Roots supercharging a Ford FE?

[RJP]

While it's true that GMC blowers are low in efficiency, especially at higher rpm and boost levels, there is a reason why GM installed same long ago in buses and heavy trucks. Although both were  in low rpm diesel applications, the tremendous boost it gave at low rpms allowed what seemingly was too small of an engine to push some mighty big loads. In fact, early drag racer efforst to improve the blowers were aimed (and still are today) at high speed efficiency. The PSI blower noted above literally was an effort to improve the original GMC blower's efficiency by using scrolled lobes (although later racing GMC' used this too) pushing the outlet air in a different direction.

We put a Dyers 6-71 in about 1975 or so on a 392 Hemi plopped into Kenny Hess' '67 Plymouth Belvidere. Even with a mild cam, tune and IIRC a 3.25 rear gear behind a Torqueflite, that car would smoke so pretty big M/T tires in 1st and 2nd as long as one kept the pedal down. Frankly, if you've ever driven a 6-71 or 8-71 blown streeter, you'd know it's all about outstanding low-mid range response that no turbo car can give.   

OEM GMC blowers were for cylinder evacuation only, they never were intended to make boost. All 53, 71, 92, 149 series GMC diesels are 2 stroke and need blowers to clear the cylinders of exhaust gases.

[fe66comet]

I am thinking on the same lines as far as torque and low to mid RPM. I have a supercharged Buick V6 in a Park Ave, it has a lot of power for a little six. I had the identical car without the blower and it was a total pig. I am amazed the difference it makes on a small displacement engine with stock parts.

[fe66comet]

A turbo does add a lot of heat, the supercharger only gets hot when you spin it beyond it's efficiency window. Generally if sized right a blower is good from idle to 5500 with no heat gains.

[machoneman]

I like turbos but one is pretty much stuck with any auto tranny to load the convertor while the turbos spin up. On the other had, stick or auto, a GMC 6-71 or 8-71 will blow away at the low and mid-range most streetable turbos....that's a fact.

[drdano]

While I'm bench racing with someone elses money...what about a compound turbocharger setup? 

[machoneman]

Hah! 

We put a Dyers 6-71 in about 1975 or so on a 392 Hemi plopped into Kenny Hess' '67 Plymouth Belvidere. Even with a mild cam, tune and IIRC a 3.25 rear gear behind a Torqueflite, that car would smoke so pretty big M/T tires in 1st and 2nd as long as one kept the pedal down. Frankly, if you've ever driven a 6-71 or 8-71 blown streeter, you'd know it's all about outstanding low-mid range response that no turbo car can give.   

http://www.superchevy.com/how-to/engines-drivetrain/0510sc-principles/

[machoneman]

While I'm bench racing with someone elses money...what about a compound turbocharger setup?

They exist yet I've never seen or even heard of one in gasoline streeter or gasoline/alky racer. This system would eliminate a lot of low end turbo lag w/o hurting that tremendous (that word again...LOL!) top end charge. 

https://www.atsdiesel.com/ats2/templates/template_06.asp?p=2029422272&c=36
http://www.dieselpowermag.com/tech/1302dp_compounding_turbo_crash_course/

[fe66comet]

I did actually consider turbo and a centrifugal blows, but for idle to 6000 the roots or screw compessor seemed the best deal. Price wise you end up the same or a little more with turbo due to an intercooler and waste gate. Plus the coolness factor of a blower and injection system sticking out of the hood is over the top. I can go E85 and go monster boost as suggested before but I am not really sure if there would be a whole lot to gain there and the fuel itself is a big pain to deal with. If it sits it collects water and causes corrosion, also fuel mixture can be inconsistent and contain water to begin with. I do have two 750 CFM Edelbrock carburetors converted to E85 that I could use but they might be anemic with a supercharger and 500 cubes.

[sumfoo1]

for the hp you're looking for  (under 1000)

two garrett gt3076rs would  make full boost before your foot made it all the way to the floor...

I know that's not going to change your mind but... thats what i mean about sizing turbos.

I'm trying to not make boost below 2500 rpm unless i use a 2 step hence i'm using turbos that flow over twice what the 3076s flow for a very similar motor.

http://www.carcraft.com/techarticles/ccrp_1004_twin_turbo_pontiac_engine/
even this engine has signifiantly larger turbos than that  (though it doesn't need them)

I like turbos but one is pretty much stuck with any auto tranny to load the convertor while the turbos spin up. On the other had, stick or auto, a GMC 6-71 or 8-71 will blow away at the low and mid-range most streetable turbos....that's a fact.

https://www.youtube.com/watch?v=AXDMXvpbJMQ

turbo LS Small block 6 speed.... need i say more

A 2 step works fine  or low rpm rev limiter that causes the car to back fire some and spool the turbos.

[TomP]

Is wasn't aware Blue Thunder made any High Riser intakes. If the claim to i'd check availablity first before getting your hopes up. They have been out of stock on lots of things for long periods.

[fe66comet]

At this point talk is all I have going LOL, I have more projects than cash. I eventually would like to build another engine for my 66 Comet, I have a aftermarket 385 block that was used in a drag car but the size and weight has me reconsidering. Another factor is cost wise the FE is actually more cost effective per HP to build and is quite a bit narrower overall. I could go with a two stage turbo but then it is twice the cost, I would more than likely go with a centrifugal blower first if I went that route. Two turbo systems are definitely cool but the complexity and cost is somewhat prohibitive. Basically I am thinking a top mounted supercharger with some sort of injection, probably Fast with two four barrel throttle bodys. HP wise it would depend on what a stick trans and rear end could be built to handle, I would want something streetable so a two speed is kinda mute.

[Ford428CJ]

You dont need a compound set up to get rid of turbo lag... You need a variable vain turbo! If it was me.... This is what I would go with! Can you say... "BAD ASS"!? LOL

http://aerocharger.com/turbo-systems/automotive/pontiacg8/

http://aerocharger.com/aerochargers/66series/

[sumfoo1]

Aero chargers used to be junk but I haven't seen one in years.

The reason you see variable vane turbos on diesel and not gas engines is usually they can't handle the egts.

[fe66comet]

Why not a turbo into a supercharger? OH wait KABOOM ,I hate when that happens LOL.

[sumfoo1]

It's done all the time

http://www.hellionpowersystems.com/index.php?option=com_content&view=article&id=140

Blower makes the motor act bigger turbos work as usual.

All this stuff is a function of intake air temp if you intercool the heck out of your boost back to ambient (sometimes better with ice boxes) you can do whatever you want without really risking detonation until you reach pressure levels that will yield the rod without detonation.