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Well I managed to finally (after over a year of searching and getting burned on deals) score a Weiand 10-rib blower setup in pretty good condition. Has the normally sized lower pulley and a slightly smaller upper, which Holley calculation estimates to be a 12psi combination. Its common for the actual boost level to decrease with heads, exhaust, cam, etc so considering my combination has an F303, 190cc alum. heads, and long tubes with off-road exhaust, I expect 7-8psi.

I already have a carb or three that I could use for this build but I thought it would be more fun to try a new EFI TBI system with it and run e85 to see if I can keep things cool and have a streetable toy. I've read that these blowers will produce some heat when driven fast (smaller pulleys) so I don't want to deal with overheating in our 100°F and 95%humidity. I also noticed the rear of the intake doesn't have a coolant crossover so I'll likely either plumb one with drilled/tapped fittings and flexible hose or just see if the ethanol keeps it cool enough.

The FiTech unit that @millhouse used is one of my options and the other will be the new Holley Sniper units. So far I'm seeing that for the same options, the sniper unit can be had for less money and has the more favored holley software and support, so I'm leaning toward that avenue, although there really haven't been any good reviews posted, so its a waiting game for me.

I don't want to expect big power numbers honestly. I already have a standalone EFI turbo/auto coupe that I'm trying to make more horsepower with and after recently re-acquiring my first mustang, an 87 5spd coupe, I think it'd be a lot of fun to drop it in and see what it'll do with that 5spd and instant-ish boost.

Now that the background novel has been written, has anybody actually installed and used these things? I've seen a few threads in my searches but it'd be nice if people came out of the woodworks with some opinions, pics, tips, etc.
 

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Years ago I installed one on a 70' Mustang with a 351W engine. It required adapter plates to fit the taller deck height Windsor. Made the carb stick up through the hood. Made for a fun car. Never put it on the dyno. Running E85 is a good idea as those Roots blowers put a lot of heat into the intake air.
 

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Years ago I installed one on a 70' Mustang with a 351W engine. It required adapter plates to fit the taller deck height Windsor. Made the carb stick up through the hood. Made for a fun car. Never put it on the dyno. Running E85 is a good idea as those Roots blowers put a lot of heat into the intake air.
Sounds torquey. :) I think it's probably sized pretty well for a Heads/Cam 302 and I think the modern EFI will make it very driveable. I've heard great things about e85 cooling the air charge so considering it's flowing right through the blower rotors, I think it should drastically help. I remember on my buddy's last turbo blowthrough setup we could make WOT hits and the intake manifold would be warm at most.

I'm making the switch on my turbo car for the same reason. IAT's in Houston are nasty.
 

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I had one on my 85 GT years ago, the fuel going through the blower will keep IAT cool. It made the 302 feel like a big block. Say good bye to your rear tires. After you will start thinking what about a bigger roots/screw blower that intake will make it easy to adapt a 3.4 Whipple with a carb top feed.
 

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I've never seen a carbed whipple setup on a ford. It'd be nice if they made a screw rotor conversion for these cases but i doubt that'll ever happen due to market size. :/ The car has 3.73's and a street tire so I expect to probably roast the tires through at least 1st and 2nd. lol
 

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My 3.4 Whipple is a top feed for a carb but I run 4 extra injectors through the hat. Whipple will sell you compressor of any size plus all the extras like snout and pulleys that's how I pieced mine together.
Ah, I've seen your build, very clean! I emailed whipple about getting some screw rotors for a weiand case and they said they can't do anything about it. I also read something about the machine precision on a roots case being looser than that of a lysholm type, maybe due to the nature of the pressure production. Maybe they're afraid screw rotors won't build boost correctly in a "sloppy" roots case. Maybe I can just design them myself, get 10 sets made, then sell 9 to pay for my 1. lol
 

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According to my source (current president at Magnuson, former engineer at Eaton), roots (including Eaton and TVS) blowers actually have tighter clearances than screw blowers, being that the screw rotors are more complex, and more difficult to machine.

In any event, I doubt you could just swap in a screw rotor pack - too many variables, I'm sure (the screw drive being 3:5; rotor diameter, outlet dimensions, inlet geometry, etc). But E85 should be excellent with that thing. Perhaps get the rotors coated with an abradable coating, run some nitrous through it - I'm pretty sure you could get to 800 hp if you try hard enough (and an aftermarket block on a 175-200 shot).
 

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Adiabatic efficiency on a Roots type compressor used to be down in the 55% range. Has that improved? The twin screw is in the 70% range, making more a lot less heat, but either way you go I'm sure you can control the heat very well using water injection.
 

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According to my source (current president at Magnuson, former engineer at Eaton), roots (including Eaton and TVS) blowers actually have tighter clearances than screw blowers, being that the screw rotors are more complex, and more difficult to machine.

In any event, I doubt you could just swap in a screw rotor pack - too many variables, I'm sure (the screw drive being 3:5; rotor diameter, outlet dimensions, inlet geometry, etc). But E85 should be excellent with that thing. Perhaps get the rotors coated with an abradable coating, run some nitrous through it - I'm pretty sure you could get to 800 hp if you try hard enough (and an aftermarket block on a 175-200 shot).
Hmm, maybe the tighter clearances on the roots case is due to the rotors moving air along the case rather than compressing between the rotors themselves. The rotor-to-case clearance would need to be very tight so as not to allow leakage over the rotor tips. With the screws, that air pocket looks to be created between the rotors instead, so you require high precision on the rotors (likely required by design anyway). Yes, screw rotor design is much more complex (I've been learning how to calculate the geometry in order to design a screw-blower) but I've found that industrial gear manufacturers are able to hob the rotor lobes so it may not be too hard to have it manufactured. Doesn't require a 5-axis, thankfully.

Although the spray sounds fun and high hp is a possibility, I don't plan to go too big on this project. with e85, the holley sniper will be limited around 400hp I believe so it may just be a street-strip car. the T5 in the car wouldn't take much more anyway I'm sure.

Adiabatic efficiency on a Roots type compressor used to be down in the 55% range. Has that improved? The twin screw is in the 70% range, making more a lot less heat, but either way you go I'm sure you can control the heat very well using water injection.
I doubt it is any different on straight lobe roots blowers now than it used to be. Even helical rotors probably aren't any different. The twin-vortice rotors that eaton developed are probably better but I still think neither are that close to a screw. I plan to run e85 in the car (passes right through the blower) so I'm hoping the IAT's are low from fuel alone.
 

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I have a 1983 mustang 302 afr 185 heads decent cam blower carburetor 373 gears and weiand 174 blower. Plan also to switch to e85. Due to the fact its cheaper than race fuel. Race fuel and a timing dial is only way i can control detonation. I will say though my setup isnt all out race worthy it is a blast to drive
 

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Discussion Starter #12
I have a 1983 mustang 302 afr 185 heads decent cam blower carburetor 373 gears and weiand 174 blower. Plan also to switch to e85. Due to the fact its cheaper than race fuel. Race fuel and a timing dial is only way i can control detonation. I will say though my setup isnt all out race worthy it is a blast to drive
Post some pics or vids bud! long tube headers? What pulley and how much boost are you seeing?
 
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