sinisterSF

I'm on the fence, rebuild it, maybe get lucky and it's just a head rebuild, or buy a LDK crate motor for 2k from ZZP. Eventually I planned on upgraded to the LDK anyways. Guess there's no time like the present!
LDK Long Block - Engine

umrdyldo

iTrader: (1)

Pull the head and check for damage to the pistons and cylinder walls.

riceburner

iTrader: (66)

When the same thing happened to me it was a fried pcm. It has enough power to send fuel to the rail, make the plugs spark and make that car crank but wouldnt let it fully start. It would crank forever then here and there like almost start but immediately die.

sinisterSF

I'm going to do a wet cylinder compression test this evening. That should tell me if it's rings or not. Then I'm going to pull the head and start checking everything. Maybe I'll get lucky and all of this buildup is preventing the valves from closing! But it's pretty unlikely that buildup would cause all 4 cylinders to lose compression at the same time.

ECaulk

iTrader: (6)

The front of the runner isn't to bad, but back around the valve seat it looks damn nasty. If you have a borescope check down the spark plug hole and see if there is internal damage before pulling the head.

ECaulk

iTrader: (6)

He has zero compression on three cylinders

umrdyldo

iTrader: (1)

Zero compression on 3 cylinders is very strange. Usually when you have ring and piston issues it's usually 1 or maybe 2 cylinders. 3 seems like it's losing air out the valves. Especially if it's showing 0 compression.

A leaky cylinder will show low compression.

ECaulk

iTrader: (6)

Just realized he could see (feel) if air is pushing out the intake valves with the manifold off, that will give him a direct answer if it is the intake valves not closing or if he some how killed 4 ringlands

sinisterSF

Yea this seems more like a valve issue than rings, since they're not getting any compression at all. But I want to try and slowly rule everything out and do as many tests as possible before I yank the head. I'll do a wet test (oil in the cylinder and look for an increase in pressure). I'm not sure how to test the valve seal, especially since I don't have anyone helping me. Maybe I'll Wiley Coyote put a stick on the clutch and run around to look and feel in the intake runners while the engine spins. I'd spin it by hand but I don't think I'd feel anything escape with it turning that slow.

ECaulk

iTrader: (6)

Find a helper to turn the key over for you

sinisterSF

I just talked to my machinist and he says before I yank the head he had some things for me to test and maybe save some $$$.

First make sure the timing hasn't jumped.... How do I check this?

Second, unbolt the cams to relieve spring tension, pump up the cylinder and look for air leaking out of the intake or exhaust. If it holds the lifters are shot. Based off the oil in the engine this may be possible, doesn't look like it was changed in the last 20k miles and smells a bit burnt. If it doesn't hold then yank the head and bring it in for a valve job.

ItalianJoe1

iTrader: (10)

A leakdown tester (available cheap from harbor freight if need be) will let you put a nice slow supply of regulated air in there and see where it's leaking from. If it's valves, you'll hear the air coming out the exhaust or intake. I'd try that before a wet compression test, as you already know if the compression is that low, there's damage.

ItalianJoe1

iTrader: (10)

Timing is best checked by turning the crank pulley until the mark lines up (It's about 11 o'clock on the front cover, a little hard to find unless you know where it is but it's there. Once the crank is up, the cams should have an even split, from the intake and exhaust marks to the outer edge of the head. I think it's 8 links or so down to the head. If it jumped, they will be different.

sinisterSF

I think it jumped, should the different colored links line up in the cam phaser arrows? There also seems to be a spot where the chain has some slack. I'll post a vid of it spinning.

ItalianJoe1

iTrader: (10)

Yeah that's too much slack if the tensioner is working and you're turning it the right way.

The colored links don't have to line up, they change places every rotation. But if you get the timing markes aligned the cams should be a 10 and 2, evenly split from the marks down to the outside of the head on both sides. If there's a difference, one of them moved.

sinisterSF

The arrows are at the 10 and the 2, with 16 links between them. I'm getting a leak down tester tomorrow and we'll see what that shows us.

sinisterSF

I did the leak down test. I undid the cams to take pressure off the valves. Air is coming out everywhere! What do you guys think? Blown head gasket, bad valve seats, and spent lifters?

ItalianJoe1

iTrader: (10)

Odds are it jumped timing and bent valves. The lifters take up slack, so if they fail the valves will open less, not more. A head gasket leak is a small leak on a leakdown test usually and will result in bubbles in the coolant or something.

sinisterSF

I'm gonna call my machinist tomorrow and ask what he'd charge me for a full rebuild. If it's more than $1500 I'm just gonna buy the LDK crate motor from ZZP, no fuss, no mess.

ECaulk

iTrader: (6)

Either way pull the head now, it's work a look.

sinisterSF

Yeah, I'll pull it. If there's no piston damage then I'll see about a head job and new timing chain and tensioner.

sinisterSF

Has anyone used the LHU as a replacement for their LNF? Looks to be the same as a LDK except you can use E85. I found a Regal with one of these motors, thinking about just swapping rather than trying to fix this tired old LNF.

Does anything need to be done to the LHU to work in the Cobalt?

sinisterSF

I put the valve cover back on, buttoned it all up and redid my leak down test on each cylinder again just to confirm. Nothing coming out of the dipstick tube. Bent valves most likely, but since I can buy a new head with everything installed I'll just do that rather than getting this head fixed. So long as the valves didn't death kiss the pistons I can toss in a new timing set, head gasket and the new head and this motor should be good to go! We'll see if I can get the timing set correctly haha!

JapEatr

iTrader: (9)

put a fuel pressure gauge on it

sinisterSF

It's been a while but I finally found time to get back to work on the SS. Once I pulled the head it's very clear that timing jumped and bent the valves, pretty much all of them. Surprisingly the pistons show no damaged and the cylinder walls look damn near new, no streaks, can still see the factory hone marks.

So after a lot of cussing and knuckle busting I've got the new head and timing set installed. I'm going to pop the turbo and all of the accessories back on today and button it all up. I was thinking about doing a compression test before I try to fire it just to make sure.

Any other suggestions or things I need to do before I fire?
Whats the break in procedure for a new head (new cams) on this motor?