1998 LS400 2 to 1 Valved Exhaust Project

[rpizzle]

Hey! this is my first time posting on this thread so ill introduce myself. My name is Rob and I live over in PA, just got my hands on a clean 98 LS400 and I plan on starting its modification journey with a valved single exhaust conversion. I'm posting here to share my thoughts and see if anyone here has any questions comments or concerns!

I plan on converting the exhaust diameter from the y pipe to a single 3" pipe that runs straight through, into a custom valved muffler at the end of the car. Right now im mostly interested in what people think about diameter for these cars and what kind of backpressure these cars enjoy, my background is in mechanical engineering so if any MECHE's out here who want to get into the weeds with the setup, im more than happy to lol.

 

[Lextreme]

Hi Rob, welcome to the forums! You got a nice LS400 there.

 

[ivan129]

Best place to start is with a good service and checks to make sure the engine and ECU are in good health.
A thorough engine wash down and oil change & filter is a good place to start.
Check clean and adjust plug gaps or replace them.
While the plugs are out, do a comp test to ensure ring, bore and valve seal are in spec and close to the same.
Then go over the electrical, dizzy caps, rotors for cracks and wear, check the leads. Check and clean any corrosion at connections.
The plug leads may need to be replaced. Use better quality aftermarket jobbies, not the OEM crap.
Some of the best bang for $ mods are a low restriction air filter and cold air pickup.
A set of good tubular engine pipes into your up sized exhaust.
An run the highest RON fuel you can afford, atleast 95 or 98.
Good luck.