well ive notice a very slight noise coming from the heads..might be a lifter...how much will it cost me to fix it?? its an 03 4.2 s type?

 

No lifters. You have a DOHC engine. The cams directly move the valves.
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These engines have overhead cams (OHC), the cam lobes use cam followers not lifters to actuate the valves. You didn't mention mileage, however since she's an 03; I'll assume high mileage (90k+). There is an allowance for low frequency ticking noises even on low mileage engines; most of it is from the normal operation of the injectors. Ticking noises could also be the result of worn A/C compressor or water pump bearings. Turn off the A/C and listen. If your mechanically inclined; remove the accessory drive belt, start her up and listen. Does the ticking noise follow engine rpm's up and down the scale? If it follows up the rpm scale but not down it may be an exhaust leak at the manifolds or down as far as the catalytic converters. The EGR pipe into exhaust manifold could leak exhaust too. The first place I'd start is: Turn off the A/C, or better, remove the accessory drive belt and start her for only a minute or two. The worst case scenarios are broken cam shims (stethescope and/or inspect top end), worn camshafts, or worn/burnt connecting rod or crank bearings (stethescope low end while on lift engine on). Otherwise a properly lubricated 03 4.2 is a venerable engine. I'd strongly suspect the diagnostic gurus of this forum will be on your thread to help you sort this out like flies on s$#%, or as one here wrote this week..."like a hobo on a ham sandwich". Let us know what's up.