Gary Z

Valve events for the stock LS7 camshaft (IO 11 degrees after TDC, EC 9 degrees before TDC) indicate that valve reliefs are not strictly necessary. Why then do LS7 pistons have valve reliefs? I see two possible reasons. To provide a safety margin in case of valve float or as a convenience because GM expects that a larger camshaft may eventually be desired. Does anyone here know more about this? I’m just curious and wondering.

ramairws6

iTrader: (33)

Allrighty then!!

kistlerjm9

iTrader: (24)

11 Degrees gives u more clearance hence the reason above is not an issue. possibly due to the stage 2 and stage 3 cams gm designed now avail through SDPP.

Greg Fell

iTrader: (9)

that gives you more clearance, not less

WE TODD DID

iTrader: (2)

I would imagine the pockets are there to help the air flow around the valves.

pcf_mark

iTrader: (1)

It gives the cast piston a nice convenient place the crack too.

I have several examples!

Andrew91GT

iTrader: (6)

Either to reduce compression or to provide for future upgrades, or both.

Schwanke Engines

iTrader: (1)

I believe it could be so the engine could be upgraded with the said aftermarket cams, especially for road racing. Not certain. Katech should be able to answer fully on this subject.

bhop42

iTrader: (2)

Must be a trend because I recently found out my LY6 engine also has valve reliefs.

edcmat-l1

iTrader: (10)

BTW, they are 12 degree not 11. And yes, the less of an angle, the more PTV clearance.