Intake Manifold....

Discussion of the 331-354-392 HEMIs.

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George
Posts: 627
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Location: Fl

Re: Intake Manifold....

Postby George » Thu Jun 23, 2011 4:05 pm

Rob wrote:
George wrote:Build a plenum box with room for 4 97s & bolt it to the intake!



Somehow "HEMI" and "budget" just don't go together George. But you know, anything is possible at this point. I have no deadline.

Edited for accuracy! :o :D

Rob
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Re: Intake Manifold....

Postby Rob » Thu Jun 23, 2011 4:25 pm

Yeah you're probably right but I can try caint I? lol

Rob
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Re: Intake Manifold....

Postby Rob » Sun Jul 17, 2011 9:38 pm

Here is my mannyfold after being broken by UPS, repaired by a good friend cleaned primed and painted. Those are carb adapters that will allow me to run 2 GM 2GC two barrel carbs. Since they come in a array of flow numbers, all the way to 600 CFM each, I should have no trouble finding a pair to zoom in somewhere around 500 FCM total. I think it turned out nice.

Image

Image

DavidBraley
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Location: Fort Collins, Colorado

Re: Intake Manifold....

Postby DavidBraley » Mon Jul 18, 2011 12:10 am

That looks great Rob!

If you want to limit your total CFM to 500 CFM or a little more, try to find a pair of the larger base two barrels. These Rochester models have the fuel inlet on the front of the bowl. The side inlet carbs are the small base and only flow about 278 CFM's at 3" of mercury each. That only works out to about 393.15 CFM's compared to a four barrel that is flow rated at 1.5" of mercury.

You will need a couple of 2G carbs close to 350 CFM's each to equal the characteristics of one 500 CFM four barrel.

The large base 2GC's come in four sizes in their stock, unmodified form. They all have a 1 11/16" diameter butterflies, and are rated at:

352 CFM's @ 1 3/16" venturi
381 CFM's @ 1 1/4" venturi
423 CFM's @ 1 5/16" venturi
435 CFM's @ 1 3/8" venturi

These ratings are all at 3" of mercury, so you will need to apply a 0.7071 factor to get your 4 barrel equivalent. You can also buy modified 2GC's in 500 CFM and higher ratings, but those are only for track use.

I hope what I said makes sense and helps.

David
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

Rob
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Joined: Thu May 05, 2011 10:15 pm

Re: Intake Manifold....

Postby Rob » Mon Jul 18, 2011 1:31 am

Sure does help. My plans are to get two of the 352 CFM.

George
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Re: Intake Manifold....

Postby George » Mon Jul 18, 2011 9:20 am

On another Forum they were talking about 2 bl carbs used on Pintos & Vegas. One barrel operates normally & the other barrel opens as needed(Progressively) basicly like running 2 1 bl carbs nonprogressive & 2 more 1 bls progressive. Don't remember the CFM though.

DavidBraley
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Location: Fort Collins, Colorado

Re: Intake Manifold....

Postby DavidBraley » Mon Jul 18, 2011 10:02 am

George,

Is this the little carb you're talking about? Looks like they came on the early to mid 70's Pinto's and Capri's. I bet these carbs can be found in any wrecking yard.

http://cgi.ebay.com/ebaymotors/1973-Ford-Pinto-Capri-122-c-i-R6502-2000-cc-Carburetor-_W0QQcmdZViewItemQQhashZitem2eb0272766QQitemZ200523851622QQptZVintageQ5fCarQ5fTruckQ5fPartsQ5fAccessories

If you look close, you can see that even the secondary butterfly is a little bigger than the primary. That's kind of cool.

Rob, don't let the price scare you. I'm sure a couple of rebuildable cores can be had for almost nothing. Where you'll probably have your money is in the rebuild kits. 8)

David
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

392heminut
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Re: Intake Manifold....

Postby 392heminut » Mon Jul 18, 2011 10:25 am

What I would like to know is how the hell did UPS manage to break a cast iron manifold?!! :roll:
Owner of the Poor Man's Hemi Cuda

Rob
Posts: 208
Joined: Thu May 05, 2011 10:15 pm

Re: Intake Manifold....

Postby Rob » Mon Jul 18, 2011 1:09 pm

392heminut wrote:What I would like to know is how the hell did UPS manage to break a cast iron manifold?!! :roll:


It was two fold and actually ended up being a good thing. First the shipper packed it good. Not great, just good. Secondly, UPS somehow dropped it on concrete. The concrete powder was still on the box and on the very corner of the broken piece. Yes, there was a hole in the box, but thankfully, all the pieces stayed in. However, had that not happened, I would have never known that the area had been previously repaired. There was bronze and brass rod, JB Weld and even some bondo there. Yeah. Anyway, now it is repaired right and is 100% metal in that area like it should be.

Now that I've had time to look at my adapters more closely and do some math with that formula David posted (thanks David) I think I might try to find some large bore 500 CFM carbs. That will only be 707 CFM. Might be a tad rich, but I am sure i can jet that small amount down if need be. I was excited just to see that the large flange carbs will fit.

George
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Joined: Wed Aug 25, 2004 4:12 pm
Location: Fl

Re: Intake Manifold....

Postby George » Mon Jul 18, 2011 2:11 pm

DavidBraley wrote:George,

Is this the little carb you're talking about? Looks like they came on the early to mid 70's Pinto's and Capri's. I bet these carbs can be found in any wrecking yard.

http://cgi.ebay.com/ebaymotors/1973-Ford-Pinto-Capri-122-c-i-R6502-2000-cc-Carburetor-_W0QQcmdZViewItemQQhashZitem2eb0272766QQitemZ200523851622QQptZVintageQ5fCarQ5fTruckQ5fPartsQ5fAccessories

If you look close, you can see that even the secondary butterfly is a little bigger than the primary. That's kind of cool.

Rob, don't let the price scare you. I'm sure a couple of rebuildable cores can be had for almost nothing. Where you'll probably have your money is in the rebuild kits. 8)

David

That seems to be the one!

George
Posts: 627
Joined: Wed Aug 25, 2004 4:12 pm
Location: Fl

Re: Intake Manifold....

Postby George » Mon Jul 18, 2011 2:18 pm

Rob wrote:
392heminut wrote:What I would like to know is how the hell did UPS manage to break a cast iron manifold?!! :roll:


It was two fold and actually ended up being a good thing. First the shipper packed it good. Not great, just good. Secondly, UPS somehow dropped it on concrete. The concrete powder was still on the box and on the very corner of the broken piece. Yes, there was a hole in the box, but thankfully, all the pieces stayed in. However, had that not happened, I would have never known that the area had been previously repaired. There was bronze and brass rod, JB Weld and even some bondo there. Yeah. Anyway, now it is repaired right and is 100% metal in that area like it should be.

Now that I've had time to look at my adapters more closely and do some math with that formula David posted (thanks David) I think I might try to find some large bore 500 CFM carbs. That will only be 707 CFM. Might be a tad rich, but I am sure i can jet that small amount down if need be. I was excited just to see that the large flange carbs will fit.
Gad! Bondo & JB weld! :o There's still the Q about weather 2 bls can flow below 3"s, with measuring @ 3" being an arbitrary thing or not. If they can't then the 600 in 2bl being equal to a 500 4 bl would be invalid.

DavidBraley
Posts: 163
Joined: Sat Jan 30, 2010 7:40 pm
Location: Fort Collins, Colorado

Re: Intake Manifold....

Postby DavidBraley » Mon Jul 18, 2011 5:38 pm

George,

You bring up an interesting idea that complicates the whole idea of the conversion between the two types of carbs, and whether the CFM equality is the most important thing to look at. The idea as I understand it, and this is straight from Tex Smith's book, second paragraph, page 65:

"The reason that it's so important to stay within the proper CFM ratings when using multiple carbs is that most two-barrels used in those applications are designed in a manner that requires airflow equal to at least 3 inches of mercury. This is the lowest volume of air flowing over the emulsion tube tips that will draw the proper quantity of fuel up through the main metering jets and mix it in the venturi. On the other hand, most four-barrel carburetors require only 1.5 inches of mercury to perform correctly."

What the author says makes total sense to me. It at least explains WHY they rate two-barrels at the higher depression (pressure). So based on that, what I get from this statement is that it's best to keep the two barrels flowing with a little more depression below them so they still work well. That would suggest to me that when using multiple two-barrels, to keep the total CFM's on the motor a little on the lower side than the higher side. Safer anyway.

Rob, I think your intuition on initially going for something closer to the equivalent of a 500 CFM four-barrel hit the nail on the head. After using the conversion, I personally wouldn't go much more with two barrels. I think those two 352 CFM Rochesters would be perfect. That gives you the equivalent of a 498 CFM four-barrel. Of course, I could be totally wrong. It wouldn't be the first time.......HA! :roll:

Just my two-dala-three-ninety-five! :lol:

David
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

DavidBraley
Posts: 163
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Location: Fort Collins, Colorado

Re: Intake Manifold....

Postby DavidBraley » Mon Jul 18, 2011 5:55 pm

Rob,

Now that I think about it a little more, even less might be better. I think I remember you saying that you where not going to rev this thing very high. Maybe a pair of the little Rochester 278's would be better. It still puts your four-barrel equivalence close to 400 CFM's. According to an online calculator I found, a 331 cubic inch motor, running at 85% volumetric efficiency, that spins up to 5,000 rpm, only needs a total of 407 CFM's of four-barrel.

Getting the carbs to mix that fuel well will make a huge difference on power output. The one thing that's nice about the small bore Rochester 2CG's, is they have the fuel inlet on the side. Makes it easier to plumb.

David
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

Rob
Posts: 208
Joined: Thu May 05, 2011 10:15 pm

Re: Intake Manifold....

Postby Rob » Mon Jul 18, 2011 6:20 pm

Yes, but remember, it is going to end up displacing 354 cubes. I plan on a 5500 max, even though it will have a solid camshaft.

DavidBraley
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Joined: Sat Jan 30, 2010 7:40 pm
Location: Fort Collins, Colorado

Re: Intake Manifold....

Postby DavidBraley » Mon Jul 18, 2011 7:10 pm

So did you find some 354 pistons? Sorry if I missed that.
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

Rob
Posts: 208
Joined: Thu May 05, 2011 10:15 pm

Re: Intake Manifold....

Postby Rob » Mon Jul 18, 2011 7:36 pm

Sure did. NOS Chrysler pieces. Real nice set.

New one on the right, old 7.5:1 on the left.

Image

DHEMI
Posts: 100
Joined: Mon Mar 06, 2006 8:01 am

Re: Intake Manifold....

Postby DHEMI » Mon Jul 18, 2011 7:53 pm

George wrote:On another Forum they were talking about 2 bl carbs used on Pintos & Vegas. One barrel operates normally & the other barrel opens as needed(Progressively) basicly like running 2 1 bl carbs nonprogressive & 2 more 1 bls progressive. Don't remember the CFM though.


I had an 1980 Toyota Carolla with a 4cyl.Hemi(rear drive).The carb operated in this exact manner.

DavidBraley
Posts: 163
Joined: Sat Jan 30, 2010 7:40 pm
Location: Fort Collins, Colorado

Re: Intake Manifold....

Postby DavidBraley » Mon Jul 18, 2011 9:41 pm

Rob wrote:Sure did. NOS Chrysler pieces. Real nice set.

New one on the right, old 7.5:1 on the left.

Image


Nice! Solid cam eh? I've always loved the sound of a solid cam.
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

Rob
Posts: 208
Joined: Thu May 05, 2011 10:15 pm

Re: Intake Manifold....

Postby Rob » Thu Aug 04, 2011 9:53 pm

Thought I would update this real quick before I hit the sack. I actually found two matching 2GC carburetors. They are the large base, 352 CFM versions, just like I need. I already have one and the other is on the way. I will post pics of the one in the morning. Slow but sho.

Rob
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Joined: Thu May 05, 2011 10:15 pm

Re: Intake Manifold....

Postby Rob » Wed Aug 10, 2011 1:01 am

A tad more progress. I now have two matching carburetors.

Image

George
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Re: Intake Manifold....

Postby George » Wed Aug 10, 2011 12:33 pm

Lookin good! I tend to paint things black or Ford blue. :D

Rob
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Re: Intake Manifold....

Postby Rob » Sat Aug 20, 2011 9:54 pm

Carburetors built. Waitin on a few small things to finish up.

Image

Rob
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Re: Intake Manifold....

Postby Rob » Mon Aug 29, 2011 5:55 pm

What a hot topic. More progress. Linkage and air cleaners. I'll make up the fuel line next.

Image

mart
Posts: 536
Joined: Tue Mar 22, 2005 2:06 pm

Re: Intake Manifold....

Postby mart » Tue Aug 30, 2011 10:03 pm

Rob wrote: "What a hot topic. More progress. Linkage and air cleaners. I'll make up the fuel line next."

--------------------------
Nice......very NICE!!!
mart
================================

Rob
Posts: 208
Joined: Thu May 05, 2011 10:15 pm

Re: Intake Manifold....

Postby Rob » Wed Aug 31, 2011 1:34 am

Thanks, mart. It's coming along more slowly than I had hopped, but at least it's moving forward.


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