Cam swap only start up help

[V8_Kind_Of_Guy]

Hey everyone, looking for a little guidance. I did a lq4 6.0 swap into an OBS truck. The 6.0 is stock except a summit racing cam 8718r1 (205/217 112+2, .500 /.500). Its got a stand alone harness instead of the factory bulky one and is cable throttle. Computer is P01 red/blue connections, stock injectors, external 255 lph pump, ~40-45 psi fuel pressure and I'm using the trucks stock but rebuilt 700r4 transmission.

I cant get the truck to fire up and stay running with throttle. If I give it a little throttle (~10-15%) to start, after about 5 seconds of me helping it idle with the throttle, it will stay idling by itself just fine. I can also at that point rev it and it will return to idle and I was able to drive the truck down the street just fine as well.

I've tried adjusting everything thats in the GM book from the tuning school, idle up to 750 rpm (have done 800 as well), base running idle airflow ( have changed slowly up to 14 g/s from stock 6 g/s), Friction airflow initial, idle startup friction, Cranking FA stage 1 and cranking spark.

Any help would be appreciated.

Chevy OBS 93 ls 6.0 swap idle.hpl
Chevy OBS 93 ls 6.0 swap Javiar codes cam airflow new 05.hpt

[kevin87turbot]

You need a few more parameters on the datalog. But, I can tell you that the IAC is around 150 when it's idling without any throttle input. That means that you need to open the TB blade quite a bit more. You need to open the TB blade until the IAC is in the 40-70 range at a warm idle. Start off by turning the TB minimum air screw by 1 full turn.

[2xLS1]

FP is too low. Gen 3 requires 58 psi FP. If using a return less fuel rail it should be constant 58 psi at the rail. If using a vacuum referenced regulator with a return line to tank it should be 58 psi at the rail with the vacuum line disconnected. A cam that small in a 6.0L should start and run on the stock tune with just adding 100 rpm to the entire idle rpm table and adding 3~4 g/sec to the entire idle airflow table. Also adjust the TB closed stop set screw to obtain .65V closed TPS voltage. If it doesn't start and stay running with those few changes then you have other problems. I would also start with a 6.0L manual trans calibration with a 700R4.

[V8_Kind_Of_Guy]

Thanks for the tips guys. I'll start with adjusting the idle screw and go back and adjust the idle airflow table.

The fuel system is a return style and that ~40-45 is with vacuum attached, i didnt check it without vacuum but ill double check that and report back.

Thanks again.

[5FDP]

Even though the camshaft is small I wouldn't be surprised if you reach 95-100% duty cycle on those injectors at high rpm as well. Just note that for the future.

[V8_Kind_Of_Guy]

Alright! Those changes worked! My idle counts is now at ~50, truck starts every time without the help of me pushing the throttle. Thanks again.

Also, the injectors are pushing about 82% duty cycle. It might be lower than what your prediction was because Im in Denver at 5000 feet (82 kpa at wot).