I've heard the ultimate 6.2/6.5 combo is as follows....

18:1 pistons
pentistar IP (300hp)
6.5 turbo with intercooler
propane injection
nitrous

I was wondering what power that package could achieve.

I personally will end up with a 6.2 turbo intercooled setup with a home brew propane system. I was browsing ebay and came across these injectors....

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7949076959&category=33554

I thought that the fuel delievery was determined by the IP? 40hp just seems too good to be true.

With all that can be done tuning wise to the engine. how durable is the engine's bottom/top end to addtional power?

I personally built a 300 hp 6.5 with 18:1 Penninsular pistons, 4911 6.5 mechanical injection pump (wide open on the fuel setting) a rajay custom turbo(non wastegated), banks turbo manifold and stock 6.2 injectors. I talk with the techs at Penninsular and they recomended staying with the 6.2 injectors since they flowed very well and that there was not any major power to be had by changing them. I would tend to agree since I could make lots of black smoke and could get into the danger zone pretty easy with egt's. A larger injector could have possibly got the fuel in a little earlier to keep the combustion a little more advanced but with the other parameters (too much boost) I don't think it would be worth while. This engine ran very well and I tried not to exceed 20 psi of boost. When I first put this engine together, with about 1200 miles on it I hit 26 psi of boost while towing my jeep to the mountains, bad news, spun a main bearing.:mad: After that I would not exceed 20 psi max. As for propane and NOS, I wouldn't do it with a 6.2, the pistons won't take it. Even with the lower compression ration the 6.2 pistons have a much thinner crown that a 6.5 does and 6.2 pistons are relatively easy to crack and 6.5's with stock compression are a close 2nd if egt's are kept too high for extended periods. I like to use 1050 max preturbo on 6.2, 6.5.

6.5L pistons crack too, you can replace them and drive on. 26 psi boost,heh. The most I've seen is 21 psi with a GM-4, with 21:1 cr but I will eventually move on to a powerstroke turbo and intercooler and drop the cr to 20:1 or 19:1.

The injectors in the 6.2 opened at a lower psi than the 6.5L TD.1750 psi vs. 2050 psi

Quantum mechanic, you doubt my 26 psi boost? First off I was at 6000 ft elev., with a 4911 mechanical injector pump with the fuel setting wide open and a custom rajay non wastegated turbo, and a very short 3" straight exhaust. This set up was also with 18:1 pistons and it halled but.:ro)