: Northstar build

01-13-13, 02:50 AM
I currently have a 02 eldorado needing head gaskets. I own my own high end car repair shop and we do these all the time. But this one I was wanting to hop up a little. This is my personal car and I have a corsa exhaust and am going to stud he heads and port match and polish them while rthey are off. Was wonder if there is any other Performance inhancements out there I could do while I have it apart.

01-13-13, 09:59 AM
GM already did it 99.9% for you. It never hurts to port-match, clean things up a bit, and maybe extrude hone the exhaust manifolds to get rid of any internal welding flash. Pay attention to the crossunder Y-pipe - where the front head pipe sticks into the rear - there's usually a fair amount of extra 'front pipe" sticking into the rear collector. Dremel it smooth and run 3 beads of S/S around the outside for reinforcement.

The intake airbox is good, and keeps air temp less than 10 degrees above ambient on the highway - as with ANY "CAI" you get pretty hot temps in heavy traffic. But, there's a tiny gain - do some stand-back arms crossed thinking about the dirty side of the airbox and how you can get a foam gasket to the body metal hole into the inner fenderwell side. I increased the cool air intake into my Seville airbox by 100% and it looks stock to the casual observer - went through the side of the box to the fender hole and made a cutout foam square "ring" to seal the space between the airbox and fender.

The twin valves per port already flow far more air/gas than the engine can handle at redline. I once read somewhere that the two exhaust valves per cylinder already flow more than the 2.02" exhaust valves in a 327 Chevy head - and this is a little 279.

That said, the entire 2000+ drivetrain is tightly controlled by the PCM, and it will NOT adjust its parameters to use any extra air or exhaust capability.

........... and the VIN Y (275 hp) engine is already limited by a 3.11 final drive - highway economy gearing. The VIN 9 (300 hp) doesn't even begin to run until it's above 3,500 rpm.

You already know what these things look like inside, but for parts and diagrams, look in my albums. Click my username, open the profile - left column - 2 albums, 6 pages of 2002 Northstar/Seville stuff.

01-13-13, 11:44 AM
Take a look inside the Y pipe at the weld. You'll find a huge restriction that needs to be ground out. That's probably the largest gain you can get. They were welded on a production line for efficiency. There is a picture somewhere in the archives.



01-14-13, 09:52 PM
Thanks for the info. I have heard about the y pipe. I appreciate it.