Hemi Head Chevy Big Blocks

Phil and Mary Leatherman’s “Wild Thang” exhibition rod

Phil and Mary Leatherman’s “Wild Thang” exhibition rod illustrates the enormous appeal of Arias heads in street rods and over-the-top hot rods. Note the spark plugs fitted to the end of each exhaust tube. Phil puts on quite a colorful show at local southern California cacklefest events.

Building Arias Hemispherical Head Big Blocks
with Mitech Racing Engines

Mitech Racing Engines in Placentia, California sports a lengthy list of record setting engines, particularly in land speed record racing. They also specialize in custom engines for racing and street applications; among them some radical Chevy big blocks equipped with Arias hemi heads. These heads are highly popular with racers and particularly with street rodders for their massive, in your face, we mean business looks that pretty much dominate a car's appearance (see photo above).

Traditional street blown Chevy engine with 8-71 blower and twin Hollwy carbs

Traditional street blown Chevy version with 8-71 blower and twin Hollwy carbs delivers a reliable 960 HP at 6500 rpm on pump gas with 10 psi boost; a perfect combination for an over-the-top street rod or a righteous street macnine like an Impala, Chevelle or Camaro.

Nick Arias, Jr. introduced his radical new 3-pushrod hemispherical-head conversion for big block Chevys way back in 1972. Intended to bring the Chevy V8 on par with the Chrysler Hemi in Top Fuel Eliminator, it never quite achieved that goal, but it quickly became a roaring success in drag boats, tractor pulling and various other drag racing classes. These early versions all used the Chrysler style oiling system. Arias subsequently introduced a follow-on Top Fuel version in 1975 called the “10-Liter.” This was a clean sheet design with greater displacement  and the camshaft raised 5-inches to provide clearance for very long strokes and to reduce valve train harmonics with shorter stiffer pushrods. It also featured shallower combustion chambers and valve train geometry similar to the Chrysler Hemi. Drag boat racers and tractor pull builders adopted it as a significant upgrade, but the NHRA objected to the technological changes considering them too far of a departure from a production-type engine and subsequently banned the engine from Top Fuel.


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The 8.3L version ultimately passed on to Fontana engines, Minor Brothers and B&B Performance where it enjoyed considerable success in Top Alcohol applications. B&B currently produces the cast versions for Fontana Engines and the Minor Brothers produce the billet versions. B&B also makes the gear drives and camshafts for both the 8.3L and the 10L engines.

Nick Arias Big Block Chevy Bonneville Lakester

Fred Blanchard's 439 cubic inch big block Chevy based Bonneville lakester engine propelled car to 250 MPH-plus speeds on gasoline.

In 1998 they revived the 10L engine to power Nick Arias III’s Bonneville lakester. The result was a 636ci normally-aspirated powerhouse built in conjunction with long time associate Mike LeFevers at Mitech Racing Engines in Placentia, California.With minor development, the 1,000 HP gasoline-fueled lakester put Nick Arias III into the Bonneville 200 MPH Club at better than 272 MPH. A second lakester owned by Fred Blanchard has run over 250 MPH with only 439 cubic inches in a big block Chevy based version also running gasoline. An ongoing program with LeFevers assembling and testing revisions and customer engines for racing and street applications has subsequently expanded the Arias head’s rising popularity in street rods and custom exhibition drag racers.

In 2004 the heads were again revised and changed to the current two-pushrod configuration with simplified valve train geometry and Chevy style oiling through the pushrods like a standard big block. For street rodders the appeal is obviously the visual charm of the massive hemi-head valve covers conveying a larger than life “bad boy” image. The Arias heads are powerful performers capable of meeting a variety of performance needs from drag racing to hot street rods and marine applications. 

Screwcharger on this 439 cubic inch Arias head big blockArias injector manifold controlled by a F.A.S.T. engine management system

Screwcharger on this 439 cubic inch Arias head big block pounds out 1200 HP with 8 psi boost.

Fuel Injected version features Arias injector manifold controlled by a F.A.S.T. engine management system. 540 cubic inch injected motor delivers 800-plus HP on pump gas.

World Products Warhawk block sporting Arias heads

Here’s an LS-based World Products Warhawk block sporting Arias heads, 406 cubic inches and 750 HP from a single four barrel. The intake manifold is a fabricated piece that Mitech can duplicate if necessary.

The heads have been FIA homologated and approved by the APBA for offshore marine racing and high-end hot rodders and show car builders love its robust, visceral appeal. We spoke with LeFevers and asked him to show us some of the many variations now available. He subsequently provided the accompanying look at the many variations of the Arias hemispherical head now in use. If you see something you like Arias is only a phone call away and Mitech Racing Engines has all the experience necessary to build any combination that strikes your fancy.

Click any image for larger view and more info:
Arias hemispherical head valve trainSmall bore race engineWorld Products iron block with an Arias copper head gasketintake pushrods and rocker arms
aluminum Merlin blockMerlin block with an Arias pistonOffset pushrod cupsNew Century aluminum block with a precision B&B Performance gear drive setup
Arias systemArias hemispherical headsArias pistonsLifter extension and long spindle dial indicator
New Century blockStroker crank gun drilled main journals, drilled crank throws and chamferred oil holesBillet main caps
 Offset distributor driveArias injector manifold 

The Arias BB-AH big block Chevy head kit easily adapts to most 10.200” and 11.200” deck G.M. factory or aftermarket blocks, with a few minor modifications. The heads are poured from 356 T-6 alloy and they incorporate full water jacketing throughout. Extra thick decks guarantee combustion sealing and resist coolant seepage. They use the conventional 2-pushrod setup, with one intake and one exhaust pushrod activating new needle bearing roller tipped rockers.

The Arias bolt-on kit or complete Crate Engine package is ready for the street rodder having the desire to stand out from the crowd; or the hardcore racer looking for the power and torque of a genuine Hemi® for their Rat Motor foundation. This is the same cylinder head that dominated drag cars & boats and tractor pullers for the last four decades, with today’s technology built in. Note the following specs.

Arias Big Block Chevy Hemispherical Heads 

Part# 101120-002-01 – Water jacketed, assembled (pair): $11,999.00
Part# 101120-001-01 – Solid, bare, with seats & guides (pair): Call


  • Fully machined 156cc hemispherical chambers
  • High-efficiency ports flow up to 414 cfm for intake and 311 cfm exhaust @ 28”, out of the box
  • 456 cfm intake and 386 cfm exhaust with “Race Option” porting. Excellent low to mid-lift flow
  • Stainless steel 2.375” intake and 1.940” diameter exhaust valves come standard
  • Titanium and Inconel valves optional
  • Manganese bronze valve guides
  • Heat treated ductile iron valve seats
  • Can accept valve springs up to 1.710” diameter, based on application requirements
  • Tool steel springs standard with custom race springs optional
  • Shaft style roller rocker arm assemblies with rocker oiling through the pushrods like stock Big Blocks
  • Investment cast 4340 steel roller-tip rocker arms with dual needle bearings and H-13 lash adjusting screws
  • Cast aluminum finned valve covers supplied with breathers, oil fill caps, o-ring seals, spark plug tubes and hardware. Choose either black wrinkle, hi-luster polished, carbon fiber or plain finish


  • Pushrod set
  • ARP head stud, nut, washer kit
  • COMETIC head gasket set
  • Oil drain back line kit
  • Hemispherical header flanges & hardware
  • Water Necks (2)
  • Water block-off plates (2)
  • Intake & exhaust gaskets
  • All related fasteners


  • ARIAS hemispherical piston kit
  • Intake manifold (carbureted/EFI, tunnel-ram or supercharger)
  • Oil drain back bungs


  • Billet valley cover kit
  • Billet carburetor/injector hat/throttle body manifold adaptors
  • Thermostat log, cast
  • Milodon Oil pan with oil drain back bungs
Arias hemispherical heads are also available for Chevy LS engines,World products WarHawk small block Chevys with LS top ends and small block Fords While admittedly expensive, Arias hemispherical head kits and crate engines are one of the best ways to make your engine package shine above all others at any street rod event. and they deliver proven racing level performance in almost any application you apply them to. 
Nick Arias, Jr. Racing Components
Mitech Racing Engines
Factory Recommended Engine Building Facilty
702 Dunn Way
Placentia, CA 92870

B&B Performance
8.3L and 10L heads, cams, gear drives