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2x4 usually produces more power than 3x2. 4-barrels also have the potential to save on fuel economy too. But, power and economy of a 2 vs 4 bbl is a separate issue.
For EFI, you have to have a fuel send and return line. The fuel is also pressurized. One line sends pressurized fuel to the injectors, while the other line catches whatever overflow there is and send it back to the gas tank.
The EFI systems for the 300 usually suck, except for aftermarket systems like the Holley Avenger.
If you want to do an aftermarket performance fuel injection (performance EFI for this motor is usually TBI), you need a 4bbl intake manifold.
If you want to do factory fuel injection, you might as well forget it. You'll have so much space issues with the size of the intake and height of the intake above the motor (it wraps around over the valve cover), not to mention hooking up all the emissions equipment so the computer won't throw codes at you.
2x4 usually produces more power than 3x2. 4-barrels also have the potential to save on fuel economy too. But, power and economy of a 2 vs 4 bbl is a separate issue.
You are a little off on that statement.
2x4's might make more power on a V8 but if you look at most of the guys racing 300's they are running 3 Holley 2V's or 3 Weber 2V's. On a inline 6 the 3-2V set up aren't set up as a progressive set up like on a V8. All three carbs are synchronized to open at the same time. The 3-2V set up gives the most even air/fuel distribution on the inline 6. Each cylinder has it's own venturi without going to an individual runner set up like the Weber DCOE's & IDA's/IDF's.
2x4's might make more power on a V8 but if you look at most of the guys racing 300's they are running 3 Holley 2V's or 3 Weber 2V's. On a inline 6 the 3-2V set up aren't set up as a progressive set up like on a V8. All three carbs are synchronized to open at the same time. The 3-2V set up gives the most even air/fuel distribution on the inline 6. Each cylinder has it's own venturi without going to an individual runner set up like the Weber DCOE's & IDA's/IDF's.
I was mainly speaking in general about 2 vs 4 bbl carburetors, not specific to inlines. Inlines suffer from poor fuel distribution because of the design of the intakes, and people racing these motors run 2 bbl's because they're trying to circumvent the fuel distribution issues. I imagine if they were able to get around the fuel distribution issues they'd be running 4bbls. Direct vs progressive linkages also aren't specific to an inline. Plenty of people run direct carburetor linkages on V8's with multiple carburetors. If I remember, from watching FrenchtownFlyer's videos on youtube, he was running 2 or 3 4bbls on his six.
If the OP wasn't concerned about hood space, I'd recommend a 2x4 intake with dual Holley 390 CFM carburetors. There was a guy a few counties south of me who had a 300 inline-6 that was built for racing. It had an offset ground crank 0.1'' and the motor was bored over 0.125''. How they did it, I don't know, but that was a huge overbore. I calculated the displacement and it came up to a 327 cu inch straight 6. It was balanced, 10.5 or 11 to 1 compression, Clifford 2x4 intake with Holley 390 CFM carburetors, roller lifters, custom roller cam, and roller rockers, and MASSIVE head work. The whole setup was for sale for 3000$. He's probably still got it for sale too. I think the shop who did it was Norwood Motors.
I was mainly speaking in general about 2 vs 4 bbl carburetors, not specific to inlines. Inlines suffer from poor fuel distribution because of the design of the intakes, and people racing these motors run 2 bbl's because they're trying to circumvent the fuel distribution issues. I imagine if they were able to get around the fuel distribution issues they'd be running 4bbls. Direct vs progressive linkages also aren't specific to an inline. Plenty of people run direct carburetor linkages on V8's with multiple carburetors. If I remember, from watching FrenchtownFlyer's videos on youtube, he was running 2 or 3 4bbls on his six.
If the OP wasn't concerned about hood space, I'd recommend a 2x4 intake with dual Holley 390 CFM carburetors. There was a guy a few counties south of me who had a 300 inline-6 that was built for racing. It had an offset ground crank 0.1'' and the motor was bored over 0.125''. How they did it, I don't know, but that was a huge overbore. I calculated the displacement and it came up to a 327 cu inch straight 6. It was balanced, 10.5 or 11 to 1 compression, Clifford 2x4 intake with Holley 390 CFM carburetors, roller lifters, custom roller cam, and roller rockers, and MASSIVE head work. The whole setup was for sale for 3000$. He's probably still got it for sale too. I think the shop who did it was Norwood Motors.
Well this is the inline forum so saying 2x4V's makes more power then 3-2V's isn't true. And in fact the 2-4V's would probably get better gas mileage on the 300 then 3-2V Holley's would.
And with those clifford 3-2V intakes you can't run progressive linkages. That only works when you have a common plenum.
And I think you need to watch the FTF's vids again. He runs 3 modified Holley 500cfm 2V carbs in his altered. I'm sure if 2-4V carbs worked better he'd be running them. I think I remember him saying he is making around 500 or 550hp.
If it was a 300 bored .125" over he must be running direct water injection( water right from the water jackets into the cylinders. Either that or he sleeved all 6 cylinders and then filled the water jackets. There might be a reason it's still for sale.
Not trying to bust your chops. I love 2-4V carbs on a 300! But for drag racing 3-2V's( or injection ) usually work better on the inline 6.
Chops not busted so no harm done. People have different opinions on what works best and what they like, and I respect that.
I know those 500 CFM 2bbls from Holley were big, but I didn't know they were that big. Those things look like 4bbls sitting under that air cleaner! He was running a progressive linkage that I saw too.
Getting back on topic, I don't know if I'd be willing to run 3 GM EFI modules and oxygen sensors on one motor. I think a carburetor would work best for the OP's application. Plus, it looks cooler than seeing all that wiring under the hood.
It had the reason that the motor was for sale in the ad: from what I remember, it had ruined lifters. I don't think I'd pay 3000$ for a motor with ruined lifters, but go figure. Sleeving the bore like that seems like the only way that would work, though. Boring it anything over 0.060'' is about a gamble for most any motor, IMO.
I know those 500 CFM 2bbls from Holley were big, but I didn't know they were that big. Those things look like 4bbls sitting under that air cleaner! He was running a progressive linkage that I saw too.
That "little" scoop sitting on top of the carbs can make them look bigger.
His linkage isn't a progressive linkage. His linkage is a bar with an arm for each carb, then a short linkage to each carb.
That "little" scoop sitting on top of the carbs can make them look bigger. His linkage isn't a progressive linkage. His linkage is a bar with an arm for each carb, then a short linkage to each carb.
Too many things on the brain lately. I can't think straight, but most people that know me don't think of me as a straight thinker. LOL
Those set ups are cool. But my opinion is they are just for looks. Since your main intake is still a single 4V intake. You aren't really going to gain any performance over a single 4V carb. If you are building a hot rod and just want the multi-carb look then the setups you posted would be the easiest way to go.
But compare that to an actual multi-carb intake which will give you a more even air/fuel distribution. No contest.
I think the best set up, if you can't build one from scratch, is still to start with an EFI lower intake and build a custom plenum. Doing that lets you evenly space out the carbs with out having to build an intake from scratch.
I agree somewhat but its still using a tri power system running off the center carb when cruising but 3 carbs still allows for greater fuel volume when the accelerator is dropped an intake designed for three carbs would definitely provide better dispersion but you should still get performance from the setup these engines don't flow the same as a v8 and may be very close to the same as a manifold for 3x2 in all honesty it is about the looks primarily but there is performance gains to be had
The look im going for is a stock appearance and a dont see a fabbed manifold looking as good as this
I agree somewhat but its still using a tri power system running off the center carb when cruising but 3 carbs still allows for greater fuel volume when the accelerator is dropped an intake designed for three carbs would definitely provide better dispersion but you should still get performance from the setup these engines don't flow the same as a v8 and may be very close to the same as a manifold for 3x2 in all honesty it is about the looks primarily but there is performance gains to be had
The look im going for is a stock appearance and a dont see a fabbed manifold looking as good as this
That's fine but you are still feeding the extra air/fuel through a centrally located hole in the intake. So your front and rear cylinders aren't going to get the same mixture as the center cylinders. So those 3 carbs won't perform any better then a single 4V. But 3 are cooler then 1!
The 240/300 is a long intake, not a short one like most V8's.
Will those adapters work, sure. But an actual multi-carb intake will perform better.
And there is nothing stock in appearance about a multi-carb set up on a 300! But I get what you mean. But I'm still building my own.
02-27-2011, 10:01 PM
There might be a reason it's still for sale.
But for drag racing 3-2V's( or injection ) usually work better on the inline 6. 
