How do you get the pins out of the rotors on a 4-71 blower?

topcatcustom · Post by **topcatcustom** » Sun Oct 05, 2008 3:37 pm

Looks like they can only go 1 way---- in! I assume they knock in then you slide the shaft out and drop the loose pins out- but dont want to try it without some re-assurance!

ukblowers · Post by **ukblowers** » Mon Oct 06, 2008 10:54 pm

why on earth do you want to take them out

topcatcustom · Post by **topcatcustom** » Tue Oct 07, 2008 7:41 am

One of them looks like it has been pushed in as is not present like the others. Also there are caps in the ends of the shafts of which 1 has been pushed in too... Hasn't been run like that tho!

ukblowers · Post by **ukblowers** » Tue Oct 07, 2008 12:10 pm

The original pins are tapered and driven in, then the hole is peened over to eliminate the unlikely event that the pin starts to back out.
If there is no pin there then ream it and fit another pin. If the pin is there but driven in deep then I would leave well alone, just make sure the hole is peened over. One of the upgrades we do to GMC blowers is to double pin the rotors to the shafts, so now would be an ideal time to do that.
I have some spare core plugs for the end of the rotors.

topcatcustom · Post by **topcatcustom** » Tue Oct 07, 2008 1:06 pm

Thanks Nigel, the plug or perhaps plugs that have dropped in are the ones in the ends of the shaft not the ones in the actual rotors, though I would like a spare one of those too- could you let me know how much for 1 spare rotor plug and 2 spare shaft plugs with the other gear (gaskets etc) I have emailed you about?

Thanks Tom.

ukblowers · Post by **ukblowers** » Wed Oct 08, 2008 5:51 pm

To be honest Tom, until you mentioned it, I wasn't aware there was a core plug in the shaft, but you are right and its fitted from the inside !!!
I would not try to remove the shaft from the rotor.....its not going to slip out as you say, it will either be an interference press fit or may even have been cast into the rotor at the foundry. If you can get the old plug out then great, as it will obviously rattle around in the hollow rotor casting.
I wouldn't worry about not having a plug in there so long as the rotor is sealed at the 6 core plugs at the end and the shaft pins.
I've e-mailed requested prices to you.

topcatcustom · Post by **topcatcustom** » Wed Oct 08, 2008 6:37 pm

Thanks Nigel, I guess without the core plugs in the shaft the rotors may fill up with oil from the reservoirs from each end though...

ukblowers · Post by **ukblowers** » Wed Oct 08, 2008 7:01 pm

No, because the front shaft is sealed with the bolt that holds the gear on (loctited) and the rear housing should be fitted with sealed rear bearings. The rears do not run in an oil bath like the fronts.

topcatcustom · Post by **topcatcustom** » Thu Oct 09, 2008 8:18 am

Found out that the shaft is in fact 2 stubs in each end which I guess is why it is important to double pin them in race situations! Out of interest why not run the rears in a bath?

ukblowers · Post by **ukblowers** » Thu Oct 09, 2008 5:54 pm

No reason why you can't run the rear bearings in an oil bath.......its just not normally done. All aftermarket GM blowers are built with heavy duty bearing plates, and the rears, without exception, have no provision for an oil bath. The oil in the front cover is primarily to lubricate the gears.

One more thing you will need to be aware of is that there are oilways in the stock bearing plates which lead to holes in the blower case which will need threading and plugging.

topcatcustom · Post by **topcatcustom** » Thu Oct 09, 2008 7:57 pm

Yup I noticed them! I guess the front needs a dipstick or filler hole (like axles or gearboxes) too, are you able to pull the spline onto a new shaft for the snout Nigel? Splines & keyways are a bit of a problem for me as dont have the tooling!

ukblowers · Post by **ukblowers** » Thu Oct 09, 2008 9:56 pm

We have had small batches of splined shafts done in the past but found it just was not economic compared to buying in complete snouts manufactured in the USA. We are distributors for Blower Drive Service.

ukblowers · Post by **ukblowers** » Thu Oct 09, 2008 9:57 pm

forgot to mention..........keyways are no problem