Ok so my lil 4.8 has 243's, what springs and valves do the NNBS truck's version of 243's come with? Are they still the 64cc chamber like the ls6 version?

 

Same casting head, standard valves, springs unknown.

 

Wrong...09's are GEN IV... Square port stuff. Unsure if chamber size is different.

 

why would they have the same casting number if they were different

 

No he is correct... 243 are 243.. There is no difference in them or they would have different casting numbers

 

Do they have the LS6 springs??

 

Pull the oil filler tube and you can see the springs easy, if theyre yellow youve got the LS6 springs.

 

From what I've found online, the only difference between them and the LS6 vette heads are that the valve seat material was changed for higher mileage durability and and the valves are standard valves not the sodium filled version, and supposedly they have the LS6 springs.

 

Popped the oil fill tube out, springs are not yellow, may call the dealer tomorrow and get the part# for them and try to cross reference them.

 

243/799/ ls2/ls6 share the same Combustion chamber ( 64CC) valves are 2.00/1.55
the only difference is that the ls6 have sodium filled valves and have ls6 yellow springs.

and they have catheral ports , not rectangle*