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Old 11-09-2011, 02:56 PM   #1
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tbi 350 cam too big?

i have a new cam in my 350 tbi and it idles up and down erratically and its very lean. i have a 504/504 solid lifter cam 284/294 duration 105 lobe sep. i think it is because of the knock sensor is there any way to figure out if that is whats wrong with it and can i just disconnect that? also i have no o2 or iac. the ecm is 16146299 $99 mask using moates autoprom package with tunerpro if you can help that would be awesome thanks
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Old 11-09-2011, 03:43 PM   #2
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Re: tbi 350 cam too big?

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i have a new cam in my 350 tbi and it idles up and down erratically and its very lean. i have a 504/504 solid lifter cam 284/294 duration 105 lobe sep. i think it is because of the knock sensor is there any way to figure out if that is whats wrong with it and can i just disconnect that? also i have no o2 or iac. the ecm is 16146299 $99 mask using moates autoprom package with tunerpro if you can help that would be awesome thanks
To big is just a function of the overlap pulling to much Air from intake as exhaust valve is opening - thus the o2 sensor will read the unburned air as a lean condition and try to compensate with way to much fueling.. Your blm will peg lean though you are rich.. Also with a cam that is loppy it causes your idle to hit multiple cells at once - you have to make some of the surrounding cells close to the actual idle value..

Not familiar with the 299 ecm - is it MAF or SD? Why not using an O2 or IAC?

PS-That is a large amount of overlap, but it can be done with some work - Just likely never be able to idle in closed loop due to the overlap.. But if you run open loop you can do whatever you want..
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Old 11-09-2011, 07:54 PM   #3
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Re: tbi 350 cam too big?

it is tbi speed density do the solid lifters cause the knock sensor go crazy because my knocks are up really high compared to the other cam i had in it its at about 300 after 2 or 3 minutes. i have a wideband o2 on it so no factory o2 never was on it and the iac is all the way open so the idle is just set with the screw because i have the 454 tb and the connector was different. iwas going to fix it later but i just need to get it to run decent first. can i just disconnect my knock sensor and maybe not have that problem? also could you help to walk me through this sometime cause this is my first time tuning with this? thanks
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Old 11-11-2011, 09:59 AM   #4
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Re: tbi 350 cam too big?

You can disable the KS in your tune or reduce the vlaue being pulled to zero. May be mechanical or real. need to determine that B4 you disable. Most likely mechanical.

Open loop is likely the way to go. Set CL to a very high coolant value. you will need a WB to get fueling under control.

IAc is nice to have but not essential. you need to extend the IAC to max to close the vac leak and then disconnect. set idle with TSS.

6299 I think is 85 vette?
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Old 11-11-2011, 08:59 PM   #5
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Re: tbi 350 cam too big?

the ecu is out of a 87-95 pickup not sure exact year but i wouldnt have thought this tune would be that far off from the thumpr cam i had in it to begin with but does anyone here know if i could maybe get a custom tune somwhere to load and maybe get me a better starting point? thats what moates said i really should look into. or if anyone has a better (cheaper) idea of how to get a decent not perfect tune for right now to get it on the road? thanks for all the info.
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Old 11-14-2011, 09:34 AM   #6
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Re: tbi 350 cam too big?

This is a DIY board. Than being said most will not suggest a chip from a pro tuner. Change of satisfaction is 50/50.

But see tbichips.com.

you may need to do datalogs and have pro do several reburns to get it close.
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Old 11-14-2011, 05:41 PM   #7
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Re: tbi 350 cam too big?

That cam has 79* of overlap, you won't get accurate o2 (narrow or wide) at lower RPMs. Yes, that cam is very big.

What are your idle RPMs at? Timing at idle? My TPI has .585/.575 288/304 (236/244 @ .050) 111 LSA. The motor is an 11:1 aluminum headed 355 and I idle at 950 RPM with 36* timing, my WB reads above 18:1 ("---" on AEM) at idle. I'm still tuning but it runs well for such a large cam.
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Old 11-14-2011, 10:31 PM   #8
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Re: tbi 350 cam too big?

my tables are still pretty close to stock but i cant get it to idle on its own almost souds like a vaccum leak but isnt it idles up and down between 600-1000 rpm it was rich with my thumper cam which had close to the same specs except it was hydraulic not solid. do you have a fuel table that might get me closer because i got a timing table that i am going to try it was from another forum i dont think it will hurt to try it.
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Old 11-14-2011, 10:35 PM   #9
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Re: tbi 350 cam too big?

i was thinking about getting a tune made to try to get it a little closer so i can tune it from there do you think that might be a good idea? i can get one made for around $150
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Old 11-14-2011, 11:33 PM   #10
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Re: tbi 350 cam too big?

I wouldn't pay 150 bucks for one. I downloaded the definition, just need to find a bin. I don't mind looking it over to see if I can get you a base tune that you can try Are you running a computer controlled HEI?
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Old 11-15-2011, 06:07 AM   #11
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Re: tbi 350 cam too big?

Moved, departed from DIY...

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Old 11-15-2011, 08:02 AM   #12
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Re: tbi 350 cam too big?

I found some bins. I really need to know some more info on the motor to get a tune somewhat close.

Under the TABLES:
1. There is an Idle Overspeed Spark Retard Vs RPM and Idle Underspeed Spark Retard vs RPM - I zeroed them out. The small fluctuation in RPM (as little as 250) would change the timing by almost 10*. Not good for a cammed motor.

2 Targe Idle RPM vs Coolant (In gear/out of gear) - Bring them both up a few hundred across the tables.
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Old 11-15-2011, 09:04 AM   #13
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Re: tbi 350 cam too big?

the ecu is a 6299 $99 mask computer controlled hei would be factory style tbi distributor right? it is elctronic timing. i am going to get out to my truck are you going to be around for a while so you can help a bit?
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Old 11-15-2011, 09:07 AM   #14
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Re: tbi 350 cam too big?

what other info do you need to know about the engine?
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Old 11-15-2011, 10:33 AM   #15
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Re: tbi 350 cam too big?

Yeah, I'll be around for a while. What BIN file are you using, AWLC_all?

Initial timing? 0, 6, or 8 degrees?
Stock 350 or bored over?
Injector size?
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Old 11-15-2011, 10:48 AM   #16
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Re: tbi 350 cam too big?

Hoogies... 36d advance at idle? What is the reasoning on that? When I raised my idle SA I lost VAC.
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Old 11-15-2011, 11:10 AM   #17
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Re: tbi 350 cam too big?

I still haven't dialed it in exactly. I was running 28* and the motor kept idling better the higher I went. Knock counts are at zero, ESC is enable above 800 rpm.
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Old 11-15-2011, 02:47 PM   #18
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Re: tbi 350 cam too big?

stock bore 55lb injectors anything else? im going to get back on here in a little bit i have to put my exhaust pipe back on. i put in a factory nb02 then i will try what you tell me.
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Old 11-15-2011, 03:29 PM   #19
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Re: tbi 350 cam too big?

Ok, 55 lb injectors were for 305 If I remember right. Stock fuel pressure (12 psi) as well?

I'd zero out the Idle Overrun and Underrun Spark Advance/Retard tables first. Those tables will change the timing based off the what motor is running vs what the ECM wants. If it calls for 700 rpm and the motor spikes up to 900, it will pull about 5* of timing. This will cause the rpms to drop, timing returns to normal but not fast enough, rpm's fall under 700, and the ECM adds 5* of timing. Not having the IAC hooked up probably doesn't help this situation.

Next, I would increase the Target Idle RPM (out of gear). Try increasing them all by 150. This should get you 800 rpm with a warm motor, once you hook up and adjust the IAC.
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Old 11-15-2011, 03:34 PM   #20
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Re: tbi 350 cam too big?

If you are at stock fuel pressure and really do have 55 lb injectors, change the Base Pulse Width Constant to 152. (Hope I did my math right)
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Old 11-15-2011, 03:37 PM   #21
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Re: tbi 350 cam too big?

I would suggest you study the stickies above. It will be of great help. also see "free tune" in TBI stickies.

Step 1 is to set BPC

" 2 is to datalog BLM values. However that cam will cause issues running CL. so datalogs may be of little help. Try anyway. You will need to run OL(IMO) and monitor >2000 rpms A/F with a wideband. <2000 rpms the A/F will not be real. you will need to check plugs or witness the ext gas quality at idle.
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Old 11-15-2011, 03:42 PM   #22
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Re: tbi 350 cam too big?

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I would suggest you study the stickies above. It will be of great help. also see "free tune" in TBI stickies.

Step 1 is to set BPC

" 2 is to datalog BLM values. However that cam will cause issues running CL. so datalogs may be of little help. Try anyway. You will need to run OL(IMO) and monitor >2000 rpms A/F with a wideband. <2000 rpms the A/F will not be real. you will need to check plugs or witness the ext gas quality at idle.
Yup, get used to reading the plugs. The exhaust is going to smell rich with the cam you have, even when the motor is at the "sweet spot". I'm playing around with the AWLC bin here, looking for ways to run open loop up until a certian point
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Old 11-15-2011, 03:59 PM   #23
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Re: tbi 350 cam too big?

Worth a try:

Under the flags there is Idle Fuel (X=Open Loop).
Under the scalars there is Open Loop Qualifier TPS% and MPH. Anything under the specified TPS% and MPH will enable open loop?
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Old 11-15-2011, 04:12 PM   #24
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Re: tbi 350 cam too big?

Absolutely. Open loop idle will help. Setting OL < 30 mph will as well. TPS% is hard to say...
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Old 11-15-2011, 11:18 PM   #25
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Re: tbi 350 cam too big?

the 55lb injectors are stock 350 injectors 65 was cop car 45 was 305 and 80 and 90 was big block i have the 90 also. how did you get the math on that? somehow i came up with 125. maybe i was wrong. i had it running earlier but couldnt rev up past 1800-2000 rpm and i need to get it about 2500 for a while to break in my cam still. i hope the cam dont get messed up.thats what happened to the last one.
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Old 11-15-2011, 11:27 PM   #26
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Re: tbi 350 cam too big?

also would it be a good idea to put in the bigger injectors then tune for them any performance gain? maybe would the cam like that any better? because i seem to think it is still too lean because it dont want to rev up very high
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Old 11-16-2011, 09:29 AM   #27
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Re: tbi 350 cam too big?

BPC is 157 for 12 lbs FP and 151 for 13. Per my calculator (BPC-VRFPR.xls)
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Old 11-16-2011, 09:52 AM   #28
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Re: tbi 350 cam too big?

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seem to think it is still too lean because it dont want to rev up very high
sounds like you are out of fuel as you stated. What fuel pump? Do you have a FP gauge?

Assuming 300 hp 350 cid 55 lbs injs you need 28 lbs FP.
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Old 11-16-2011, 11:33 AM   #29
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Re: tbi 350 cam too big?

it is a stock fuel pump 18lbs shutoff i am running 12 lbs fuel pressure should i put the bigger injectors in it? would it help me out any? it only takes about 10 minutes to do that.
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Old 11-16-2011, 11:35 AM   #30
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Re: tbi 350 cam too big?

and yes i do have a fp gauge and aeromotive adjustable fpr boost or vacuum referenced but i dont have a vaccum line hooked to it. should i hook that up?
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Old 11-16-2011, 11:36 AM   #31
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Re: tbi 350 cam too big?

Needs more juice!

Let's see if I can remember this right.
BPWC = 1461.5 * cylinder volume (.7126 for 350) / (fuel injector size * .126)
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Old 11-16-2011, 11:54 AM   #32
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Re: tbi 350 cam too big?

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Needs more juice!

Let's see if I can remember this right.
BPWC = 1461.5 * cylinder volume (.7126 for 350) / (fuel injector size * .126)
i am coming up with 1.45805086 is that right? that is if i use the 90lb injectors.
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Old 11-16-2011, 12:15 PM   #33
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Re: tbi 350 cam too big?

I got 91.84 for the 90# injectors.
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Old 11-16-2011, 12:23 PM   #34
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Re: tbi 350 cam too big?

what about this website? i got 103 from there and 135 for the other injectors is this site right?http://www.fortunecity.com/rivendell...24/gm_inj.html
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Old 11-16-2011, 01:19 PM   #35
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Re: tbi 350 cam too big?

From what I've heard the injector flow rates aren't accurate on that site. You can try the 90's with a 103 BPW, it's in the ballpark (on the rich side) and see how it reacts. Around 2500 rpm I would guess the WBo2 should be somewhat close to what the actual AFR really is.
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Old 11-16-2011, 01:31 PM   #36
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Re: tbi 350 cam too big?

Whoops! .7168, not .7126. Either way the difference is minimal. 92.38 vs. 91.84. Both round to 92, right?

BPWC = 1461.5 * cylinder volume (.7168 for 350) / (fuel injector size * .126)

Edit: If 90# injectors are rated that at 13psi (92 BPW), 90# at 12psi would need a 100 BPW. If it only revs up to 2100 rpm at ~100 BPW, increment it higher and check again recording any change i.e. 2200 rpm. I've read that people with a 90 calculated BPW actually had to run 140 or so to get their motor to run.

Last edited by hoogiesngrinder; 11-16-2011 at 01:42 PM.
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Old 11-16-2011, 02:09 PM   #37
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Re: tbi 350 cam too big?

Quote:
it is a stock fuel pump 18lbs shutoff i am running 12 lbs fuel pressure should i put the bigger injectors in it?
I dont believe your fuel pump is up to the task. Under severe load FP will fall off. DC will show that. I see highest DC% at a 2nd gear pull of 4(manual). I would suggest a TPI Delco brand pump.
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Old 11-16-2011, 02:59 PM   #38
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Re: tbi 350 cam too big?

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From what I've heard the injector flow rates aren't accurate on that site. You can try the 90's with a 103 BPW, it's in the ballpark (on the rich side) and see how it reacts. Around 2500 rpm I would guess the WBo2 should be somewhat close to what the actual AFR really is.
Actually, with the exception of the 5.0L injector flow they are correct. The 5.0L injectors are 55#/hr, not 49 as listed.

There are no 90#/hr injectors that were used in the USA BBC trucks. They are either 75, 80.5, or 46 #/hr, all rated at 13 psi. The 46 #/hr BBC injectors were used in '94 & 95 at 30 psi. This increased the flow rate and reduced the odds of vapor lock.

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Old 11-16-2011, 04:46 PM   #39
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Re: tbi 350 cam too big?

i crossed the part no. with gm and they are the 90# injectors but its really not that big of a deal though. now with my fpr should i be using the vacuum port or not? my fuel pressure should not increase or decrease on a tbi setup right?
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Old 11-16-2011, 04:56 PM   #40
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Re: tbi 350 cam too big?

so im understanding from you is id be better off running the 90s? right and use 13 psi?
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Old 11-16-2011, 07:47 PM   #41
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Re: tbi 350 cam too big?

Ahh, ok. That's why I thought 55# were 305 injectors. I knew the 94-95 were the high pressure. Good to know

Quote:
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Actually, with the exception of the 5.0L injector flow they are correct. The 5.0L injectors are 55#/hr, not 49 as listed.

There are no 90#/hr injectors that were used in the USA BBC trucks. They are either 75, 80.5, or 46 #/hr, all rated at 13 psi. The 46 #/hr BBC injectors were used in '94 & 95 at 30 psi. This increased the flow rate and reduced the odds of vapor lock.

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Honestly, if I had to break in a flat tappet motor (like the last one I built) I would run a carb setup then switch it over to EFI so I could tune it without fear of wiping out the cam.
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Old 11-16-2011, 10:16 PM   #42
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Re: tbi 350 cam too big?

i went in to the main fuel table and from 0-60 map in all rpm i added 20 and it runs alot better and i can rev up as high as i want so i will break in the cam tomorrow but i need to change the starter and flexplate because something happened with the teeth wearing off so when i get that done it should be good to break in then tune from there. i may still have more questions but thanks for all the good info.
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Old 11-17-2011, 11:50 PM   #43
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Re: tbi 350 cam too big?

ok next question got the cam broke in runs decent but if i have an exhaust leak at the collector will my wide band be reading extremely lean? also the blm is at about 105 and it dont change to much when i mess with the ve table. that was above 2500 rpm what else do i need to look at? my map was between 30-40. also what should the nb 02 be reading i think most of the time it was about 700-900 is that rich or lean? never messed with nb02?
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Old 11-18-2011, 08:53 AM   #44
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Re: tbi 350 cam too big?

Depends on how big the leak is. The motor with a cam like that will likely read lean at lower RPM and no load. But with that being said, 105 BLM and 700-900mv both indicate rich If the o2 is after the collector, and your running long tubes, it is likely that it will need to be a heated sensor. Is it a sigle wire?

Adding 20 degrees to the entire spark table is probably 10-12 too much. Knock counts through the roof still? Adding 20 would put you at 40* advance at idle

Try unchecking the open loop flag, drop you BPWC by 10, and see where it goes from there.
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Old 11-18-2011, 08:38 PM   #45
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Re: tbi 350 cam too big?

i am not running long tubes and i think my factory 1 wire o2 is fine i am talking about the wideband o2 i it is reading about 17-20 and sometimes it will come down to about 13 or so i will try to recalibrate it with the controller tomorrow and see what happens. and i was talking about adding 20 to the main fuel ve table not the spark table. i used a spark table that someone emailed me a while ago and it seems pretty close and havent figured out what to look at to find out where to change the fuel table. i will also fix the exhaust leak tomorrow and play around with it and let you know how it goes. also the wbo2 readings are all through the rpm range in park so it is not just at lower rpm. and the exhaust is obviously rich because the ground under my exhaust is very black so it is rich.
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Old 11-19-2011, 08:48 AM   #46
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Re: tbi 350 cam too big?

It's really hard to say, but get the exhaust leak free. Free air calibrate as well.

I'd change the BPWC to effect fueling across the board instead of adding 20 to all values of the VE table. I don't know what your vacuum is but it is probably a chunk lower than stock. Maybe take the stock VE values and shift them one or two columbs to the left?
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Old 11-19-2011, 08:48 AM
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