GXPJAY

I'm hoping you guys can help shed some light on this problem we are having.

I have a 06 GXP with a LS4 turbo making ~450whp at 12psi with Alky injection. The motor is stock and the LS4 motor has LS6 heads but has LS1 Valve springs which are 76lbs I believe.

We are getting misfiring around 4500-5200rpm at WOT, we tried everything, new plugs, coils, smaller gap, bigger gap, cranked the dwell setting for the coils, turn off the Alky etc. etc. we still get the damn P0300 code for random misfire.

I was reading a lot of posts where people mention they are getting misfiring because of the valves prings being too weak however usually only after a cam/rocker change. Do you think this could be our issue just because of the increased boost now making the already pretty weak LS1 valve spring even weaker? Or would someone have a suggestion as to what we can check next?

thank you for your time!

Jay

hellbents10

iTrader: (10)

I would be putting springs in it for sure. looks as though the boost is holding the valves open.

Pro Stock John

iTrader: (34)

Got your pm, yes you need more valve spring.

GXPJAY

Ok, great.

Are LS6 springs recommended or should I jump to a 918? And then I would need retainers etc. because the stock ones wouldn't work right?

I also read up on the Patriot Springs, they seem a good price and come as a kit are these ok?

Where is the recommended place to buy?

hellbents10

iTrader: (10)

Patriots are the best route to go,call texas-speed for those. Stay away from the 918's, LS6 will work fine if you don't plan on making much more power though.

GXPJAY

I don't want to have to buy new springs when I put a cam and heads etc. on the car. I had never heard of Patriot's before but they seem popular here so that's good.

hellbents10

iTrader: (10)

I have never had any trouble with them either I think they are great. TS sells them as PRC units. I always go through them for springs.

Pro Stock John

iTrader: (34)

Anyone have the Patriot spring specs?

I would go with a beefy spring, you need to run a lot of spring pressure with FI, and to me LS6 and 918 springs don't make the cut.

Ryne @ CMS

iTrader: (10)

regular patriot golds are are 125-130 seat 360-380 open @ .600 with 1.800 install height...... dont quote me on that..... the open pressure may be a little higher