Convert ford 302 into air compressor

[Warpig Racing]

My brother has mentioned this to me and he is thinking about having me build one for him. he has a lot of sand blasting to do (1974 bluebird school bus).

He said that there has been people building these from v8 engines where one side runs on gas and the other acts as a high volume air compressor.

not sure if anyone here has done one but here is my thoughts.

-Salvage yard engine- carb version (complete non cash for clunkers)
-Remove lifters, push rods, and rockers from one side
-Replace exhaust valve spring with a very weak spring.
-Replace the 4 spark plugs with one way check valves (http://www.surpluscenter.com/item.asp?U ... powerTrans)
-add air filter on the exhaust header
-plum 4 check valves to regulator
-air hose for sandblasting

here is my thought. as the 4 run the engine and turn the 4 air pump... when the pistion goes down it will create a vacume in the cyclinder and will open the exhaust valve (weak spring) and the intake will remain closed. the cyclinder will fill with air via exhaust and when the piston reaches bottom. the exhaust valve will close and the compressed air will be forced through the one way check valve. This process would happen every revolution since it is not compressing and firing like typical engine.

Since the 4 intakes will be permantly closed there would be no need for intake mods other than jetting the carb down.

Thoughts?

[Warpig Racing]

Hmm.. just thought that if the lifters are removed the oil gally would need to be pluged otherwise you would loose your oil pressure. Path of least resistance. seems like the the a plug on the back side of the engine that that could be remidied.

[Warpig Racing]

Hmm.. no oil to the air pump top side.... think that would be an issue? Intake valves arent moving just the exhaust. But i suppose it is not under any pressure and would have little friction. And that side would not have a lot of heat as ther is no combustion on that side.

[MalcolmV8]

Very interesting but isn't it going to be expensive to run that for long periods of time? It might be cheaper in the long run to just buy an electric air compressor.

If you guys do build it though please post pics as it sure sounds like a fun project.

[Dave]

I remember this being done a long, time time ago with a flathead, not sure how they did it. I'm not really working so I got time to do some interesting digging.
Dave

[Dave]

Found some of what I was looking for but lost one link in the process.
Dave - take a look, been done for a long time with different approaches, different motors.
http://cgi.ebay.com/ebaymotors/Ford-Oth ... sQ5fTrucks


PapaG's Project Journal

Somewhere they have stuff-information on how to make a compressor from a VW air cooled engine. 1/2 if it is the compressor.

Also you might want to add a 2nd tank to this. I didn't see how big the tank was. On a cheap 110 volt compressor it seemed to be always running. I added a 2nd tank and it would last longer with the pressure I wanted, but it did take twice as long to get back up to pressure. So it is always a trade off.




There really is nothing new about those 50/50 engine/compressor outfits and they have been around just about forever. Back in the fifties the old Ford flathead was popular for this conversion with more than one company building them. I have seen them (commercially built) from Ford 302s, 351s, VWs and Buick V6s, at least one outfit is still building the V6s but these things are not really good for much unless you need a heck of a lot of air. They work OK on a large service truck that might need to run something like 1" drive impact wrenches for extended periods and such as that but otherwise they are more trouble and expense than they are worth. They are for commercial use and will cost a ton of money to operate plus they are extremely noisy so there is really very little demand for them.

[plowboy34]

I have a farmer buddy who bought one of those big service trucks from a city utility place and it had a 351w air compressor in the back of it. I have never really checked it out but I will now and see how maybe it was done. Will try to get pics also.

[Warpig Racing]

Very interesting but isn't it going to be expensive to run that for long periods of time? It might be cheaper in the long run to just buy an electric air compressor.

If you guys do build it though please post pics as it sure sounds like a fun project.

Electric compressor could not supply the volume that he is wanting. He is wanting to sandblast a 40' school bus. I cant imagine how long that would take especially with a 60 gal electric compressor.

With all the extra 302 parts that I have on the shelf, I would imagine that I could build one for $400-$500 excluding the price of the trailer, that would be about the same as a 60 gal compressor. At the loacl pull apart i can get a complete engine w/ brackets and accessories for $150 regular price and the typically have 1/2 off sales around the holidays. This would be similar to the large commersial trailer compressors that are used for construction companys jack hammers.

Yes it will consume the fuel but will also produce a lot of CFMs. So assuming a stock 302 requires 425cfm carb to run all 8 cyclinders. That means that each side would consume 212.5 CFM. And youe would get compressor on each stroke on the compressor side to it would produce 425 cfm at max RPM. I doubt that it would actually yield that amount but im certain that it would easilt produce a constant 100+ cfm at 1800 RPMs or so.

[Warpig Racing]

this weekend is the 50% off sale at the local pull apart. Long block including intake, pan,flywheel, and balancer is reg $135 + 30 core. plan is to go fetch a 302 or 351 friday.

ill keep you posted and ill be sure and take pics of all mods and get a parts listing together.

[cgrey8]

Just some ramblings to consider...

While I'm sure an engine/compressor like this can move a LOT of air, I'm not convinced that it'll be moving a lot of air at high pressures. Engines aren't designed to be high pressure compressors. Typical 9:1 CR engine can get the aspirated air up into the 150 PSI range in the chamber before detonation. A high compression engine can get into the 200s. But really whipped engines with worn rings and bad seals may only be able to get ~100 PSI. A "real" air compressor will have the cylinder and head optimized for moving air by minimizing the volume of the chamber when the piston is at TDC. The more volume there is in the chamber when the piston is at TDC, the more the piston will have to drop before vacuum is attained. By minimizing the TDC volume of air still in the cylinder, a compressor reduces the amount of piston drop required before vacuum is attained thus aspirating atmospheric air into the cylinder to be compressed. Fortunately, most air tools can work with 60-90 PSI. So what you may find is that the compressor takes a long time to get a tank up to say 90 PSI, but it can supply air tools all day ~60 PSI with as much air as they can use. It's just something to think about if you happen to have tools that MUST have a high pneumatic pressure in order to work right.

Now of course you could do mods to the compressor side of the engine if you were looking to put that much time and thought into it. Since that side of the engine won't be a high temp producer, you have a few different materials available. For instance, you might be able to goop a bunch of high temp orange silicone sealant in the valve reliefs on the pistons (no need for them on that side) and goop-fill the compression chambers of the head as much as you can without obstructing the sparkplug hole & the exhaust valve. You could even goop up a mass on the exhaust valve itself to fill the void right under the valve to get that much more compression. Then go back together with a really thin head gasket (.021") to minimize the volume produced by the gasket. Or you could lay down whatever gasket you have on the head and fill the thickness of the gasket with silicone as well. Doing that, I'd bet you'd get significantly more flow at 90 PSI than leaving the engine as-is on the compressor side. And even if the silicone gooped too thick in some area or completely failed, the silicone is so soft that it'd just yield right out of the way of the piston doing no damage. It might clog the checkvalve and make a mess. But I doubt it'd do any damage. But with all that in the compression chamber, you probably wouldn't want to rev the engine too high. But to be honest, I'm not sure you'd need to.

Again, just things to think about...

[MalcolmV8]

When this is built I'd love to see some specs on CFM and at what pressure this produces. I googled around a bit and was unable to find anyone who's actually made a v8 air compressor and posted any specs or numbers as to how well it worked.

When I was a kid my dad owned a swimming pool company and when blasting the wet concrete into the hole dug in the ground, known as gunite, it required a massive air compressor. My dad had these massive air compressors permanently mounted on a trailer. They were inline 6 cylinder supercharged diesel motors and they had no tank. They drove some sort of twin screw compressor and put out more air than anything I've ever seen in my life. The hose going down into the pool was thicker than a fire hose and had a dry cement and sand mixture blasting through it. There's a water hose at the end wetting the mixture as it comes out.

Well that hose had enough pressure when we revved up that diesel I've seen 2 people on the end of that hose holding get lifted into the air and tossed around like rag dolls. Insane amounts of air. Now that may be way overkill for sandblasting your bus but maybe you could find a simple twin screw compressor somewhere drive it with the v8? I know they put out a tremendous amount of air.

My concern with your idea of half a v8 is how is it going to run? seems like it would be very rough and stumbling? or would it be just like a 4 cylinder? I need to go look at the timing order a little closer. You could even convert a 4 cylinder motor into an air compressor and use your v8 to drive it? Just throwing out some ideas.

When I sandblasted my red truck's frame I used an 80 gallon 220 volt air compressor that put out 10.3 CFM at 90 PSI. The tank doesn't matter as much in sandblasting because you need a constant volume of air. It's more the compressor part that plays a roll here. In my case 10.3 CFM at 90 PSI. It worked quiet well for a truck frame but I sure wouldn't wanna do a bus with it. You'll need a LOT more air for that.

Good luck man and keep us posted.

[usmcrp1044]

My concern with your idea of half a v8 is how is it going to run? seems like it would be very rough and stumbling? or would it be just like a 4 cylinder? I need to go look at the timing order a little closer. You could even convert a 4 cylinder motor into an air compressor and use your v8 to drive it? Just throwing out some ideas.

Go pull four spark plug wires off one side and see how it runs.

A four cylinder only has to move four cylinders, not eight.

I'm somewhat doubtful, but would love to see the attempt.

Good luck and take alot of pictures.

[Warpig Racing]

Well i believe that this is what these models are. http://www.aircompressor.com/gasptcomp.html
You can get them in 302 or 351s.

based on these, they put out 125-150 psi and the 302 model puts out 44-48 HP. My guess is that this is a 4 cyclinder power and 4 cyclinder air pump. The HP and PSI seems about right.

Also "SCFM Displacement" is 151.. i am assuming that is the displacement of the 4 cyclinders.

[usmcrp1044]

I was browsing the local craigslist, and I thought of this thread when I saw this thing.

http://albany.craigslist.org/for/1476635121.html

I guess it has/can be done.
How's your project going Will?

[Warpig Racing]

Awesome. Thanks for the link. I have emailed him for some information and detailed pics.

i havent started this just yet. My brother wanted to wait till after the holidays. Thats fine by me cause i got another motorcyle project to chop up. I gotta take apart my motorcycle engine and replace the timing setup. I also gotta re ring the new project that I got. Too much stuff and not enough time.