BBC Cylinder Heads? (oval port)

[56-210Sedan]

I am trying to get some answers/opinion on something i am investigating on BBC Cylinder Heads. To start i can buy a set of cast iron 049 cylinder heads ( $350) that have been ported and polished, flow benched, CC'd, the 049 has 112CC combustion chamber 255 Intake and 119 exhaust ports

GM Performance oval port aluminum heads (12363392) have 110 CC combustion chambers 290 intake 110 exhaust ports price anywhere from $1,800 to $2,000 on average

AFR 290 aluminum heads 112 combustion chamber 290 intake ports, could not get exhaust info online i will call Monday $2,800 to $3,000 on average

So to the meat of my thread i am researching is to see if the cast iron head would work effectively with the ramjet setup for the 540 i am going to run in my 56, i know right off that the cast iron heads are around 60lbs heavier then the aluminum counter parts and intake runner numbers are up against the cast iron, but how do you think the cast iron 049 heads would work for a street driven car? i have no plans or racing this engine. The savings dollar wise is what really makes this interesting for me what are your thoughts bad or good i put my feelings on the shelf LOL

[chevynut]

I thought the weight difference was around 85 pounds between aluminum and iron. One thing to keep in mind is the aluminum heads also allow you to run a little more compression ratio. $350 seems like a steal compared to the price of aluminum heads, but I'm not sure what your objective is. Obviously OEM heads work, just not as well. I'd try to do some comparisons of the performance the way you intend to use the engine and consider your budget.

Here's some articles:

http://www.superchevy.com/technical/engines_drivetrain/completebuilds_testing/sucp_1208_big_block_heads_shootout_the_o_vs_r/

http://www.carcraft.com/techarticles/ccrp_0803_big_block_cylinder_heads/

http://www.chevyhardcore.com/tech-stories/engine/ultimate-guide-to-budget-bbc-cylinder-heads-under-2000/

[Maddog]

Even for a "street engine" those 049 heads are too small for a 540, so are the GM perf heads. I would use a slightly larger AFR head (305-310cc). The 049's would be OK if you were using a 454 cu in. Of course AFR is about the best out there and are costly but why bother with the cost of a 540 and ramjet to choke it with low budget heads.

[56-210Sedan]

I found this part out of one the articles very interesting,

Budget Big Block Chevy Cylinder Heads For Entry Level Street
Looking for an entry level set of heads for street use goes beyond price. Given that GM factory production heads commonly had runner volumes of 230 to 270 cc. Larger volume runners were used in GM’s performance versions. Aftermarket cylinder heads have improved airflow but must be matched to the camshaft, intake and exhaust systems for the optimal results. The heads listed below are good choices for an application that is intended to be higher performing than stock and still used on the street for daily driving.
Smaller ports and runners will keep the mixture of air/fuel at a higher velocity making driving from stop light to stop light and idle quality a lot more steady. With too large of a runner volume, a basic stock type engine will lug at low RPMs until it gets to cruising speed. Entry level heads are designed for engine where there are not too many high performance upgrades already installed and the engine will be running on mid to high octane pump gas. Optimal runner volume for these conditions is somewhere in the range of 270 cc to 290 cc.

The 049 are at 255 so that is below what they have but they also have had some extensive work done to them and so there flow numbers should go up. Maddog i understand some of what you say but as far as to small in what direction due you mean? valve sizes are the same as the aluminum heads 2.25 in 1.88 ex on all that are listed

[Rick_L]

On the valve size, it doesn't matter how big the faucet is if the pipe leading to it is small.

[Maddog]

290 cc intake runner volume is too small for 540 cu in. 290cc is a good performance street size for a normal BB, up to about 460 cu in. An engine is an air pump, you limit it's ability by restricting the air flow, 290 cc heads will stop the 540 at about 4500-4800 rpm, it's like putting late model "peanut port" heads on a 454-stops making power at 4500RPM. You need 305-310 cc heads, if you were building a 540 with more of a high performance (race) type you would need 320cc heads. The low end will be very responsive with the smallish heads but will fall flat on it's face above 4500 RPM. Honestly, I can appreciate the "cost" factor but if you half ass the 540 you'd be better off building a 454. 305-310cc heads are small enough for a 540 to keep the low end peppy.

[JT56]

If your going with a 540, finish the deal and put some good heads on it. I believe you will be kicking yourself later! Now if you had a 454 or 496 then that is an option.

[56-210Sedan]

well then getting back to the drawing board then this is the biggest set i could find out on the market that comes close to those volumes. Remember i have to stay with oval port to make the ramjet intake work. http://www.race-mart.com/product.asp...ciGfgodlA0A9g#

[Maddog]

Or consider the AFR 300, a little more money but AFR quality is hard to beat. Either will work well.

[56-210Sedan]

Yikes!!! by almost another grand LOL i understand you on the AFR being a better quality head, problem is i am to old to sell myself to make that kind of coin LOL. Well then how about them ore-ida tater tots.

[Maddog]

I would also be concerned if that Ramjet will function well with a 540. Hopefully you've looked into this. I would call AFR and talk to their tech dept about what you're doing and want and see what they have to say. AFR is probably the leading expert in head flow.

[chevynut]

On the valve size, it doesn't matter how big the faucet is if the pipe leading to it is small.

Conversely, it doesn't matter how big the pipe is if the faucet is too small.

At some point the port size is bigger than the valves can flow with a given camshaft. Most performance BBC heads have 2.25" intakes and 1.88" exhaust valves. How big of a port can those valves support, with a cam designed for the street?

I really think you can over-do the port sizes to the point that they don't help anymore, and may actually hurt. Bigger isn't always better.

"While intake port volumes are a valuable guide in cylinder head selection, remember that port volume is not necessarily proportional to port flow, and that just because one design has 340-cc runners and another has 320s, that doesn’t mean that the larger head flows more air or makes more power, although that is usually the case. In fact, if two heads with different- size runners have the same flowbench numbers, you are generally better off with the smaller runner head, especially if low-RPM throttle response and drivability are important. Also, when comparing port volume of spread port cylinder heads, remember that because these heads have raised runner locations, they are longer than conventional cylinder head intake ports, and the port volume is greater due to the extra length. A 400-cc raised-runner intake port may actually be smaller in cross-sectional area than a 380-cc conventional intake port. Be careful when comparing apples to oranges.
There are aftermarket oval port heads with about 290-cc intake runners, and small rectangular port heads with around 300-cc ports. I’ll bet you a year’s supply of donuts that the power difference on the dyno is minimal, and you could never tell the difference from the driver’s seat."

http://www.cartechbooks.com/techtips/killerbigblockchevy/

If I were you Marty, I'd select a camshaft that you think will work well on the street and see what heads work well with that camshaft. Whatever you do, don't try to use the GM Ramjet twin 48mm throttle body or everything else is worthless. It only flows 635 CFM and was designed for a 350.

[chevynut]

Yikes!!! by almost another grand LOL i understand you on the AFR being a better quality head, problem is i am to old to sell myself to make that kind of coin LOL. Well then how about them ore-ida tater tots.

Some guys just like to spend other guys' money.

Keep your objectives in mind, and don't try to build an engine with as much horsepower as you can get, or it won't be streetable. On the street, torque is king. IMO you should try to maximize torque in the 4000-6000 RPM range and don't try to push over 6000RPM with a BBC. Think about how you drive the car on the street. I would look for a head with ports and valves that don't restrict flow with the cam that you choose. Trying to maximize airflow when you don't need the horsepower will just cost you more money.

[chevynut]

I see all sorts of aluminum BBC heads on eBay from under $1000 to $2000 a pair.

[Maddog]

Yup, other peoples money, the best kind to spend and freely