I just bought LT1 and it has 306 cam. The old owner changes only the new stock time chain. What another else do I need to change?

 

definately have to change the stock springs, a good tune will also make some power

 

Yeah springs and a tune are manditory and you will be amazed at what they gain you.
What other mods are done to the car? Think about putting a sig together to help us better help you.
I went the route of a cam before headers,stall, gears and even with a MUCH milder cam it didn't work too well till I began to get those other parts on the car then it REALLY woke up.

 

comp cams recommends some port work to your heads to get the max performance,also headers,gears,stall.

 

Must have proper Valvesprings other items should be from stock: CAI, headers, catback, roller rockers, tune, and head work if you can afford it. I got #'s in sig with stock heads though.

 

Do I need to change the stock rocker and Pushrod?

 

You need new springs, retainers, seats, valve seals, roller rockers (the stockers suck, and will deflect at higher lifts), new pushrods (hardened) if you're using guideplates (non self aligning rockers), stock pushrods with self-aligning rockers, new timing chain, new gaskets, probably new opti and waterpump while it's all apart, you need a tune (mailorder at least). You'll need some other misc. stuff depending on what year your car is. Do some searching. http://shbox.com/ci/cam_install.html

 

another one http://shbox.com/ci/cam_removal.html

 

I'd recommend:

Comp 918 springs
10* steel hardware (titanium if money is no object. Also do a search for 918)
Cloyes Double roller timing chain (requires 95+ opti, electric wp, clearancing)
Intake, timing cover, waterpump gaskets
1.6 Roller rockers
Tools

Look at the pictures in my thread a couple up from here

 

Short headers, custom mid pipe, Flowmaster cat-back, CAI K&N, TB 52, 306 cam.... which is better for this cam shor or long headers?

 

Long tubes, better with any cam, even stock.