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Maximum CFM question for a 3.7 Liter 225 Super Six
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Author:  Hatchworx [ Fri Sep 12, 2014 1:26 am ]
Post subject:  Maximum CFM question for a 3.7 Liter 225 Super Six
Hey guys ... I am extremely curious if any of you have experimented with pepping up a 1977-era 3.7 Liter 225 Super Six with one of those aluminum Oddenhauser 4-Barrel intakes before.

The reason I ask is that a buddy of mine who has been an amateur racer for decades now has tons of spare MOPAR parts laying around and he often gives me stuff for next to nothing cost wise.

A year or so ago he gave me all sorts of extra MSD stuff he had laying around for pennies on the dollar.

He told me today that he was digging around his storage room and uncovered an old NOS Offenhauser aluminum intake for the Super Six I am currently running in my 1973 Dodge Dart. The engine and tranny in my Dart was snatched out of a wrecked 1977 Dodge Monaco. It is a Super Six package.

I have had headache after headache with remanufactured 2-barrel Carter and Holley carbs and a couple of years back following tips from this board, I upgraded to a Weber conversion.

But after rejecting three times, I am disgusted and totally dissatisfied with the performance and fuel economy of the Weber set up. I paid a small fortune for the Weber and had to have a machine shop customized and in ten permanently ruin my Super Six intake to mount the Weber properly.

So, here I am now currently rewiring my electrical system from kind tips to Bill Evans whom along with Tommy over in Wisconsin are custom building a new series of wiring harnesses to handle my 100-AMP MSD system. And this is not an inexpensive endeavor but I am confident once done, these new slightly altered and customized MOPAR harnesses will provide me great spark and performance.

But I a still left with that crappy and overrated and overpriced Weber carb system. That 2-Barrell overpriced piece of garbage has given me not in but headaches. Bog, bog and more bog in lower RPM range to the point where the car accelerates like a granny jalopy on the way to the social security office.

My racing buddy is a 35-year veteran ASE certified mechanic who is also an amateur racer and hotrod enthusiast. And he told me that switching to the Offenhauser 4-Barrell intake with 400 to 460 range CFM 4-Barrel carb (wither Edelbrock or Holley) would provide me the zip and power I so very desperately desire.

Again, I have a line on getting both an Offy intake and a Holley 4548 460-CFM carb for $174 for the pair. My other option was biting a brand new Offfy aluminum intake fem Summt Racing for around $300 along with an Edelbrock Thunder Series AVS Carburetor 1801 Performer Series model rated at 400-CFM. My racer buddy told me I'd be pleased with both options and that my 3.7 Liter 225 Super Six can handle that level of gas flow with no issues whatsoever.

Presently, the 2-Barrel Weber configuration is running too lean and choking the motor in low RMPs off the start in first gear and in turn bogging out with no power. Now at interstate speeds in hight 3rd gear traveling over 65 MPH, the Weber finally flows right and my engine runs smooth and fast only accelerating slowly and pegging out at 105-MPH tops.

But this scenario is i my Dodge is on a level road with at least a solid 1/2 mile to a mile straight shot acceleration. Up a sudden hill, and then the motor actually drops dramatically in pull and slows down by 20-MPH within seconds forcing a manual downshift and to compensate and regain my power band of acceleration, I have to manually downshift ad override the Lokar kick down I have installed.

Pardon the long windedness, but this performance issue has been my nemesis for years now. And I know my Super Six has to potential to scream and maintain power if properly gassed and breathing. Because my former 1986 Dodge B-150 van with a single barrel Slant Six would outperform my current Dart which weighs almost half what that big heavy van used to be able to do.

So again dear MOPAR buddies, I desperately seek your wisdom. I want to make my Dart scream and go as fast as possible. Will the Holly 4-Barrell comoo work well as well will the Edelbrock combo work well? And if so, which configuration is better for my car?

Thanks a million in advance. You kind fellows over the past decade or more have made my life a lot easier with all of your advice. Lastly, keep in mind that I do not want a stock system and I a building a hotrod-ratrod version of a 1973 Dodge Dart I want to squeeze as much horsepower and performance out of by running a straight gas system such as a 4-Barrel intake.

You hep is not only appreciated but desperately needed as I am waiting for your replies to do the work and finish it all by end of this weekend.

Thanks!!!
Jason
Author:  wjajr [ Fri Sep 12, 2014 6:13 am ]
Post subject: 
Quote:
My racing buddy is a 35-year veteran ASE certified mechanic who is also an amateur racer and hotrod enthusiast. And he told me that switching to the Offenhauser 4-Barrell intake with 400 to 460 range CFM 4-Barrel carb (wither Edelbrock or Holley) would provide me the zip and power I so very desperately desire.



Won’t help much if engine is stock build, you need much better breathing, and lower end build that can spin to high rpm to come close to 400 cfm. If you don’t have oversized valves, enlarged exhaust system high lift performance cam forget it.

Quote:
That 2-Barrell overpriced piece of garbage has given me not in but headaches. Bog, bog and more bog in lower RPM range to the point where the car accelerates like a granny jalopy on the way to the social security office.
I would bet that thing is going lean or rich in a big way when throttle is opened; bog is classic symptom in either direction, and I’m leaning to lean direction. I’m not going to discuss how to bridge or tune out bog condition under throttle opening here, as I have no experience with Webber Carburetors.

You need to determine on WOT, or just tip-in which way A/F mix is going during bog. One way to figure out A/F mixture is to install an o2 sensor and gage; read this site several times until you understand what the guy is talking about, and go from there. I understand this site is geared to Holley carburetors that use power valves & jets dissembler to your Webber, but the engine can’t tell the difference of how the air & fuel is mixed before it enters the intake manifold, only that that mix is right under all conditions, or not. Once you know for sure what is happening, you can easily tune the damn thing.


Below is Holley’s air flow/ displacement chart, and a carburetor caculator. Forget about it being Holley, displacement is displacement and flow is flow:
here, and here.
Author:  sandy in BC [ Fri Sep 12, 2014 6:30 am ]
Post subject: 
I would spend my money on making sure the thing can run right as a Super 6 long before I would spemnd money on a 4 bbl for a stock motor.

Best carb I ever had on a slant was a BBD Carter...
Author:  Hatchworx [ Fri Sep 12, 2014 7:13 am ]
Post subject: 
Guys,

Thanks a millón. The guy who built the motor told me it had an oversized cam in the motor and cold handle more gas.I am not opposed to putting a Carter on the engine, my issue is finding one that is not a pile of crap remanufactured in Mexico. I have been through three the far. If you would, can you please list me the exact Carter Carb Model Number? Wrose case, I could have my racer buddy break down one of this remanufactured Carters and build it back proper. I just want to squeeze as much power out that I can. And that 2-Barrel Weber is a slow dog. It's embarrassing how slow the car is off the line. In higher RPMs over 65-MPH, the car open up and breaths and breaks 100-MPH. But from a dead stop, it bogs and limps its way up to about 45-MPH before finally showing some reasonable power.
Author:  Hatchworx [ Fri Sep 12, 2014 7:21 am ]
Post subject: 
Guys, id this reman carb from Rock Auto the BBD you are mentioning. If so, I can have it torn down and properly rebuilt by my racer friend.

http://www.rockauto.com/catalog/moreinf ... cc=1093429

I need to get an answer thus morning as I have to make an order today. The scar is stranded and my frailly driver.
Author:  Hatchworx [ Fri Sep 12, 2014 7:28 am ]
Post subject: 
One last request. And trust me when I say that you fellows are saving me a lot of stress and anguish in this matter. What size cam is ideal for a 4-Barrrel set-up and where's a good spiller for the part?

Secondly, where a reasonably priced o2 sensor I can buy?

Lastly, should I consider running an inline fuel pressure system?
Author:  Rick Covalt [ Fri Sep 12, 2014 7:47 am ]
Post subject: 
If you have access to an Offy manifold for pennies on the dollar then buy it regardless. If you really need a 4 barrel the Edelbrock is much easier to get running well than the Holley (My opinion). You can also drop the linkage off the secondary and run the carb off the primaries if you only want a 2 barrel. You really need to have an idea of what cam is in there before you will really need a 4 barrel. Although I have run 4 barrels on stock motors several times, it is probably not ideal.

Rick
Author:  Hatchworx [ Fri Sep 12, 2014 7:58 am ]
Post subject: 
Thanks my friend. You guys on this site have saved my neck countless times. I read the following article thoroughly:

http://www.slantsix.org/articles/Josh_Carb_Article.htm

I think I am going to take the Offy intake since my friend is selling it to me for $50.

My last question is about the following Edelbrock Thunder Series AVS Carburetors 1801 Model. It is a 500-CFM carb. You think I can tine this one in to avoid the low RMP bogging once mounted on the Offy?

http://www.summitracing.com/parts/edl-1801
Author:  Hatchworx [ Fri Sep 12, 2014 8:23 am ]
Post subject: 
One last urgent question. What size and where can I purchase a hotter cam for my Suepr Six? As well, what size exhaust should I upgrade to after potentially changing the cam? Any online suppliers?
Author:  Hatchworx [ Fri Sep 12, 2014 9:10 am ]
Post subject: 
Guys, maybe I am just trying too much. My buddy who runs a restoration shop just told me that I need to add a competition cam and have head work done in order for the Offy intake and 4-Barrel to work properly. I am in over my head. I just want my Super Six to scream as best as it can. So I am probably better off running s 2-Barrell Carter BBD with a standard 2-barrel Super Six intake. All you advice is highly appreciated. In feel like I am fighting a losing battle. Maybe you wise gentlemen can help me out. I am a younger novice mechanic doing the bed that I can do on my own.
Author:  Hatchworx [ Fri Sep 12, 2014 9:42 am ]
Post subject: 
Okay, one last begging for help. The Holley my pal is offering me now for FREE is an older 360-CFM 4-Barrel. Certainly my super six can handle that one. Right?
Author:  Junior [ Fri Sep 12, 2014 9:53 am ]
Post subject: 
im not going to discredit anything anyone has said. that was their experience. my experience with putting a 4bbl holley 390 on a stock motor with 2 1/4 exhaust was great. good punch off the line and power up top. the fuel economy was better then i had with the 1&2bbl. also dropped my ET in the 1/4 mile by 2.3 seconds. ran the holley 4bbl on the stock motor for a decade without any major problems.
Author:  51Cambridge [ Fri Sep 12, 2014 10:25 am ]
Post subject: 
I have a 390 with a comp cam, rv. 3 angle valve job. Now I didn't drive this before the modifications, but I feel a lot of low end. Top end kicking down into passing gear could be a lot better. [/img]
Author:  Hatchworx [ Fri Sep 12, 2014 10:49 am ]
Post subject: 
Junior, thanks for you words. And thanks to everyone else really. So, you guys think I will be alright with a Offenhasuer 4-barrel intake running as much as 450-CFM? Turns out my buddy was wrong with his information. The Holley he is offering me for free is a 450-CFM 4-Barrel. Pretty small so far as 4-Barrels go. I am just confused. I have some folks saying no way anything over 350-CFM will work right and others saying I can go as high a 500-CFM. Worse case scenario, Summit offers a competition cam for $139. I could add that cam and run a 500-CFM Edelbrock all day long I'd assume. But then I get nervous about the valves. But then again, I thought the Super-6 packages had higher output parts compared to the standard 225. Jeg's has a 390-CFM 4 Barrel for $450. Maybe the Offy intake with the Holley-390 from Jegs will work good on a Super-6 without a cam modification. MY main complaint is the low RPM bog with that damned overpriced Weber I put on two years ago. I really hate that Weber carb.
Author:  Junior [ Fri Sep 12, 2014 11:08 am ]
Post subject: 
comp cams have a habit of eating distributor and oil pump gears. if you do a search on this site you should be able to come up with a couple places that will re-grind the cam you already have. i dont have any experience with the eddelbrocks or the 400-450 holleys so i really couldnt say anything about them. as far as the super six goes, the only parts that were different were the intake, carb, head pipe to the manifold, kickdown linkage and the governor in the distributor. to the best of my knowledge everything else was normal slant.
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