Repairing blower rotors?

I have a 4-71 with some nicked rotors. I considered brazing them with some of that brazing rod for AL, but it seems like they would warp in the heat.

I have read that some modern factory superchargers have an epoxy coating, so I wondered about trying an epoxy repair. Seems sketchy.

I plan on running about 6 pounds of boost on 351 that will stay under 6K Rpm.

I do have a lathe if needed to true the rotors up a bit.

I am a cheap bastard, and I get a special feeling out of putting parts back into use that others may have (wisely) discarded.

 

How bad are the nicks? Can you just leave them there?

 

If you use gas brazing, you could place the rotor in a tub of water to keep it cool... Just an idea.

 

TIG small areas and allow to cool completely. Then TIG another area and allow to cool agin and again until repaired. Is balance an issue?

 

Balance is always an issue on a rotating mass at 1500+ RPM. Anyone with a Stewart Warner or Sun engine balancer can balance those rotors.

 

There is one big one on each rotor tip, About 1/8" deep. Looks like someone used a mounting bolt somewhere that was too long.

 

Do you have a pic?? Mine has a gouge in one rotor where it looks like maybe a screw fell in it...My blower guy said "don't worry about it"

I worried about it for a long time, but after about 50 thousand miles, I don't even think about it anymore.

-Abone.

 

Interesting. The working temperature of the brazing rod is 730 deg F. It may be hard to get part of a hollow AL rotor to that temp while the other end is in water. It may work though.

 

Cool. How much boost do you get?

 

I like Handy's idea better! It's up to you!..

 

No tig at my house, I expect that is the best fix though.

 

For a Street blower with 6lbs of boost, it's not worth fooling with. Run it as is...

 

Agree...
Just de-burr the nicks and or radius them to head off any cracks forming and run it.

 

Parts like that should be welded by Tig welding. The person welding should be using a 50% or higher Helium mix. Welding with a high percentage of Helium eliminates the need for heat to build up in the part being welded. Some call this cold welding but its really the opposite as the helium is a very hot weld making the weld time very short = no heat buildup.

 

Trying to fix nicks in the rotors will probably lead to screwing the blower up. I would run it as is and save up my money for a rebuild. I have run several over the years with nicks and scratches.

 

I've used those Al brazing rods in the distant past. I'd be far more worried about the brazed bit falling out and going through the engine than I would about a little bit of leakage between the rotors.