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The 6.0 I'm looking at already has an aftermarket cam — what do I need to know about its valve springs?

Find out what cam and springs are in it. Springs have to match the cam's lift and duration: too weak causes valve float at rpm, and too little travel causes coil bind, which can damage the cam, lifters and retainers.

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  • Ask for the cam card. It lists the recommended spring rates.
  • If nobody knows what springs are in it, plan on replacing them with springs matched to the cam.
  • Installed height depends on any head machining and gasket thickness, so check it as assembled.

How to choose:

  • Start with the cam card. Cam makers list recommended spring rates for the lift and duration, even if they don't name a spring.
  • Lift: more lift compresses the spring further. The spring has to handle it without coil bind (coils touching), which can damage the cam, lifters and retainers.
  • Duration: longer duration keeps the spring compressed longer; higher-rate springs prevent valve float at rpm.
  • Your heads as assembled: installed height changes with machine work (decking or surfacing) and head gasket thickness, so check it on your engine.
  • Type: single springs suit stock and mild cams. Performance cams want dual springs or high-rate singles. Beehive and conical springs cut weight at the top for rpm without going to duals.
What we recommend

Assume the springs need to match the cam, because stock springs are barely adequate for the stock cam. For reference, 01 LS6 springs are good to about 0.540 lift and 02-up LS6 springs to about 0.580, so anything bigger needs aftermarket springs. A common budget upgrade is the Comp beehive, and there are two versions: the original 918 is rated to 0.600 max lift (130 lbs seat at 1.800 inch, 318 lbs open at 1.200, coil bind 1.085), and the redesigned blue-stripe 26918 is rated to 0.625 (about 125 lbs seat at 1.800, coil bind about 1.100); for more lift, Crane duals and Comp 921s go to 0.650, while Comp 977/978/987 duals need pocket machining. If the seller can't tell you which springs are in it and what lift they're rated for, budget for a full spring upgrade or walk away.

Check this first:

  • Cam lift versus the spring's max lift rating
  • Which springs are actually installed (ask for receipts or part numbers)
  • If they're Comp beehives, whether they're the original 918 or the blue-stripe 26918 (different ratings)

Careful: Springs that aren't rated for the cam can fail or float the valves, which risks valve-to-piston contact and serious engine damage.

Based on what we've seen work across our own builds, our friends' builds and the wider LS community, reviewed by our lead shop tuner (over 20 years of LS and LT tuning experience). Every combination is different, so use at your own risk and check our safe tuning limits before any wide-open pass.

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Check this first

  1. Cam lift versus the spring's max lift rating
  2. Which springs are actually installed (ask for receipts or part numbers)
  3. Whether the 918s are the later blue-stripe 26918 version

Try this, then this

  1. Identify installed springs by part number
  2. Compare cam lift to the spring's max lift
  3. Upgrade to a spring rated above cam lift with margin if mismatched

How you know it's fixed

  • Installed springs identified by part number and rated above the cam's max lift with margin

Still not fixed?

  • If the seller can't identify the springs, budget for a full spring upgrade matched to the cam

Time and cost: A spring upgrade is a few hundred dollars in parts; unknown springs are a walk-away signal or a priced-in upgrade

How do I check pushrod length and lifter preload on an LS engine?
What we recommend

We recommend checking pushrod length by putting the lifter on the cam's base circle with the EO/IC method, finding zero lash with a checker, then torquing the rocker to 22 lb-ft while counting the turns. One turn of the stock M8x1.25 rocker bolt equals about 0.047 inch of lifter preload, and the target is roughly 1 1/4 to 1 3/4 turns. Starting around 7.400 inches is a reasonable baseline; in the builds we've seen, 7.425-inch pushrods commonly gave about 0.050-0.060 inch preload with LS7 lifters, stock heads, MLS gaskets and cams over 0.600 lift. Re-check length any time you change the valve job, mill the heads, or change gasket thickness, deck height or cam base circle.

Check this first:

  • Lifter is on the base circle (EO/IC) before measuring
  • Any changes to head milling, gasket thickness, deck height or cam base circle since the last check

Careful: Wrong preload can cause valvetrain noise, lifter failure or valve-to-piston contact, so measure rather than guess.

Check this first

  1. Confirm whether the lifters are hydraulic or solid before setting preload
  2. Make sure the cam is in a known position

Try this, then this

  1. EO/IC method, 1/2 to 1 turn past zero lash
  2. Recheck any noisy rocker

How you know it's fixed

  • Quiet valvetrain, even preload across all sixteen

Still not fixed?

  • If it's noisy after, recheck preload — one loose rocker is the usual culprit

Time and cost: An hour of patience; free

What should you do about rod bolts and valve springs on a stock-bottom-end LS that will see 7,200 rpm?
What we recommend

We recommend upgrading the valve springs and rod bolts, along with the camshaft, before regularly spinning a stock-bottom-end LS to 7,200 rpm. Stock springs and rod bolts are the weak points at that rpm, so they should come first. If you keep pushing for more, the next step we've seen work is a forged rotating assembly (crank, rods and pistons), which has held up at 7,200 rpm in a 383ci stroker.

Check this first:

  • That the springs match the cam's lift and rpm range
  • Rev limiter set to your intended redline

Careful: Sustained 7,200 rpm on stock rod bolts and springs risks valve float or a broken rod and a destroyed engine.

Check this first

  1. That the springs match the cam's lift and rpm range
  2. Rev limiter set to your intended redline

Try this, then this

  1. Springs + rod bolts + cam
  2. Forged rotating assembly if pushing further

How you know it's fixed

  • No valve float, rod bolts upgraded, rev limiter set sensibly

Still not fixed?

  • If you want sustained high rpm, forged crank/rods/pistons are the next step

Time and cost: Springs and rod bolts are cheap insurance; a forged assembly is the big step

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