Magnus McLaren Head Studs and L19 Main Bolts



The Magnus Motorsports L19 upgrade can be purchased as a set of main bolts or head studs that are direct OEM replacements.

  • Main Bolt Kit : 10 Large Main Bolts with sealing washers and 10 Small Main Bolts with sealing washers
  • M12 Studs : 20 L19 Studs with nuts and washers

We used bolts on the mains instead of studs as original to stop any oil leakage that could occur, we also offer new sealing washers.

The dimensions are exactly to manufacture specifications and no adjustment to the block is necessary.  As with our other track application engine programs, we reached out to ARP to manufacture these bolts out of L19 to ensure a clamping force of over 1000psi.

These bolts are used exclusively in our 1300hp+ crate engines, McLaren M838T and M840T will also work on M838T.

Why L19 and not 625 Custom Age?  L19 and 625 custom age are both brand names of ARP INC.  They are not the actual name of the alloy.  L19 is similar to H11 tool steel and offers the right amount of stretch and torque holding capacity.   Over torqueing and torqueing to the yield with a 625 custom age bolt can cause undue stress on the engine block castings and can cause warping or cracking.  Always torque to the recommended specifications never more.

L19: This is a premium steel that is processed to deliver superior strength and fatigue properties. L19 is a very high strength material compared to 8740 and ARP2000 and is capable of delivering a clamp load at 260,000 psi. It is primarily used in short track and drag racing applications where inertia loads exceed the clamping capability of ARP2000.


Part Numbers

MMCENG7204-001 & 002 L19: M12 x 1.75 Larger Main Bolt (10pcs) & L19: M10 x 1.5 Smaller Main Bolt (10pcs) (20pcs total)

MMCENG7204-003    L19: M12 Studs (20pcs) with matching Nuts and Washers

Additional information

Weight 7 lbs
Dimensions 15 × 5 × 5 in
McLaren M840T Shortblock

Main Bolts Large (10pcs) and Small (10pcs), Studs (20pcs), Main Bolts and Studs (40pcs)