4.3 to 6.0 Swap Complete..Slooow

[RichardLSX]

Before you go to the tune or parts swap route, answer a few more q's.

1) You said it goes like a bat outta hell when cold. This makes me think that you have an open loop-closed loop issue. When you motor is cold, and the ECT is below a certain threshold (which I need to look up for the exact temp), the engine runs on preset a/f ratios. When the engine gets warm enough, the engine looks at O2's, your MAF etc, and tries to correct for rich/lean conditions. This might be as simple as you have the left O2 plugged into the right bank and vice versa. I have found things like this more than I can count.

2) Are you sure you don't have any codes? Do you have the SES light wired up? Even if you do, not all codes are equal, there are many that do not trigger teh SES (check engine) light.

3) Do you have a scan tool? Drive the truck and look at parameters to make sure all your sensors are actually working. While an open or shorted circuit almost always triggers a code, a lazy sensor may not.

When you say you are not tuned, do you mean that the PCM in the truck is the 4.3L PCM or is the untuned 6.0L PCM that came with your motor? Hopefully it's at least the 6.0 PCM. Really, while the 6.0 you chose is not the strongest one you could have used, it should still be able to run a 4.3. And no your 3.42 ratio with a 3.73 cal will not cause all that degradation too. REally, your speedo, and what the PCM reads is off by 10%, that affects shift points a bit, but not alot.

Just some thoughts before you start plunking down cash on speed parts. You might be throwing money without know what the real issue is.

Yes Iv'e noticed it runs good when its cold. Yes I do have a check engine light on, I scanned it and it shows Oxygen Sensor codes (o2s). More than likely, it's because I have only two o2s and no cats. Would this be the problem? It's the stock tune 6.0 PCM BTW

[GasGuzzler]

Need the codes.

[ff_jeff]

I think with a tune, you will see a major difference. But I agree on swapping out for 5.3 heads. Preferably the ones with the 799 casting number on them.
Flow great, and still bump up compression.

[beertestr]

yes it runs good when its cold..yes i do have a check engine light on..i scanned it and it shows up about the Oxygen Sensors (o2s) its because i have only two o2s and no cats..would this be the problem..and its the untuned 6.0 PCM BTW

Do you have a dirty MAF? Check your knock sensor wiring. A tune is not a bad idea, but I really think you have something else going on there. Open loop good to closed loop bad .. 99.99999999999999% or the time it's a bad sensor, or wiring issue.

Need the codes.

What he said..

[RichardLSX]

Need the codes.

Cool, when I get a chance I'll scan it again. I forgot the codes.

[RichardLSX]

Do you have a dirty MAF? Check your knock sensor wiring. A tune is not a bad idea, but I really think you have something else going on there. Open loop good to closed loop bad .. 99.99999999999999% or the time it's a bad sensor, or wiring issue.



What he said..

Would me just having 2 o2 sensors and no cats at all be a problem? They can turn off the o2 sensor from being read with a tune right?
Also, how bad are my heads compared to a aluminum headed 6.0 like in a 0-100% performance wise?

Thanks for all the help.