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I purchased a 70 Mach 1 H code that has 4 barrel heads and 4 barrel carb. Original owner said I should convert back to 2 barrel heads because he said it bogs out at low RPM? Does 4 barrel intake manifold fit the 2 barrel manifolds? Any tech help would be appreciated. Car seems a little rough at idle but runs fine.
 

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I am not sure what the H code engine is so I will ask. What engine do you have, 351W, 302 or a 351C?
 

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I assume you have a 351C. I have had both a 2V version and a 4V version. I agree with the previous owner, the 4V heads (closed combustion chambers) have larger valves with larger intake runners, but don't really put the power to the road well until you get into the higher RPM's. The 2V heads (open combustion chambers) and intake have smaller valves and runners that produce better low end torque and thus more "seat of the pants" accelleration. In my opinion the best system is the 2V heads (Aussie version if possible, they have closed chambers) with an aftermarket aluminum 4V intake.
 

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It really depends on what you want to do with the car. If you want to return it to original condition and drive to shows and cruises, then by all means, swap out your heads.

If you want a little extra performance, and are willing to make a few "adjustments" to suit the particular requirements of the big ports and valves, then we will go from there.

The Cleveland 2V vs 4V head debate can get a nasty as a Ford vs Chevy argument at a backwoods tractor pull. The 4V heads are perfectly streetable, you must understand where they do their job the best, and the rest of the equipment must support them as well. 2.79 gears, 28" tires, a 4000 lb car, 5 passengers and a trunk full of junk are not where you want a 4V head.

Just fishing for opionions without divulging your intentions or desires for the car can get ugly......
 

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The 4V heads have huge ports (can just about stick ya head in them)& designed for top end power,like flat at open track racing,on the street thier preety doughy down low. If you want low end power go with the 2V,s.
 

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Stick with the 4v's. Trust me I've had about every combination of cleveland at one time or another. Quench chamber 4v's rock and will out pull any 2v that hasn't been to a profesional porter and a ton of money put into them. The trick to the 4V's is don't go to big on the cam or carb. A 270 or 280 cam works well on a mild street car, the cam should be a little bias on the lift side and not duration.A carb of 750 cfm or less. One thing to think of who cares if you have 1000 ft lbs @ 1500 RPM and nothing up top how long are you at that RPM in a race and street traction is limited anyway.
 

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I would check into some port stuffers for the 4v heads you have. They should pick up the torque down low without losing top end power. I have the Aussie 2v heads myself & the main drawback is the availability of intake manifolds... there is no high-rise dual plane (Edelbrock RPM-style), whereas the 4v heads have the Blue Thunder. If you haven't been there already, check out the 351 Cleveland Engine Forum . There is a ton of info there.

Doug
 
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