This is HPI's Nitro Star K4.6 .28 size Engine with the pull-start.  This is a direct bolt in to any Savage monster truck, including the Savage X trucks.  This would be a great upgrade for any monster truck that uses a standard big-block engine.  This will get a stock Savage to about 45MPH, and with additional upgrades, higher speeds are easily attainable.  This engine has a quite a bit more power than a stock Savage 25.

Features:

• Composite construction slide valve, 3 needle carb with hand adjustable high speed needle (the stock carb settings are made flush for convenient "back to factory settings")
• 8 port chrome plated brass sleeve
• True ABC cylinder construction
• Purple anodized machined aluminum heat sink head
• Rear exhaust round port
• Cast aluminum crankcase features heatsink fins
• Machined pilot shaft crankshaft with collet preinstalled
• Knife-edge billet aluminum connecting rod with dual bushings.
• Dual stage air filter dramatically reduces intake restriction as it smoothes and straightens air flow

Includes:
Nitro Star .28 (4.6) glow engine
Glow Plug - HPI R5 cold plug
FREE Dual Stage Air Filter INCLUDED
Instructions and parts break down

Specifications:
Crankcase: 3.29" (83.5mm) (from rear of case to front without shaft)
Height:    4.40" (111mm) (from bottom of case to the top of the head)
Width:     1.81" (mount flange)
Mount Holes: 1.42" (measured from center to center width)
Mount holes: .82" (Between holes front and back)
RPM:         Max 39,000 RPM
Horsepower:  2.9 @ 35,000 RPM
Crankshaft diameter: 5mm (clutch bell area)
Crankshaft diameter: 6.7mm (threaded portion)
Crankshaft screw: 3 x 12mm caphead screw
Capacity:    4.60cc (.28 ci)