Well I got a 408 stroker from texas speed for my suburban. 2000 suburban 2500 gen III 408 from tsp. It has a fairly mild cam and nothing to extreme. When we first got it all installed the driveability was great but it was missing a LOT of power. After getting it tuned, putting a new tci 4l80e in it and more it still just seemed way underpowered for what it should have been. We ended up putting long tube headers and that seemed to make all the difference. Shortly after, and around the time it started getting cold the truck started stalling when I'd start it cold. It just would stay running at idle and if I blipped the throttle it would die immediately as the rpms came back down. It has continued to get worse, so I thought it must be the FAST lsxrt intake manifold. We got a new one, made sure it wasn't warped and put it on, but it still stalled on cold starts. I finally gave up one fast, put on an nnbs and it is STILL stalling! I have replaced map, maf, o2, iac, tps, and taken it to the tuner multiple times but it will not stay running unless i keep the throttle up to about 2000 rpms for 30 seconds or so. once it is warm it runs and drives amazing, but just won't start. any thoughts?

 

Lots of part swapping. What tuning / logging have you done?

 

haven't done any logging as i don't have the capability yet, but have had it to a highly recommended tuner locally here in VA 3 or 4 times trying to get it dialed in. trying to read through some tuning books and forums so I know what we are looking at when i take it in.

 

you need a tune for the mods you have, not all tuners are good at what they do

as for power, the power from a 408 truly comes from its heads/cam package...400 cubes need exhaust and air intake to support the power otherwise youll have a combo where a HCI 6.0 will out perform

 

got it fixed! sent my computer back to texas speed with specs for them to tune, and it starts and runs perfect! something was off in the tune. man it feels good to have a good driving truck! thanks for the replies and suggestions!