LT4 Hot Cam Specs:

    The hot camshaft is designed for all hydraulic roller camshaft small block engines produced from 1986 to present including the Gen I, Gen IE, and Gen II variety. This camshaft will not work with the latest small block Gen III engines such as the LS1. Proper valve lash is maintained on LT4 engines which are equipped with the production "net lash" non-adjustable rocker arms. The camshaft includes a fuel pump lobe for those applications requiring a mechanical fuel pump.
Hot Camshaft (P/N 24502586 Specifications
  Intake Exhaust
Lobe Lift 0.328” 0.328”
Valve Lift    
@ 1.5 ratio
@ 1.6 ratio
@0.006 cam lift 272° 281°
@0.050 cam lift 210° 228°
Lobe Centerline 109° 115°
Lobe Separation 112°

Camshaft Dowel Pin
     The dowel pin length is configured for the “pin drive” cam driven distributor used in some model year LT1 and all L99/LT4 applications. If the camshaft being replaced has a shorter dowel pin, lightly tap the dowel pin in so that it protrudes 0.310” from the front of the camshaft surface.

Roler Rocker Arms
     The 1.6 ratio self-aligning roller rocker arms (P/N 12370839) included in the HOT cam kit are to be installed per the instruction sheet contained in the rocker arm box.

LT4 Valve Springs
LT4 Valve Spring Specifications
Part Number 12551483
Material Chrome Silicon SuperClean
Outside Diameter 1.337”
Inside Diameter 0.906”
Installed Height 1.780”
Seat Load 101 lbs.
Average Spring Rate 331 lbs./inch
Solid Height 1.215”

     Using the supplied LT4 spring seat (P/N 10212809) and retainer (P/N 10212808) with a late model aluminum head (350 HO, LT1, LT4) will provide the correct 1.780” installed spring height. Other small block cylinder heads may have to be machined to accept the valve spring diameter or for proper valve seal to retainer clearance.

Balancer Hub Removal
     Kent-Moore tool J-39046 is required when removing or installing the balancer hub from the crankshaft on 1992-97 L99/LT1/LT4 engines. The tool is available from Sallee Chevrolet or directly from Kent-Moore at:

Kent-Moore Automotive Group
Spx Corporation
29784 Little Mack
Roseville, MI 48066-2298
1-800-345-2233/FAX 313-578-7375
Monday through Friday 8:00 a.m. to 8:00 p.m. EST

Heavy Duty Timin Chain Set
     A heavy Duty timing chain set is mandatory for engine operation above 5,500 RPM. A 1/2” roller timing chain, crank gear, cam gear, and billet water pump gear are available under part number 12370838. The cam gear in the above kit is configured for “pin drive” applications. Non- “pin drive” applications will require updating the front cover, distributor, and distributor vent harness to “pin drive” configureation components.

From SDPC website