Engine - air compressor conversion?

[PHILIP8N]

The weak spring is only on the exhaust and the conversions I've seen were Model A and Chrysler flathead 6 so they weren't terribly high speed engines. I suppose if you had a high enough reving one, it could be a problem but as you mentioned, they run at about 2400.
I remember I had a 283 Chevy in a Jaguar XK120 roadster and had to go over 6000 before it started breaking down, which we attributed to valve float, but never new for sure that's what it was and didn't want to push it any further to find out the hard way. Of course a weak spring would aggravate the problem.

The weak spring is always on the intake of a hit-and-miss engine and the discahrge valve is controlled by the governor and eccentric, and these engines only run a few hundred rpm. The two way concentric valve used on a high speed (1800 - 2400 rpm) compressor is quite sophisticated. Total lift may only be 2.5 mm and typically contains one seal ring, 6 lentoid springs, and 1 backing ring. Philip.

 

[handirifle]

I love this idea. You sound like you've done this before! What do you use for the two plates?

Nope never have, but I've seen valves like this before. can't remember where though.

I think you could make them on a lathe with 1/4" low carbon steel. You'll only be dealing with a couple hundred PSI, tops. A small lathe could easily turn them to match the head valves you removed.

The center hole for the threaded rod is the only one that needs to be centered, the others are not critical, as long as they are covered by the movable plate.

The movable plate should be some thing spring steel. Spring steel is less likely to warp, thus keeping a tight seal on the holes.


I love this thread, it makes me think it might be a cool project to take a 4 cyl engine and turn it into a 2 cylinder generator/compressor to pull behind the tractor when needed.

 

[old1mech]

There used to be a company in Longview Texas that converted V6 and V8 engines for half and half use, Ford made a small one, 4 cyl I beleive and continental made a 4 cyl inline,I have one of these but it is not operational at this time. I built one from a VW engine years ago and about 2 months after I put it on the shelf Dunn Wright I think that is the name of the company that offers the conversion kit through mail order posted an add in Hot VW's and Dune Buggies. I had the idea 2 years before they did but didn't have the cash to really persue it the way I wanted to. One main thing to remember is you have to have big enough outlet valves or multiple valves to handle the heat generated by the air compressor. If not then you will be running along just fine and all of a sudden the disc valve will shatter on one of the cylinders. The VW engine will self govern it's speed at 1600/1700 rpms and it puts out a lot of air. If Dunn Wright is still offering these conversion kits it might be the easiest and cheapest way to go. I had an engineer tell me it couldn't be done because of the heat it generated, I don't put much stock in what some engineers think although just like anything else there are good ones and there are some over educated idiots out there. I'm one of the uneducated variety. If there is a problem with something there is usually a way to overcome it. Good luck with your project. P.S. If you can access The Farm Show magazine archives, they ran an article of someone who did a 350 and powered it from a pto.

 

[Travelover]

I've seen "L" head engines converted to an air compressor where the valve springs were replaced with a very weak spring and the cam followers were removed. When the piston moved down it sucked in air through the valves (weak spring allowed this). When the piston moved toward the top, the valves sealed closed and the air was expelled through the spark plug hole. Of course, on an overhead valve engine, the weak valve springs would allow the valves to collide with the piston.

 

[pat32rf]

I've always thought of powering one engine from a second unit because I could never figure out how to stop the intake valves from pulling in an air/gas mixture without a special intake manifold. Might be simple to do on a slant six though.....

 

[SPYDERLK]

zmoz:

I don't think the Chevy 350 will work without some extensive modifications.

Firing order on that engine is probably 1-8-4-3-6-5-7-2 which means it fires on the same side of the engine on consecutive firings.

The reason the Ford 302 worked so well was because it fired on one side, then the other throughout the revolution of the engine. You could block off all the cylinders on one side and it would still run smooth since you took out every other firing.

I hope this makes sense. It's a lot easier for me to see it in my head than to actually put it into words.

Put a heavy flywheel on it.

 

[PHILIP8N]

Put a heavy flywheel on it.

Lot of truth in that!

 

[PHILIP8N]

The reason the Ford 302 worked so well was because it fired on one side, then the other throughout the revolution of the engine. You could block off all the cylinders on one side and it would still run smooth since you took out every other firing.
QUOTE]

The 302 had two different firing orders throughout the years. Which one worked best? Compressors were also made from the 460, which has 2 cylinders on one bank fire simutaniously, it worked just fine. Philip.

 

[smiley]

I've always thought of powering one engine from a second unit because I could never figure out how to stop the intake valves from pulling in an air/gas mixture without a special intake manifold. Might be simple to do on a slant six though.....

Here are photos of the slant 6 manifolds. As you can see, each cylinder has an individual intake and exhaust tube. This is the exact reason I have one in inventory awaiting conversion. It should be quite easy to cut and block the manifolds, and build a new intake with filter, for the 2 compressor cylinders. Because the exhausts are also individual, they could also be cut and plumbed back into the air holding tank so you wouldn't have to use weak springs, thereby no possibility of valve float, which I don't think would be a problem anyway at normal engine speeds.

 

[zmoz]

I think I'm going to see if I can have a custom cam ground for the 350, with an extra lobe 180* apart from the normal ones on the pumping cylinders like with the VW kit. I don't think it would be too difficult to modify an intake so one side doesn't get fuel.

 

[Hooked_on_HP]

One thing I haven't seen addresed yet is stopping fuel from going to the cylinders used as the compressor.If you don't you are building a BOMB.
You also have to figure out a govenor set up to control the engine .
If this was an easy conversion engine compressors would be cheap and easy to find.
Bill

 

[zmoz]

One thing I haven't seen addresed yet is stopping fuel from going to the cylinders used as the compressor.If you don't you are building a BOMB.

The intake of many different engines can be easily blocked, allowing another hole somewhere else for air intake. I thought that was obvious...the same as redirecting (part of)the exhaust into the air tank.

The more I research the more I see these are actually quite common in industrial compressors. You just don't notice them because they're inside a beat up old trailer.

 

[smiley]

One thing I haven't seen addresed yet is stopping fuel from going to the cylinders used as the compressor.If you don't you are building a BOMB.
You also have to figure out a govenor set up to control the engine .
If this was an easy conversion engine compressors would be cheap and easy to find.
Bill

If you look back at the photo's of the slant 6 manifolds, it's simply a matter of cutting them off and welding up whatever is needed for the conversion. Not quite as easy on V-8's or 6's with integraly cast manifolds but certainly do-able. Just look at headers and early 6/8 carb or fuel injection setups.

 

[dcyrilc]

I have an old Grimmerschmidt compressor which used the ford V8. They still sell parts for them. Worst case senario, buy an intake and head.

 

[Hooked_on_HP]

The intake of many different engines can be easily blocked, allowing another hole somewhere else for air intake. I thought that was obvious...the same as redirecting (part of)the exhaust into the air tank.

The more I research the more I see these are actually quite common in industrial compressors. You just don't notice them because they're inside a beat up old trailer.

Using a chevy 350 as the op wants to how are you going to block off the intake to prevent fuel from entering and still get air in to compress with out building some exotic intake.
Bill

 

[handirifle]

Using a chevy 350 as the op wants to how are you going to block off the intake to prevent fuel from entering and still get air in to compress with out building some exotic intake.
Bill

I would the KISS method. Why try to cut and weld on an aluminum manifold, unless you're skilled with TIG. I would make a sheet metal "plug" by bending some light guage steel to a shape that would fit about 2 or 3" inside the manifold, from the head side. I would bend it so you have a flat baffel, with tabs bent on 4 sides. I would then place it inside the manifold and drill through the top and bottom of that runner and run a sheet metal screw through each hole, into the baffle.

I'd then remove the baffle, and apply a liberal coating of JB Weld on the outer edges.

Once dried, I would then drill out an opening in the top of the runner, BETWEEN the baffle and the surface that contacts the head. Make it large enough to provide sufficient air flow (3/4" or larger) and thread it with a pipe thread to allow fittings to be attached. If you could, it would be better to totally open it, ie. cut it off from the baffle out. The more air in, the more efficient it will be.

Maybe some else has a better method.

Anothe thought might be that if you're using only one bank of the engine, have the manifold cut with a metal cutting bandsaw, to a straight flat, surface, that cuts off all the compressor side ports. Block them off with sheet steel and JB Weld (there's no pressure coming out the manifold) with the JB on the OUTSIDE of the manifold, and make new adapters to attach to the head and routed to your intake air filter.

 

[smiley]

Using a chevy 350 as the op wants to how are you going to block off the intake to prevent fuel from entering and still get air in to compress with out building some exotic intake.
Bill

Or keep it really simple and buy four of these, ( Spark plug "air compressor")
stick them in the spark plug holes and be done with it. If I remember correctly, they have one way valves that allow intake of air on the downstroke and close on compression out the hose. I have one in the barn and will check it today. Then you can close off the manifold any way you want. Even stuffing rags down it--- until they worked through to the valves--which could make for some interesting noises and air output.

 

[PHILIP8N]

Or keep it really simple and buy four of these, ( Spark plug "air compressor")
stick them in the spark plug holes and be done with it. If I remember correctly, they have one way valves that allow intake of air on the downstroke and close on compression out the hose. I have one in the barn and will check it today. Then you can close off the manifold any way you want. Even stuffing rags down it--- until they worked through to the valves--which could make for some interesting noises and air output.

I believe the 'spark plug' compressor inserts only work on the compression stroke, and will still discharge a combustable mixture. Still uses inlet air from the engine intake valve. Think about the discharge area the compressed air can exit thru the spark plug hole, about the size of a pencil. A 1/2 horsepower compressor will flow more air than that! The old monoblock Grimmer-Schmidt 302 and 351 compressors with dedicated head and two way concentric compressor valves make 125 scfm and 175 scfm. They also had automatic variable speed control to control capacity and automatic unload when discharge pressure was reached. How is you homemade machine going to do this? The death of the monoblock compressor for commercial use was Ford obsoleting the 302 and 351 engines and the necesary EPA requirements a new engine/compressor configuration would have to meet. Electronic controls did not help either since you are now using half an engine. To do it right, investment cost would be huge. Cost of the diesel rotary screw compressor was now near equal to the monoblock compressor, so this is all you see on the markert now. Plus, the diesel rotary screw compressor will have a much longer life than the reciprocating monoblock compressor. Philip.

 

[westcliffe01]

Home

I believe this is one of the companies who started the conversion of VW engines and they still do them, even turnkey compressors on a trailer.

They drive all the valves with a cam, this is much more efficient than incurring pumping losses when working against spring loaded valves.

 

[Mace Canute]

Regarding the "spark plug air compressor"...the engine piston stroke is used to operate a simple diaphragm by the action of suction & compression. The air that goes into the tire is drawn from atmosphere and the unburnt fuel from the cylinder goes out the exhaust pipe.

The "combustion chamber" size also affects the efficiency of an compressor made from an engine and by quite a bit. That's why commercial compressors have a very small volume above the piston @ TDC. The smaller the better actually.