First, if you are gonna forge dump the unichip. I would consider different EMS cuz of the difficulty of tuning the unichip. I have a friend who drove 6 hours to have his unichip tuned. While there the tuner couldn't pull any fuel so it was a big waste of time and money. Maybe this was an isolated incident but I've heard bad stories about the unichip if you are going big with the motor. You will need connecting rods, pistons, main bearings, thrust bearings, rod bearings, ARP head studs, OEM gasket kit, 440's or bigger, and a larger turbo for 300 whp and an upgraded clutch. Since your tranny will be more accessible during the build you should put a weld around your LSD. And you will need to have your block honed for bore unless you buy a built block. I'm assuming you are talking 300 whp on dyno dynamic dyno or something that reads low. You could get to 300 dynojet whp with the stock turbo maybe. I would go +.20 on the pistons and stick with stock compression of 9.1:1. 7 heat range plugs are a must. I would call Cullen from street unit. He could walk you through it. Just give him a budget you wanna stay under and he will work with you. You could also order a built short block. It would probably be cheaper buying everything and paying for labor. Think about it: if you buy a pre built bloack for 3200-500 core charge you still have to pay someone to take out your existing block and put the new one in.
Price estimates:
Pauter rods: $799
Wiseco Pistons:$499
ARP head studs:$119
OEM Gasket Kit:$175
Clevite main bearings:$65
Clevite thrust bearings(2 sets):$38
Clevite rod bearings:$36
Spec Stage 2 clutch:$296
LSD Welded:~$100
Block machined:~$150
Engine build:~$1000 to ?
GT28RS:$950.00 shipped from turbochargers.com
My friend's MSP that is fully built with most of the aforementioned parts just put down 260 hp and 270 tq at 11.5 to 12 psi with a gt28rs, 550 cc injectos, and a bigger fuel pump. And this was on a dynodynamic dyno which reads about 13 to 20 percent lower than a dynojet. So in theory he has over 300 whp on a dynojet dyno. He couldn't bring it over 13 lbs because of detonation. The detonating might be from bad gas hopefully. Anyways, he is gonna solve the detonation problem and run 18 psi and will probably see 320 to 330 hp on that same dyno or very close to 400 hp on a dynojet.
So getting to your 300 hp goal is very achieveable. Thats my .02, Joe.
