ACE MAMMOTH – Gen III HEMI CGI Engine Block | 4.300" Honed, Tall Deck, Naturally Aspirated

Maximum cubic inches. ACE MAMMOTH is the big-bore block — 4.300", the largest bore we make, plateau-honed at our shop and ready for ring fit, on a tall 10.75" deck with 937 roller-guided splay lifter bushings and a non-VCT 60mm roller cam tunnel. It is the only block in the fixed lineup that arrives finish-honed, which takes a machine shop operation and its cost out of your build.

Naturally aspirated only. At 4.300" the cylinder walls are specified for naturally aspirated use. This block is not rated for forced induction — do not run a supercharger or turbo on it. Building boost? Use ACE BOOST, or call us and we will spec a boost-safe big-bore combination for you.

This build

• Deck height & lifters: Tall 10.75" deck, 937 roller-guided splay lifter bushings
• Timing drive & cam: Non-VCT, 60mm roller cam tunnel
• Bore & finish: 4.300", plateau-honed — naturally aspirated only
• Price: $6,700 — direct from the manufacturer

Fitment

Max-displacement naturally aspirated Gen III HEMI builds — pro street, show, and NA race engines. Tall 10.75" deck, 937 splay roller-guided lifters for high-RPM valvetrain and ACE INC high-flow heads, and a 60mm roller cam tunnel for big lift. If your combination is naturally aspirated and you want every cubic inch available, this is the block.

Machine work required — none

Plateau-honed to final size at the factory. Ready for ring fit, no finish-honing needed. Against the rough-bore options that is a real saving in both machine shop time and cost, and at 4.300" it matters more than usual — this is the largest bore we cut, and it is finished on the same CMM-verified equipment that machined the block.

Supporting parts — read this before ordering

Three things about this block drive your parts list:

• Naturally aspirated only. No supercharger, no turbo. See the note above.
• Tall deck. Requires tall-deck-length intake, pushrods, and matching front-drive components. Standard 9.285"-deck parts will not carry over.
• Non-VCT. Runs a fixed-timing front drive, not compatible with factory variable cam timing. Needs a non-VCT cam ground to suit the 937 roller-guided splay lifters.

Call before you order and we will check the whole combination with you.

ACE CGI engineering — on every block

• Compacted graphite iron, 450 MPa minimum tensile strength (GJV-450)
• Big bore capability with 4 mm minimum cylinder wall thickness at maximum bore
• 6-bolt 4140 billet steel main caps on all five mains
• M14 head stud threads in the deck; 9.5" studs for roughly 50% more stretch compliance, so clamp load stays stable through a knock event
• True priority main oil gallery, dedicated lifter secondary circuit, and a straight filter-to-MOG feed with no 90° turns
• Dry sump feed provision; cast-in -8 ORB oil drain-back ports at the pan rail by cylinders 1 and 2
• Stroker clearance for 5.100" stroke with 2.200" rod journals
• Fully water jacketed — race block strength, street driveable
• Serialized casting, shipped with its CMM report and full casting and machining QC documentation
• Cast and machined in-house at our Michigan foundry and CNC cell

Ordering

PRE-ORDER — reserve your block now. Orders are fulfilled in the sequence received, and we confirm your production slot by email once your order is placed.

Full payment at checkout. Direct from the manufacturer — same price for everyone, no dealer markup, no middlemen. Free shipping within the USA.

Planning a big-bore build? Talk to an ACE engineer first: eric@aceinc.shop · (615) 924-2737. We will confirm the right bore and deck for your power target before you commit — especially worth a call if there is any chance boost is in the plan.

Need a different bore, deck, or cam setup?

ACE MAMMOTH is one fixed configuration. Every other combination — standard deck, stock lifters, VCT front drives, smaller bores rated for boost, rough finishes, and the 82mm Pro-Stock cam tunnel — is available on our Build Your Own Gen III HEMI CGI Block page.