One thing leads to another, don't it?
12-20-2005, 07:36 PM
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One thing leads to another, don't it?
I have a 88 rclb silverado, I rebuilt the 5.7 with a few mods and I just can't seem to work out all the qwerks. It is the factory block, punched 30 over with flat tops. Hydraulic roller cam and lifters, with roller rockers. I am useing world products sportman2's for heads and a holly projection intake. I purchased a aftermarket throttle body pumping 750cfm and a high flow fuel pump. I had a chip made at TBIchips.com for the motor. I have tried many things but the truck still seems to be down on the power I was expecting to make. With wide open throttle I just blow a lot of black smoke out the back, its moving, but you can tell something is there holding it back. and at cruising speed, when you dump the gas to it, it sometimes chokes back before it kicks in. Everyone I talk to said to just up the fuel pressor, it is now at 15psi. Then they said I wasn't getting enough air in the heads, so I put in a injector spacer. Any recommendations or products out there that can help? I have used up all my resorces, TBI knowledge is limited in my area.
12-20-2005, 07:42 PM
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Im not that handy with tbi, but it sounds like its running rich. How does it start and idle? Sure you have the plug wires in the right order. Are you sure the timing is right? IE the distrubitor is stabed right?
12-21-2005, 12:01 AM
#3
black smoke typically means richness coming out of the exhaust. What size cam are you running.
I have a 383 TBI in my truck about a year ago running 13.5 psi on 65 lbs/hr injectors. The holley injectors are about the same if I'm not mistaken. I would drop your fuel pressure down to about 12 psi and then tweak it from there with the g-tech(if you have one). If you don't have a g-tech...then listen to your idle. Check your spark plugs for the proper gap (.035 I think) and get back with us about what its doing. This should be the first place you start. As, you engine should be around 6 degrees timing and one more thing to do...check with your chip burner and see what he thinks about where to start your fuel pressure at. I bet it should be around 12 psi or just a fuss higher depending on your cam. Hope this helps.
I have a 383 TBI in my truck about a year ago running 13.5 psi on 65 lbs/hr injectors. The holley injectors are about the same if I'm not mistaken. I would drop your fuel pressure down to about 12 psi and then tweak it from there with the g-tech(if you have one). If you don't have a g-tech...then listen to your idle. Check your spark plugs for the proper gap (.035 I think) and get back with us about what its doing. This should be the first place you start. As, you engine should be around 6 degrees timing and one more thing to do...check with your chip burner and see what he thinks about where to start your fuel pressure at. I bet it should be around 12 psi or just a fuss higher depending on your cam. Hope this helps.
12-22-2005, 07:14 PM
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Tried a few things
My cam is fairly mild because the guy who built my motor said anybigger and the computer wouldn't run it. As for the timing, it is about 13 degrees. Any less it it starts to idle rough and sputter. Would my valves have anything to do with my problems, also it has a factory torque converter and 700r in it, could this be hindering all the benefits of my engine modifications? Anybody know any good TBI engine specialists in Indiana? I also turned the fuel pressure down to 12 psi, still a little black smoke. What about MSD, I have accel plugs and MSD wires, would a 6A box and blaster 2 do the trick?
12-23-2005, 10:53 PM
#5
Well, you are still going to see a little black smoke....do you have a custom chip for your engine? Complete cam specs should would be nice to get into this thing. The cam starts to get cranky about 204 degrees intake b/c the map sensor just can't take it. Once you get around this range a custom chip is mandatory almost. Leave your psi at 12. All the MSD stuff is improve the spark going to the plug...would it help performance...yep...would it fix the problem....problem not unless you got a bad set of plug wires.
Your torque converter is fine in your 700r4...I have the stock one in my 450hp 383...so, its not limiting you by any means.
Sounds like your cam is about the size I am talking about and the lobe separation probably sounds about the 108 marker.....give us some more cam info so we can help you out more.
Also, did you check the gap on your spark plugs? And do you have a good batch of gas and was compression are you running....all key elements in problem solving.
Your torque converter is fine in your 700r4...I have the stock one in my 450hp 383...so, its not limiting you by any means.
Sounds like your cam is about the size I am talking about and the lobe separation probably sounds about the 108 marker.....give us some more cam info so we can help you out more.
Also, did you check the gap on your spark plugs? And do you have a good batch of gas and was compression are you running....all key elements in problem solving.
12-24-2005, 01:32 PM
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Well my plug wires are brand new 8mm MSD heli-core wires, so I now they are good, I pulled plugs out today, they look clean, not wet or corroded. Gap cheked out fine.My cam is about112 lobe separation with 252/260 duration at 425/440 lift. As for compression, I am right about 10:1, I like the pump gas you know.
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12-26-2005, 07:58 PM
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I sent all my engine info to TBIchips.com and he sent me the chip for my install. Yeah it takes 93, like it's going out of style. It will take the cheaper stuff, but it runs a little ruffer. It is also EGR delete, the chip was set up for that, is that why I get a little black smoke at WOT? Also, every now and then I get a pop in the Throttle body, usually when I a cruising at a steady pace for long periods, then when I punch the gas, it will make a little backfire in the Throttle body. Am I over fueling my moter with the bigger Throttle body? My chip tuner recommended the bigger TBI. What else can I try?
12-26-2005, 10:27 PM
#9
I ran the stock TBI unit just with the cop car injectors and mine ran very strong on my 383....wish I was near by to help....let start by this checklist that we have done:
1)Checked spark plug gap
2)Check plug wires for no wear
3)Turned psi down to 12psi
4)Has a custom chip
That's what we have done so far....has it made a difference?
What size injectors do you have....sounds like you are still over fueling it to me....why don't you try going to 11 psi and see what that does....I ran 13.5 psi on 65 lb/hr injectors with my 383....I probably should have tuned it down to 13psi but I was changing fuel injection systems so...i didn't worry with it.
If you don't mind....give me a list of your mods like headers/exhaust, intake....etc. See if we can't get this thing any better. But I would try 11psi and see how it runs. Get back to me after you do.
1)Checked spark plug gap
2)Check plug wires for no wear
3)Turned psi down to 12psi
4)Has a custom chip
That's what we have done so far....has it made a difference?
What size injectors do you have....sounds like you are still over fueling it to me....why don't you try going to 11 psi and see what that does....I ran 13.5 psi on 65 lb/hr injectors with my 383....I probably should have tuned it down to 13psi but I was changing fuel injection systems so...i didn't worry with it.
If you don't mind....give me a list of your mods like headers/exhaust, intake....etc. See if we can't get this thing any better. But I would try 11psi and see how it runs. Get back to me after you do.
12-26-2005, 10:43 PM
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Big Fish- From what you discribe (black smoke, backfire, need to run advanced), it does sound like the engine is running very rich. First, the stock 350 TBI injectors are 55lbs/hr (65lbs/ hr for cops), the Holley projection TBI injector is 85/lbs/hr, and the 454 injectors are 80 & 90 lbs/hr. Which one are you using and did your programmer know this? If it was programmed correctly you shouldn't have to turn up the fuel pressure.