Is redrilling blower tapings acceptable?

Larry B · November 14, 2011, 06:23:45 PM

I have an 8v71 and decided to change the seals in the blower as oil traces where noted on rottors. After taking apart a small piece is found to be missing in main blower body directly below one of the 3/8" air shut down tappings, about the size of a peanut. The threads on this hole are badly stretched a few missing. This missing piece has left no marks anywhere main body housing or the rottors. Does anyone see a problem with increasing this hole size to 7/16" bolt ? Shut down housing hole size will also need to be increased. I asume at some time too long a bolt was installed and popped a piece of aluminum casting out.

hargreaves · November 14, 2011, 06:34:00 PM

Heli -coil it. it will be stronger than original. Gerry

Larry B · November 14, 2011, 06:42:02 PM

I thought about that but is it possible that with no botttom the bolt could push the heli coil into the blower? Once the shutdown housing is installed there is no way to check and see what happened inside blower.

hargreaves · November 14, 2011, 06:46:55 PM

Use a pair of needle nosed pliers to break off the helicoil tab so it will lock in place and you can recover the piece. Gerry

Larry B · November 14, 2011, 06:54:03 PM

I have never used a heli coil , only read about them. I will buy some, so I can see how they work. As long as the bolt won't turn a part of the coil into the blower . Thanks

hargreaves · November 14, 2011, 07:05:14 PM

Once you break off the tab it locks itself in the hole. the helicoil threads are a different pitch than the bolt. good luck Gerry

TedsBUSted · November 14, 2011, 08:02:25 PM

You might consider an insert-type thread repair, which is essentially an inside and outside threaded sleeve that positively locks at the top of the threads. I would feel more comfortable with an insert repair where damage has lessened the depth and bottom of the original threads - especially in a blind assembly over a spinning rotor. Keensert and Time-Sert are two big names.

Ted

Oonrahnjay · November 14, 2011, 08:11:57 PM

Quote from: TedsBUSted on November 14, 2011, 08:02:25 PMYou might consider an insert-type thread repair, which is essentially an inside and outside threaded sleeve that positively locks at the top of the threads. I would feel more comfortable with an insert epair where damage has lessened the depth and bottom of the original threads - especially over a spinning rotor. Keensert and Time-Sert are two big names. Ted

Yeah, I've used these in the threads in aluminum castings for the engine mounts in my VW TDI diesel. They're NOT going anywhere. And if you'd feel better, you can Loktite the outer threads, too. They are very good.

Larry B · November 16, 2011, 06:56:57 PM

I drilled the hole today and installed a heli coil. i am happy with results. The heli coil tap was not run all the way through the blower casting, as a result the taped hole threads taper below the heli coil depth. This should keep the heli coil in place. A little lock tite would not hurt. For my NEXT QUESTION. I bought a blower rebuild kit- seals, bearings, and rotor seal rings. I have a lathe so I will build my own bearing insert pieces. The series 71 repair manual just says use tool #xxx to install bearings.The gear end has double row ball bearings, so make tool flat and large enough to press on both races when installing bearing. The govenor end has a roller bearing with an inside race that will move back and forth (approx 3/16").This time use tool#yyy. When making this bearing install tool, is the thought here to make tool with a step so that half the 3/16 distance is placed on either side of the bearing wideth when installed? This would allow for different rates of expansion aluminum(blower) and cast steel(engine block). Can anyone remember what the face of this install tool looked like? Thanks Larry