Engine - air compressor conversion?

[zmoz]

In the past, I've read about and seen many examples of large engines turned into air compressors. Sometimes they convert the entire engine and drive it with another, sometimes they might use half the cylinders to drive the other half as a compressor. This sort of thing seems to have gone out of style with the advent of more modern air compressors, but I've always wanted one...

Anyway, I want to try and build one out of a V8. I have a running Chevy 350 sitting around doing nothing. I would love to let the engine run on one bank of 4 cylinders, and use the other 4 as a compressor. I was thinking I could remove the head on one side, and replace it with a flat peice of steel/aluminum with holes drilled in the correct places. I've played around with it before and the engine will run on as few as 2 cylinders.

What I wonder about are the check valves. I would mount two on top of each cylinder, one intake, one exhaust. What kind of check valve would I need for an application like this? Obviously I can buy a million different types of check valves online, but the thing is, it needs to be able to open and close as fast as a compressor works. This might wear out a standard check valve very quickly, let's say one meant for water. I guess I could try and make some sort of reed valve? Or maybe there's some part I could use from a 2 stroke engine that would work? The easiest would be to find a valve with ~1/2" NPT threads that could handle that kind of duty cycle...

Just thinking outloud here. Anybody ever done anything like this before?

 

[Egon]

Do a Google on Compressor Valves. A plate valve is what you would be looking for.:thumbsup:

 

[brokenot]

Back in the early to mid 80's we had three or four 100 cfm compressors in the fleet that were made by the Gordon Smith company....later known as just "Smith" compressors.

Here's a "non-working" one on eBay right now that will likely go cheap:

Smith 100 Mobile Air Compressor - eBay (item 250728128030 end time Nov-23-10 13:55:31 PST)

They used 302 Ford V-8 engines, with one bank serving as the power unit and the other bank pumping the air. I had a couple of them apart for cleaning when they wouldn't build air pressure rapidly any more, and the compressor head used plate valves, if memory serves. There was a stack of plates over each cylinder and I think they were arranged, (once again....this was quite a while ago), so that the plates served as springs as well. They were slightly convex in profile. Wish I still had copies of the manuals, but you can probably find shop manuals for them, either from the Smith archives, or from eBay.

While the compressors built plenty of air and worked fine, the valve assembles did need period attention, especially if the machines sat for any length of time. The other drawback to the Smiths, was that the discharged air was pretty hot. Mind you this was back before all of the jackhammer manufacturers had cushioned or spring-loaded vibration reducing handles on them. All the hammers in our fleet had the handles cast as one piece with the upper hammer body. Having solid cast steel handles and being fed air from a Smith compressor meant that sturdy gloves were mandatory because of the heat transmitted.

Smith has been sold a couple of times I think, but their current owner is still in business. Check with them first about manuals or assembly drawings to see how the valve chest was arranged. A simple check valve like people use in a spark plug hole won't cut the mustard when it's asked to cycle open/closed rapidly and for an extended period of time.

 

[smiley]

Just for ideas ----- I had a temporary use for a larger compressor for sandblasting and had several engines laying around so started researching these conversions. A couple friends had them with Model A Ford and Chrysler flathead 6's and I saw a commercial one with the 302. Looking around at what I had available for a easy , cheap conversion, I saw a Chrysler slant 6. It has individual intake and exhaust tubes on the manifolds so should be easy to cut, block and convert the cylinders used for the compressor. I had figured out which 2 cylinders to use for the compressor so the other 4 would run the smoothest, but have forgotten which ones, as I did not build it because a friend wound up with a commercial jackhammer compressor that we used for my blasting job.
The engine is still in inventory and oiled up for long term storage, so if I ever get all the other projects done, it may still become a compressor.
Smiley

 

[TraderMark]

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.

 

[zmoz]

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.

That does make sense, unfortunately. Hmmmm. I still want to make one though...maybe I'll have to find a Ford. I was thinking it would be cool to attach a belt driven welder to the thing too...

Do a Google on Compressor Valves. A plate valve is what you would be looking for.:thumbsup:

Ok, I googled, still a little confused. I have an idea what you are talking about...but...is there anywhere I can actually buy a "plate valve" that I could possibly adapt to the engine?

Does anyone know what valves they use in the commercial units? Do they have a custom "compressor head", or do they just modify the stock one?

 

[Raspy]

I fixed a Model A compressor engine years ago and went prospecting with it.

It had a special aftermarket head that let it run on 1 and 4, while 2 and 3 were the compressor cylinders. That thing ran great and would run a big jackhammer.

It had a bad rod bearing when I got it so I had to remove the head and pull the piston and rod. The compressor part of the head was thin and flat, and in the process I broke it in two. No problem. I just Permatexed it at the joint and put it back together! Ran fine. :laughing:

 

[PILOON]

Often the valves on compressors are reed valves.
Best described probably as a piece of thin hacksaw blade without teeth, in other words thin flexible high tension steel.

For a project such as you want to do, I will suggest that something like steel strapping, the HD stuff used for shipping ie, 1 1/4 X 035 would be ideal.
One end is loosly anchored to allow flip flop or hingeing and aligned over the intake or outlet holes.
Naturally the inlet ones need to be on the piston side of your 'plate' head and the exhaust ones the outside.
Your fun will be to fabricate the exhaust manifold as you need one outlet for each cylinder that is linked for common outlet point
Since an engine compression is in the 100-150 psi range you'll need good welds to join that together to a common outlet point, and hopefully with minimal warping of the 'plate' head.
I'd consider the openings for valves would be better to have 3 smaller holes, like 3 x 3/8 (or 1/2) with one reed valve per set rather than on larger , say 1" hole.
This would lessen the strain on the reeds but still allow sufficient air flow.

Have often thought of a similar project, mainly as I'd like a decent sand blast unit, and for that you need CFM's

Another engine I have often thought of was the VW air cooled flat fours, and I know that there has been a commercial version of that idea.

Good luck with the project.

 

[wldrbob]

we have used feeler gages for valves for air compressers works good they come in any thickness you need and are pretty cheep

 

[smiley]

Does anyone know what valves they use in the commercial units? Do they have a custom "compressor head", or do they just modify the stock one?

My intention is to cut the intake manifold off from the carburetor and install an air filter system on those cylinders, remove the exhaust pushrods so the valves remain closed and install one way check valves in the spark plug holes piped to an air tank. With the exhaust valves out of action, every up stroke of the piston becomes a compression stroke and you get twice as much air. The one way valves used to be available to screw in directly but you might have to manufacture your own nowadays. The spark plug air compressors (Spark plug "air compressor") are still available but they had a valving system that allowed intake of fresh air before compressing if I remember correctly.
Smiley