blower on a 4bbl intake

I think you have WAY too little clamping to hold the blower down. These things take a lot of horsepower to turn and therefore will apply a lot of torque to those four little 4-barrel bolts. Also, the outlet of the blower is a big long rectangle, not a small square hole - so you'll severely limit the boost potential. BUT - if all you're going for is 'blower looks', then maybe it isn't an issue for you.

Me, I'd machine the heck out of the manifold and weld up a mounting structure to solve both problems . . . or buy a 4-71 blower manifold that is designed from the get-go to work.
 
For reasons B&S mentioned, unless you'll be putting a dummy case on top, either machine the top off and weld a proper plate or get a blower manifold. If not, you would need some type of plate to mount it to close the bottom and the case would look like it's teetering up on top of the mounting flange.

I appreciate the ambition, but I think there are better ways to go about it if you aren't going to machine the heck out the 4 bbl manifold.
 
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1931flathead said:
my boss has a 671 on a chevy sbc but they have plates weld to the intake to hold it down been on there for years
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Dude, do want you want to, but you've asked. I'd be very surprised that your boss just welded a plate on top of 4 bbl. intake without opening up the hole and then welding his plate to the intake after opening up the intake.

If that's your plan, then go for it, but your you weren't specific in your original question.

Putting a roots-type blower on a 4bbl intake without (again-without machining is the crucial part here) machine work defeats the entire purpose of running a blower since you are choking off a good portion of the charge.

I think 'Ol Ron made a blower intake by machining off the top of a Fenton intake and welding a plate to it.
 
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No need to start messing with a blower unless you are wanting to spend LOTS of money, the manifold is just the tip of the iceberg as far a cost goes.
 
sidevalve8ba said:
I guess you have looked at this.

http://www.fordbarn.com/forum/showthread.php?t=197279&highlight=blower+intake
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Looks about like a Mitchell - and in my mind, not an optimal design. The inlet on the manifold is more along the size of a SCoT blower, nowhere near what a 4-71's outlet looks like. Also, don't see a burst panel - which is the way to go (instead of a suspect pop-off valve, that may NOT pop-off when you need it).

Truthfully, I've not seen a good 4-71/6-71 blower manifold design (cast) that takes into account the two things I mentioned above. The only good ones I've seen were fabricated.
 
I think what you really need for this project is a 3-71 as the outlet is a single opening and will be much more adaptable to a 4 bbl. manifold. The 4-71 has two discharge openings and would be more restricted by the 4 barrel type manifold. With the carburetor base of the manifold machined you need to fabricate and bolt on a 1/2" thick plate to support the blower and for sure you will want to weld on some supports from the plate to the manifold. I'm sure your boss's SBC manifold has added supports on it. You mention you have pulleys, what style? V-belt, Gilmer, serpentine? Regardless of what you have to drive the blower you also need to engineer a way to drive the water pumps. You might find some inspiration by visiting this website- http://uncommonengineering.com/
 
yes has one on each end and couple on the side his has a 3 inch belt I'm going with 8mm belt his was built long time ago in the twincitys in MINN
 
By the way, that 8MM belt puts all the more torque/load on the blower (no slippage), so really make sure you engineer enough strength into the manifold design . . . as you can imagine the carnage if the blower were to break loose at high speed. Yikes!
 
Yes i knew that still thinking about it the blower manifold you can buy looks like the open is not big enough on it might have one made i know a shop that would help me he does a lot of TIG welding
 
Be sure and address crankcase breathing or you will also be cleaning oil off of the windshield.
 

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I used a one inch plate with a fifth hole in the middle and have a pop off valve on the side of the manifold and I needed it on first drive due to magneto and carb problems. I run a max of 4 psi of boost with two 5/8 belts. Be sure and use the old style manifold where the carb mount surface is parallel to crank. The plate sits on top of the front of the manifold with a couple of gasket pieces as a shim. To date it has survived about 500 miles.
 
thanks your are wright on the set up the intake I seen has to small of opening they are about 1 7/8 not wide enough and about 1 inch not long enough

think about making one out of alum sheet metal
 
woodypecker said:
I used a one inch plate with a fifth hole in the middle and have a pop off valve on the side of the manifold and I needed it on first drive due to magneto and carb problems. I run a max of 4 psi of boost with two 5/8 belts. Be sure and use the old style manifold where the carb mount surface is parallel to crank. The plate sits on top of the front of the manifold with a couple of gasket pieces as a shim. To date it has survived about 500 miles.
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I have an old Magnuson blower that is design to mount to any 4 barrel intake. A very cool blower. It has a plate that bolts to the 4 barrel intake then the blower has 2 holes in-between the twin blowers that bolt to the plate. A very simple set up.
 

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