Natural gas has an efective octane of about 130. It is a pretty good fuel for stationary engines, not so great for cars and trucks. All of the OEM,s have stopped offering CNG vehicles except Honda, they still sell cng civic's.

I agree I have help my Father over the years build Irrigation engines and seems like the more compression we had the better they ran.. We used alot of Impco Carbs for this and seem to work great. Built a few for Propane also and they also like compression..


Randy
 
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