V6 to V8 problems

94CheyenneSuper · May 23, 2016

I swapped a 4.3L for a 305 I with 350 heads, .470/.480(big for a 305 I know) cam, Jet stage 1 chip, 350 throttle body, and Hedman headers. Already have a NGK O2 sensor and a ACDELCO idle air control.

But my problem is turning it over it starts up and runs good till you put it in gear and it dies. Leave it in park and rev it up and it dies and I just can't pinpoint the problem

Justin S · May 23, 2016

you swapped to a v8 computer and harness right?

94CheyenneSuper · May 23, 2016

I ha

Justin S said:
you swapped to a v8 computer and harness right?

I have changed the eprom in the computer and the harness from what I have read is the same as the V8.

Justin S · May 23, 2016

Years ago I did a swap from a 4.3 to a 350 in a 94, and the computers were different, I ended up having to do the harness on mine. It was 5 speed so not sure if I would have had trans issues though

skylark · May 23, 2016

Set your base timing at zero. Jumper a and b on the aldl like you would for checking codes. The iac will bottom out in the throttle body. Leave the key on and unplug the iac. Shut off the key and remove the jumper. Try to start the truck. It should idle around 550. If it won't then you need to adjust the minimum idle air screw on the throttle body. It is on the drivers side facing forward under a domed cap. Poke a hole in it and throw the cap away. Tighten the screw about 1/2 a turn and try again for your 550. Once you are there shut off the truck and plug the iac back in.

michael hurd · May 23, 2016

305 and 350 TBI have different injectors with different flow ratings measured in pounds per hour.

If the injectors are bigger than what the computer is expecting, then your A/F ratio will be out.

Verify the distributor reluctor magnet is crack free, and if so, then check and set the ignition timing to 0 degrees.

Is the camshaft a roller, or a flat tappet? If the overlap and duration is radically different than the stock profile, your Jet chip will be basically useless, and you will require a custom chip.

94CheyenneSuper · May 24, 2016

I just thought of this on the way to work, could it be the map sensor from the V6 on the V8?

michael hurd · May 24, 2016

Manifold absolute pressure sensor doesn't care what engine it is connected to, unless of course, it is an incorrect unit designed for turbocharged applications installed on a naturally aspirated engine.

V6 to V8 problems

94CheyenneSuper

Newbie

Justin S

Truck Hoarder

94CheyenneSuper

Newbie

Justin S

Truck Hoarder

skylark

I'm Awesome

michael hurd

Stalker be gone.

94CheyenneSuper

Newbie

michael hurd

Stalker be gone.

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