getting back into it

[BReal669]

Hi guys I am a long time reader first time Poster my name is Brian. 46 in cencal doing a 5.3 LM7 swap on a 76 gmc shortbed 4x4 6" lift 35" tires 4:56 gears with trutrak lockers front and back NP205 and SM465 trans. Was building it for my kid till he said he doesnt want anything to do with it so i figured i would build it for me for fun. Then got the news a few months ago that I have stage 3 lung so the direction of my energy is changing a bit as i am sure you could imagine. Motor and wiring harness is in and i have gotten a cough out of it but the decapped injectors and stage 3 cam on fresh rebuild are nit agreeing with the stock tune as one would suspect. Got the free software and the obdxpro cable and standing here like a deer in headlights trying to get my brain wrapped around it but the first round of chemo has me in a cloud still and i could use some guidence. thanks in advance

[MO LS Noobie]

First, my condolences for your situation, you probably have enough on your mind without project. I don't know your mechanical expertise, but a with a project like this it helps to have somebody local to help you through it. Is there anybody local that can help you?

The problem is that this engine has never run (fresh rebuilt) and the engine swap has never been verified. My first step would be to verify the engine. Could be cam timing, pushrods length, etc. I would remove bank 1 (left side while sitting in the driver seat) valve cover and confirm cam position while watching cylinder #1 rocker arms. Turn the engine over by hand until the exhaust rocker is almost closed and the intake rocker is just beginning to open (this is called TDC, top dead center, exhaust stroke). Then take a screwdriver down the #1 spark plug hole and the piston should be near top dead center. You can confirm TDC by slowly turning the crank shaft one way, then the other. If the cam timing is correct the next step would be compression. Test it wide-open throttle, all eight holes. Should be over 100 psi (actual numbers depends on compression ratio and camshaft) and all cylinders within 10 psi of each other.

Next would be to confirm the engine swap part of things. Once the base engine has been verified, you need to double check all of your wiring. Especially all grounds, and power to your ECM, ignition coils and fuel injectors. All coils and injectors should have 12 V key on engine off (KOEO), and while cranking. All eight spark plugs should spark once every other revolution of the crankshaft, same with fuel injectors. The wiring especially is suspect because the original wiring is 50 years old and the LM7 engine control circuits take a higher amperage current.

After we have confirmed all of this, we can look at the "tune" and make sure it is correct and the computer is appropriate for the engine.

God bless and Good luck.
Jeff

[BReal669]

Ok I will run thru the list and report back but just a few points to add. Wiring harness is swapped from the 03 there is no 76 wires left on the truck and I ran multiple grounds I understand the importance. By grounds I'm talking g from frame to body in four places engine to body in one heads each to body once and ecu chassis to frame. I verified TDC when I built it by 1:30 position and visual piston at top of block I will re verify at same time do compression check and let you know. Rockers were tightened using GM specs to 22 lbs following directions for which valves to do first and then the others on the 369 rotation. Pretty sure it is going to be an issue of tune because of the decapped injectors and stage 3 cam I have a hoollset hx40 turbo lined up haven't picked it up yet that is the reason for the injectors. I will report back on compression in a few hours.

[In-Tech]

Hiya,
Have you ever seen these "decapped" injectors on a flow bench? Disgustingly horrible.

[steveo]

you know learning this stuff is a lifelong thing, so you should really focus on beating the odds on your health issues

don't worry about the cloud man i have done some of my best work while in a fog

you need to get proper injectors to tune with, they are one of the pencils you're using to draw the picture that is your tune, and your pencil is not sharp enough.

all your instruments need to be accurate, both input and output, to achieve your results

keep in mind though that an engine should run even with a relatively massive error in fuel or spark, it should still kinda run, like i can start my lawnmower with no carb if i dribble gas into the hole, so if it isnt' starting you have a way bigger issue than a tune

[BReal669]

Agree fully with all points from all. Let me clarify a bit. I went to DeAnza Auto Tech when i was 16 for 3 years and have been working on cars my entire life. This is my 4th "frankenstien" project i have tackled previous being a S-15 305 TBI convert a 71 240Z 327 convert, subaru hatch converted to FI and CARB smog ref approved. But this is my first time really getting into doing my own tunning all my Subarus before this I took to Vishnu and let him do it cause he knows what he is doing. At this venture in my life i cannot afford to pay someone else to do it for me and just hope to build something that can be enjoyed for years to come by either me or my son or hopefully both of us. Working on it is a distraction and hobby but my health does come first and is my first priority trust and believe that.
Back to the truck. Verified motor all good and it does start and run with peddle play it will not idle on it's own and doesn't like getting below 1200-1300 rpm or so. at first start up it is pretty bad but as it warms up and I am guessing the lifters pump up it smooths out rather nicely but still smells rich. Wide Band sensor and gauge is in the plans but not the budget just yet. Any advice on tunning in the idle and running quality in general or any common things I just don't know about would be appreciated greatly and I thank all in advance for any help you can give and for your time spent doing so.

[steveo]

if you are certain there are no mechanical or sensor issues, and the idle will not come down below 1200rpm, you have a huge timing or fuel error

the huge fuel error, look at a spark plug to see if you need to add like 15-20% fuel or subtract like 15-20% fuel to get it in 'yay i run kinda' range...?

the monster timing error is another matter, but larger cams usually need more timing advance at idle, try like 5 degrees more than a stock calibration and see how that goes

[steveo]

i should also mention that i don't know what a 'stage 3' cam is, some engines i've tuned with pretty big cams, i've set to like 1000-1200rpm idle. you want to run it where it's happy, not force it to go where it doesn't want to..?

[BReal669]

Steveo I think you are dead on right. my problem is i have obdx cable and tuner pro and ls droid and universal patcher and tuner studio and no idea how to use them.

[MO LS Noobie]

Post your .BIN and we can look at it. If is stock (not modified) the hardware and Operating System also. It helps to know your experience level. Or send a PM and I can give some tips on how get this info. It is also helpful to know it runs, and not just "coughs".

[BReal669]

Yeah I am making progress on it still won't idle but I need to verify no vacuum leaks first thing then I will see if I can't post up my bin for you guys to check out l. Thanks for all the help

[MO LS Noobie]

The LS vacuum port for the brake booster is often overlooked.

[BReal669]

Got it to idle at 1200 but had to shut it down for the night. Heading back to check for vacuum leaks and run it/tune some more. It's a sloppy stage 3 cam if anyone has any more suggestions for specific tables to pull up and values to punch in that would be great. I look at some of these other bin files and see the massive number of tables that have been changed and it is kind of hard to know whats what and what can be skipped.

[MO LS Noobie]

When you get it to idle at 1200 RPM, what is your wideband reading or oxygen sensor voltage? It should be quite a bit rich, if you lower the values 20% in the VE table 1200 RPM and lower that will probably bring it closer anyway. Typically with large camshafts you need to lower the VE below 1200 and raise the VE above 4500. These are just general guidelines, follow your wideband readings for your situation

[steveo]

it has to be a decent sized error, not just 20%.

most engines will idle as low as 9:1 and as high as 16:1

you can keep an engine idling with no carb by pouring any fuel down the intake. alcohol, gas, whatever

if it's not running enough to start and stay idling, it has to be way way way out on timing fuel or both