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Old 12-17-2004, 11:13 PM
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671 rear cover plate question?

Can somebody tell me the function of the rear cover plate on a 671 Blower? A friend of mine said he,ed machine me a 1 piece cover with the 2 holes machined to fit over the rear bearings. Would that work? Thanks, Marty

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Old 12-18-2004, 12:20 AM
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stock blowers had a bearing plate similar to the front one with a separate cover plate that had a power takeoff to drive accessories off the back of the blower. Racing after-market guys made up rear bearing plates that did away with the extra piece and their rear blower cover was a ribbed plate that held the bearings. Smaller and lighter and stronger. All the rear plate needs to do is close the blower chamber and hold the bearings.
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Old 12-18-2004, 05:39 AM
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Re: bearing plate cover

Thanks! sounds encouraging! Up here they want $350 Cdn. for a new polished weiand covered end plate! Thats what i paid for the whole GMC used blower thats in mint condition! Ive just about finished polishing the blower, talk about a career job! lol. Marty
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Old 12-18-2004, 08:02 AM
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If I were you , I would look around the classified ads on race sites etc. to see if you could find a used plate somewhere. There,s got to be one sitting somewhere.Machining one is certainly an option, but you will need a piece of aluminum about an inch thick to start with,in order to face off the inner side, and have enough thickness for the bearings. All of your measurements will have to be "very" accurate to keep the rotors positioned properly.If this is an old detroit blower there is more rotor to rotor and case clearance than a race type blower.
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Old 12-18-2004, 09:01 AM
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jcarter,
Is right on the money.

I would not try to have one machined personally. The rear cover does more than just hold the bearings, it also has to be positioned correctly to keep the rotors "EXACTLY" where they need to be. If you have one machined and it is slightly off you could ruin your whole blower.

You might want to check E-bay there are usually a lot of blower parts on there for a reasonable price.

Royce
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Old 12-18-2004, 07:43 PM
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Re: bearing plate cover

Thanks guys for the advice! Its going on my 427 chev. powered 47 International. After 18 years i thought it was time for a change in the truck! Middle Age Crazy i guess! lol Marty
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Old 12-19-2004, 09:20 AM
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Re: 671 rear cover plate question?

Quote:
Originally posted by binder47
Can somebody tell me the function of the rear cover plate on a 671 Blower? A friend of mine said he,ed machine me a 1 piece cover with the 2 holes machined to fit over the rear bearings. Would that work? Thanks, Marty
The rear of the blower was driven by a splined shaft driven direct from flywheel thru gear up or down ratios.

have a look ,, and tell me what you see >??

if it is the normal truck blower set up the plate is just a cover ,..

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Old 12-19-2004, 10:46 AM
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The rear plate is NOT just a cover, it holds a set of sealed bearings. These sealed bearings are what the rotors ride on/in. They must be properly aligned or your rotors will not be in spec. If you look at the rear plate of a automotive roots blower you will see two raised round parts, that is where the bearing are pressed in. When they align the plates they install dowels (drill and press) so the end plates stay aligned and can be removed. Unless your machinist can duplicate that perfectly I wouldn't fool with it.



Royce
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Old 12-19-2004, 11:18 AM
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Re: bearing plate cover

Thanks again now here we go again...... case cast number is 5138725. I took my tape measure....the impellers of course are 15" long. Now ive kept both bearing plates which are 1.25" in thickness. both are ribed on the outside. Ive now noticed most weiands have the back plate removed ( that held the rear bearings) and machined a new one to hold the bearings in place, is that correct? with oversized dowls. I would like to keep the original 1.25" plate and just add a cover plate behind it. Is that possible? sorry for being a pain!!!!!!!!!!!!!!!!lol thanks, Marty
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Old 12-19-2004, 11:48 AM
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Marty,
Upi are not neing a pain at all. That is what this noard is all about. I wish I could answer all your questions but, I can't. I am not a blower builder. I did a little research before I bought my blower. Thinking I couls save a few bucks just building one myself. After the research it was clear to me it would be better to buy one already set-up.

With that said, I am sure you can contact any of the blower shops and get your answers. I think that is your best bet. This is not something you should guess of fool around on. One mistake could be VERY expensive.

Try calling, BDS, Hampton, The Blower Shop, Mooneyhan, Littlefield, Kuhl, etc... I don't know that you could get your answer from Holley (Weiand). The other shops I mentioned actually build blowers from scratch and do all the machine work. They KNOW their stuff.

Royce
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Old 12-19-2004, 03:00 PM
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Re: bearing plate cover

Thanks Royce!!!!!!!! Marty
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Old 12-19-2004, 08:00 PM
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Re: Re: bearing plate cover

Quote:
Originally posted by binder47
I would like to keep the original 1.25" plate and just add a cover plate behind it. Is that possible? sorry for being a pain!!!!!!!!!!!!!!!!lol thanks, Marty
Yes, if you have the stock bearing retainer plate you can simply make a 1/4" thick plate and bolt it on. That has been a standard practice sine the beginning.
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Old 12-20-2004, 12:09 AM
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Re: bearing plate cover

Thanks! I just came across a pic of an old weiand cover like you stated.
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Old 12-20-2004, 10:18 AM
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AH!! Duh, I was thought he was talking about making a rear cover with the bearing "retainers" in it. Now I see what he is doing. You want to keep the originag bearing plate but, make a different bearing cover. After reading willys36@aol.com reply it all became clear. I agree you can machine your own bearing cover. I thought you were dealing with an aftermarket style blower. My mistake, sorry if I steered you wrong. My blower is aftermarket and it doesn't have the 1.25" bearing plate. The bearings are pressed into the rear cover.

Royce
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Old 12-20-2004, 10:34 AM
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Quote:
Originally posted by camaroman7d
AH!! Duh, I was thought he was talking about making a rear cover with the bearing "retainers" in it. Now I see what he is doing. You want to keep the originag bearing plate but, make a different bearing cover. After reading willys36@aol.com reply it all became clear. I agree you can machine your own bearing cover. I thought you were dealing with an aftermarket style blower. My mistake, sorry if I steered you wrong. My blower is aftermarket and it doesn't have the 1.25" bearing plate. The bearings are pressed into the rear cover.

Royce
You weren't wrong. Early in blowerdom they started doing away with the rear bearing plate and making integral bearing retainer/rear plates for GMC blowers. And you are correct, if you go this route, precision is the word. People who aren't totally up to speed on these monsters don't have a clue to how much of a precision instrument they are. Tolerances of the internals are in the 0.0001" range.
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