351c 4bbl open chambered heads any good?

Have a look at these:

http://www.powerheads.com/351c.html

http://www.chiheads.com/heads.html

This one has some chamber size data:

http://www.wrljet.com/fordv8/cleveland.html

1973mach1 said:

Could anyone tell me if the 4bbl open chamber heads are any good and would I notice much difference over my 2bbl heads in HP or torque? Are the chambers any smaller then the 2bbl OC heads?

Thanks,
Jim

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If you are thinking about unbolting your 2v and bolting on the 4v opens you will not like it. It will increase your car's HP by alot, but unfortunately you won't notice it since it happens in the upper RPM range at the cost of low end (street needed) grunt. You will also need to change you intake and your exhaust for the new heads. For that price you could pull your old 2v, get them ported and polished, new stainless valves, 3 angle valve job, and then re-installed...you could also mill them for screw in studs, add roller rockers, new springs, and swap in a larger cam then and see a real change in your car's characteristics.

If you are dead set on swapping heads for one reason or another and not doing much else, you will want 4v closed chamber heads, this will up the compression (the 4v closed have 63-65 cc chamber while the 4v open have 76-78 cc) on the motor. Do you know what compression you currently run? you need to be careful because you can easily get too much compression in the motor and have a detonation problem.

All that said, I run 4v open on my 408c stroker and I love them. They were less expensive to aquire than their closed chamber brother. Since my pistons were custom made I just had them made to create a quench effect in the open chamber heads and make 10.6:1 compression.

With the cam you have 4v heads should work well. Are you rebuilding the engine? If so, you could buy a set of Keith Black pop-up pistons for $200 that would get you 10.5:1 compression, otherwise a set of flat-tops would get you around 9.5:1. If you aren't rebuilding the engine you may want to get a set of quench heads.

4v heads are great, they make a lot of torque too if you set up the motor correctly.

1973mach1 said:

Thanks for the reply's. IM rebuilding the engine and planning on getting new pistons. Is this the cam your talking about which would be good? This is the cam I have Summit #5200
Specifications:
* Advertised duration: 262 intake/272 exhaust
* Duration at .050 in. cam lift: .204 intake/.214 exhaust
* Gross valve lift: .484 in. intake/.510 in. exhaust
* Lobe separation: 112 degrees
* RPM range: 1,500 to 4,000

Would you go any larger on the cam? With the Keith black Pop up pistons would it be the same as running 4v closed chambered heads? Hopefully the OC 4bbl heads, pop up pistons, cam, headers, intake and 4bbl carb I should make 300HP? or is this a far fetch?

Thanks,
Jim

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That would be a disappointing cam unless you wanted something very mellow. Ironically, that small cam would do better with the bigger 4v heads because they need less cam with the big ports. But it really depends what you want to do with the car; if it is your daily driver then that isn't a bad cam, though I would still go a little bigger. If it is a weekend car or cruiser, or you don't use the highway much then I would definitely get a bigger cam and put some gears in it. You won't believe how fast a Cleveland motor can be with a big cam, carb and gears.

I'm running a 240/240 duration solid cam with .588 lift. It's pretty mellow - though solid cams tend to be more mellow compared to hydraulic cams at the same duration because of the lash that needs to be set at the valve.

But 300 HP, that's nothing, you can build it cheaply with OC 4v heads and get 425 HP at the flywheel, which equals about 350 at the rear wheels.

Just tell us how you want to use the car, and how you want it to behave and we can give you some good advice.

Everything you have is for a 2v setup so you may want to consider using it. But if you want to go with 4v heads this is a general prescription for a streetable, fun, go fast set-up:
750 Double Pumper carb
Blue Thunder intake for the heavy car and automatic
Solid cam – spec’s depend on your tastes but I’d recommend this cam for your application: 226 duration on the intake side and 235 on the exhaust, with lift .540/.560, LSA 110. Should give a nice idle and run to about 6200-6500 RPM’s.
10” 2500 RPM stall convertor
10.5:1 compression so you can run premium pump gas
Titanium retainers and roller rockers with screw in rocker studs
3.73 gears

The engine will rock. Figure around 410 - 425 HP with the 4v heads.

Remember, it is important to setup the heads perfectly with the right valves and hardware. Don’t skimp, and have it assembled by a professional you can trust.

72 351C 2bbl rebuild

Gentlemen,

I’m rebuilding a 72 convertible with a 351C 2bbl. I’m in the planning stages of a complete overhaul of the 351. I plan to keep the 2bbl heads as they’ll give me the low end torque I’ll need to get this big heavy beast moving down the road. I have many of the same questions as Jim, but from a 2bbl perspective. I don’t wont to step on his thread here, should I start a new discussion for a 351-2V performance build out? I wouldn't want to confuse the 4v build with the 2v head build recommendations.

Thanks,

Joe
Austin, TX.

1973mach1 said:

What would I have to change to go to a solid lifter cam and are the titanium rockers and screw in studs necessary? Would a setup like this pull hard off the line?

Thanks for the reply,
Jim

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You'll have to convert to screw-in studs for the roller rockers and a solid cam. No the titanium keepers are not necessary, but I think that some upgraded rocker arms are necessary. The stock ones are a liabilty for performance applications. You can keep the press in studs and run the stock rocker arms with a hydraulic cam to keep the costs down, but it is far from optimal. A good hydraulic cam will benfit from better valve train equipment. The better componenets help performance because they are lighter, more precise, and the aluminum dampens some of the bad harmonics. That's the reason for running titanium keepers, too - they allow the valves to operate better as the RPM's increase, thereby freeing up horsepower (not making more horsepower).

That particular combination should be very responsive.