Eek-bay has alot to answer for. A what if conversation with my son ended with the purchase of a 6V71 GMC blower as removed from whatever. In my haste/enthusaism/naivety I did not realise they where any different to aa 6-71, untill yesterday when I picked itup from shipping agent. I was prepared to machine and weld a manifold anyway, but how do I mount this with weird angled bolts. Someone must have done this before. Any pic, info, advice, appreciated. Cheers, Simon.
Not quite sure why E-bay is responsible for your ****up but here's a pic anyway http://www.jalopyjournal.com/forum/showthread.php?t=146890&highlight=6v71+gmc
I have a 8V71 on my project and mine looks exactly like the one above. Same upper and lower plate. I will post photos as soon as I go to the shop
My fault not ebays, guess i'm not the first or last to buy something that is not quite what you think it is. Blowers not easy to find in UK so ive got to make this work. Appreciate some detailed pics. Cheers, Simon.
If I wanted to do it I would get a 1/2 inch piece of tooling plate and cut it to the size and shape of a 6:71 base. Then I would drill it and drill and tap the bottom of your blower to use countersunk screws to bolt that plate on. Now you should be able to bolt your blower on as though is was an inline 6:71. Of course I have never done it. It just looks like it would work.
Hey dude....you got a good deal, I prefer the 4v871's myself. As you were told, Dyers redoes them, you can send it to them and they'll rebuild it for a little of nothing and pin the rotors. If this is your first blower, have a pro do it. Next time when you learn about it and really get familiar with your blower, they do sell rebuild kits that you an install yourself. Only do this if your really mechanically inclined, because the pinning the rotors and endplates have to be done correctly. The bearings and the endplates will have to be replaced. To make good boost pressure down low at low rpms takes tight tolerances. You can run about 20 % underdrive, your gonna want to redline about 5,000 to 5500 with good heavy duty components in the lower end. It isn't totally necessary, I've run them on motors in good shape, but they were put together with good parts. Don't try to stick this monster on top of a 2 bolt main chevy smallblock that has 200,000 on it, cause its probably not gonna last the week! Whatever you put it on, put a good rebuild kit into it at least. All the goodies in it if you can afford it, cause it'll make the motor last. A good built Blown Big Block motor will make a respectable 500-600 horses on pump gas and lasy 4 or 6 years with no problems, if done correctly. That being said, it mounts just as the fella said, 1/2 to 3/ 4 tooling plate,mill the top of the manifold align it and clamp it down and have a good welder TIG it down. I do about 4 to 6 of these a year. Then its off to the Bridgeport, tilt the head and drill & tap for the studs on each side. Make sure you mill the top of the intake along the crankshaft centerline. You want the blower setting level with the engine! Also, give yourself about 1 to 1 1/2 clearence on the dist. on the rear. Gotta time that puppy! Then, you open the plate up with a endmill with use of a bottom blower gasket that Dyers will supply you with. And ask for the lower blower gasket with a screen in it. They'll tell you why. And on the rear of the manifold, machine yourself a small pad about 1x2, make a corresponding plate to fit it, drill and tap 2 holes for the plate use 2 studs coming thru the plate on the ends, and put 1 spring of about 10 psi between the nuts on the studs and the plate.....Wola.....pop-off valve. Of course, you have to glue on some gasket material between the plate and the manifold. I ran one about 5 years on a Pontiac BigBlock, rain, shine, sleet or snow. I parked agianst a curb once in a snowstorm, I couldn't get away from the curb because I had so much torque it'd just sit there and spin. Your gonna have to take it to the engine for several test fits. Get yourself a bottle of ****m with a brush, a scribe and a 6" and a 18" flexable machinists scale, your gonna need them. After you get the thing where its sitting on the motor, tape up the opening so no crude can get in there. And avoid the temtation of spinning it over by hand....I'll tell you why later. Now, The thing with a 4v or a 6v871 blower is that you can turn them slower, not heat up your incoming air as much, get by with a lower blower speed. Gotta decide if you want the Gilmer belt or V-belts. V-belts are safer, if anything goes sideways on ya, and you have a problen, the V-belts will slip. Problem is, you gotta run matched belts. The Cogbelt and the pulleys and idler is gonna run you about $550 to $750, if you find a good deal new. Then you gotta line the lower pulley up with the crank pulley. Gotta machine out a alum. pulley spacer to get the blower pulley to line up there. Also, you CAN NOT RUN A STOCK HARMONIC BALANCER, if its got the rubber isolator band in it....thats just asking for trouble. It takes about 40 to 50 horses to spin that blower, and its enough to have your Harmonic balancer seperate and shove everything thru your radiator. Ask the Blower co that rebuilds yours for their recommendations on a steel aftermarket balancer. I have welded mine before, just to start it and break in the motor and tune it. This can be a safety issue....you can mess up a whole lot of money really fast this way. Now, get your top plate or make it, 2x4's or 3x2's or whatever, mount then on top. Hook everything up, double and triple check things and fire her up. Let her run for only about 10 seconds. Then, shut her down. Double check all your pulleys are tight, hoses are tight. Start her up and run her at a high idle for about 2 minutes, doublecheck everything agian. Crank her up agian and let her run to break in the cam and motor....let her idle.... Shut her down and doublecheck everything, if its OK, your pretty well safe nothing is gonna break. I build these things for racing folks and all, so, if somethings gonna give, it would've probable made some noise by now. Start her up and now put your timing light on her, give her as much advance as she'll take, when she starts to labor just the slightest, snug down the distributor. Now your ready to drive her around the block. Blown motors cannot be run lean, so check for that. Also, they're gonna run hotter than normal motors, so make sure you have a decent cooling system, they make alot of power and put alot of strain on the front of the crankshaft, so don't try to shim up something unsafe to line up the pulleys. Make a solid alum.pulley spacer for your setup. After all the tuning is done, go out and enjoy that 250 to 350 extra horses you now have!.... Do a burnout for me! Oh yea, carry a extra blower belt......
I have seen a lot of 71 series blowers. 6:71-8V:71-6V71-2:71-3:71-4:71. I am not fimilar with the 4V871 or the 6V871. What do the numbers 4 and 8 refer to? I have seen lots of 4 valve 71 series Detroit engines. Never a 6 valve. Dosn't mean they never made them But I am thinking 8 (cylinders) V (it's a V8) 71 (cubic inches per cylinder)
So you think he is refering to the very large 48 cylinder 71 series Detroit? Thanks for setting me straight on that.
"After you get the thing where its sitting on the motor, tape up the opening so no crude can get in there. And avoid the temtation of spinning it over by hand....I'll tell you why later" Apparently, he also lives next to one of those uncapped Oklahoma oil wells...
whoops didnt see that sorry. maybe its a typo? i never heard of a 6 valve detroit and i work on them almost everyday. and i only know of the side mount , top mount and internal blowers.
Me neither and I have never worked on a Detroit. But i was just guessing as to what a 6v871 could be. A 6 cylinder V type engine with 871 cubic inches per cylinder would be hard to start I bet. Big battery
The 4v871 came off a cat stationary power generation unit, there were 2 blowers up top, one right behind the other, 4 valves per cylinder, 8 cylinders for that bower, x2. A V-16....it had 2 blowers.....
OK it was a 16:71 and used two 8:71 blowers. Right? Why would a Cat stationary power generator use a Detroit engine? I would expect it to use a Cat engine.
Cheers screamin metal for someone who takes the time to answer a question and not give smart*** comments. Blower will go on a stout pontiac 400. Simon.
If you are talking bout the old 2 stroke detroits first number is the number of cylinders and the second number after that is the displacement per cylinder. unless it is a inline like a 4-53, 6v71 would be 6 cylinders and 71 cubes per cylinder.
Great. Maybe you ubderstand his answer. I don't. But as I said, I never worked on a Detroit. So the only way I will learn anything is ask. You may consider that to be a smart*** comment.
Oh yes, 4 valves per cylinder, had a 25 KW gen. with all the controls. Port. Power station for remote locations....like jungles, offshore, mountaintops (Still not quite sure how to hell they got the huge thing up there), Islands, oil rigs, stuff like that. They use them up in Canada and Alaska alot. They're normally used in 3's..with 2 banks of these things..2 running, one always as a backup, at peak conditions all 3 run. For maint., the other 3 run.....usually small towns or settlements, mining or drilling.
Detroit Diesel has produced quite a few engine configurations over the years- 2cyl , 3 cly , 4 cyl , etc. Most commonly known engines are the 53 cu in (per cyl), 71 (per cyl) & 92 cu in (per cyl) models. They made both inline & V configurations. All those engines have been used in many applications--boats , trains , cranes , etc, etc, etc. The "V" designation simply denotes a V engine design. I talked with Gary Dyer , back in the early 70's about using a 6V92 blower & at that time no one had geared up to mount & use the V series blowers , but , Gary said he was working on that at that time. Gary also mentioned that he believed that the "stubby"\shorter blowers (V series) would be a lot more rigid & stronger being spun at higher speeds , with a lot less flex on the rotors. Happened pretty often that a guy would bring a V series blower into the shop & ask if it could be set up for his gas engine. Old Detroit Diesel mechanic
The Jalopy Journal
