99 Suburban, looking for more power and mpg! I got a 1999 Suburban 1500 5.7L with 250k. Been family owned since purchase, had great care, and is now been passed to me (the 17 year old highschooler). I would love to replace it, but i dont have the money... so, i have to keep her going and baby her through my highschool career. Its been getting tired lately, and my mpg and power has been dropping (my dad said its been doing this over the time he has owned it). I am looking for some options to bring some power and mpg back, but not make it so loud. Was thinking about some exhaust and intake/tuning options but most of them are louder than I'd like. Just looking for some suggestions and help! thanks.

 

to me, 250K is about the life expectancy of a SB 350.
If it were me I would run compression test, to see how it is.
Give it the best tune up job you can afford.
I would also test injectors or replace. Use fuel injector cleaner replace the catalytic convertor.
Look at your plugs, take them out and let us see them, that will tell a story as to how your engine is working.
See how much blow by you engine has etc.


Lot of wear happens at 250K likely your cam is no longer near the lift and duration it used to be. Rings are likely weak, and valve stem seal are no longer working well.


Anytime I buy a used car I work at making a steady baseline, meaning all stock parts are in best working condition. This includes suspension and tranny.






Then save for a rebuilt SB Chevy and make that a fall project.


As for performance, make sure your vehicle can breath