HELP PLEASE.

[Maximus1]

Ok, I have a 2004 LT 5.3L Flex fuel L59 engine. I currently have the cast #862 heads. I just purchased a rebuilt set of cast#799 heads. I'm sending them off to have them CNC ported and milled .030 to match the 862 compression ratio or maybe even .040 to up the compression ratio. Will I still be able to use the same pushrods or will I need to purchase shorter pushrods. I think the stock pushrods are 7.4" in length. Theoretically if I mill the heads .040 then my pushrod length needs to be 7.36 in length? Is this correct? Is that much really going to matter on a hydraulic lifter and if so can I buy a pushrod with that exact length.

 

[Maximus1]

Also is there anything else that I need to know or have before I do the swap. I'd like for everything to go smoothly. I do know that if I go with the .040 milled I will have to have the intake milled as well. Any help or advice would be greatly appreciated.

 

[RED TAHOE LS]

Tom, pushrods should not be a problem, although as a mere suggestion, extensive cylinder head " port/polish" is normally used in high rpm applications for the best benefit. For street use, leaving the runners in the original cast(rough) condition works better for street use. If the heads are using the 2.02 intake valves, have the 5 angle valve job with bronze vavle guides along with 64 cc combustion chambers for optimum performance. That patacular configuration was earlier used in the fuel injected domed piston 327/4.0 x3.25 engines and required two (2) of the steel GM type head gaskets to attain descent compression ratio for street use and pump premium gas. Just a suggestion that I've learned through trial/error in my earlier years, good luck.
David g..............

 

[Maximus1]

Tom, pushrods should not be a problem, although as a mere suggestion, extensive cylinder head " port/polish" is normally used in high rpm applications for the best benefit. For street use, leaving the runners in the original cast(rough) condition works better for street use. If the heads are using the 2.02 intake valves, have the 5 angle valve job with bronze vavle guides along with 64 cc combustion chambers for optimum performance. That patacular configuration was earlier used in the fuel injected domed piston 327/4.0 x3.25 engines and required two (2) of the steel GM type head gaskets to attain descent compression ratio for street use and pump premium gas. Just a suggestion that I've learned through trial/error in my earlier years, good luck.
David g..............

Hey thanks David,
I should be getting my heads next weekend. I think he said that the intake runners will flow 330cfm's per cylinder and will keep the same vortex shape. Exhaust will flow 220 or 210 CFM'. I can't remember. 2.0" intake and 1.55 exhaust. The flow rate is with a .560 lift. My cam is only a .525 lift so I'm having him change the springs and I will change my 1:7 ratio rockers to a 1:8 ratio. This will put me at about .555 lift.

 

[Maximus1]

Also the 799 heads have already been milled .030 to match the 862 heads combustion chamber of 61 cc. I told him after I saw your post that I wanted the 5 angle valve job and the LS6 valve springs. You probably wouldn't believe me if I told you the amazing price I got to have both done. I should have a compression ratio of 9.5 to 1 with the dished pistons. I decided on this so if I want to supercharge or turbo it later. But now that I am thinking about it I may switch to a 6.0L then mod the hell out of it.