Crank mounted blower for 300-6?

[Anonymous]

I may be a ways off, in actually seeing this ideal become reality, but I figured I'll start doing my homework now, and be prepared for the future. What I'm planning is a vintage-style (think Mooneyes dragster) front engine slingshot dragster, using the 240-6 from my '66 Club Wagon for motorvation. In thinking about the old Mooneyes slingshot, although it ran with a V-8, I'm thinking about a crank mounted supercharger for the 240. In my mind, routing the induction on the inline six seems like it'd be a bit easier than with a V-8.

Now, what size supercharger should I run? I figure going with a 6.71:1 Roots-type "Jimmy" blower will be a no-brainer, but how many cubes can I get away with, especially with the blower mounted directly to the crankshaft? Or is there some sort of crankshaft mounted gearbox that the blower would mount to, in order to adjust the amount of boost? And since I'll be using a supercharger, how low should I go with the compression, to include lowering it somewhat with the use of a 300 head?

Matt in Indiana

 

[Anonymous]

1) find other supercharged engines of similar displacement

2) find out if their supercharger is "overdriven" or "underdriven" by the number of teeth on the pulleys.

Since crank drive is 1:1 without a gear box, you'll need something close.
I think a 6-71 will be a little too big, unless you like LOTS of boost - - -then you'll be fine!! A 4-71 or one of the B&M offerings might work, also that big eaton used on Ford Lightnings?? Maybe??

 

[Anonymous]

i just had a deam while reading this post....

CVT transmission ie - Snowmachine transmission with clutches and belt....except backwards, high RPM driven output at lower RPM inputs for boost at lower RPM's and then gradual down gearing as the engien speeds up to prevent too much superchager overspeed. This would be crank mounted and boost pressure and charger speed would be governed by spring tension, ramp angle, and pulley size for drive and driven clutches.

Ok, who thinks im crazy?..would be interesting....i ahd to share my wild thought as this post conjured it...

 

[wallaka]

That actually sounds like a great idea. Even more so for centrifugal superchargers, but still good for regular superchargers if it would fit under the hood.

 

[Anonymous]

Linc's 200, I'll have to check out the various supercharger sources, and find out just how many cubic inches their superchargers displace. The only two numbers I can remember are 140 cu. in. and 177 cu. in., and I may be wrong but it seems they were 6-71 and 8-81, respectively, and I think they may have been part of B&M's MagaCharger line. Like I said, I don't know just when I'll get around to a project such as I'd mentioned, with other toys to be played with that I already own, but I can at least be doing my homeworknnow.

That said, if I happen to come across an Eaton from a T-bird SC, it's likely to find its way onto the forced induction 2.3L I'm planning to build for my '80 Pinto wagon, by way of some good old fashioned "redneck re-engineering" in the intake manifold department. Otherwise, I'll stick to my plan for a turbo 2.3L...not quite as much "redneck re-engineering" involved there, with turbo 2.3L parts for Mustang SVO/T-bird TC and Merkur XR4ti available from various sources.

Emerald 74 4X4, that was a cool idea that you dreamed of, and wallaka, I wouldn't have to worry about "room under the hood," if I'd be installing such into a front engine slingshot dragster frame...might have to go with a longer wheelbase, but it'd fit.

Matt in Indiana

 

[wallaka]

There's a chart at the bottom of this page showing the displacement of various Roots blowers, 6-71 and up.

Extrapolating down, I'd say a 4-71 or an Eaton 90 would be much better suited to a 200.

 

[Anonymous]

There's a chart at the bottom of this page showing the displacement of various Roots blowers, 6-71 and up.

Extrapolating down, I'd say a 4-71 or an Eaton 90 would be much better suited to a 200.

Thanks a bunch for that one, wallaka! Even if I bored/stroked the 240 out to 300, or even sold the 240 to finance a second 300, I'd probably only get away with a small bore 6-71 without the danger of things wanting to exit the engine on each pass. So it looks like I'll be shopping for a 4-71 blower, when it comes time to rebuild the 240-6 for drag racing.

Matt in Indiana

 

[Anonymous]

i just had a deam while reading this post....

CVT transmission ie - Snowmachine transmission with clutches and belt....except backwards, high RPM driven output at lower RPM inputs for boost at lower RPM's and then gradual down gearing as the engien speeds up to prevent too much superchager overspeed. This would be crank mounted and boost pressure and charger speed would be governed by spring tension, ramp angle, and pulley size for drive and driven clutches.

Ok, who thinks im crazy?..would be interesting....i ahd to share my wild thought as this post conjured it...

If you had a flathead six, I would definatly be 100% for it. I was looking at a rusted out nash with a striaight-6 sitting in a field not too long ago. Head bolts were recessed into the metal, its just somethin else seeing something so neat, square, and vintage. Snowmobile clutches have springs and weights inside the clutches, they are fairly tunable for whatever load you might have, but it might cause some lag.

If your straight-6 goes from low rpm to near redline, its going to take some time for the CVT system to shift, take up the slack, and acclerate the blowers internals to match. Although it may just be a fraction of a second for that to happen. Im not quite sure if a CVT system woudl work good enough to drive a blower the way you would want it, but like I usually say:

If you have the money and the motivation to get the project done, go ahead and try it.

 

[StrangeRanger]

The problem with crank mounted direct-drive blowers is that they have to be large and heavy. To get 12 PSI of boost on a 200 would take a blower displacing something in excess of 365 CID per rev. That's not going to spool up quickly. On a Bonneville car that may be less significant than the reduced frontal area and resultant reduction in aerodynamic drag when compared to a smaller overdriven top mounted blower; on a dragster it will matter a lot.

The VS drive you're proposing, would it's fianl state be 1:1 or would it have an overdriven ratio? If it is 1:1, you're not likely to like the net performance very well.

 

[Anonymous]

Kinda off-topic, but I don't want to create a thread just for this question...

How tough is it to find stuff for the 4:71's and 6:71's?

 

[Anonymous]

How tough is it to find stuff for the 4:71's and 6:71's?

Extremely easy.

All the "stock" components are available from any Detroit Diesel supply house.

The "good" parts (better tolerances, higher strength) come from Bowers Blowers, Mert Littlefield blowers, Weiand, etc.

 

[Thad]

The crank driven blower system ala Mooneyes and others of that period was Potvin.

Bear in mind, driving the blower off the crank the rotation is reversed compare to a blower on top or beside the engine. IIRC the Gimmie blower takes the drive to one rotor the other rotor is driven by a connecting gear set. The Potvin setup "flipped" the input to the other rotor. Can't be difficult, there are jillions of counter-rotating Gimmies in fishing boats,smalltugs, etc

 

[Anonymous]

Bear in mind, driving the blower off the crank the rotation is reversed compare to a blower on top or beside the engine.

Not a big deal if you set it up to suck from the outlet and blow out of the inlet