1 (edited by Parkwod60 2012-05-13 08:05 PM)

Topic: Blower Box vs Hat - Discuss

Not for the next race, but by next year I hope to have a supercharger to cram air into the log intake manifold that all Ford 144/170/200/250 straight sixes are blessed with from the factory. It literally part of the cylinder head.  So the question is, do I attempt to just blow down the throat of the carb (or carbs by then) or do I build a box and try to seal up the linkage. I was leaning toward a simple hat and screw any boost that leaked past the throttle shafts because of the kick down linkage. In order to put make a carb-in-a-box I'd have to either say screw the kick down linkage for the C4, or fabricate some sort of sliding push-rod that worked thru the box.

I doubt we would want more than about 7psi. We'd either be blowing thru 1 1bbl Holley, 1 2bbl Rochester, or maybe either 2-3 1bbl Holleys, or 2-3 1bbl Carter YFs, or 2 Carters and a Holley.  At the moment I own 2 Carter YFs, 1 Holley, and 1 Rochester 2GC. I've been trying to find another matching Carter to build a tri-power for this motor, but so far no luck. I know I can get 2 more of the Holley that came stock on this motor pretty easily by digging in the junkyards.  (the reason this is so up in the air is that I need to modify the existing log for any of these, there is no "catalog" solution)

The blower will most likely be a Ford Thunderbird SC from a 3.8l. I'm a complete novice when it come to boosted applications, but I would assume a blower intended for "dry" efi usage could not, or should not be used for a draw thru "wet" carburated application?

Anyway, lay some knowledge on me.

Constructor/Owner/Driver - Billy Beer Ford Futura

2 (edited by Maxzillian 2012-05-13 08:50 PM)

Re: Blower Box vs Hat - Discuss

I'd consider a draw through application before attempting a blow through, whether through a hat or box. One thing to consider if doing a hat is that you may need to make provisions to pressurize the float bowl, depending the carburetor.

Many modern superchargers use a coating on the rotors that is worn to fit. I am aware that in some of the earlier Eaton units, the coating could be removed using solvents so gasoline may remove it and reduce the efficiency of the supercharger. Later units (late 90s) used a sort of rubber coating that is much more durable.

I don't know if the Thunderbird units ever had a coating on the rotors.

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3 (edited by Bayley 2012-05-14 05:57 AM)

Re: Blower Box vs Hat - Discuss

Well, with a carb "hat", the biggest issue is fuel escaping out the throttle shafts during high and / or extended boost.  However, I'm not exactly convinced that the "box" is any better as it would tend to pool the excess fuel from the throttle shafts in the bottom of the box.  I'd almost feel more comfortable just letting the fuel escape into the engine bay and hope evaporation takes care of it before it collects enough to cause a fire (just call me Dr. Greenpiece / Professor Safety).  Consider a large sheet of steel or aluminum as a separator between the carb and anything else underneath it.  Add LOTS of hood vents directly above the carb as well. 

Not sure what carbs you are using, but consider marine carbs.  US Coast Guard mandates special "grooves" in the throttle shaft that supposedly reduce or eliminate the amount of fuel that can escape past the throttle shafts in the event of a back-fire through the carb.  Granted, this was never designed for continued positive manifold pressure, but it's likely better than nothing.   

-Andy

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4 (edited by jrbe 2012-05-14 06:28 AM)

Re: Blower Box vs Hat - Discuss

Maxzillian wrote:

I'd consider a draw through application before attempting a blow through, whether through a hat or box. One thing to consider if doing a hat is that you may need to make provisions to pressurize the float bowl, depending the carburetor.

You will probably need to raise fuel pressure with boost as well so it can refill the bowl.  At worst the boost will blow air back through the pump and leave your engine fuel starved as well as the bowl eventually empty/engine lean.  Not sure if they make 1:1 vacuum/pressure reference regulators for carburated pressures but im sure you could find a lemony solution...

-Killer B's (as in rally) '84 4000Q 4.2V8. Audis never win?

5 (edited by Junkyard Dog 2012-05-14 06:50 AM)

Re: Blower Box vs Hat - Discuss

Those Holleys vent the bowl into the carb throat so that if it floods fuel won't pour out into the engine compartment. The problem is that if you pressurize the bowl with either method the jetting now gets all kinds of weird under boost (long drawn out explanation possible) and things like the vacuum dependent power valve (full throttle enrichment) won't work properly. You'd have to start with rerouting the bowl vent system and making it safe so you wouldn't start fies every ten feet, you'd be forever trying to get it to work. Maserati tried the box with not very good success, there's plenty of others who have tried hats n' boxes with carbs downstream of a boost deviceand not had very good success.

It's possible to convert the carbs to floatless and solve some of those problems, but you now have to add a return fuel pump and a return line to the tank (similar to a FI system) and that could get difficult/'spensive.

For LeMons I'd go with a wet system like drag racers have used since the Earth's crust cooled, use a single 2300 Holley/Motorcraft 2 bbl and have fun.

Philosophy of life: old age and treachery will ALWAYS overcome youth, enthusiasm and cash. General smartass know it all beer swilling ne'er do well. Avoid eye contact with this person, best avoided completely. 2008 Animal House Racing CMP 'Most Likely To Leave In An Ambulance' 2009 Blind Rodent Racing CMP 2010 Team Galileo CMP 2011 Roundhouse Kick Racing CMP 2012 Road Kill Grill Racing CMP (x2)

Re: Blower Box vs Hat - Discuss

jrbe wrote:
Maxzillian wrote:

I'd consider a draw through application before attempting a blow through, whether through a hat or box. One thing to consider if doing a hat is that you may need to make provisions to pressurize the float bowl, depending the carburetor.

You will probably need to raise fuel pressure with boost as well so it can refill the bowl.  At worst the boost will blow air back through the pump and leave your engine fuel starved as well as the bowl eventually empty/engine lean.  Not sure if they make 1:1 vacuum/pressure reference regulators for carburated pressures but im sure you could find a lemony solution...

I forget exactly how you go about it, but you can reference the mechanical fuel pump to the boost by adding a fitting to the side of the pump that typically has atmospheric pressure on the other end of it.

Constructor/Owner/Driver - Billy Beer Ford Futura

Re: Blower Box vs Hat - Discuss

My gut says figure out a way to do a draw through setup, and make sure your supercharger can deal with little droplets of dead dinosaur juice.

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Re: Blower Box vs Hat - Discuss

I believe Spank got a blow-through setup working on the LeMini without a a carb-box.

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Re: Blower Box vs Hat - Discuss

Easy! Just grab yourself half a rack of XJ650 Turbo carbs- they were designed to work under pressure (up to 12 psi!) just sideways... Otherwise I see Mega/Microsquirt in your future.
Spank  used an SU with the bowl vent referenced to the pressure side. But he's got a pile of melted pistons/toasty headgaskets to show the efficacy of that plan...

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Re: Blower Box vs Hat - Discuss

X-args wrote:

Easy! Just grab yourself half a rack of XJ650 Turbo carbs- they were designed to work under pressure (up to 12 psi!) just sideways... Otherwise I see Mega/Microsquirt in your future.
Spank  used an SU with the bowl vent referenced to the pressure side. But he's got a pile of melted pistons/toasty headgaskets to show the efficacy of that plan...

Sure, those will be easy to find. I may just try it as a draw through, it really saves on machining the intake log. Occasionally I see early carburated 2.3 ford turbos with a draw thru turbo on them. I'm sure that 2bbl Holley would have plenty for my 3.3 motor.

If I was gong to do a Mega Squirt or side draft motorcycle carbs I'd likely be able to get it to breath well enough that I wouldn't need a blower at all.  Hot Rod magazine had them running on SUs and Honda CB450 carbs in the 60s and getting plenty of power out of them. They just brazed a couple of spigots to the stock log between 1-2, 3-4, and 5-6. I think I am going to try that too. This is the nice thing about not having to worry about drivability. As long as I get WOT close, who cares how it carburates at 1/4 throttle?

Constructor/Owner/Driver - Billy Beer Ford Futura

Re: Blower Box vs Hat - Discuss

Positive displacement superchargers are different than turbos because they are, well, positive displacement.  Think about what that will do to the pressure upstream of the carb during throttle-lift.  They really are designed for draw-through applications.  And many a blower has lived "wet".  Like in every supercharged hotrod ever built.

Scott

Re: Blower Box vs Hat - Discuss

X-args wrote:

Spank  used an SU with the bowl vent referenced to the pressure side. But he's got a pile of melted pistons/toasty headgaskets to show the efficacy of that plan...

Hey, not entirely true. Only 2 pistons on the same motor and they seem to have suffered FOD before burning finally burning through the ring land late Sunday. And that was also after a year of turbo use.

The head gasket issues (detonation and mis-matched cooling jacket ports) aren't singularly because of the carb. But there was a known lean spot that in the rev range that we never fully sorted.

But converting an SU car so you can pressurize it isn't too difficult. I mean, heck, i did it!

Didn't someone back east use an ammo can to pressurize their whole carb?

--Spank

Re: Blower Box vs Hat - Discuss

Forget it, I think I'm just gonna set it up so the blower sucks the carb. That makes it easy. Now its just a plumbing project, I can put any size carb on the blower itself and cram it into the hole that is already in the log manifold.

Constructor/Owner/Driver - Billy Beer Ford Futura

Re: Blower Box vs Hat - Discuss

Team Turbo Schnitzel used an ammo can on their intake to pressurize the carb. I don't know what they did about the bowl vents etc.

http://blog.caranddriver.com/wp-content/uploads/2012/03/6.jpg

Philosophy of life: old age and treachery will ALWAYS overcome youth, enthusiasm and cash. General smartass know it all beer swilling ne'er do well. Avoid eye contact with this person, best avoided completely. 2008 Animal House Racing CMP 'Most Likely To Leave In An Ambulance' 2009 Blind Rodent Racing CMP 2010 Team Galileo CMP 2011 Roundhouse Kick Racing CMP 2012 Road Kill Grill Racing CMP (x2)

Re: Blower Box vs Hat - Discuss

Is an air filter being used as a connector?  Wouldn't that be a minor boost leak?

Jim C.
If God meant for us to race, we'd all have baggy Nomex skin.
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Re: Blower Box vs Hat - Discuss

Poor man's popoff valve would be my guess

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Re: Blower Box vs Hat - Discuss

FJ40Jim wrote:

Is an air filter being used as a connector?  Wouldn't that be a minor boost leak?

Yes. At best I would think their turbo set up works about as well as a ram air scoop producing a couple of PSI extra into the carb, but not much real boost.

Constructor/Owner/Driver - Billy Beer Ford Futura

Re: Blower Box vs Hat - Discuss

Junkyard Dog wrote:

Team Turbo Schnitzel used an ammo can on their intake to pressurize the carb. I don't know what they did about the bowl vents etc.

http://blog.caranddriver.com/wp-content/uploads/2012/03/6.jpg

I know this is YEARS later, but I stumbled upon this just now. To set the record straight, the Team Turbo Schnitzel setup was originally a "blow-thru" carb. That got a bit out of hand, so we created a patented "blow-by" induction system to reduce the engine-killing boost. I'm pretty sure the result was warm, oily air being blown at the carb with a net negative performance increase considering the exhaust restriction and dirty air.

The carb had been modified to accept boost, but was not generally happy seeing the original 20+ PSI generated by the Navistar diesel turbo.

Also noteworthy is the blowoff valve on the ammo box. This was added after the first time the boost came up under load, the throttle released to shift, and the resulting back pressure ripped the threaded rod out of the carb and sent the ammo can 30 feet in the air.

The carb was swapped out in favor of a microsquirt built into an EEC-IV case. A whole lot of heat shields were fabricated. Larger fuel lines were added to allow more fuel to return to the tank under low loads. We had an air-water setup on the car using some A/W IC I had laying around, a pony keg, a trans cooler, and Ford Explorer fuel pump, which I think may have worked okay. The Merk ran pretty good like this for a few races, then the rear end literally fell out of the car at CMP in 2012.

The next iteration of the car/engine is sitting in my garage now as a project car.

Re: Blower Box vs Hat - Discuss

The box is more cumbersome as ALL of you linkage, cables have to pass thru it. I'd also consider running a FoMoCo 2bbl or a large Holley ONE carb. You can boost reference the carb for a "hat/bonnet" or you can send it out and have it done for about $200, well worth the headache. Try Scott at SCDE. You will also have to boost reference the fuel pump.. as for "unit" I'd use a centrifugal pump. It will be MUCH easier to fab up that anything from the 80-90's production cars.

"get up and get your grandma outta here"

Re: Blower Box vs Hat - Discuss

also... it WILL NOT leak out the shafts. I have made 2 S/C'd motors with bonnets make well over 600hp. The carb will need to be boost referenced, meaning it will need special floats, certain holes drilled here. On top of most fuel pumps  there is a hole...a vent. Jam a piece of tubing in that and hook it up to the pressure and WHAMMO you have a boost referenced fuel pump. Don't forget your BOV. I tend to use Bosch valves off of Audi's.

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Re: Blower Box vs Hat - Discuss

There's a draw through Eaton supercharged 4.0 in Colorado that's lasted several races now, and I know of several rat rods and such that haven't destroyed supercharger bearings yet.  Since the street value of a M62 is about $50-75, I'd go that route over boost referenced float bowls, fuel pressure regulators, and other complexities.

Scroll down a bit for an underhood picture.  He used a small CV carb as a higher rpm boost limiting device.  It worked.
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Re: Blower Box vs Hat - Discuss

(Just a reminder that this is a recently-bumped 5-year-old thread. I don't think Parkwood races that car anymore.)

But yeah, for future reference I've heard of at least one guy in the Slant Six world who removed the coating from the rotors on an M90 and used it quite successfully with a draw-through carb.

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