Hey guys, I've spent a lot of time on this board trying to learn as much as I could over the past couple of months while I worked on getting my engine together and in the car. Well, it hasnt really paid off. Here is the specs on the engine thats in the car.

Vortec heads
357 ci
SD base and SLP runners that have been ported, the runners partially siamesed.
zz4 cam
LT1 24 lb injectors
Underdrive pulleys
Edelbrock headers, hooker exhaust.
Swapped from an auto to a 5 speed.

The engine is definitely more potent than stock, but still not wild by any means. I'm having great difficulty getting it to idle, and just plain run correctly. Through the help of you guys, and from many hours of reading, I constructed a bin file based on an 89 305 bin to give me a decent starting point for this new engine (or so I thought). Here are the changes I made.

-Changed injector constants to 24 lbs
-Changed MAF tables and scalars to ARAP Specs
-Scaled the crank pulsewidth vs engine temp for the new injectors
- Disabled EGR, as it is no longer hooked up
= Changed initial timing to 8 degrees, as thats what it was timed for
- Changed a few flags that have nothing to do with how the car runs.

Anyway, started the car up, and it runs like garbage. Doesnt want to idle, when you hit the throttle, it stumbles. I have the correct plugs, my fuel pressure is adjusted and is about 45lbs. I've tried to eliminate all mechanical elements.

I didnt think the tune would be THAT far off. The funny thing is, that when I put the stock chip in (89 350 automatic), it still idles poorly, but the throttle response is MUCH improved. I tried taking the bin I made, and adjusting the first maf table in very small increments, didnt really seem to do much. (although I didnt really change it much) I tried the pulswidth vs voltage too, but without much change.

I've been using a tech 1 for data collecting, as my 3 transistor circuit I built must have a problem. I've been seeing blms around 150ish at idle (lean) and IAC counts in the 40s. What should my next moves be? Should I adjust the pulse width vs voltage more? If so, which way should I go with them? Also, what about the first maf table? which way do I need to take the grams per second, and how cavalier should I be about it? Also, are my underdrive pulleys affecting the amount of voltage the injectors are getting, and adding to the problem?

Sorry for the long post guys, but I wanted to try to get as much information out there as possible, so you guys can shoot me some ideas. I want to get this thing running decent enough so I can break the engine in, and make sure the rings are seated properly. Thanks a lot for the help!

 

I think you have a mechanical problem. Even at 150 blm it would run good at idle. Mine ran smooth at 160 blms. What is your vacuum like? I think you have a vacuum leak somewhere. Go back over everything on the intake and make sure you don't have any intake leaks, and check all the bolts to make sure they are tight.

If you are at 150blms and you want 128, then 150 / 128 = roughly 17% lean, so multiply the values in the 1st maf table by 17%(1.17 in tunercat). Increasing the number adds fuel, decreasing subtracts fuel.

 

Yeah, I will have to take a look at that. Whats the best way to try to find a vaccum leak? Spraying some gum cutter around the base and intake components?

I will try that tonight, and report back. I've read where some guys have had some difficulties getting vortec intakes to seal properly. I hope its not the base, but I have a feeling it may be. Thanks for the help.

 

Well, it turns out that an alarming number of runner bolts had come loose. So your advice was dead on. Thanks a lot!

I'm got a ball ended allen wrench last night so I can tighten up all the bolts without taking the valve covers off. I'll do that this afternoon and make sure they are all tight, and try it some more. I just tightened the ones I could get to, and it definitely made a difference.

I still think I'm going to be lean though. What should I hit first? Maf table 1, or should I bump injecter pulse width vs battery voltage?

Thanks again!

 

Anyone?

Also, when I move on to my spark advance table, what would be a good starting point? Guys running speed density are told to look at LT1 SA tables when they are tuning for vortec heads. (I'm assuming for impala SS's or anything else with cast iron lt1 heads) However, I dont think that will really help me.