I had a reliable mechanic tell me the other day that he can tweak the cams on my 07 3.5 monte and it would make me gain 20-40 hp. My question is: is that possible? If yes, does it void my warranty? Is it bad for the engine? will it really help that much with hp? And most of all what does tweaking the cams mean?????

 

Well I know he can't tweak more than one cam. The 3.5 isa cam in block motor and these new motors are controlled by the PCM.

The LZ4 3500 is an OHV engine based on the 3.9 L LZ9 V6. It was introduced for the 2006 model year in the Chevrolet Impala and Monte Carlo. It includes continuously variable cam timing (fixed overlap). It has a cast iron block and aluminum heads. Output is 211hp (156.5kW) at 5800rpm and 214ft·lbf (298N·m) at 4000rpm. Bore is 99 mm, stroke is 76 mm for a displacement of 3510 cc. Horsepower rating changed for the 2007 model year to Horsepower: 224 @ 5800 rpm and Torque: 220 @ 4000 rpm. The Chevrolet Malibu, Pontiac G6, and Saturn Aura are to be equipped with this engine for 2007 (previously the Malibu and G6 had the non-VVT 201hp (150kW) 3.5L LX9).

Based on this, You have the LZ4 and therefor probably cannot tweak the cam due to the variable cam timing. However, maybe some of the '06 and '07 LS, LT owners can shed some better light on this subject than I. But I would say no. I would say "tweaking the cam" means advancing timing and if that's the case, timing is continuously monitored and controled by the PCM and knock sensor. I would definitely say nobased on that. As far as the warranty if it is possible: I would say it does void it. Any major engine work, and I would consider this major that GM doesn't approve or do themselves based on a TSB (Technical Service Bulliten), voids warranties. Normally.

 

^x2

 

so what about the 3.8 can this be done to it and if so what are the power gains

 

IMO its a huge waste of time. Just getting to the cam is a nightmare- if you're gonna go that far, you may as well put a new cam in. The rollmaster timing chain has multiple keyways (so you can line up the dots and have a dead nuts on +2, +4, -2, etc). AFAIK no one has ever messed with playing with cam timing with one of those chains because it is such a nightmare. Plus, you really need to keep an eye on piston-valve clearance which is almost impossible on an assembled engine.