Subtract a couple hundreths for safety and you've got your available clearance for valve lift. 480 without cutting the guides.Īn exception would be using a cut down keeper or retainer for a bit more clearance,but not enough for the LT4 cam.Įasy to measure,simply measure from the bottom of your keeper to the top of the valve guide. With stock heads,you will not go farther than. The article your referring to stating it's safe to go farther with vortecs is more than likely talking about one of the other vortec heads.īesides the stock head that came on the truck,there are aftermarket (from GM) vortec heads that come with the machine work done already. The spring/keeper will bottom out on the guide.
480 lift on stock vortec heads,after that you have to machine down the valve guides. PCM tuning will bring all this stuff together, and will bring out the power and drivability you seek. I would go ZZ4 cam, 1.5:1 roller rockers (narrowbodied rockers are what you need(GMPP has both 1.5 and 1.6:1 roller rockers available as does Crane Cams), Comp Cam Beehives, 787-16 steel retainers. The GEN 3 LS1, 5.3, 6.0 4.8 use a different valvestem diameter thus the stock GEN 3 retainers cannot be used even though their valvesprings can be used on the GEn 1E Vortec 元1 head.Īny of the above combos will run the ZZ4 cam safely.Ī ZZ4 cam will not affect your towing adversly, it will probably improve it. You can install a set of LS6 Beehive springs or Comp Cams 26915 or the firmer 26918 springs with the 787-16 steel 7° retainers or 788-16 for the titanium retainers.
525"/.525" with 1.6:1 rockers.Īt the higher lift levels I would be looking into screw in rocker arm studs or at least pinning the stock studs into the heads. If youw ere runningteh LT4 Hotcam 218/228°. I might be tempted to stick with the 1.5:1 rocker ratio with the ZZ4 cam. Stepping up to a 1.6:1 roller rocker will make that lift.
Too much for the stock 元1 Vortec heads and stock retainers/valveseals.
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