671 vs 871 size comparison

Anyone have some side by side pics or dimensioned drawings of the two.
Weiand's web site says the 871 is one inch longer but doesn't show were the 1" is compared to the mounting holes.

And is the charge hole the same size ?

Thanks

 

I don't see it on their web site, but BDS had a very good chart with most of those measurements in their catalog.

I do know the bottom opening on my 8 was longer than the opening for my intake that had a 6 mounted on it.

If you cannot find the info you are looking for there is an 8 sitting on my workbench and I can go measure what you need.

 

Well lets see what pops up here.
I may take you up on that

 

Bump

 

Here's a 671 - and the charge hole on the bottom is 12.125
I need the same for a 871
Thanks

Lets label these dimensions from left (front) to right(back) ABC

A 1-9/16 front end of case to bolt hole
B 15 case length
C 1-9/16 rear end of case to bolt hole.

 

There is no such thing as an '8/71 blower' really. It is an after-market item, never produced by GM, so there could be difference depending on who makes it.

 

I realize the 871 is an aftermarket item.
I did not realize that they were not all similar in mounting and size.

 

Bump

 

There is a spacer between the bearing plate and the case. That is were the extra 1" comes from. I believe the case is the same. JC

 

here's some info http://www.kenlowe.com.au/Superchargers.htm ,,, Tim Jones

 

That is technically correct... sort of. The 8-71 made by GM is really a 8V71 so the blower for it is set up for a V configeration in that application. The 2-cycle Detroit Diesel won't run without a blower so every engine has to have one.
The inline versions mount flat to the engine block so they have a nice outlet configeration that makes it easier to mount to something else in a different than stock application. So the aftermarket 8-71 blowers are re-popped with that in mind. So as Morrisman stated the dimensions etc will be dependent on who manufactured it. I suspect one could use a stock GM 8V71 or 92 blower for that matter if the time was taken to match/modify the housing to the application.

LJ

 

When we switched from a 6 to an 8 on a top fuel car in the late 70s, I had to machine three 6:71 manifolds to accept the larger opening of the 8:71. It amounted to adding a piece at the rear and making the opening longer toward the rear.

 

I'm not looking for a V model comparison .

Weiand , littlefield, Hampton, etc. all have a 8-71 and are they really all externaly different measurements ?
Their 671 is pretty much the same as gmc 671.

Every damn blower part you ever see is "671-871" meaning it fits both and presumably all of them

 

I have a TBS 871 the charge hole is 12.125 by 3 7/8 and the mounting bolt holes are the same as the 671 and this 871 is a billet one.

 

Great how does the TBS compare to the pic I posted
Case length an mount holes to case end

 

Weiands cases all have the 1 inch added to the front of the case to maintain the clearance of the dist, or mag. ect, just like a 6. Bolt spacing is the same as all 671s. Actually the 871 case is .979 longer than a 6. R&P BLOWER SERV.

 

I have an Ed Pink 8 71 and the discharge hole is 13 7/8

 

I have an older 871 BDS and a 671 GM and both of them bolt onto the same pattern as for as the manifold goes. The case is longer behind the main body and the front is the same length as in the drive will be lined up the same on either unit. I was told by BDS that every size increase is 1 inch longer than the one below it(ie,a 1471 is 1 inch longer than a 1271 a 1471 should only be 4 inches longer than a 671 but they sure do look much longer).The discharge on mine are the same also, when you get bigger as in 1071 and up they I believe start to open the manifold top up to accomidate the larger units. My manifold has been opened up and I had to make up a 1/2 inch plate to bring it back to the size for the smaller blowers. I hope this helps. Rocky

 

The TBS if checked on pass side the rear is 3 and the front is 3 1/4 w/plate and 2 w/o the case is 15 15/16 w/o plate and 17 3/16 w/ plate the plate is the one added on the front I guess to make it a 871

 

Ok so if I were to look at the pic I posted with dimensions
the 871 would be :
A 1-9/16 from front end of case to bolt hole
B 16 case length
C 2 -9/16 from rear of case to bolt hole

That leaves the drive in the same location and crowds the dizzy
Am I correct with my interpretation

 

When I check from the discharge hole the front is 2 5/8 with the added plate and the rear is 2 1/4 to the end of case.

 

Ok I just set a 671 on a small block manifold and the the TBS 871 on same manifold and I say there is 3/8 more room at the dist with the 871 and the front is the same so the rotors are longer on the front and the rear mostly the same. I dont have any drive for the 671 it is fresh off a detroit and the drive for the 871 is 5.15 billet snout for a big block build project.

 

The 871 has 3/8 more room at the rear?
How much of that is plate variation ?
--------------
We know the manifold surface bolt patterns are the same for 671 and 871
We know the case is bigger for a 871 by about an inch.

I'm just trying to find out where they put the extra inch or so in relation to the manifold surface bolt pattern? Is it 1/2" front and rear , is it more biased to the front or rear . A measurement from the bolt hole to the end of the case will tell me that . In the pic i posted on tge first page, the 671 is 1-9/16 from the end of the case to the bolt hole.

 

It does not have a plate on the rear and some of the differants my be that this is a billet case? The plate on the front is 1 1/4 inch thick. This was a done with out the studs so may be off just a little but definity no crouding of the dist with a 871 or at least with this one . I guess the deal is the rotors are longer witch you know and the plate in the front let the rotors pass through it and the rear is some what the same between the 671 and 871.

 

31 Vicky, It's been a while since I messed with a small supercharger, but the one in your pic looks like a 871 to me. The 6 does not have the plate between the case and the rear bearing cover. Correct me if I am wrong. JC

 

All but the 14-71 are longer in the back so your drive snout will still work.
this is a gasket for a 6- 71 to 14-71 the opening is for the 6-71 . You cut it out for the bigger blowers. You need to call manufacturer.

 

As far as I know that is a genuine GMC issue 671.

As far as plates and covers I don't know. The rear end plate could be pruned back around the perimeter and a small dog bone bearing cover used.

 

Your picture is a 6-71 with a factory bearing plate. I think a 8-71 is only 5/8 longer on the center case.

 

Well I thought I was doing just that ??? Asking for measurements .
I suppose I could go down to wallmart and measure one
Or just have one shipped here and see if it will fit . Cheap enough to do that right .

Perhaps you may have the wording I should use to ask the owners or sellers of 871 blowers to get the dimension I need . Apparently I've failed and the picture isn't clear enough. It's the dimension from the end of the case to the blower hole

 

Ok on the rear from blower outlet hole to rear of case is 2 1/4 and the front is 1 3/8 without plate and 2 5/8 with plate hope that helps.