School me on blower delta discharge holes please

From what I gather and this is very loose so far ...

Roots style Blowers aren't the master mixers they appear to be . The natural consequence of the rotors it to push the fuel heavy out the rear of the blower, and this can leave the front cylinders lean. The delta hole is supposed to help move the mixture forward.

So I find myself in need of an adapter plate under my gmc issue 671. I could incorporate a delta hole in the plate. However I have no clue on exactly how to size it .

Thanks

 

No real first-hand blower experience, but this is what I have always heard, and I recall seeing a plate or blower case like you describe somewhere.

 

Think it was a case on a TAD in the nineties, my brain is saying high helix screw-type that was banned later.

 

Heres a picture so you can see it here too
This is an 871

 

Blowers squeeze everything foward and is a reason why some racers move the blower "BACK" to get the discharge more towards the center of the manifold. Some racers have even turned the rotors around bacwards and discharge to the rear but found out the air made an "S" bend thu the case instead of the normal "C".
The "DELTA" plate was just a cheap gimmick that didnt do anything on a standard opening case and if one isnt driving the blower with a whole bunch of overdrive, the air and fuel stall between them. To really take advantage of a "DELTA" style opening the blower case itself must be machine to what racers refer to a "RETRO" (retrofitted not nostalgia) and those are in the $5000 range new

 

Thanks Dr e.

So there's "0" benefit with a delta plate ?
Ill be making it and there would be no cost difference it the cutting of the hole

 

If you take apart a retro case you will see that there is no discharge opening in the back half and continues the arc of the case. What it is doing is compressing the air/fuel longer and making the blower think it is bigger then it is. So by just cutting out a piece of tin with a pie shape opening in front underneath a stock case with a seperation bar (bottom of the blower case) pooling some fuel in the back half, doesnt do squat. Now strip the blower down and machine a large plate of aluminum so it tightly fills the bottom openings and remachine the inner case and opening, you could see some benifit if you really get after the % overdrive, but then other things take over.
I run a stock opening 6-71 @ 18% over and make 23# of boost for a 375ci SBC and run in the 6.90 range. Get your combo together and quit worrying about tricks and gimmicks, There are none out there, just better parts.

 

Why dont you go over to SSI in cleveland and talk to Rich or T.J. They are the pros in delta setups. R&P BLOWER SERV.