Quote Originally Posted by Fast355 View Post
That is painful! 1 ton 8.75:1 TBI 350 in my 83 G20 Van with 1.6 roller rockers, tri-y headers, 3" single exhaust, edelbrock performer rpm intake, 2" marine TBI unit and adapter put down 200 rwhp and 300 rwtq.

My Express van with basically a 300 hp Marine L31 350 with 2.02/1.60 valves and milled 906 Vortec heads put down 230 rwhp @ 4,400 and 303 rwtq @ 3,400 through a 4L85E and 9.5" 14-bolt despite having weak valve springs and less than optimal spark advance. That was with the tiny GM 196/206 @ 0.050 marine cam and 1.7 rockers. Springs were so weak changing them out for LS6 springs and Comp 787 retainers bumped me to 257 rwhp @ 4,800 and 310 rwtq @ 3,200. I added a flex fuel sensor and tuned it on E85. 272 rwhp @ 4,700 and 325 rwtq @ 2,900. Even with the 1.7 rockers my cam was still shorter duration than yours.

What is the exhaust like after those headers? What about the air filter side of things? What kind of timing advance values are you running. What is the Base timing? It is running really lean in that graph as well.
After the headers I have a Magnaflow Y Pipe, and Flowmaster catback. All 3" mandrel. I ran an exhaust back pressure gage at the header and its readings are flat. The exhaust isn't limiting me right now at all.
Air filter I have a 3" tall 14" diameter round open element.
I don't know timing as I had paid someone to tune it. He said he set it at 19 degrees across the board. I am hoping he was not serious, though I think he was.
Base timing is still 0.
Yeah it is running lean. The tuner dropped the fuel pressure down to stock tbi. He didn't like the increased fuel pressure it had when I brought it in.