Roots supercharging a Ford FE?

[fe66comet]

Just theoretically what would have to be done on a 500 cube FE with an iron block to support a 871 blower, it of course would be an aftermarket cross bolted block. And what kind of HP could be realized on pump gas with a 7.5:1 compression ratio. The limitations or a Roots is generally idle to 5500 rpm so the camshaft would not have to be a monster and I would say a Blue thunder high riser head would be in order along with the intake.

[ScotiaFE]

Well you would need to spend a few bags of money to get all the goodies.
Other than that you would need to spend a few more bags of money to get all the goodies
to put the power to the ground.
Other than that it's totally doable.

[fe66comet]

Actually a Roots engine is a mild build, some good forged pistons, forged crank,scat H Beam Rods and hydraulic roller would do the bottom end. The heads are 2500, block 3500, supercharger with intake 4 grand from Gary Dyre. Roots is a totally different thing from a centrifugal or turbo engine.

[machoneman]

Just theoretically what would have to be done on a 500 cube FE with an iron block to support a 871 blower, it of course would be an aftermarket cross bolted block. And what kind of HP could be realized on pump gas with a 7.5:1 compression ratio. The limitations or a Roots is generally idle to 5500 rpm so the camshaft would not have to be a monster and I would say a Blue thunder high riser head would be in order along with the intake.

BDS and a few other blower specific sites like Dyers has some pretty good basic info on blower engines. One of the big issues is the huge cost of the intake, blower, drive and carb & linkage setup, something I'm sure you already know and can easily exceed $7,000 bucks. 

http://www.blowerdriveservice.com/common-questions.html

Opinions here may vary (LOL!) but:

-with a 500 CID FE, not sure one would need or want to invest in a blower as hp at even 1.25 per cube would be 625. 
-you didn't mention the blower ratio or boost level. It's easy to get in trouble trying to run pump gas and any kind of boost over say 7-8 lbs or so.
-Hp wise, it's easy to get about 1.3 hp / CID with a lightly boosted 8-71 or about 650 hp with a 500 CID engine.  But, one can also attain that level of hp, and more, as Jay, Barry and Brent have shown with numerous builds w/o supercharging.
-Most charger'ed cars are set-up for show as opposed to gargantuan hp levels. Still, one could easily top the 1,000 hp mark with the right parts in that 500 CID FE but now we're talking major boost levels (think: 50% and more over crank rpms) and the highest octane racing gas.
-JMO! 

This site has a nice generic chart on boost /gasoline types as boost goes up.

http://www.superchargerusa.com/tech_boost_fuel.htm
 

[fe66comet]

I was thinking about 10psi with maybe 20 % overdrive. And using 98 octane fuel with a TBI system to keep detonation down. I actually am looking for about 800 HP whether that cam be achieved with 98 octane would be an issue?

[sumfoo1]

It all goes back to how much power do you want??

I mean if you just want a chrome thing coming out of your hood with a pulley on it you don't have to do much...

Forged low comp bottom end for 8+ psi imho

and I mean if you really want power....

Screw it...



But it sound like you know what you want... as far as FE parts go a cross bolted aftermarket block with a forged bottom end is all you really need.

[fairlanegt427]

i really like the high riser blower motor you want to do. but if you run medium riser stuff which is much more available. your check book wouldnt be taking as much of a beating.  also look at jays intake adapter he makes for the fe.  that way you can buy a cleveland blower intake and go that way it would be much cheaper.  also big air flow is fine but the chambers are only gonna use so much air and  fuel no matter how much you stuff it,  the rest just goes out tailpipe.

[machoneman]

Jay's adaptor with a C blower intake may also solve another big issue with GMC superchargers and FE's: getting the ditzy in and cap/wires to clear is a bitch.

The added height may just solve that issue as well. JMO!

Btw, I've never seen a really high boost blower like the PSI blower on a streeter.  Now that would be cool!

[hotrodfeguy]

I think a good book I have read and done most of my research from is street supercharging. I forgot who wrote it as someone loaned it from me and it never came back. But as I understand it on a roots system it gives more of a bottom end punch. A centrifcal supercharger is mor mid range power. Roots types are right there off idle and are not real suited on top end like the others. I think its becaise the design is similar to a turbo. Just a hunch. Now something to consider is E-85 as a fuel it can withstand the CR much better in a boost application than what Gas does. go to E-85.com and do some reaserch you will find some guys have gone to 40PSI!!!! This means you could build a engine that would be a normal NA engine and just put your supercharger on it. Save for the cam events you want a wide LSA. As the boost would push your un burned gas out the EX with a overlap situation. Now if your not in a area with E-85 you are on the right track. But there are many old versions of the JIMMY 6-71 with the lip and thats the pre cursor to the B&M AND AFTERMARKET 8-71 ect. these companies have made copies of those, thus there parts interchange. If you find a core like this you can get a cheap economical blower. As you said keeping the revs down also mean syou do not need crazy Stell cranks or Hbeam rods ECT. I think as long as your keeping everything under 6k Forged pistons and rpm rod bolts would be about it. even for a 390. The Weiand 7282 and the cousin OFFY 360 2x4 make the easiest intake to put a plate on. I know I made this intake for a FE BLOWER combo. Sold it at Jefferson swap meet here 2 years ago. But once you have the 2 just make a plte to bolt one way then the other. ALSO Note make support stands L/R of the carb mounts as the bloer take alot to drive it. Anyways.DYERS in Chicago will make you ANY custom drive you want or need. You do not need the 3"TOOTHED NHRA TOP FUEL style drive you see most folks running for a 8-10 psi set up. Just talk to them. You can get by with far less. I had a small supercharger one time on my 2V 351C Mach 1 2" serpintine belt. And it would clobber a 69 Green 428CJ GT coupe yes coupe "built up" back in 1990 he put more soup to it and still walked over it although he was hanging with me better . I mean it was not even in the same zip code I would granny shift and walk off with him with the stock 2v cam and 3.00 open rear. But that gives you an idea of what a roots does for bottom end. I later put a OD toploader in it and a better cam in it. It then would do 140-145 in Montana when they had that reasonable and prudent speed thing they shut down soon after When the Germans would come to vacation here to drive Montana instead of the autobahn.

Hope this helps.

[fe66comet]

I saw a lot of Gary's work back in the early 90s. He makes about any intake you can think of. I am waiting for one of Jays adapters for my 445 right now to mount a Trick flow BOX R intake, I can see then what kind of clearance I have. My next build I am doing for my 66 Comet, I am looking for about 800 HP total, any more than that the transmission and rear end would become a concern.

[TomP]

Why use an adapted intake on HR heads when a Blue Thunder one already meant for that blower on MR heads is available?  Don't crutch the belt drive to fit a distributor, that can be solved with a shortened, angle driven or relocated distributor.

[fe66comet]

For that matter you could just run s crank trigger and coil packs. I would go with fuel injection anyhow to control detonation and keep a closer eye on my AFR. I saw at the speed shop the other day MSD makes a distributorless universal ignition system with coil on plug. I might be able to get away with a 6-71 but I am not sure it would be real efficient on a 500 cube engine. One reason I was thinking of the high riser heads was because Blue Thunder already had the intake and heads set up for it and with forced induction there certainly would be no lag off the line.

[sumfoo1]

No roots style blower is very efficient... Hence i posted a twin screw.
6-71 i agree will only flow about what a well built 500cid FE should anyway.

but... for grins... http://upload.wikimedia.org/wikipedia/commons/thumb/d/dc/Roots_Supercharger_efficiency_map.jpg/640px-Roots_Supercharger_efficiency_map.jpg

[machoneman]

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 efforts 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' s used these as well) 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.     

[sumfoo1]

Ohh NO! you stepped on my turbo toes!

I completely agree with everything you said...

That last line just hurts me though...  Depending on the goal of the engine you can size turbos for crazy quick response or for huge power... just not for both without using variable geometry or something.... I mean i'm planning on two 80mm turbos for my FE just to slow down spool not because i plan on hitting the 2400hp+ they should be capable of.

8-71, 10-71, screw superchargers... all have their place  just  in my opinion 6-71s usually cause so much sacrifice to make up for their efficiency that a well built n/a motor will be able to keep up or eclipse. Also not too many aftermarket roots blowers have intercooler provisions in the intake to compensate for the heat they add to the air.   

http://www.turbos.bwauto.com//aftermarket/matchbot/index.html#version=1.3&displacement=8.4&CID=512.5680000000001&altitude=500&baro=14.502&aat=75&turboconfig=2&compressor=91s74&pt1_rpm=2000&pt1_ve=85&pt1_boost=5&pt1_ie=99&pt1_filres=0.08&pt1_ipd=0.2&pt1_mbp=0.5&pt1_ce=66&pt1_te=75&pt1_egt=1550&pt1_ter=1.18&pt1_pw=1.89&pt1_bsfc=0.43&pt1_afr=11.5&pt1_wts=300&pt1_wd=83&pt1_wd2=74&pt1_wrsin=69033&pt2_rpm=3000&pt2_ve=95&pt2_boost=5&pt2_ie=95&pt2_filres=0.1&pt2_ipd=0.2&pt2_mbp=1&pt2_ce=70&pt2_te=73&pt2_egt=1600&pt2_ter=1.36&pt2_pw=48.95&pt2_bsfc=0.45&pt2_afr=11.5&pt2_wts=320&pt2_wd=83&pt2_wd2=74&pt2_wrsin=73635&pt3_rpm=4000&pt3_ve=95&pt3_boost=5&pt3_ie=95&pt3_filres=0.12&pt3_ipd=0.3&pt3_mbp=1.3&pt3_ce=74&pt3_te=72&pt3_egt=1650&pt3_ter=1.61&pt3_pw=67.8&pt3_bsfc=0.48&pt3_afr=11.5&pt3_wts=340&pt3_wd=83&pt3_wd2=74&pt3_wrsin=78238&pt4_rpm=5000&pt4_ve=95&pt4_boost=5&pt4_ie=92&pt4_filres=0.15&pt4_ipd=0.4&pt4_mbp=1.5&pt4_ce=76&pt4_te=71&pt4_egt=1650&pt4_ter=1.81&pt4_pw=73.5&pt4_bsfc=0.5&pt4_afr=11.5&pt4_wts=368&pt4_wd=83&pt4_wd2=74&pt4_wrsin=84681&pt5_rpm=6000&pt5_ve=95&pt5_boost=5&pt5_ie=90&pt5_filres=0.18&pt5_ipd=0.5&pt5_mbp=1.8&pt5_ce=72&pt5_te=70&pt5_egt=1650&pt5_ter=1.98&pt5_pw=74.52&pt5_bsfc=0.52&pt5_afr=11.5&pt5_wts=400&pt5_wd=83&pt5_wd2=74&pt5_wrsin=92044&pt6_rpm=7000&pt6_ve=95&pt6_boost=5&pt6_ie=90&pt6_filres=0.2&pt6_ipd=0.6&pt6_mbp=2&pt6_ce=66&pt6_te=70&pt6_egt=1650&pt6_ter=2.18&pt6_pw=36.06&pt6_bsfc=0.55&pt6_afr=11.5&pt6_wts=400&pt6_wd=83&pt6_wd2=74&pt6_wrsin=92044&

1400hp capable... spools by 2000 rpm.