should i be running a 2.5 single or 3 inch single exhaust????


truck and specs

1989 f250 351w ported stock upper and lower intake and ported d8oe heads 1.7 roller rockers longtube headers y piped into a 2.5 inch single exhaust with a gutted cat and flowmaster 40 series

 

3inch. I had that on my old 88 F250 351W and it sounded good and had a power difference.

 

2.5" is honestly probably fine for your engine, but you can go 3" if it makes you feel better.

 

Use 2.5" tubing. There won't be a lot of difference with either size but the motor will lose some low rpm torque with the larger tubung. You can't use the stock cat with longtubes so just use an aftermarket cat it won't be restrictive.