4.3 to 6.0 Swap Complete..Slooow

[RichardLSX]

So I'm basically screwed with that motor or is it still better than a 5.3. Also 4.8 or 5.3 aluminum heads should work correct?

[George C]

so im basically screwed with that motor or is it still better than a 5.3..also 4.8 or 5.3 alumn head should work correct?

its up to you. i think the ironheads are only 295 or 300. a 5.3 is 285 for the older ones and have a better cam in them with decent flowign heads.

for now just get a proper tune

[RichardLSX]

its up to you. i think the ironheads are only 295 or 300. a 5.3 is 285 for the older ones and have a better cam in them with decent flowign heads.

for now just get a proper tune

If I'm not mistaken, the only difference between iron headed and aluminum headed 6.0s is just the heads correct..lol..

[George C]

if im not mistake the only difference between iron headed and aluminum headed 6.0s are just the heads correct..lol..

no, less aggresive cam, weak rods, bastard crankshaft, tad lower compression, heat holding iron heads.


yes you can swap out parts just like any of the gen 3 motors, yes youll gain performance but think of the ironhead 6.0 as the old TBI 350s. solid workhorses but not performers

[RichardLSX]

Alright, so internals are crap. I have a 4.56/Posi-Unit on the way, and might start on internals next.

[beertestr]

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.

[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

[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..