Can’t ID This?! Any of you real knowledgeable roots-type supercharger historians know the manufacturer and year of this blower? Or who made the drive? Detroit-GMC-Eaton? Hamilton-Whitfield? Buda? Thanks! ~David
Any measurements? case length? Looks like a GMC 2-71...almost. The 2-71 had a side inlet, and was (I think) used on small generators. 'Just a guess. ?
I wanted to say a 1-71 just to be a smart ass, Oh did I just say that out loud? 2-71 would be correct or if not a damned good copy of one. There should be some markings as to who built the drive and or rear plate unless it is a one off made in someone's machine shop.
Just curious, since that thing was designed for a 142 cu. in. engine, is it capable of pumping enough air for twice the cubic inches? It looks neat, but I wonder if it does much...
keep in mind that ANYTHING driven off the crank eats horsepower to some extent...I have a 4-71 on my flathead and I know just turning that thing to make a humble 6psi of boost is probably using as much power as it makes....but it sure does look AND sound cool....
A Detroit 2-71 is a two stroke so it should pump enough air to fill a 284 four stroke. Weather it would provide any boost would depend on how fast it was driven. I suspect that any power gained from the boost would be more than absorbed driving the thing! However you can't argue with the cool factor.
The thing with the smaller blowers is that they make boost when driven correctly but they make heat as well. That is the real reason to go with the bigger super chargers if you can, they don't work as hard and make a cooler intake charge when compared to the smaller version make the same amount of boost. When people were using the baby super chargers or eve the super chargers that came stock on some vehicles they were only looking @ about 3 pounds. that little super charger should make 3 pounds easy and that will make the little mill a little bit more peppy. besides it should, also whine and whining is good.
How cool is that,,it looks great whether it's beneficial when it comes to any significant horse power gain in my book would be secondary! HRP
If its going on a flatty HP gain is not going to be much anyway you look at it. Building a high horse flatty is more cubic dollar then it is cubic inches. The little blower is cool as hell and if you are happy with a flathead (many are) you should be happy with whatever it makes for you.
Thanks, Fellas, for all the excellent input! What's the earliest year this Detroit Diesel 2-71 would have been available? My plans are to put it on a medium displacement flat motor. Is there a practical way to ameliorate the inevitable excessive heat? Does using Teflon inserts help reduce heat build up significantly? I am very grateful for your knowledge and experience!
I can't answer the detriot 2 stroke question, but there are some heavy mechanics here that no doubt can answer that for you. On the Teflon insert question if you go close tolerance and Teflon strips you are going to make it more efficient and yes it should make equal boost as stock with less heat. I don't know how much boost you intend but if you keep your boost levels low ( 3-5 psi) you should be fine either way. One thing that we used to do in the past prior to heat exchangers (I am helping with a big boost streeter that has a refrigerated heat exchanger under the blower), we used to water spray them, or sometimes methanol. There used to be a cheapo setup from JC Whittney that had a squirt bar that set across the air horn of the carb. it was basically a windshield washer pump and a receptacle that held the liquid and a squirter bar. There is a company called Snow that makes them now for an a outrageous amount of money. I have also used cool fuel cans, which is no more than a copper tube coiled inside a can with Ice in it. Either will help cool your fuel charge and both will be way less expensive to set up and maintain then Teflon strips. There is a problem with Teflon stripped rotors. The blowers that run them are very close tolerance and it doesn't take much of a piece of foreign material to trash one. Just a thought.
I have no blower experience but isn't heat a byproduct of compression? It's the principle that allows a Diesel engine to work. Tightening up the tolerances and adding Teflon strips would increase the efficiency of the blower, but would generate more heat due to less air being lost between the rotors and the case. Is my thought process flawed???
One way to reduce heat is to reduce boost, and using a 2-71 blower will sure do that for you Good question about the efficiency thing...I was thinking the same thing.
On the subject of blower volume.......what may not always be recognized is, the GM 71 Series inline engines did not use the 'blower' as a supercharger...as rodders do. The 'blower' was literally that....it is mounted on the side of the block, and as mentioned in a post above, is two cycle. There are ports in the block/cylinder wall and as they are uncovered on the power stroke, the blower purges the exhaust gasses. Indirectly, this allows the engine to make more power, but not in the same manner as a supercharger. Ray
Carl your logic is good, I don't think that it works exactly as you say in application though. Think of it this way, heat as a by product of work instead of compression. Take two identical blowers and then set one o up with Teflon strips and the other set up as original without. Now drive them to make the identical amount of boost. The one blower which is looser (for lack of a better term) may have to be over driven to make the same amount of boost as the Teflon lined blower which is under driven. That is the same reason that a 4-71 makes more heat for a given amount of boost as a 6-71 and the real reason for driving a bigger blower. The only reason I am thinking in this direction is this, a blower is just a screw compressor that is on a car instead of an airline. I had a Denver's that I used to work with that made and maintained 150 PSI. It began to get a little worn and when it did, although it was still producing the air needed to run the equipment the air was becoming too hot and damaging components. The boss thought that the intercooler was plugged with paper dust, but I knew that it was not because I maintained the compressor. So the boss and I blew it out together and the air temp remained high. he asked me "what's wrong?" I said, "the compressor is getting old." So he had me pull it down and it was loose as a goose. We set it up with new helices. After machining the tolerances were on the close end of too tight, we dropped the discharge air temp nearly 20 degrees. Never the less your logic is good.
The heat Beaner is referring to is blower heat. One problem with small blowers is they have to be spun so fast to create boost, this excessive spinning heats the intake charge. Heat makes the air less dense, thus reducing efficiency. One reason you see coolers on blowers, or N2O charges being shot before the blower.
Basically Carl, yes, a blown motor will produce more engine heat just from the power (compression) it puts out, where as a smaller (less efficient) blower will create more intake charge heat compared to a bigger blower, or one made to be more efficient (such as teflon strips).
I'm no expert on anything, but isn't boost proportional to the amount it's overdriven?In other words, pulley size.If it's driven 1 to 1 or even under driven won't it make less heat since it's not really moving much air? ?
The faster its driven, the more heat it makes. Even if you massively underdrive it, the rotors are still adding heat, although much less than overdriven. But you are also making less boost. Small blowers, like a B&M 144, are run about 2:1. They have to spin that fast to make any reasonable boost. The upper pulley size allows you to dial that ratio (boost levels) in. Because they spin so fast and add so much heat to the intake charge, once they hit 5-6k rpms, the power drops off VERY dramatically. If you can cool that intake charge (cooler or nitrous) the blower will again make power above that range. I used to have a 302 with a 144 and when I hit about 5500rpm, it nosed off, wouldnt go faster, but I had N2O on top of the blower, as soon as I hit the spray, the blower came back into effect (due to the denser intake air) and it made power again.
Makes sense. Do you remember the blown AMC Javelin from the AMC commercials? "It's a great car, I only made it better"? That car had a carb inside a 6-71 case, no rotors at all, just spinning a pulley. I'm not saying he should do that, just a possibility.Personally, I'd love to hear a flatty with that thing whining!
If you keep the boost down to 4 or 5 pounds you will save yourself a lot of trouble. That amount of boost will give you 30 - 40% more usable HP but will not blow head gaskets, overheat the engine, cause knocking or other problems that go with too much boost. It is always tempting to turn it up a bit more (FREE HORSEPOWER!) but it pays to go easy, especially on the street, especially with an engine that old.