(Engine Trashed?) Thread of Unfortunate Events

I’m not boosted yet. I’m sorting out all the kinks this motor has before I decide to boost, but from what I’ve heard people have seen a big difference with them. I’m pretty sure there’s a few people in that thread who were having the same issues you were who got those fuel rails and they were resolved. I’m not saying this is your way out of a new motor, but it sounds like the same issue.

 

Tonight we wrench!

 

Okay guys. Here's how it went.

1.) Put the piston on cyl 4 to top dead center on compression side.
2.) set the gauge to 90psi and pressurized cyl 4.
3.) pressure went smoothly to 90psi and held.
4.) removed oil cap and pressurized again. tiny bit of air coming from oil cap which I believe is normal. Pressure held at 90.
5.) removed cyl 6 spark plug (air fuel imbalance cylinder)
6.) pressurized cyl 4 again when it reaches about 60psi you can hear a blow out the gauge will go down to about 20psi then charge back up and hold at 90. This will consistently happen Everytime you do a fresh pressurize of the cylinder.
7) put the spark plug back into cylinder 6 and pressurized cyl 4 with no blow out of air. Held 90.
8) removed radiator cap, no bubbles.

https://imgur.com/a/GlQNvXq

 

So 4th cylinder only loses pressure when cylinder 6 plug is out? Does not make sense.
The firing order is 1-2-3-4-5-6. I would think the intake valves are still opened on 6th.
Have you tried pressuring 6th?

 

Correct, I did not try to pressurize 6.

My assumption is cracked head or the guys who did the valve job didn't install the head gasket correctly and under fast pressure air bursts over to cylinder 6. But the issue was there before the valve job.

Cylinder 4 should be isolated right now. If a valve was open it would be going to the exhaust or intake with cylinder 6 spark plug in. It seems like it needs to see a fast burst of air for the leak to happen. But won't do it with cylinder 6 spark plug in. Has to be head gasket?

The way it's acting is weird and I don't understand it. Why would the cylinder hold pressure fine if you climb it slowly but then temporarily loose compression if you shock it with air? Could think valve spring but 90psi is 90psi. Shouldn't matter how fast you get to 90psi if it's going to leak it should.

Edit:
I see what your saying about the intake valve being open on cyl 6. With the plug in, technically cylinder 6 should still be open because of the valve being open...so yeah why am I not losing air the same way it's acting with the plug out?

 

Pressurized cylinder 4 again this morning with 6 plug in and it discharged about 20psi of air before reaching 90psi. Then I re pressurized multiple times and never lost air. I removed cyl 6 plug and pressurized cyl 4 again multiple times and I was not having escaped air like last night. Nothing has changed.

 

Oh well...my cylinder isn't at top dead center anymore...how did it move if my truck is in first gear and the truck never moved forward?

 

So it's mechanical. Best case is a head gasket or hairline crack in cylinder head?

 

I would check the torque on the bolts that are between cylinder 4/6

 

Okay I'll check that now. Looks like the cylinder was moving on me and maybe that's why the air was being surged because the cylinder was opening up and needed more pressure. This cylinder might be fine

 

The piston is at the bottom now and I'm assuming that the quick burst of pressure was pushing the cylinder down a tad bit which maybe made it sound like a burst of air? With cylinder 6 plug out it might have been easier for the engine to rotate and what sounded like air flowing into cyl 6 might have just been the cyl 4 piston pushing down slightly at a time which then drops the pressure until it charges back up to 90. Now that the piston is at the bottom there's no loss of pressure at all in cyl 4. I assume the exhaust valve hasn't opened yet with it at the bottom of the stroke.

This is my unprofessional opinion

 

Leaning towards misfire issue on cylinder 4 is the high pressure fuel injector.

Still need to check cylinder 6 with leak down test.

 

Any recommendations for upgrading the injectors to be able to use less of the port injectors under boost?

 

Intake has a lot of air coming out from the cyl 6 leak down test.

 

I'm going to figure out how to remove the valve cover and inspect the valve spring.

 

https://www.monkeywrenchracing.com/product/mwr-fuel-injector-set-6-2gr-fks-650cc/
Just giving some random ideas now. Maybe those will help though

 

Throwing different injectors at a vehicle that isnt running right to begin with will compound the issue instead of sort it out. These require more tuning. His best bet is to get another spare injector and put it in and see if that fixes the issue.

 

Yeah I never said it was gonna fix every issue lol. I’d be trying everything I could if I were in his shoes though, it seems nobody knows what the issue is.

 

Alright guys. Started tearing down the engine a bit. Removed the lower intake to verify both valves were closed when doing leak down test on cyl 6. After making sure they were I put pressure into the cylinder plugged the 2 valve case hoses and when opening the oil cap the oil cap flew off.

My only chance is removing the head and seeing if it's cracked and only replacing the heads. If no crack must be piston rings.

Once this is back together I'll never mess with rpm again. I'd say the tune allowing me to go to 7k rpm along with me having 5.28 gears in a manual which climbs the rpm wicked fast just caused me to screw this engine up. I was honestly chasing boost with rpm and I should have been conservative with it. Kept a 5.5k rev limiter to be safe and maybe changed the supercharger pulley to get more boost. Lesson learned. I'll keep everyone posted on the process. I'm not paying no stealership to do this work so I'll be wrenching when I can after work or weekends.