Emglo/Jenny compressor rebuild help

[Hchrist]

I'm into rebuilding a compressor. It's a four cylinder electric (converted from gas) emglo which is now Jenny.
It sat inside my shop for a couple of years and when I tried to fire it up it said, "not today". Short story it needed cylinders and valves at minimum. I'm also doing rings and crank bearings.
My question is about the con rods. Two of the rods have slight scoring. The crank has a tiny bit of aluminum from these two rods that will polish of easily. I'm leaning to NOT messing with the rods but thought I'd ask here. These rods dont have bearings BTW BUT bearings are available. I'd have to bore the rods but that's not a problem. The problem is these little bearing will add another 50 clams to this project and I don't want to spend the coin unless I'm risking a blown compressor.
Any ideas?

Galaxy S4, Slimkat
If I wasn't married I'd quit fishing

 

[mikegt4]

I have a Emglo compressor, Honda 8hp powering a 2 stage 4 cyl. "GT" pump. My parts diagram shows replaceable rod bearings. What pump do you have?

 

[Hchrist]

I have the same pump or one very close to yours. The diagrams all show bearing shell inserts with the con rods. The deal is that anyone looking for a replacement con rod will get the bearing shells with the "new style" rods. The older units didn't use bearings-just direct rod to crankshaft.
I've been looking into resizing the crank end of the rod but it looks like a special rod honing machine is needed to get the big end of the rod back to the proper size round hole. The rod and cap get a couple of thou taken off to shrink the hole. This creates an oval so the valve Hone makes it round again.
Thanks

Galaxy S4, Slimkat
If I wasn't married I'd quit fishing

 

[mikegt4]

Any competent automotive machine shop should be able to "resize" your old rods to original specs, they do it every day. You may want to take your crankshaft with you so that they can get an accurate measurement of the journal and determine the rod big end ID for proper oil clearance. I am sure that you would want to do all 4.

Here is my Emglo, best compressor that I have ever owned.

 

[Hchrist]

My pump is almost identical except there is no oil line coming out of the crank bearing cover.
It was recommended to not go to an engine builder because their machines have steel in the honing fluid from previous jobs and it would become embedded in the aluminum con rods.
I plastigaged the rods and they are .002" or less. This is good enough for me.

Galaxy S4, Slimkat
If I wasn't married I'd quit fishing

 

[The Tool Tyrant]

Unless you're VERY good friends with the machine shop owner, I can't see how you could beat this price X4...http://www.ebay.com/itm/L21-Emglo-A...842970?hash=item3caa65e7da:g:WlcAAMXQkN1Rz2O4

Then you would have rods WITH bearings, which is much better IMHO.

Good luck

 

[Hchrist]

True. I'm just going back with mine. I got all the parts for my rebuild from the same seller.

Galaxy S4, Slimkat
If I wasn't married I'd quit fishing

 

[mikegt4]

That is not an oil line, it is part of the unloader system. To be clear it's a GTU pump, 2 stage with an unloader so that it doesn't start pumping until the engine gets up to working speed. The unit only has a 8 gal. capacity tank (a 30 gal. tank was optional) but that is what makes it portable. It can go from 0 psi to 175 psi tank pressure in under 45 seconds.

Soon after I got it my son was having trouble removing the crankshaft damper on his mother's Acura SUV during a timing belt change. His trusty SO impact couldn't budge the bolt with his 125 psi compressor. I rolled the Emglo into the back of my pickup and went over to his house. He connected his impact to 175 psi and the bolt spun out as if it was on ball bearings.

Good point on the honing fluid contamination.

 

[Hchrist]

I guess the unloader system work differently for the two stage. Mine is a gu pump and has the head unloaders like the gtu but is single stage. I have only one line coming from my bearing cover and its called out as the unloader tube? Yours is a "breather tube" so the other one is for the unloader I guess.

Galaxy S4, Slimkat
If I wasn't married I'd quit fishing

 

[mikegt4]

Yes, one is a "breather", the other is a "unloader" tube. The unloader tube goes the cylinder that serves as the second stage. There is a centrifugal unloader (bob weights) on the end of the crankshaft, hence the large crank end cap. Also the piping and "left" cylinder head on the 2 stage pump is different than that of a single stage version..

The single stage compressor takes the output of the "right" head and combines it at an external "T" fitting at the output of the "left" head and then to the tank.
1+2> T <3+4, then from T to the tank

The 2 stage takes the output of the "right " head and combines it with the output of one cylinder of the "left" head then puts that into the intake of the other cylinder of the "left" bank for the 2nd stage of compression. It's done externally with piping and internally with manifold passages in the head casting.
1+2>4<3, then from 4 to the tank


for comparison:
GTU
http://www.aircompressorpartsonline...rts-gt-series-parts-jenny-parts-p-545594.html

GU
http://www.aircompressorpartsonline.com/jenny-pump-repair-parts-gu-pumps-jenny-parts-p-545583.html

 

[Hchrist]

Good explanation.. My "main" compressor is a two stage IR 80 gallon two stage. Not the box store IR BTW but a "real" one purchased decades ago. It's never given me any trouble but I've educated myself one the two stage/single difference but your explanation will be helpful if someone were to come here trying to get information.
The newer heads, like yours, use a different unloader system with the centrifugal weights. Mine uses the system with the unloaders as shown in the upper right corner of the schematic for the gtu. There appears to be several upgraded parts in the gtu pump like needle bearing at the wrist pins. These are a big deal imo. Actually the whole con rod, with the needle AND crank bearings is a whole lot better than what I've got. That compressor should last as long as the owner if it's cared for. I originally got mine from a national tool rental company. After that it was used a lot while I built my house. It was on a 30 gallon tank and ran on gasoline. Once that project was done I lopped off the tank and used a 5hp electric to use it as a secondary unit in tandem with my IR. It feeds a second 80 gallon tank so I have two pumps and 160 gallons of storage. I'll be glad to get it back on line because I'm about to start on a car and will be using my blast cabinet a lot. It's nice to blast parts and not hear the compressor running most of the time. Blasting parts is a crappy job without extra noise.

Galaxy S4, Slimkat
If I wasn't married I'd quit fishing

 

[mikegt4]

I got my Emglo to run a newly purchased blast cabinet. The cost to upgrade my detached garage/shop wiring alone was much more than the cost of the Emglo much less the additional $2K for a new 5-7hp electric compressor. The noise of the engine does get annoying but I can put up with it.

I bought my compressor from a guy that has a duct cleaning company. Apparently they are quite common in that industry. He had purchased another competing company from a guy that was retiring and my machine came from that business. IIRC I paid $350-375 for it in the condition shown in the photo above. He had it on CL for some time with no takers. I was happy to get it. I still have a CH 3hp 240V compressor but the Emglo gives me air almost as fast as it takes just to plug in the CH much less wait the 5 minutes it takes to fill the tank. If the Honda doesn't start by the second pull I check the on-off switch.

 

[Hchrist]

Why not convert it to electric? The noise and exhaust would (did) force me to do that. I hate loud noise. I can hear a gnat fart 100 yards away. The nose of the blast cabinet and the vacuum are even borderline unbearable. I need to rig my vacuum up so it isn't so loud. I used a motor from a central vacuum unit and I made a plate for the bottom to adapt the suction. The exhaust just goes out a window but the motor is really loud so I'm going to put some sort of surround on it.

Does your compressor keep up with your cabinet? I imagine it does. I'm hoping the newly rebuilt compressor gives me well over 35 cf/m when coupled with my ir. I found a cracked valve while rebuilding mine so it was really only putting out 3 cylinders.

You got a great deal on your unit for sure.
This is the model cabinet I have. I bought it used too.

Galaxy S4, Slimkat
If I wasn't married I'd quit fishing

 

[mikegt4]

The compressor keeps up with the cabinet.
I live on 5 acres out in the country, cows, sheep and corn across the road, horses next door so noise is not a problem to anyone but me. I keep the compressor right by the garage door with the exhaust pointing outside. I always open the door when using it. I roll it outside if I plan on extended use like with the blast cabinet. Usually I only run it up to full pressure then turn it off as mostly it is just to fill a tire or blow off something. The only air tool that I use is an impact gun.

I really enjoy the portability as I have several boat trailers kept about 100 yards behind the shop and at times need to fill a low tire. The gas engine makes that easy. If the Honda gives out them I might consider an electric motor and even mounting the pump on a new stationary tank.