(US Patent #5,007,387)

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Chevy big block motor with Arao 32v heads. Heads bolt onto all 454, 502 or larger big block Chevy’s. All high performance camshafts can be used. All standard flat top pistons can be used up to 11.0:1 compression ratio. Higher compression pistons available from all piston manufacturers. 8 exhaust ports on each head is standard. Adapter available to bring 8 ports into 4 so  standard headers can be used. Intake ports are higher than Big Chief heads. Special sheet metal intake manifold is needed. Heads are fully water jacketed billet aluminum.

Download Big Block Chevy Brochure (Adobe Acrobat)

Big Block Chevy 32 valve heads

4.5" bore Big Block (502 based)

32v heads for the Big Block Chevy 502 cu in 4.5” bore and larger, standard 4.840” bore centers. Uses standard head bolt locations, standard performance cams, pistons, exhaust headers, and accessory holes in ends of heads. Mounted on 4.5” bore block. Note: Height of intake port that is located on bore centers.  Custom sheet metal intake manifold is necessary. No compromise in port flow here. Note:  Water ports in front of heads, water to be collected and returned back to radiator. Use external thermostat housing as used in conjunction with some brands of blower manifolds.

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INTAKE PORT FLOW @28”
             LIFT                        CFM                                 
             .100”                        137.
             .200                          214.
             .300                          326.
             .400                          410.
             .500                          470.
             .600                          508.
             .700                          561.   
Valve covers, spark plug installs through valve cover. No gaskets in covers, uses endless “O” ring in face and “O” rings around spark plug tubes.

Shaft mounted intake rockers at top, exhaust rockers at bottom. 4150 Chromoly rockers. Standard big tube headers bolt on. Slight notching of the top corners of the block necessary for exhaust pushrod clearance. Similar to Chrysler Hemi block notching for exhaust pushrod clearance. 

Dual valves with a huge increase in valve area is accomplished with smaller valves. Hence less lift is necessary before peak flow is reached. This results in better high speed valve control and much better valve spring life. Valve lifts can be .200” less for the same application of motor use with the 4v heads. Also camshafts with 15 degrees less duration can be used for the same application, with still a huge increase in Horsepower and Torque .This is due to the way 4v heads breath, much, much more air flow right off of the valve seat, all the way up to full lift and back down. This is called more area under the curve. 

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Exhaust rocker on left, Intake rocker on right. Shaft mounted rockers are bolted directly to cylinder head. Valves are adjusted with swivel adjusting screws. Use standard over the counter performance cams. Use all standard valve lash as recommended with cam manufacturers.

Light, strong, high speed valve train. Ratio of rockers is 1.5:1 so that over the counter performance camshafts can be used. Remember that with dual valves much less lift (.200” less) and duration (15 degrees less) can be used for the same shape of power curve, just more power everywhere on that curve. 

32v heads fit 4.5” bore or larger. Dual 2.02” intake valves have curtain flow area equal to a single 4.04” intake valve. (curtain flow area is defined as the area of perimeter of the valve multiplied by the height of the lift multiplied by 2 valves). 

Dual 1.6” exhaust valves have curtain flow area equal to a 3.2” exhaust valve. Note: Centrally located spark plug. The second spark plug is at top of chamber between exhaust valves (at the 1:00 o’clock position in this photo. Standard head gaskets can be used, with all water holes in gaskets aligning with water ports in heads.

Lug for 6^th head stud at 10 degrees can be drilled to align with aftermarket performance blocks such as a Dart

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Standard big tube headers bolt directly to heads. 2.250” headers recommended. Exhaust flange is 1” wider out toward the wheel wells. Heads are fully water jacketed billet. Note: Large water access plate to machine in huge water jackets. Also note second spark plug in approximately the same position as in the stock heads, underneath exhaust headers. 

4.25" bore Big Block (454 based) Heads

• All standard high performance cams can be used
• Standard flat top pistons up to 11.5:1 comp. ratio. Higher compression ratio pistons available.
• Standard exhaust headers will bolt up with the 2 into 1 aluminum adapter available. 
• Combustion chamber volume variable from 90cc to 125cc depending on bore size.
• All accessories on the ends of the heads can be bolted on.
• Sheet metal intake manifold must be used. We can fabricate this for you also, either blown or normally aspirated.
• 200 + hp more than 2 valve aluminum racing heads.
•  2: 1.94” intake valves have curtain flow area equal to a single 3.88” intake valve.
• 2: 1.6” exhaust valves have curtain flow area equal to a single 3.2” exhaust valve.
• Intake ports over 500CFM @ 0.700" lift @ 28" test pressure.
• Exhaust ports over  400CFM @ 0.650" lift @ 28" test pressure.

• Pair of valve covers
• Rocker Arms
• Heads, Complete with springs, and valves, assembled

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Combustion chamber volume variable from 90cc to 125cc depending on bore size.  Intake valves. 2: 1.94” have curtain flow area (perimeter of valve X height of lift, the actual window that the air flow sees) equal to a single 3.88” intake valve! Exhaust valves. 2: 1.6” valves have curtain flow area equal to a single 3.2” valve! 600 CFM intake and 400 CFM exhaust flow!

Can yield up to 200 hp more than 2 valve aluminum

All standard head gaskets can be used, all water passages in head are same as standard heads.

All accessory holes in ends of heads are drilled and tapped.

Performance mechanical roller lifters can be used, if vertical bar type cut open for lightness.

All performance mechanical roller camshafts can be used.

One pushrod operates two valves simultaneously, through a shaft mounted, forked rocker arm with an adjusting screw at each valve tip.

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Showing intake ports, 3” wide X  2” high.

Ports are centered to cylinder bore and higher than Big Chief heads. Up near valve cover sealing edge.

Sheet metal intake manifolds must be used. Available from Arao Eng. Inc. or other manufacturers.

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View through intake ports. One intake divided into two.

500 CFM with 454cu in 4.250” bore and 2 intake valves at 1.840” each

600 CFM with 502+ cu in 4.5” bore and 2 intake valves at 1.940” each

Hidden head bolt in intake tract to use standard bolt pattern. Similar to SB-2 small block heads.

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Exhaust port comparison. Upper head is standard iron 454.

Center head is adapter installed on 32 v. to bring 8 ports into 4 using standard bolt pattern headers.

Lower head is the 32v head with standard 8 port exhaust, one port per valve

430 CFM with 8 ports. 400 CFM with 8 into 4 adapter

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View through exhaust port, from outside in.

8 pipes, 2” diameter each needed to bolt up to these 430 CFM ports.

8 port Steel flange available. or 8 into 4 aluminum adapter available.

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This is how the valves are actuated. The standard pushrod pushes a shaft mounted rocker arm with instead of one arm extending from the other side like a Chrysler hemi, it has two arms. With separate adjusting screws for each valve. They have a swivel foot adjuster like a Turbo Porsche, or (like a “C” clamp end if not familiar).

4 valve heads have a different rate of flow than 2 valve heads. Not only do they flow more at full lift but their full flow lift occurs at a lower lift. This is because the increased valve area is done with 2 smaller headed valves. (full flow of a valve is reached at a valve lift of 30% of valve head diameter, with the heads of the valves being smaller the full flow lift is also smaller although still much more). So instead of lifting the valves as high as the regular 2 valve heads do, we opted to have better high speed valve control and not uselessly lift the valve further than needed. To accomplish this and still be able to use over the counter  big block camshafts, we levered the ratio of the rockers back from the standard 1.7:1 to our optimum 1.5:1. In doing this all standard camshafts are now usable. Although with caution, for they can still be optimized upon for 4 valve operation. This is due to the way that 4 valve heads breathe. Not only do they reach their full flow condition at a lower lift, but they do so with a much fatter flow curve. Meaning they flow much more and at a faster increasing rate than  2 valve heads. For instance, at only .050” lift they already flow 50% more than the best 2 valve heads. And this is amplified throughout the lift curve and the lowering curve. This means that there are many more crankshaft degrees of high flow cylinder filling, and cylinder exhausting. 

Our experience with the 4 valve breathing characteristics enable us to design a camshaft with the right profile for your application. All optimized special camshafts are available through Arao Engineering.

The pushrods see approximately the same pressure as in a two valve operation. This is due to the generally lower valve lift, and the generally less radical cam profile with the 4 valve configuration.

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Download Big Block Chevy Brochure

(Adobe Acrobat PDF Document)

Starting at $10,000.00

Complete Head Package