Hot Rods 471 with (2) 2-barrel Carbs

Flatrod17, boom!

That is exactly what I had in mind. Are those 350 CFM? As GearheadsQCE mentioned, this may require some blending of the outer- end edges of the blower opening to match the carb openings in the adapter plate. As an option, the carbs might be able to be spaced a little closer together?

We should coordinate our efforts. I am a pretty good fabricator, and I have plenty of aluminum plate stock. If you can give me some input on initial dimensions, I can build a few adapter prototypes. I don’t have the 471 yet, but will soon.

I am now retired, but spent a lifetime in engineering and am well versed in CAD. I have a local guy who can take almost any design I come up with and mill it on a 5-axis CNC machine.

Let me know if you are interested, and if not that’s ok. This is encouraging and I may just go ahead with experimentation on my own.

 

I just use medium (80 mesh) glass beads that I get at Tractor Supply. I usually use them a bit before doing aluminum. The finish resembles new cast aluminum and the Gibbs seals and gives a nice light gray tone.

 

If you got creative with the throttle linkage you could reverse the back carb (so the float bowls are on opposite ends) and place them closer together to avoid that step entering the blower case. Wish I would've taken a pic of a a similar setup at Walden's Speed shop, but they were using the Holley 2300 Sniper fuel injection units on top of a 4-71, with one reversed, and they had a cool throttle linkage set up with several bell cranks and rods to take the linkage around to the other side. Maybe give them a call and see if they can help you sort it out.

 

Gearheads, yes it will all get blended together.
Jmountain, My brother wants everything polished, so it will get some more finish work when I get closer to finishing it,
Just thought I would post a few pics of what can be done so the OP can get a idea of what it will look like with 2300 Holleys. Still have to work on a air cleaner though.

 

Flatrod17, still nice work and looks like your brother is a lucky guy. Nothing wrong with polished if you have the time. Guess I am more of a work horse than show horse guy.

 

JimVG, yes they are are 350 cfm. With the chokes cut off they should flow a bit more. I'm hoping they will flow around 400 cfm each, that would put you right where you wanted cfm wise.

If you go to square fuel bowls they could be put them closer together, we liked the look of these. A little blending of the blower case will be no big deal.

I cut it out on a piece of 3/4 alum plate stock I think it was 6061. I have no cnc, so all hand cut, but yes I can measure it up for you if you want to try to make one. The other one that was pictured looks like a two piece, that would be easy to build, a o-ring seal between carb plate and blower plate should seal just fine if making a two piece.

 

...and you'd have a Holley 4bbl carb!

 

Keep in mind, 2 barrel carbs are rated differently for flow than 4 barrel carbs. Somewhere earlier in this thread carbking Jon mentioned this. 2-barrel carbs are rated at 3" hg; 4-barrel carbs are rated at 1.5" hg. The formula I've found on the net says to divide the 2-barrel rating by 1.414 to get the equivalent 4-barrel rating. So those 375 Holleys, equal about 265 cfm if rated as a 4-barrel. Holley 500's would be equal to 354 cfm.

 

Yep, funny how that works. But being spread out a little they have a different aesthetic, and you can install separate air cleaners for a multi-carb appearance. Basically, it's a way to arrive at a multi-carb visual effect and maintain the tune-ability of a single 4-barrel. Plus, the cool throttle linkage is good for some discussion.

 

Thanks, Jim! Just what I wanted to know.

 

Perfect. Thanks!

 

Thanks for the info! If you pick through Walden's Speed Shop’s website, Facebook, and Instagram pages you will find a few pics of Holley 2bbl’s on 471’s that they did mount opposite each other with the fuel bowls at each end. One pic is of black 4412’s with no cutting, mounted opposite easy other, which are probably for a 671. Looks like they also have a 2x4 adapter for the 471.

 

Very nice work! I am researching 471’s now. Considering a purchase from Gary Dyer. Once I have it I will start working on a full scale CAD drawing. Thanks!

 

I wasn't very happy wit the Dyers 8-71 blower I got a couple years ago...it has all this cnc stuff all over it, instead of good old castings (case, bearing plate, covers). But I guess if you're into that cnc stuff, it would work fine.

I picked up a 4-71 core at he swap meet a few years ago, still haven't done anything with it. Except steal the front cover, to put on the Dyers to try to make it look a little better.

 

Thanks for that info, Jim. Can anyone recommend a shop that either sells complete 471’s or rebuilds them? I have looked closely at Blower Drive Service (new billet 471), The Blower Shop (6v-71 small bore - no 471’s), Gary Dyer (mixed reviews), Mooneyham (purchased Munro 471 intake & sent it back - terrible quality), and Hampton Blowers (mixed reviews).

 

If you want OEM style casing and end plates, perhaps track down a decent core and strip it down and clean, inspect, and do the metal prep. Only a few critical steps to the disassembly, like pulling the drive gears together, but it's all documented. Not a significant amount of special tools needed. The rotor lobes leading edge should me smooth and free of major gouges and the case inside should be as well. Then either get a kit and do it yourself, or send it out. There are a few basic mods done during the conversation, but again well documented.

 

Thanks, Jim. Hard to find a good case here. Searching the Internet, most are not checked for cracks and no guarantee that they are good. Not sure what else to check for. I assume that “well documented” refers to this forum?

 

Lots of places. Search on this site, google, Pat Ganahl's book. etc. For basic info and tooling the original Detroit Diesel maintenance book is a good reference. But you can find lots of articles on converting to street use and mods to do so. I think Dyers rebuild kit even comes with the extra long feeler gauges you need to set rotor clearance. Hot rodders been putting GMC roots blowers on auto engines since right after WWII.

 

I have a cast 471 adapter for two 2g rochesters that I never used.


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How about a picture of that one?

 

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I say do the Rochesters too.

I made this carb adaptor for 6 large base circle track 2gs.

Like guys are saying earlier, should be around 350 CFM each. You could do a couple of the large base or 4 of the small base ones. I would think that should get you in the ballpark of the cfm you want.

My set-up worked great and wasn’t hard to build. I even figured out a progressive linkage.





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@32fenderless

Thanx, that's pretty cool.

 

Now if we are talking Rochester's, I made this simple two piece for my small rotor 6-71 on my Ardun.

 

Looks awesome. Thanks for posting!

 

Has anybody ran (2) Jet Performance 500 CFM Rochester 2g’s?

 

Thats what mine are. They work great. Plus having the Holley jets makes it much easier to tune.

If you decide to go this route. I’ve messed with these a lot. I’d be happy to share whatever info you need.

The biggest thing I could see you having to change besides the main jets is the idle air bleeds and modifying the accelerator pumps. I had to fatten mine up to get it to idle. Which you will need to make the air bleeds smaller in the cluster.

I also had to drill my nozzles and adjust the throw on the accelerator pump linkage. This was only after I put the setup on top of the blower and when I was at the track. On the street it worked fine. On the street all it did was spin when you wacked the throttle. So I don’t think it was really under load until it was hooked up on the track. Then it has a terrible bog off of the line.






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Good to know. Thanks for that!

 

Are there any 2x4 471 adapters out there?