Asking for help to figure out what's going on, white exhaust valves?

[L31MaxExpress]

Tan valves are normal. The darker valves are rich. Its not unusual to have the fueling on one bank be different then the other and have the O2 sensor wrongly compensate when you have a mechanical issue like that, remember there is only an O2 on one bank.

305s actually have 3 02 sensors ahead of the cat. One on each bank and a 3rd one that is in the Y-pipe ahead of the single cat. All 3 are responsible for fuel trims.

 

[MIHELA]

GM does such weird stuff. Like putting a linear EGR valve on the 4.3 manual trans and giving them the 8695/7427 PCM, then saddling the 5.7 manual trans with the old junk. Buy a better optioned truck and get hosed.

 

[L31MaxExpress]

GM does such weird stuff. Like putting a linear EGR valve on the 4.3 manual trans and giving them the 8695/7427 PCM, then saddling the 5.7 manual trans with the old junk. Buy a better optioned truck and get hosed.

Would much rather have the dual cat setup from the 350. The 350 ran at about 1.5 psi less backpressure than the single cat on the 305 stock for stock. With the 350 dual cat setup a 305 Vortec makes about 240 HP. The 1-ton 350s used the 454 cats and had even less backpressure. I had a used 305 in my Express van for nearly 2 years. It was down on power from the 350 in the lower revs but as the RPM climbed intp the midrange and beyond it felt just as strong as the 350. The 218/218 @ .050 cammed L30 305 in my 1999 Tahoe pulled like crazy from 3,500-5,500 rpm and was pulling a solid 50 gms/sec more airflow than a stock 350.

 

[MIHELA]

Honestly I think the better exhaust setup is why power jumped so much in the L31. The roller cam and heads helped a lot but if you've ever messed with the stock exhaust on a TBI you know how much gain can be had.