Hot Rods 4/71 blower rebuild

Just be careful using the aluminium and things to hold the drive gears while tightening the drive gear bolts. Forty years ago I started out as a Detroit Diesel mechanic. We just used a red shop rag to bind the gears. Works well. Doesn't hurt anything. Just double check when you are done that should a bit of rag tear off just you get it off the gear.

 

Hey Jim,
That is a good idea,,,a rag would work just as well.
I just used a thin gauge aluminum strip to lock the gears.
I have seen several videos that they used a hammer handle jammed inside the housing between the rotors,,,that made me feel uncomfortable.
Thanks for the input!

Tommy

 

Here are a few more pics of my progress.
I decided to make a rear cover plate out of some stock I had.
It started out as 1/2 inch plate ,and then I outlined the pattern on it with a scribe.
I transferred and drilled the dowel holes first to lay out the pattern,,,,then drilled the bolt pattern next.
Next I trimmed the excess off with a band saw from work,,,,and ground the outside edges with a belt sander while I was at it.
Then it progressed to blending the edges with a 90 degree sander.
I always like to add a nice radius to anything I am working on,,,I can’t stand sharp ,blunt edges .
Then I added a 1/8inch pipe plug for an oil fill hole.
Then the polish work and then the mounting and mock-up.

And I add this disclaimer again,,,the polish work is not show quality!

The only reason I used 1/2 inch plate,,was because that was what I had.
1/4 inch,,or maybe even 1/8 ,,,would work as well.

I plan on running oil in the rear,,,30 weight oil,,,,just my own idea.
The reasoning being that I wondered about lube for the rear seals.
I have sealed bearings,,,,but what about keeping the seals lubricated.
I may be overthinking this,,,,I’m not certain.

Almost there,,,I think the Tri plate for the front is all I still need,,,I should have it worked out soon.

Tommy

 

I use anti seize on any bolt into Al.

 

Sorry guys for the lack of anything new,,,I have been busy,,,and it was almost done anyway.
I made a tri plate for it,,,,it’s not too bad if I do say so.
It is from some old s**** stock I had and it barely fit the pattern,,,but it is close enough for me.
I put it on with some temporary bolts,,,,,and I used anti seize on them as well.
I will wait and make those bolts match whatever I use for the drive when it goes together.

Tommy

 

That’s it for now guys.
I have put it away until the rest of the future project comes together.
The main reason I did this ,,was to show that it is not all that hard to do.
If a normal guy like me can do it,,,anyone can,,,,just take your time,,,read up on it.
Ask advice,,,,buy a good core,,,,,use good quality parts.
Then your project will turn out just as well!

I still plan on using a fuel injection system on it in the future,,,still building that too.
Just on the back burner at this time.

Right now my attention is on a Flathead that I just purchased.
I’m really gonna have fun with that!!!

Tommy

 

Thanks for taking us for the ride. Hope to see more when you can get to it again.

 

Hi guys,
I realize it has been quite some time since I made any progress on this build,,,,,,,but life got in the way and I have recovered to the point that I was able to do an addition .
I found a nice drive snout,,,,,and also purchased a spacer to make it more compatible with my application .

Tommy

 

Now,,,,,,after I received it,,and an inspection,,,,,,I decided I had better purchase another for my other blower application,,,,,,”why just buy one,,,,when you can have two for twice the price,,,,,LoL .
They are satin finish ,,,,,,as you can see,,,I polished this one slightly,,,,,and will do the other when the need arises.

Tommy

 

Now,,,,,after installing the drive coupler,,,,,,and bolting it up,,,,it really looks great .
Tommy

 

As I have always said,,,,,none of this is show polished,,,,just decent enough for the street .
This is a 6 inch drive with a 2 inch spacer,,,,I think it should be very close to what I need to position the blower in the correct location on my manifold .
I have an adapter plate for the blower,,,,..which will go on a plate to the manifold,,,,,,I should be able to drill and mount the blower for the best fit to the manifold .

I also purchased two idler arms for the drives as well,,,,,great price .
I do a lot of shopping on price,,,,,(when I find a deal) ,,,,,I have to do all I can to keep my investment low .
The drives were 285 each,,,,,including the coupler,,,the spacers were right at 50 each .
The idler arms were 82 dollars each,,,,great price .

Tommy

 

Keep up the progress. I would love to put a a blower on my coupe. Once you drive one with a blower, they all need one.

 

Dig it!
Funny thing about people though, someone finds a Jimmy blower at a swap meet cheap, missing the drive, they get all excited about finally getting a supercharger......... until they have to buy NEW PARTS then everything comes to a halt, now what, well pack it to the next swap meet or spend the $$$.
You get it, stuff doesn't just fall into your lap, ya gotta want it.

 

4-71 GMC Diesel Engines is where they come from. 4 cylinder, 71 cu.in. per cylinder.

 

Damn, that's a cool looking blower!

 

Everyone seems excited to find one, until they realize that manifolds are like hens teeth, and often painfully expensive when they appear. Drives can be built from common parts, but it adds up.

 

It is a good idea to use aftermarket bearing plates because they have reinforced bearing retainers...They use to machine the stock plates collars and press on steel rings to make the bearing plates stronger...

 

Yeah,,,,,depending on the application,,,,,manifolds can be very scarce .

I’m gonna use my factory 4 barrel Desoto intake,,,,,I’m planning on milling the center open and cutting the opening to a larger 4 barrel base size.
Then having it all milled perfectly flat,,,,,and bolting on an aluminum plate which I can adjust,, front to rear if need be,,,and get the blower centered correctly.
I’ve seen a lot of regular intakes modified to work ,,,,especially if there is not an application available .

Tommy

 

I didn’t read anything about “pinning”the rotors to their respective shaft. I use a “pruned”3-71 blower on a homemade intake and as the initial use of these blowers were in a diesel that only sees 1200-1500 rpm makes it NECESSARY to “pin” the rotors as they are only pressed on to the shaft. Now that they are turning 6-7-8 thousand it is a must for higher rpm useage. The man who helped me with my 3-71 had over 50 years GM blower experience. Mine was able to set up .010 clearance anywhere you wanted to measure it. It could have been set up slightly”tighter” but he explained to me that tightness invites heat and we know how things expand as they get hotter. He also said he would run oil even in the sealed back bearings to make them “happy. Flatheads Forever!!! Just stating some of his opinions—-right or wrong don’t know.

 

All of the 3/71 - 6/71 blowers have 1 pin per rotor ,,installed from the manufacturer .
I feel that the smaller 3/71blowers are okay with a single if you have to ,,,..the 4/71 are much safer with at least a double pinning,,,2 pins per rotor .
The 6/71 rotors are quite a bit longer and with much more m***,,,,and will really survive better with a triple pinning .
You just have to add 2 extra pins per rotor,,,,not hard to do .
There are instructions available to show how to do it .

Tommy

 

Not wanting to argue with you, but my 3-71 blower was NOT pinned at all. I only found out they needed to be pinned because my “blower guy” told me they were only pressed on the shaft and that high rpm might cause spinning on the shaft. Wasn’t trying to hijack your post,only wanted to add the facts about the pinning that were expressed to me. I only wanted a 3-71 blower because the Italmeccanica blower(made in Italy) are too expensive. My 3-71 only costs $100, but I had to do a lot of “farm out” work because I lacked the experience to do it properly.

 

Great job on the 471 and love the old school black inserts . Are the snout s new and do you have a link to get one.

 

I get most all of my blower stuff from here: https://www.goodvibesracing.com/

They have snouts, some quite long, which help with the shortness of a 4-71, or even a 3-71 case.

The longest one they stock is 8-1/8", before you need to resort to spacers, or flipping the upper pulley.

 

Sorry Flathead John ,
No insult intended or received .
It has been my experience that they were pinned,,,,,,all of the ones I have are pinned .
From the factory judging by the tool marks .
I will try to get some pics of my 3/71 rotors tomorrow ,,,,,,no problem .

Continental John ,
I got my drives off eBay ,,,,,,they came out of Michigan,,,,,a guy that goes by the handle of wild child,,,,,,I’ve bought several blower and injection parts from him,,,,,new and used stuff .
The drives are brand new,,,,,good quality.

Tommy

 

Gimpy,
Yes,,,I buy a fair amount from good vibes,,,,,,very good group to deal with,,,,,excellent quality,,,,,fast shipping and reasonable shipping price .
I went with the spacer on this application because it Is a 4/71,,,,,and it’s not driving very large rotors.
The spacer will not weaken it in the least,,,,,especially on the street at my low boost levels .

Tommy

 

Bobby Walden sells the pieces for a beautiful V belt set up.

 

You may find some early 3-71 blower rotors not pinned, but the vast majority of the 71 series were factory pinned. The inline 71 series engines typically had no load speeds between 2150 and 2450. The blower drive ratios varied between blowers and application, but generally were between 1.7 and 2.05 of engine speed. So for the average street application there is no need to install additional pins in the rotors beyond the factory pins. However if you are going to spin up a 6-71, you should install additional pins and improve several other items. It's a matter of knowing what you have and what you want to do with it.

 

Do you by chance have any pics of you cutting out the rib in the top of the case? I think you mentioned doing it in earlier post. Also what did you use to drill rotors to install the pins? Mill? Drill press?
Just bought a 4-71 case to rebuild for a 1966 Chevy 327. Still researching CR, pistons, rods, etc to get idea of how to make it all work without imploding.
Thanks in advance!
Great read Great job!

 

I cut the ribs with a cutoff wheel, specifically for aluminum, on the grinder. The go away quickly.

A drill press can work fine for drilling for pins. Supporting the rotor is the trick.

It is easier on a vertical mill, as the table is bigger. That's where I do mine. Supporting the rotor from the shaft is easier on a bigger table.

 

Thanks for all the info!! I really appreciate it!