Technical Blower rebuild gurus too the bat phone please.

Ok, gurus, I need your advice. I just got this 671 blower from a local guy (no money traded yet as we have known each other for years). It wouldn't roll completely around, so I started blowing it out with air and parts cleaner and finally got it turning completely (I didn't force it), it's obvious it had some moisture in it. Without tearing it down further yet to inspect the case, would you say the rotor is screwed? He has another complete engine, so he's gonna pull that blower off for me to look at. The picture makes it look worse than it is. There really isn't any pitting, just surface corrosion. Can this be saved provided the case is OK?

 

@squirrel

 

How much of that will come off and did it harm the parent material?

-Abone.

 

The corrosion damage is too deep and the rotor is at a weakened state, Might be OK for some people, but I myself ,personally would not run it

 

I'd run it, but I'm an idiot.

 

I gave you a like @squirrel , not because I also think you’re an idiot, but because I’d run it too.

 

It's a supercharger, not a lawn mower engine that was stuck and you free'd up. It's a precision clearanced unit. If you care nothing about anything but just having it sitting on top of your engine for show, go ahead. I personally would send it off to a blower shop and pay to have it re-built. JMO. Lippy

 

There's probably more corrosion in there. Needs further inspection. Then maybe call Dyer's for their opinion. No offense to anyone here, but it's probably junk.

 

My only experience with GMC 6-71 blowers .. was selling a pallet & a half of cores to Gary Dyers of Dyers Blowers in Summit, Illinois.

No pricing on my cores, until he disassembled and inspected. Luckily I did fine. Of the 15 cores, 3 had bad cases, 2 had bad rotors. Basically, can't tell sh*t with photos.

There are decent rebuild guides on the internet, some would even glass bead those rotors, if the case is good.

I of course, dunno' sh*t .. unless I'm selling, & shipping to Gary. That's my expertise. Yep, you're welcome.

 

What tom said junk

 

If you listen to these guys and scrap it, let me know I’ll pay the shipping to me…I’m looking for one.

 

I don't know shit about blowERs, but from the perspective of a blowEE, I'd say it depends... Are you up against John Force in the next round, or are you driving it on the street?

 

I've overhauled several 4-71 and 6-71 blowers as a part of a rebuild of engines in heavy equipment we own. I wouldn't see any problem in running it based on the appearance of that rotor alone since it doesn't touch anything if the blower is properly clearanced, but the final decision would depend on the condition of the case bores as well.

To collect that amount of water, the blower would have to be laying on its side, either in the normal mounting position on the engine, or possibly laying out in the weather. I'd be more concerned with the case and whether it may have frozen while holding water, or if water may have bypassed the seals and got into the gear case.

All that said, 6-71 blower cores are not rare parts and useable ones aren't worth much because 2 stroke Detroits have been out of production for 25 years, so the demand for parts for the diesel application is shrinking every day. Any blower coming off an engine that has run even in the not so recent past will have its internals protected by a coat of oil that creeps by the seals between the gear case and the rotors,. They may have some minor scoring of the case bores and rotor tips, but they won't be corroded. Based on that, I'd keep on looking. If the guy is gonna pull one off another complete engine, it should be in much nicer condition. Remember, you're buying a used part for an obsolete but very common diesel and not a hot rod part. I can't imagine paying more than a hundred bucks for a decent used one, and that makes all the checking necessary to verify the useability of a corroded one a not very worthwhile venture.

 

Next question....if he brings me the other blowerand it isn't any but it has a good correct side rotor, can I use rotors from 2 different cases or are they a matched set? I hope the next one he brings is better. Around my neck of the woods, these blowers are starting to get harder to find actually. As said, these engines aren't as widely used now as they once were so alot of them have been scrapped.

For anyone interested in history of these old 2 strokes, here's a picture of a road grader I bought about a month ago. This has a 451 Detroit (not a 453). These are very rare engines. They have no valves at all. And the exhaust comes out of the block. This one starts to run away after 5 to 10 minutes and I think it's the blower seals causing it. Parts seem to be unobtanium though. Terrible picture I know.

 

Again .. you're asking the internet, to judge a picture. When you already did say there is no pitting, just corrosion.

That blower has your eyeball & it's in your hands .. don't un-trust your first judgment.

Disassemble the unit. Check it out.

 

Me too, on both counts.

I would scuff off the loose stuff with a red pad and go!

 

2X what gimpy says!

 

If you're building a AA/G car I'd agree probably pass..
I bought a blown up engine (350sbc) that sat in a 55 chev no hood an a leaking roof.. looked exactly like Yours, same deal could turn to a sticky point..
Knocked it apart, carefully sanded the heavy "fur" off the one spot, Sanding with the grain shall we say, Don't carve the "lip" of the rotor's..
Bought a bearing/seal/gasket kit off eBay.
Regularly ran it up to 6,500 trouble free on a standard bore 327.

 

Since your friend has another blower, look at that one before going further. Tear down the better looking of the two, if any. It may be way better.

 

Not sure if this applies or not. Jaguar used and Eaton blower on there V8’s

they had a nylon coating on the blower vanes that would wear off if the customer liked “ spirited “ driving .

would still give tons of boost amd run completely fine for many many miles.

they just became noisy .


I would do like others said , clean it up with a scotch brite pad and run it .


Might be noisy but should still work just fine.

 

@gimpyshotrods and @squirrel, I’m equally idiotic! I agree with cleaning it up and running it. @borderboy1971 if you end up with two, I’m seriously interested in one.

 

Keep in mind, I'm just suggesting that the corrosion on the rotor does not necessarily make it unusable...I have no idea how the rest of the blower is. Maybe it's OK, maybe not, but he didn't ask about that, he asked about the rotor.

 

Oh I understand that Jim. It’s a core no doubt about that.

 

If I understand this correctly, is the blower going onto the Detroit?
Max revs would be under 3k RPMs I’d guess.
Should allow for some more wiggle room v a 10 second ride?

 

Thankyou all for the advice. I do hope blower number 2 is in better shape. I was asking about the rotor in the picture, because if it was deemed no good then there would be no point in tearing it down further to inspect the case. Once I have a decent one, it will be tore down and built up for a 392 hemi for street use. And sorry to 57fargo, but the worse of the 2 will be going to another friend nearby as a display piece apparently.

 

Hello,

When we decided to go the 671 blower route on our next build/rebuild of the 283 SBC motor for our 1940 Willys Coupe, we went looking for a good condition blower. Several of the speed shops had their versions of "set up" blowers and it was tempting to dig deeper into our cash account and just get one. But, our friends at Reath Automotive told us that if we brought a used one into their shop, they could rebuild or set up the blower, using racing specs and allowances. The cost of us supplying a used blower would be less than just getting one already sitting on the display.

So, we lived near several diesel truck shops and went to look at what they had. The first shop was too expensive to just get a new 671 from the factory. It would have been better to spend that kind of money on one that was built to race specs from Reath.

The second shop we went to, closer to our house, had all kinds of engines with different GMC blowers. But, they had no new ones to sell. As we were walking out, the sales guy said that if we wanted to buy the display model, he could give it to us at a discount price. The reason was that they wanted a new one to get chromed for the new display and the old aluminum color was last season…etc.

So, we walked out with a new/never been used display 671 blower. Immediately, we took it to Reath Automotive and they said as good as condition as it was, they still would go completely through it and get is set up for our new Isky-Gilmer Belt Drive we had just gotten our hands on from our Los Angeles contact.

Jnaki

For as something as powerful of an addition to any motor, why mess with something that is in a condition that is questionable. Get those blowers to a shop that specializes in supercharging and is current on rebuilding or at least give you some direction on what you can do.

(If you call, the whole So Cal area has now, gone to the 10 digit dialing from any phone, unless you already have it programmed to direct dial.)

The companies mentioned, so far, are names in the industry and I would add the following two So Cal shops:
https://www.hamptonblowers.com/superchargers

1-562- 8039484 Downey, CA

Don Hampton has been in drag racing since before most of the HAMB folks have been alive. We knew of him and his exploits through drag racing at Lion’s Dragstrip and other So Cal places.

one of my favorite recorded films from our collection of action drag racing from 1959.

actual footage from 1959 and real sound from September 1959 of the Kenny Lindley/Don Hampton FED


The other shop has been around after we were teenagers, but originally developed and run by a friend of mine from high school, Mert Littlefield. He developed his skills and became a builder, racer and specialist in the industry. He is now gone, but before he left us, his company, Littlefield Blowers is still going strong with the skill and knowledge from the history in So Cal.
https://www.littlefieldblowers.com/
1-714-9929292

 

Well I tried…

 

I would think that cleaning everything up and polishing the surfaces would not hurt anything. Increased clearance (within reason) may make it somewhat less efficient, but I don't see how it would actually cause any problem. Since its for a street driven vehicle, I don't see any reason itcouldn't be used.

 

Yeh, like Jim said, run it, it's not a race car.
Of course, standard practices, just like an old engine freshen up, cleaning, inspection, quality bearings, etc. and careful assembly.
And learn how to start a supercharged engine, yes there is a "right" way.

 

When rotors don't seal properly, they heat the air much more. The over heated air charge lessens power and causes increased detonation. I'm going to pass on what happens to me with age: every time I try to cheap out or take a chance it comes back to eat me alive. Blowers spin at tremendous rpm and are a danger when things aren't correct. Even if some flakes come off and go through the engine, you may lose it all. Is it worth the risk. It's your decision but I have 20 years exp. with blown alky dragsters and I wouldn't risk it. Good luck with your decision.