[oldman]

My engine still has cam and ported heads as well as a slightly lazy centri (d1x), I'm comfortable at 10 PSI on 93 with forged pistons.

I have not looked into pullied 1.7 on a stockLT1 engine, I think the LT4's stock boost is in the high 9 range, so we know what GM believes. I would look at a shop or somebody that has the car and see what they think. There have to be many guys now with this setup. IMO I like only builds capable of 100,000 miles. My first build was temp till I retired and even then within 5k or so miles I had a lifter failure. No bigs as I was going to change the cam and lifters on the rebuild, but scary it could have taken out the engine. My pistons look fine... mint in fact, don't know if I was lucky. Nut shell even at stock LT4 boost, you are starting with an engine with higher CR and cast pistons, at some point getting rid of pumping losses makes more sense vs boost.

I do think the front cats are very restrictive and will be putting in CA front cat deletes with Borla 60608 twin resonator mid-pipe (hope this keeps the sound near stock. If this does not work, I will put two high flow cats into the system, bringing the total to 4 cats, two resonators, two crush pipes, stock exhaust pipe. At some point, it has to be quite? I have tried 20 different combinations to find something I'll be happy with over the life of the car (1 to 20 years).


IMO this would be my first mod after blower; my only issue with any upgrade to the exhaust is my M6 car with my mods sounds terrible with no cats and just plain heck of loud with LT and cats. I'm looking for something fast but near-stock at 45 MPH or completely stock.