Speedmasterª LS-series cylinder heads is rapidly expanding. The LS (Gen3/4) platform has many design benefits over the earlier SBC engine designs, most notably the cylinder heads. Although the GM heads are good pieces, We have developed a superior line of heads for modern performance enthusiasts. Like all Speedmaster cylinder heads, the LS-series heads are produced using our -Gravity Casting- process. This process ensures a more uniform and robust casting, laying a strong platform to build on. Take a look below at our offerings, surely you will find a head to suit your application. If you require any additional information, or help selecting the correct cylinder head for your application, please feel free to call one our techs.
INTAKE / EXHAUST GASKETS
Unlike most other Chevy V-8's, the LS-series engines utilize individual O-rings around each port to seal the intake manifold to cylinder head. The LS1 / LS2 / LS6 style heads & manifolds use GM pn# 12533587 and the LS3 / L76 / L92 style heads use GM pn# 1290125. On the Exhaust side of the head, all non-LS7 heads utilize the same MLS header gasket. The part number of the exhaust gasket is GM pn# 12901125.
Speedmasterª is currently working on a line of MLS exhaust / header gaskets. Check with your salesman to see if we have a MLS exhaust gasket available for your application.
Because there are so many different bore sizes for engines in the LS-series, below you will find a list of Speedmasterª and Fel-Pro head gasket part numbers and their bore size:
Bore SizeSpeedmasterª MLS#Fel-Pro#
3.945" SM5221(pr.) 1160L/R (ea.)
4.100" SM5223(pr.) 1161L/R (ea.)
4.170" SM5224(pr.) 1162L/R (ea.)
These Speedmasterª MLS head gaskets feature 100% stainless steel construction. We don't use inferior mild steel like some other aftermarket gasket suppliers. To aid in sealing, both outer layers of our MLS gaskets are covered with a high temperature coating. You won't find better value in head gaskets for a LS anywhere.
HEAD BOLTS / STUDS
Unlike the early GM heads, Speedmaster heads use common length head bolts / studs. Starting in 2004, GM heads went to the same common length head bolt arrangement. By using bolt / stud registers that are all the same thickness, equal clamp load is created all the way around each cylinder. Our part number for the correct head stud kit is SM2464.
The ARP part numbers that work with our LS-series heads are # 134-3610 (bolts) and #23-4317 (12pt. stud kits)
Torque the 11mm. bolts / studs to 65lbs and the 8mm bolts / studs to 20lbs. using high pressure moly lubricant.
*Please consult your hardware supplier for their specific torque recommendations!
Be careful with your selection of sparkplugs in the LS-series engines. The Stock plug is a NGK TR5. We recommend that you use NGK TR6 sparkplugs on performance oriented engines. If you require a sparkplug colder that a 6 heat range, you will have to switch away from resistor style plugs, and into the NGK R5724-7 or R5724-8. These colder plugs dont have an internal resistor, so they my cause some slight RF interface. Usually it's not a problem unless you have a really sensitive aftermarket ECU, and even then it's not normally a problem.
If your prefer Autolite sparkplugs, use the AR103 for street / strip performance engines. The AR94 is quite a bit colder for those of you looking to squeeze N20, or heavy boosted engines.