Vortec heads on stock TBI 350

[OBSlates]

Hi. I’m new to the forum and had some questions about my 1992 Chevrolet Cheyenne. It recently had a set of 906 vortec heads installed on an otherwise completely stock tbi 350, now it’s not running all that well. When accelerating hard it chokes and wants to stall. Sometime backfires. It also does not idle well when it is cold. I’ve been told I need to put in a newer model vortec fuel pump, and up the fuel pressure to 18 psi. Also upgrade the exhaust and get a chip installed. Any guidance and help from anyone on here would be appreciated. Thanks!

 

[Nad_Yvalhosert]

Instead of loading up the parts cannon, diagnose the problem.
Vortec heads won't cause your running problems, installing a fuel pump capable of over 70 psi won't fix them.
Regulating the psi to 18 (when stock is 9-13) will cause more issues than it will fix, same with the chip. Ignore the heads for the moment, if the TBI is stock, wiring, sensors and ECM are stock, then stock fuel pressure is more than sufficient.

If it was running well and has declined, fix that problem before upgrading.
Have you scanned it yet?
What stands out on the datastream?
What is the fuel pressure?
What is the timing set at?
What is the ECT & fuel trim?

Back to the heads, what intake was used? Are you sure the intake gaskets aren't leaking?
What about vacuum leaks?

 

[L31MaxExpress]

Instead of loading up the parts cannon, diagnose the problem.
Vortec heads won't cause your running problems, installing a fuel pump capable of over 70 psi won't fix them.
Regulating the psi to 18 (when stock is 9-13) will cause more issues than it will fix, same with the chip. Ignore the heads for the moment, if the TBI is stock, wiring, sensors and ECM are stock, then stock fuel pressure is more than sufficient.

If it was running well and has declined, fix that problem before upgrading.
Have you scanned it yet?
What stands out on the datastream?
What is the fuel pressure?
What is the timing set at?
What is the ECT & fuel trim?

Back to the heads, what intake was used? Are you sure the intake gaskets aren't leaking?
What about vacuum leaks?

Having actually run a Vortec head TBI, it is time to load the parts cannon on all items he mentioned. The stock fuel pump and injectors are pretty much maxed out with the TBI heads. The pump capable of 70 psi works beautifully at 18 psi and was the same pump GM put into the 94-95 30 psi TBI systems. Either the fuel pressure needs to increase or it needs 454 injectors. Also it needs a chip that is remapped appropriately. Otherwise its a lean running, cannot get enough to drink, undriveable mess, that tends to spit fire into the air cleaner if you stab the throttle.

 

[Nad_Yvalhosert]

Otherwise its a lean running, cannot get enough to drink, undriveable mess.

Which would show up in the trim numbers, possibly by a lean DTC. So scanning it first is better than try-agnostics.

 

[L31MaxExpress]

Which would show up in the trim numbers, possibly by a lean DTC. So scanning it first is better than try-agnostics.

It will not really show up lean on the scanner. Where he would notice it would be looking at the 02 voltage. Stab the throttle and the 02 volts would bottom out. Go WOT and it would fall completely on its face and the 02 voltage be single digit numbers.

 

[Nad_Yvalhosert]

It will not really show up lean on the scanner. Where he would notice it would be looking at the 02 voltage. Stab the throttle and the 02 volts would bottom out. Go WOT and it would fall completely on its face and the 02 voltage be single digit numbers.

So you're saying scan it first yes?

 

[Nad_Yvalhosert]

Hey, @OBSlates scan it first!!!!!!

 

[L31MaxExpress]

So you're saying scan it first yes?

No I am saying he can scan it all day long and is still going to end up back at the same problem and needing to load the parts cannon.

 

[Nad_Yvalhosert]

No I am saying he can scan it all day long and is still going to end up back at the same problem and needing to load the parts cannon.

Agree to disagree

 

[someotherguy]

Hearing from someone who has already "been there, done that" is often very valuable information and what forums are great for.

However, it also assumes the installation is correct and there are no other issues besides insufficient this or that which can be solved with different this or that.

Richard