Best manifold to convert to 4-71?

So I got a 4-71 I'm gonna put on my 327. Found tons of great info here on converting it, setting it up, and so forth. Manifolds for a 4-71 seem to be pretty hard to come by these days. I know back when guys would convert what they had. Whats best to start with. This will be a mild set-up running 4-5 lbs of boost. Just a nice driver. I know they make a plate to convert a 6-71 manifold but I've got several manifolds laying around and if I could use one that puts me ahead of budget already. Thanks ahead of time for any help. I'm a visual guy so pics would be great.

 

I rolled around this very thought in my mind, hoping to find a home for the nicely prepared 4-71 I have sitting on the shelf.

I think that a dual plane manifold that has a lot of metal to work with up near the level of the carb flange would be the way to go.

The only thing that I have not worked through it the pop-off valve, though.

Grab or make a replica of a base gasket and lay it down on a couple of manifolds. See which ones have enough material in the "hole" area.

 

I'm looking at an old Edelbrock dual four manifold. Wondering if i could just mount a plate for the blower on top and cut out what I need from the middle.

 

Maybe, but that manifold might be worth something.

Keep in mind, on almost all manifolds, the carburetor mounting surface is not parallel with the crank center-line. They are customarily about 3º, to compensate for drive-line angles.

This would have to be machined parallel before attaching the plate.

 

Look up Steve Sellers.

 

Ok, I did, He makes some really cool stuff. Did not see anything for a 4-71 on an SBC, unless I missed it.

Front-mount really is not an option on a street vehicle.

 

I milled a 4V manifold and built a steel plate to adapt a 4-71 to a 283. I cut the divider out for more flow. No pop-off, just drive it with V belts so it can slip if there's a backfire. 5 or 6 pounds boost works with 2 belts.

 

Yeah I figured it would need to be milled flat. That shouldn't be to much material though, especially off a single four manifold. Plan is to run a dual or triple v belt set-up. Anybody else run v-belts with-out a pop-off? Also thought about if it would be easy to convert a manifold like the weiand they make for the 144 or 147 series street blowers. That opening looks really close to the same as the 4-71.

 

Pics of this? Sounds cool..

 

Most of the blower companies (BDS, etc) start with one of the old single-plane Offy dual quad intakes. Mill the carb flanges parallel to the mounting flanges and bolt on an aluminum plate that fits the blower. Very easy to do and very effective.

 

Anybody got pics of some done?

 

Sort of on a related note, someone please comment on the SBC's crank snout not really being able to take the strain of a gilmer type setup for roots blower?

 

I have seen literally hundreds of successful setups of an SBC and a Glimer belt, with cast and forged cranks.

Have not heard anyone complaining about the crank snout, so far.

Anyone else?

 

The only concern I've heard re: gilmer belts and the crank snout is the need to mill a second keyway for the pulley/crank.

 

I ran a 2" gilmer belt on a 4-71 with a cast crank 283 but used a billet steel harmonic balancer with a single key way making 9 lbs boost without any issues. I rang it out often but never really raced it and treated it fairly although it saw 6000 RPM a lot. The second key way is a good idea and I did it on my second engine.

 

Hmmmm ....

May I suggest an alternative solution?

Do the dual-quad manifold's two carb mounting flanges sit on exactly the same plane? In other words, if you lay a straight edge on top of one of the carb flanges does it also lay exactly on top of the other carb flange? If so, then make up a plate that bolts to the top of those two flanges and has openings that match both of the carb openings. Now build up a perimeter spacer around the two flanges that is perhaps an inch or two tall, and then machine the top of that spacer flat and parallel to the crank so that it no longer has the carb base angle at the top and weld a bower mounting plate on top of the spacer.

Build it that way and you should be able to remove the angled blower mounting adapter without altering the dual quad manifold at all. I expect it'll flow pretty well too.

Best of both worlds, if it can be made to work, eh?

Just a thought.

 

Hadn't thought of that, just assumed the two carb mounting surfaces would each be the same height in the back and angle down 3 degrees to the front. Anybody know if there's one that mounts them on the same plane?

 

Or, you could switch to a 6-71. 4 and 6-71 cores go for about teh same money and it costs the same to rebuild one, so in theory, you could trade your 4 for a 6.

The benefit of teh 6-71 is the front snout is MUCH easier to find (the 4-71s take a real long and expensive snout.) And, the manifolds are WAY easier to find. 250 bucks will score you a dedicated 6-71 blower manifold with a blowoff valve.

Just a thought....good luck, -Abone.

 

That's the best idea - they make more HP too!

 

Well I'd be happy to swap my 4-71 for a 6-71 if ya got one. I got the 4-71 almost given to me. My 327 is pretty mild and will be daily driven so I'm not trying to make a ton of power or boost. Only gonna run 4-5 pounds.

 

Ive seen that smaller Weiand 144 series supercharger in the summit catalog , is that manifold close to the 471? ....Just kinda brainstorming here

 

Is it already built and ready? The cost between a 4 and a 6 to get redone is minimal as the ends are the same. The only difference is the length of the rotors. Most places would take a 4 as a core anyway. Call Rick Dean Blowers. A quick google will get him. I also understand if you want to stick with a 4 they look cool on top.

 

stude_trucks had a Cragar setup for sale

 

But then he'd have a 6-71, the bellybutton of blowers, just like every wanabee glass gasser and gold chainer.

 

HaHa, right gimpy. I do find myself somewhat partial to the 4-71 for this particular project and mostly because it's not what's typical. I have alot of stuff on it that I've collected up that are rare or very unique things. Just got the Ganahl book on Supercharging today and am about to see what I can learn.

 

Yup. 4-71's are traditional!

 

So right now I'm thinking I may just find a good used large plenum single plane manifold and build a plate for the top. Should still flow pretty well. Anybody running this set-up? How's it work?

 

be sure to post pictures, I'm going to be doing the same thing. I have the 4-71, drive system, etc.

 

how is the 471 working on your SBC. Looking for a 471 to put in a 327. Looks like you have done some research. Anything work and do you have any pics ?

Thanks

V

 

I used a four barrel manifold with my 4-71 setup because the outlet port in the blower is too short to span the distance between the carb holes in a dual four manifold. It just works better with the smaller base.
The 4-71 fits a SBC better in my opinion. The distributor crowds a 6-71 too far forward, it looks awkward, especially on an open-engined rod.
BTW, I never got my drive made, the 283 went away before I got it all finished! One day I might get back in to it, I have a 305 that needs a little help in the HP department.