Engine exhaust diagnosis

[Eric]

I recently fired up a fresh motor build. The block and heads are 2001 LM7 (5.3). Block is bored 0.020 over with new everything except crank and rods (which were both checked and machined as needed). Heads were completely rebuilt; new everything except the casting. The motor is running an LS1 intake, headers, and comp cam "XFI Extreme Truck" camshaft. As per Comp Cams this cam works best with programmer. The motor is running a new OEM-style computer from PSI conversion. Stock tune but with VAT and emission deleted.

The motor fires right up and sounds fine. Exhaust is barely visible. Once the motor comes up to temperature some white-ish smoke starts coming out of the exhaust. Not like huge cumulus clouds but it definitely changes. No noticeable smell of coolant. Temperature is holding steady at about 190 with one of two fans running (triggered by the computer). I'm holding the RPM between 1,500-2,000 for initial break-in. If I shut down and let it cool the coolant level in the radiator does not appear to have changed and it remains perfectly clear.

I'm thinking two possible issues:

1.) Once engine comes up to temp and coolant starts to flow there is a head gasket leak.
2.) Once engine (o2 sensors) comes up to temp the computer switches to closed loop and the tune is too far off.

Who knows what the next step is?

 

[gt1guy]

How long have you let it run for?

Can you get a log of what it's doing at idle?

Stock tune with a cam that wants some mods to the tune would make me want to get a log going as soon as I could.....just for a sanity check if nothing else.

 

[Eric]

How long have you let it run for?

Can you get a log of what it's doing at idle?

Stock tune with a cam that wants some mods to the tune would make me want to get a log going as soon as I could.....just for a sanity check if nothing else.

Between 20-30 total minutes so far. Mostly between 1,500-2,000. Shut it down twice to check oil and coolant and fix leaking oil pressure sensor. Smoke has been slowly subsiding. The video below was a while ago. Much less smoke now.

Other thoughts: Blow-by as the rings seat or I fawked up the pcv routing.

No logging. Really wanted to buy efi live but this project has already blown the budget to pieces. On the other hand, I guess efi live is less expensive than the tuner I plan to bring it to.

 

[TrailTamer]

I’d Run it some more before I’ll get too worried, unless there’s bad noises.

Probably just a bunch of stuff getting burned off from a fresh build.

How did the smoke smell?

 

[TrailTamer]

2.) Once engine (o2 sensors) comes up to temp the computer switches to closed loop and the tune is too far off.

Have a scan tool to look at long & short fuel trims?

 

[Eric]

How did the smoke smell?

Did not smell like coolant or engine oil. I think it was just some residue burning off or rings seating. Basically gone now. Planning to buy EFI live or similar so that I can read real time data. All I have now is a basic ODB II code reader.

Thanks!

 

[4Eyedturd]

Compression check it if you’re worried but I’d let it run more.

 

[arse_sidewards]

Until you notice a fluid going missing I'm in the "shit burning off" camp.

 

[Eric]

Ran it all day Sunday. Good to go.

 

[gt1guy]

Ran it all day Sunday. Good to go.

Great news. Now get to beating on it.

I'd still get a tuner, there's so much info you can get from them.

 

[BUCKWILD]

no load on the engine? just running at 1500-2000rpm will never load the rings and allow them to seat, it requires load on the engine to do this you need to drive it and run the piss out of it rods will not stretch so go balls out