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Old 02-13-2012, 11:23 PM
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Big block chevy heads

hey guys,

wanting some general info on big block heads for a street/strip type aplication.. Im trying to learn more on big block heads but seems there are alot more options and varables with bbc heads vs sbc heads.. i can look at a sbc heads and know if its small or large in different ways, but bbc heads i dont know whats big or to small.. like combustion chambers, intake runners, exhaust ports valve size etc.. from what i have read tho it seems 119cc combustion chambers are more common, just like a 64cc heads for sbc.. any general info is appreciated to help me understand a bit more..


Jon

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Old 02-14-2012, 07:11 AM
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Jon,

Choosing a BBC head can be an exercise, alright. First you must establish what you want to "do" with the engine. Then, what "size" engine (displacement). You'll get bombarded with "bigger is better" but that's not always the case. And what you WANT is really the "bottom line". Some will bad-mouth 396 or 427 because they're "too small". I disagree. Either is a very effective street engine OR "race" engine when properly built. What they lack in low-end power they make up for with rediculously high revs.

"Oval port" (referring to the intake opening) heads tend to make more low-speed and mid-range power. "Rectangular" port heads are the factory "high perfromance" heads. Rectangular ports tend to NOT make any low-end power, and revs usually need to be at least 3,500 before power production begins. And this is true of 454, as well as 427 and 396.

The aftermarket throws MANY "wrinkles" in. The engine size is also very important. The larger engines (500-plus) don't have near the issue of low-end, but conversely can run "out of breath" before they reach their true power potential.

What exactly are you after?

Jim
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Old 02-14-2012, 10:10 AM
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Quote:
Originally Posted by 67-4-fun
hey guys, wanting some general info on big block heads for a street/strip type aplication.. Im trying to learn more on big block heads but seems there are alot more options and varables with bbc heads vs sbc heads.. i can look at a sbc heads and know if its small or large in different ways, but bbc heads i dont know whats big or to small.. like combustion chambers, intake runners, exhaust ports valve size etc.. from what i have read tho it seems 119cc combustion chambers are more common, just like a 64cc heads for sbc.. any general info is appreciated to help me understand a bit more..Jon
Here's a piston that will work nicely with the 119cc heads in a 454....
http://www.kb-silvolite.com/kb_car/p...tails&P_id=117
It makes 10.2:1 static compression ratio. Use a cam that closes the intake at around 45 degrees ABDC to make the dynamic compression ratio work out.
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Old 02-14-2012, 05:23 PM
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Street/strip could mean a 632 bruiser vs a baby 396.Obviously once size does not fit all.
Imo...anything less than a 500 incher or a high winding 427 will not require large by huge rectangulars for cylinder filling.
The bathtub chambers where a dirty head and shroud the intake valve.The open chamber solved these issues..but had a not so friendly high dome to achieve a decent static cr.The modern day semi open is miles ahead of the old oem heads.Best of both worlds..with a kidney/heart shape semi.
Split pattern cams have bandaided bbc,s for ever.The modern head typically has a raised exhaust port for improved flow.
Without knowing your combo..a healthy 454 street/strip deal would sport a oval/roval type port 290cfm/semi open 110cc chamber and a raised exhaust port .
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Old 02-14-2012, 06:03 PM
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I really have nothing in mind as far as a build goes, just basically details on different heads for bbc.. I've terms like peanut heads and such and I'm just trying to fimilarize myself a bit with bbc to know what can be good or not so good
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Old 02-14-2012, 06:26 PM
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Yeah..lotsa stuff to consider.Peanuts for a grunt motor right up to spread ports for a Pro Stock,and everything in between.Toss some Aries hemi heads in..and you could research for hours on end.
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Old 02-14-2012, 08:15 PM
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In my opinion the best street heads ever made for a mild to mid hi performance built BBC were the early oval port heads with 113cc chambers. If you can find a set o those you can build a BBC 427 or 454 up to around 450-475 hp easily, and still have plenty of good low to mid range power.
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Old 02-14-2012, 08:32 PM
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Peanut ports are the small ones. They are best for mild street stuff, although there are a couple builders out there putting together crate engines with Peanuts in the 350-400 hp range.

Oval ports are in the middle and usually flow quite well. 049 and 781 casting numbers are the go-to factory street performance head for BBC.

Rectangle ports are huge. IMO they should be left to race-only or a massive-cube shortblock. They flow better than most oval-ports, but the ports are so massive that velocity is pretty crappy.

Here is a photo that shows the Ovals next to the Rectangles, then a photo showing a peanut port head with an intake gasket designed for a rectangle port head.



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