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Discussion Starter · #1 ·
What are the differences in the square and oval port bbc heads?I have 69 427-390h.p.motor in my 68.I have heard of open and closed chamber,what is the difference?I want to put square port heads on it,but not sure if I'll run in to any problems.ThanksMIKE
 

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Oval port heads were more for the every day driver. The combustion chambers on the are open for less compression. The square port heads were used on the hi-perf 390 and up horsepower engines. They won't have much bottom end torque just top end. These will have the closed chamber design. If you turn the head upside down, you can see how small the chamber is as opposed to an large open chamber.
For streetability stick with open chamber oval ports. Track would be the opposite.

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67 SS
70 Z/28
 

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Cast iron ssquare port (actually rectangle) heads up to 1970 were closed chamber except for the 1969 L88/ZL1 aluminum heads. From 1971 up they were open chamber. Open chamber heads flow better because they unshroud the valves.With the right pistons , they make more hp.Cast iron oval port heads came in closed chamber (rare), semi open chamber(common) and open chamber. Just be sure to use the right pistons for the heads. Oval port for street/strip, rectangle for racing (aboove 6000 rpm).
 

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what's up with rectangle bashing? why does everbody say that these head suck on low end?, boy an ls6 or L88 has no low end right!
or the 454 with square ports in my camaro that will blow off the tires in any gear. have any of you ever ran a set open chamber rectangle ports?
 

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I agree with the guy above. I would make sure that your compression ratio will remain reasonable and that the pistons will not hit the new heads. Switching heads on a big block is much different than on a small block. I would consult with a machine shop before you buy any heads.
Rick
 

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mike, first off, check to see what type of heads you got, open or closed chamber, because depending on what you have, you may or may not be able to switch heads. i have a 396 with open chamber heads, but my pistons are made for closed chamber,(so i can have a higher compression ratio). now this can be done, but for some reason, you cannot run open chamber pistons with closed chamber heads. i believe it has something to do with the top of the piston hitting the head. so this is one thing you got to look out for.
good luck,
bruce69camaro
 

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To SS396CAMARO; yes I have a set of rectangle port, open chamber aluminum GM heads on my 69 427 Camaro street car and they work great. But most people are going to be happier with the oval ports on the street.I'm not bashing rectang ports. I love them.
 

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Discussion Starter · #8 ·
I guess I'll stick with what I have.I don't plan on doing any drag racing,just cruising mainly.Thanks for the info and saving me some money.
 
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