Jim85IROC

iTrader: (2)

Hi all. My Vortec TPI swap in my GTA is almost done, so it's time to start thinking about developing a reasonable tune as a starting point. I'm a novice tuner... I built the tune for the same motor when it was in my IROC, although my knowledge at the time was quite limited. That tune was a modified APYP tune that had a ton of spark advance, which my old 461 fuelie heads needed. The same motor has Vortec heads now, so I've been searching for a spark advance table to use as a starting point. For the most part, all of the vortec-specific maps are for an automatic, as is the often referred-to Caprice LT1 spark map. I came across one here for an LT1 T56 f-body, but that table seemed to have a lot more SA than I would expect to be ideal for Vortec heads.

If I grab that Caprice SA table, how far off is it going to be for my manual transmission application? Is it going to be good enough for me to at least drive the car and start doing some data acquisition?

Orr89RocZ

iTrader: (20)

Just about anything will work as a starting point. Wouldnt use a lt1 t56 one or 113 L98 tables peak values but you can take them and cut out say 5 deg for now.

Or try a manual 305 tpi car one. They all will work for starters, fueling is more inportant to get close first, then adjust spark. Vortecs i would try 30-32 deg peak trq wot and 32-34 peak hp rpm depending on your comp and cam size. If closer to pump gas limits back down a few. If lower then it may need more.

Idle areas 20-30 deg dependin on cam size monster cam needs timing 28-30. Stocker cam, stock timing 20-24. Middle ground cruise areas will just be a mix of inbetween values and some slightly higher like low load higher rpm areas, 36-38 deg. Shouldnt need much more than that imo but give it a shot. They are suppose to have very good chambers and i would treat them like newer faster burn designs like AFR eliminators. They dont seem to require alot of timing

Jim85IROC

iTrader: (2)

Hopefully my fueling is going to be ok. I don't expect fuel to be drastically different than it was with the old heads. While my old tune was hardly optimized, it was good enough to keep my BLMs close to 128 pretty much everywhere, and the wideband o2 stuck in the tailpipe during my dyno runs seemed to indicate a pretty good mixture.

Overall, the Caprice table doesn't sound a heck of a lot different than what you're describing, so I'll start with that and make some tweaks once I get my datalogging set up. With the IROC I just used a handheld auto x-ray and observed everything in real time, but this time around I want to pick up one of the Moates data loggers. In the meantime, I just want a "ballpark" tune to use to get the car running and driving so I can have something to sort out all of the inevitable external issues I'm sure I'll have.

RBob

iTrader: (1)

Note that the f-body LT1 engines used aluminum heads.

RBob.

Jim85IROC

iTrader: (2)

Yeah, but there was a lot of banter about that SA table being good for Vortec heads, but to me it looks totally wrong.