80Sierra

Hey guys!

I recently installed a 89 TBI setup onto the 83 1 ton High Output 350 that I've got in my 77 C19 (try and say that three times fast! ), and I think I've got it to the point where all I can do is start tuning the prom now.

The 83 engine is actually very well suited to the TBI, the cam profile is slightly more biased towards making big torque as compared to the regular output 350, but doesn't give me a rich idle due to any valve overlap.

While the fueling is actually pretty close, less in OD, I find that my biggest problem is actually the timing. With the timing set at stock, the truck lacks power, and runs rich all the time, though the idle quality is amazing, and I can easily crawl around with very little pedal, and have no problems. I've found that if I add about 8 - 9 degrees of initial timing the top end is awesome, and makes the BLM readings well within reasonable spec (between 120 - 135 or so), but makes my truck bog / stall at low speeds, such as trying to back into a parking lot, or creeping through a playground zone. I also have my BLMs drop straight down to 108 whenever I am in OD, and going less than about 55 - 60 mph or so.

So, basically my plan at the moment is to leave the VE tables, and start on the spark timing first. I think that my timing is out far enough that it could very well be affecting the readings that the MAP is giving, and therefor also my BLM readings. I know this is a slightly backwards approach, at least from the point of view given in the stickies, but it seems to make sense that I should get my timing close first, then start fiddling with VE, then finally start the long process of tweaking the two until it is nearly perfect.

What do you guys think? Should I do the VE first, and then the spark, or the spark first, then the VE? Or, am I missing something else all together that is making the truck have timing issues instead? All the sensors are brand new AC-Delco components, and appear to be working correctly. The fuel system is fine, and the exhaust shouldn't be causing a problem either (dual 2" pipes with factory manifolds, bit small, but they work fine)

dimented24x7

iTrader: (2)

The timing and engines VE are coupled together. If you change the timing, its probably not a bad idea to at least rough in the VE after each change.