350 Chevy V8 engine for power generation?

[BioHazard]

I have a small industrial shop where I have no heat and expensive electricity. I also happen to have a good running 4 bolt main heavy duty 350 Chevy truck motor. Clearly this engine is much bigger than needed to run a generator, (175hp) then again, it could power quite a lot at less than 1000 RPMs.

When I'm at the shop there's an easy 4kw continuous load from the lights alone, not including everything else. I would mount the engine inside my shop to capture most of the heat, also thought about using water cooled exhaust manifolds designed for boats. I was thinking it would be useful to leave it attached to it's manual transmission and I could use that as a PTO to power larger tools like a welder, air compressor, etc.

Everybody seems to be into diesels for CHP, but, I don't really see the cost advantage unless you're burning waste fuel. Chevy V8s in good running condition aren't really worth much more than $300-500 vs $1500-$5000+ for a good diesel. Gasoline is only slightly more expensive than offroad diesel/heating oil/propane.

My main question is am I going to have a problem running an automotive engine that large that slow for hours on end? Would it be advantageous to come up with some sort of heavy flywheel...or do all the extra cylinders negate that need? Are there other modifications I might want to make for low speed use? (not that it was ever meant to be a high revving engine, it's out of a 1 ton truck) I'm looking at possibly running it for around 4 hours a day.

I understand that this is not the most efficient way to make a kilowatt out of a gallon of gasoline, but since all the waste is heat, and I want that too, I'm not too concerned about that. Am I wrong? Any "inefficiency" there is just ends up as a heat product. The engine would be run for heat demand, and not electricity. Electricity is the "waste" product.

[mobile_bob]

i am not crazy about any engine being mounted in a habitated space, however
the 350 chev as a prime mover is solid in concept.

even though it is rated at 175hp, it is unlikely that it ever produced that amount of power on a consistent basis
most automotive gas engine's produce a small fraction of that amount of power on a more or less continuous basis
otherwise their gas mileage would be abysmal

i am not as keen on the use of the transmission, mainly because it eats power and really is of little use for what you
are trying to do, if you plan on running the engine at 1000rpm the trans will only make it slower in all but high gear anyway.

i would just use the bellhousing for the standard transmission, and mount an outboard flange mount brg to support an output shaft
you could use a clutch if like and an input shaft from a trans for the parts to make the accy drive shaft and mount a suitable multigroove
pulley outboard of the brg.

if your engine is a computer controlled model, perhaps you can determine the idle rpm program setting for that engine and set the pulley
ratio to take advantage. also it is possible to trick the puter into thinking the engine is running cold and have it set the idle speed higher?

it may be stable enough to keep the rpm/frequency stable for generation?  but i am not sure.

couple it to an st15 or st20 and have fun

leave the Air conditioner compressor in place and you could also have space cooling for a decent size office while the engine is running, also
you could easily drive a large frame alternator for a battery/inverter backup system too.  the p/s pump can be retained for some hydraulic requirements in the shop as well, and you can also drive a nice size air compressor if you like.

in a home environment the 350 chev makes little sense, in a medium size shop... done right it just might.

bob g

ps. i really like the idea of thinking of the heat product as the primary and electrical production as the secondary or waste product.

[AdeV]

The biggest problem you face with a petrol engine is its power curve. Most of the power is concentrated in the 3-7krpm range. Yes, it may well be rated at 170+hp (most likely at 5000rpm), but at 1000rpm - a bit over tickover - you'll find it very easy to stall, and probably surprisingly feeble. It will also be desperately slow to respond to the throttle as the load changes. Startup is hard because you have to juggle choke & throttle, all while maintaining a super-accurate rev range...

I know all this from trying to make a 6kw generator using a Rover K-series engine - only a 4-banger, and probably only 100bhp compared to yours, but it was a nightmare from start to finish. We were trying to run it at 1500rpm IIRC, and it was a properly ticklish business. We gave up in the end and went with a 4-cyl Ford diesel (1.8 litre IIRC) which isn't perfect, but 1500rpm is much further into the diesel's power band, so it takes the load changes without bogging down so badly.

The control system is a custom made microprocessor job using servos to operate the throttle (and, formerly, the choke) and relays to control the electrical output.

[billswan]

Welcome to the forum Biohazard

My first thoughts are you will be surprised at how much gasoline that large of a displacement can eat in a 4 hour run.

I agree with bob forget the transmission it will just cause you grief.

I hope your shop is large enough so you can put up a sound deflecting enclosure around the unit.

I am heating my shop with a 10/1 listeroid but the noise is deafening, hopefully in another year or 2 when the project reaches completion I will then move the whole thing into an adjoining cold storage building. Of course that will be a major under taking to the enclose the unit and pipe the heat and electricity to my shop and house.

But if you do build it please report back, some of us here will love to here of the outcome good or bad.

Billswan

[BioHazard]

Thanks for the quick replies everyone. I should have been more clear before, I was thinking about mounting a generator head to the front pulley of the engine and leave the trans in back - in neutral if I'm just generating electricity. I would build a small dedicated engine room in my shop, appropriately fire proofed inside.

As for the speed, I have yet to think about any way to control it. It is a 1979 model engine so no computers. Does anybody sell a semi-reasonably priced "off the shelf" governor for an engine like this? Also, I know the 350 has been used in many industrial applications over the years, I wonder if it would do me any good to find a special cam designed for low speed?

As for the loads I was thinking about the 6 cyl engine in my Jeep - it idles at 600 RPM, and at that speed I can heavily load the alternator, turn on the A/C, and turn my wheels real sharp (power steering pump), also add the clutch fan and water pump, and still the engine stays about 600 RPM without much difficulty.

Just thinking out loud here. I need to go to bed, I've been up all night...

[BioHazard]

Another question - just how much fuel do you think it would use in an hour with a very small load? For some reason I have the number of roughly 1 gallon/hour for idling a V8 in my head, but I don't remember where I cam up with that number...

[mobile_bob]

if it burns a gallon an hour just idling i would expect another gallon per hour for each 6kwatts of electrical production

the carburated engine will be a real hassle as outlined by Ade,

as for a governor, woodward build or at least built a belt driven governor, which is the one i would use for this engine
"if" i were to try and use the carb system.

i think you would be far better off with an injected computer controlled engine myself, the startup issues will be much less
the rpm at idle much more predictable and the engine will be much more stable in operation.

btw the '79 350 was rated at 175hp at 3800rpm, however all car engines are rated at that level for intermittent use
in my opinion

i think you could pull a max of about 10kwatts electrical at engine idle, with a computer/injected engine, and likely half that
with a carb engine because of rpm stability issues.

now if you were to set it up for 1800rpm operation, then you might get closer to 50 kwatt electrical production and a bunch of heat
which you likely will have no use for unless you have a big shop.

just more rambling here

bob g

[Ronmar]

If you are going to run it at around 1000 RPM, you will want a different carb.  carbs are flow dependent devices.  The stock carb is designed to feed that 175 HP at 3800 RPM.  If you are trying to get it to drive 10-12 KW of electric generator(20-24) HP, the original carb will be doing this at a nearly closed/near idle throttle position.  This means a very tiny throttle response will be required to make control changes, so it will be difficult to deal with load changes.  This is probably the biggest problem AdeV encountered with his auto engine conversion.  It is difficult to control at such a small throttle position.  IMO, to feed around 20HP, you need a carb sized to do this nearer a 50% throttle position.  Since the smaller carb holds sway over less HP, it requires larger more easilly managed throttle movements to deal with load changes.  A large riding lawnmower carb might work for this.  A large flywheel will also help here by storing energy and delaying the effects of load changes.

I think I saw belt and gear drive governors at surpluscenter.com...

Good luck.

[bschwartz]

Would a cheap aftermarket cruise control work for speed management.  I added one to a jeep years ago.  It ran off of engine vacuum to control the throttle, and used a magnet on the drive shaft for speed sensing.  You could put the magnet on any other rotating shaft i'd imagine.  For the carb, how about a holley 390, or a small two barrel?

[vdubnut62]

I would adapt a single barrel off a six or 4  banger.  I had a mechanic neighbor who used cruise controls for governors, but for a generator setup, I would think it would have too much droop, ( not hold a close enough rpm range). But I've been wrong before,a bunch of times .
An old power unit would be almost ideal for this application.

Ron.

[BioHazard]

I definately like the idea of a single barrel carb. Right now it has a 4bbl and I was thinking as long as the secondaries stay closed, the primaries are smaller than a standard 2bbl carb - but you're right, trying to adjust the throttle such a tiny amount would probably be very difficult. Not being much of a carb expert, I wonder if I could simply plug up 3 of the 4 barrels in my current carb?

I'm starting to think maybe I could just generate DC current and use one or more power inverters, that way RPM control wouldn't be terribly important. (I already have a 3kw Xantrex I'm not using)

A nice computer controlled fuel injection setup would be great too, though, I think that would be too much work to add to my old engine. One of the things I like about old Chevies is the only tool you need to work on them is a 9/16" wrench, some duct tape, and a good vocabulary of cuss words.

This is obviously more of an experiment/hobby than an actual functional heat/power source. Honestly installing the engine in my shop is as much for "decoration" as anything else. But, if it works out well, I want to scale it down and do something similar with natural gas at my house...


Also I should point out my shop is an uninsulated concrete building, so I need LOTS of heat.

[Lloyd]

Reasonably thinking...insulation is going to be a bunch cheaper then the road you are contemplating.

Now if Power demand is big enough, and no three phase available...your project might just come in a little bit cheaper then solar....

And almost no solar installation makes any economic sense against the cost of grid-power today. The long term is debatable, but any real savings today will be lost to amortization of the obsolete equipment purchase made to have solar today.

So if this is more of an...I can do that, as opposed to beating the meter charge, then it sounds like fun.

Which we all know is the biggest hole in our wallets.

Lloyd

[KeithO]

I did something similar to this years ago with a LPG (propane) fueled Mazda, charging batteries for an inverter at a high idle.
After a while it began carboning up ,then oiling up the plugs.
I don't think the combustion chambers were getting hot enough and the rings gummed up .

I think a V4 Wisconsin would be a better choice

Keith

[BioHazard]

Reasonably thinking...insulation is going to be a bunch cheaper then the road you are contemplating.

Good point. This is a commercial building that I lease, thus, I do not want to invest in insulation. I plan on building my own shop in 1-2 years, at which point my generator can follow me or I'll use what I've learned and come up with a better system.

As for cost, that's why I'm designing it as a "heater that makes some power" rather than a "generator that makes some heat". I'm sure KWH for KWH, mine will cost significantly more than the power company. BUT - the power company doesn't give me heat. I've only done very rough math so far, but if you consider how much oil or propane (or electricity) I would have to burn in a heater to get the same amount of waste heat as my engine, I'm alot closer to the break even point. I still need to do some more math. Also, the commercial 3 phase power I have cost more per kilowatt than the juice does at my house from the same utility.   The most cost effective fuel available here is natural gas, but, it's conveniently not available in my shop.

Also I don't presently have a heater in the building, besides a little electric space heater, so I'd have to spend some cash on an oil or propane furnace of some sort anyway.

I did something similar to this years ago with a LPG (propane) fueled Mazda, charging batteries for an inverter at a high idle.
After a while it began carboning up ,then oiling up the plugs.
I don't think the combustion chambers were getting hot enough and the rings gummed up

Interesting point, I wonder if I should try an extra hot thermostat - maybe around 210 degrees?

[KeithO]

Interesting point, I wonder if I should try an extra hot thermostat - maybe around 210 degrees?

I don't think it would hurt.
Also a regular high rev/load run to get the piston crowns up to temp might help too.

I've got my doubts about its long term life, but if you have an engine lying around to experiment with by all means have a crack at it,