Looking to buy a 6.0 short block to build during winter. Came across a rebuilt 6.0 that is bored 20 over with ls2 rods and speed pro piston heads and stock crank. My question is will it work with my 799 heads milled .035 ? Anyone done anything similar I know you should check for clearances but the heads on my current motor. I only have 91 octane max available.

 

Do the pistons have valve relief? It can work. I've cut my own valve relier into 2 motors now.

 

Depends what height the pistons are installed at and the cam.

Also what Txsilverado mentioned above.

 

Comp ratio is going to be really high, maybe higher than 11:1 just FYI. What's a regular ls2? 10.5 or 10.9:1? Add to that you have cut heads and a larger bore. She'll run good, just hit her with premium and probably retard some timing.

 

they are flat top pistons

 

Well they are asking 1600 for the short block. There are also reconditioned lq9 short blocks for 1500 out in California that's pretty much the price am I better off going with a stock reconditioned lq9 instead ? Really just looking to run n/a I have a heads cam 4.8 currently and it's fun to drive but now I found myself wanting more

 

Ls2 is 10.9:1 stock so you will be well into the higher 11's depending on gasket thickness. I would be concerned about piston to valve depending on the cam choice. Of ccourse piston height matters here too....... LS2 and LQ9 use the same rods.... and if the speed pro's are just some flat top it's just a rebuilt LQ9 no different than the remans other than maybe piston brand. If you want answers on specifics you need a grind in mind to start from.

 

let's say the cam choice has low lift I was thinking some where around 228 duration

 

228 isn't lift... that's duration which plays a major role. 228 with a .600 lift like TSP offers would be in the realm of valves kissing pistons.

 

Im a fan of stock bottoms. I would get a stock bottom lq4 if you insist on using your 243 heads.

317 heads are cheap and have the same flow characteristics as a 243 with less compression. You can probably sell the 243 for 400 and pick up 317 for 200 and come out even