The best for what? Drag racing? Street car? It all depends on your budget. Closed chamber hi perf heads are the best. Good luck finding any for cheap. Open chamber oval port are nice street heads. And are every where..
Its the way the chamber looks closed chamber looks way different than open chamber. The pistons you use for both heads can be different depending on wich heads you use also. If I remember right closed chambered pistons will work in open chambered heads. I think that an open chambered head is better than a closed chambered one. Google up some pics. I am sure some one out there has pics. A really good book to buy on big blocks is called How to hot rod big block chevys. Its full of good true info. For me it's a bible to build a good working big block. Built several using this book.. One other thing this is just general info. I only know what I have learned by reading and doing it for years. The heads are only a part of the building of a good running engine. And the entire package is what really matters. Some guys like 454 some like 427 some like 396-402. I prefer 327's and 427's. You have to realise that in the 60's we used to have good fuel. Today it's not even close to the way it was. And unless your willing to run 110 octane fuel your never going to feel what one of these motors is really about. A 12:1 to 13:1 big block is something to drive!! It sounds so good and you can hear the difference. I say go oval port 049 with pocket porting and manley street flo valves with roller rockers, choose a roller cam according to engine size and gear ratios. Best bang for the buck that I have found so far. But it all depends on what you want to do.
The early heads are closed chamber...
Oval port heads had 97 cc chambers and the Rectangular hi-perf heads had 106/107cc chambers. Closed chamber heads can be identified by the fact that the combustion chamber is not much bigger than the area of the two valves. Note: In later 1967, 68 and 69 oval port heads, the chamber was slightly opened and volume grew to 101cc.
In 1969, we saw the LIMITED introduction of open chambered oval port heads in 2-barrel applications an later 1969 production Aluminum head, late L-88/ZL-1.
By 1971, Hi Perf Rectangular heads were now 118/119cc and in the open configuration. This is to say the exhaust side of the ports had been opened up to reduce the quench and emissions. Look like 1/2 dome; flat on the intake side tapering to the exhaust side. Oval port heads were now in the Open configuration too. Note that 049 and 781 heads have chamber sizes that vary between about 115cc up to even 122 cc from reports I have seen here on Team Chevelle.
By selecting pistons and combustion chamber sizes, you have a lot of compression ratio options. Early style shortblocks came with domed pistons. Then domed piston with open chamber to use regular fuel in fleet applications. Then open chambers and flattop pistons for 70s trucks etc.
Good low-buck engines are flattop 454 shortblocks fitted with early closed chamber heads. Other guys use the later open chamber 781 and 049 heads but the 454 shortblocks require a small dome piston to get the CR from 7.9--8:1 up to 9:1 or greater.
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