Atomic

iTrader: (37)

Just got my engine back together after having a head repaired. Only thing that was changed is new gaskets and new headstuds. Engine is a 402 with holley intake and holley fuel rails, 127lb bosch injectors.

Issue im having is bank1 is 15-20% leaner than bank2. I have tried hotter plugs with more gap, triple checked wires, and checked for intake and exhaust leaks. The injectors just got back from being cleaned and tested. Fuel pressure is right where it should be. All exhaust primaries appear to heat up evenly to the touch. Plugs look good, just lean. Fuel crossover is clean and rails are clean. Compression test shows all cylinders are about the same and number is fine. Idle vacuum and speed are fine...

Im out of ideas, anybody got a guess?

Undertow74

iTrader: (45)

Have you tried swapping o2 sensors

Atomic

iTrader: (37)

No because one is really hard to get to, but my wideband is agreeing that the total mixture is lean. Bank2 shows rich, bank1 lean, wideband lean. So I have no reason to suspect its faulty. They are both brand new as well.

LilJayV10

iTrader: (39)

You said the head was repaired, did it blow a head gasket? If so coolant could have killed the 02.

How are you checking for vacuum leaks? The best way is to watch your STFT's and 02's then spray carb cleaner around the intake.

Let us know what you find.

Atomic

iTrader: (37)

Yes, it melted a section from the edge of a chamber to a coolant passage, but didnt burn all the way to the edge of the head. I had it repaired and surfaced and it looks good as new.

I replaced both o2 sensors after blowing the head because they were both dead.

Checked for leaks by spraying starting fluid around the intake ports and not a single flinch. The ports all look flush to the head and I checked the orings before putting it back on. The top and bottom sections of the intake were never separated.

LilJayV10

iTrader: (39)

Try using carb cleaner instead of starting fluid. Starting fluid is REALLY dangerous to use. The starting fluid might be evaporating/burning too quickly for the 02's to see it.

LilJayV10

iTrader: (39)

Are both banks firing correctly? If one side isn't it will show the same thing.

poltergeist 02

iTrader: (65)

Did you only have the one head resurfaced? If so, how much did they take off of that head?

realistyc

iTrader: (5)

i understand u have new o2's but just for the hell of it do a full visual inspection of both upstream o2 bodies. i have seen this a few times where the body of the o2 has a slight ding, if so, 99% of the time its damaged internally. just had one on a 5.3 that i had done a head job on

Atomic

iTrader: (37)

Both banks are firing and the plugs on the lean side look lean, so I think its a real issue not a faulty sensor.

Both heads were surfaced 0.005 to clean them up.

I plan on taking off the exhaust to see if I can see a leak around the gasket surface.

Undertow74

iTrader: (45)

you sure your tune is spot on with those bosch 127lb. injectors?...seems like the issue is in the tune then.

Atomic

iTrader: (37)

Yes, this same tune was been in use for a couple months, so its well dialed in. Just in case it is an injector/tune issue, I bought some stock LS1 injectors to try in place of the 127s to see what happens.

Even if the tune was wrong, I would not expect to see such a large difference bank to bank.

poltergeist 02

iTrader: (65)

It really sounds like an injector or O2 sensor issue. Were all of the plugs on bank 1 the same color?

Atomic

iTrader: (37)

Yep all plugs were same color.

I took the exhaust off and there are no signs of leakage on the gasket on either side.

Also took the intake off and both sides were flush the gaskets are all fine and in their slots.

Still looking for that smoking gun :/

poltergeist 02

iTrader: (65)

Man, I know you said they were new O2's and they are a PITA to get to but I would try to swap them just to rule that out.

LilJayV10

iTrader: (39)

How hard is it to swap O2's from side to side?

Atomic

iTrader: (37)

I have to take the wastegate off to get to the passenger side, but I think I found my problem.... did a leak down test and cylinder 7 has 54% leakdown and is leaking out of the exhaust valve. Interestingly, cyl 1 has 80%, cyl3 has 87%, and cyl5 has 94%.

Looks like the heads are coming back off....sigh...thanks for the help guys.