Chevrolet and GM Performance Parts - 3.98” Bore Bow Tie 2 Bolt Bare Block

Chevrolet - CAST IRON BOW TIE BARE BLOCK (3.98” BORE)

This updated design has a decidedly different appearance, but retains its original part number. New tooling procedures have significantly improved the quality and dura-bility of this third-generation casting. This heavy-duty cast iron Bow Tie block has rough-bored 3.98” diameter cylinders, which can be bored to a maximum diameter of 4.090”. This block is recommended for maximum effort competition engines.

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Updated 09-08-2004.

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Street 10051181	Street 10051183	Amateur Comp. 10185047	Sportsman 12480047	Sportsman 12480049
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DESCRIPTION

3.98” Bore Bow Tie 2-Bolt Bare Block

P/N 10051183
This updated design has a decidedly different appearance, but retains its original part number. New tooling procedures have significantly improved the quality and dura-bility of this third-generation casting. This heavy-duty cast iron Bow Tie block has rough-bored 3.98” diameter cylinders, which can be bored to a maximum diameter of 4.090”. This block is recommended for maximum effort competition engines. The deck surfaces are thicker than production blocks, and the head bolt holes are blind tapped to improve head gasket sealing. The main bearing bulkheads are .900” thick and the front and rear bulkheads are reinforced with strengthening ribs.
The updated design on this Bow Tie block’s oil galleries now extend to the front and rear faces of the cylinder case. The ends of the galleries are machined flat, providing a smooth starting surface for the drill bits that bore the oil holes from the front and rear of the block. These extended front galleries can interfere with some camshaft drive systems; therefore, the clearance should be checked before engine assembly. The revised Bow Tie block has a boss below the bellhousing flange behind the #8 cylinder that can be drilled and tapped for a lifter valley oil scavenge line. Bosses were also added to the outer water jacket walls to allow coolant passages to be drilled between adjacent cylinders which have siamesed cylinder walls. Oil drainback holes in the lifter valley are now drilled instead of cast. Locating pads in the valley have been revised to accommodate the new tooling; although the pads differ from previous designs, they do not affect the block’s functionality. The updated design provides more consistency in the thickness of the cylinder walls and water jackets. The siamesed bore have a nominal cylinder wall thickness of .340” at the casting parting line (measured 2” below the deck surface).

Technical Notes: Oil dipstick hole is not drilled and the lifter holes are finish bored to production diameter .842”. 2-bolt main bearing caps are installed to simplify the installation of the heavy-duty steel main caps with splayed outer bolts. Bow Tie blocks are designed for crankshafts with 2.45” diameter main bearing journals. The Bow Tie casting block P/N 10051184 is machined for a one-piece rear main bearing seal used on 1986 and later production small- block Chevrolet V8s. Crankshafts designed for two-piece rear main seals can be installed in Bow Tie blocks using crankshaft seal adapter P/N 10051118. These blocks weigh 181 lbs.

SPECIFICATIONS:

Block Material:
Cylinder Wall Type:
Cylinder Deck Height:
Cylinder Bore Range:
No. Bearing Cap Bolts:
Cap Bolt Orientation:
Bearing Cap Type:

Cast Iron
Siamesed
9.025”
4.000”-4.090”
2
Straight
Gray Cast Iron

Crankshaft Journal Dia.:
Oil Sump Type:
Crankshaft Seal Type:
Design Max. Stroke:
Weight (lbs. - bare):
Intended Max. Hp @ RPM:
Intended Usage:

2.45”
Wet
1 piece
3.75”
181
400 @ 5750
Street