Running on 7 cylinders
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 1,021
Likes: 52
From: Coral Springs, FL
Running on 7 cylinders
I recently replaced my heads on my blown c6 that was previously making 888whp on pump and meth. I upgraded to trickflow heads, measured out the pushrod length and put it back together. Ever since, I can feel like it is missing under load. Right around 2000 RPMs and up. I pulled the plugs, and found one to have the porcelain cracked. Replaced and it felt great for a bit. Soon after, same issue. Cracked porcelain near the electrode tip. I got busy with buying a new home and moving so 3 months passed by. Now that I'm settled, I'm picking this back up. I changed coil packs, and wiring and pulled the plugs after a long but judicious drive and found this
It smells like there is fuel, but the plug looks perfectly clean. Definitely no combustion happening here. I've replaced plug wires also but the issue persists. What are my next steps?
It smells like there is fuel, but the plug looks perfectly clean. Definitely no combustion happening here. I've replaced plug wires also but the issue persists. What are my next steps?
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,562
Likes: 4,034
From: Cape Coral, Florida
For a DIY’er without a scan tool and scope it basically comes down to playing “swaptronics” or just replacing parts !!...if all ignition parts have been replaced (you still have to verify wiring) you would have to think fuel injectors or its wiring or something mechanical !!...put the gas pedal to the floor and hold it there and try to start the car. (Clear flood crank)..car will just crank but listen if the car cranks over evenly..if it doesn’t I’d worry about something mechanical.
Last edited by C5 Diag; May 12, 2021 at 01:41 PM.
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 1,021
Likes: 52
From: Coral Springs, FL
For a DIY’er without a scan tool and scope it basically comes down to playing “swaptronics” or just replacing parts !!...if all ignition parts have been replaced (you still have to verify wiring) you would have to think fuel injectors or its wiring or something mechanical !!...put the gas pedal to the floor and hold it there and try to start the car. (Clear flood crank)..car will just crank but listen if the car cranks over evenly..if it doesn’t I’d worry about something mechanical.
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 1,021
Likes: 52
From: Coral Springs, FL
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Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 1,021
Likes: 52
From: Coral Springs, FL
Found the issue. I removed the intake and found this:
The intake was full of gas/oil.
After removing the valve cover, I found that my yella terra pedestal bolt had snapped in half. Pushrods are straight, valvsprimgs are good and rockers look good. This might have been the best case scenario.
The intake was full of gas/oil.
After removing the valve cover, I found that my yella terra pedestal bolt had snapped in half. Pushrods are straight, valvsprimgs are good and rockers look good. This might have been the best case scenario.
Pro
Joined: Feb 2017
Posts: 611
Likes: 79
From: Fallbrook SanDiego county
I sure wouldn't have thought that that much oil could get past the rocker stud into the intake runner! Did you use tread sealant on the rocker studs? What's going on with that valve cover? is that a hole in it? is that from the stud breaking? Cylinder was full of oil and the intake valve was hydraulicing ???
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 1,021
Likes: 52
From: Coral Springs, FL
I sure wouldn't have thought that that much oil could get past the rocker stud into the intake runner! Did you use tread sealant on the rocker studs? What's going on with that valve cover? is that a hole in it? is that from the stud breaking? Cylinder was full of oil and the intake valve was hydraulicing ???
Last edited by slow goat; May 14, 2021 at 01:27 PM.
Melting Slicks
Joined: Nov 2009
Posts: 3,297
Likes: 1,151
From: Klein TX
2023 C6 of the Year Finalist - Unmodified
2022 C6 of the Year Finalist - Unmodified
Saw that happen to another Yella Terra setup a few years ago. That time the threaded part of the bolt stayed in the head. 
. Glad you found your problem and it was simple
. Glad you found your problem and it was simple
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 1,021
Likes: 52
From: Coral Springs, FL
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,562
Likes: 4,034
From: Cape Coral, Florida
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 1,021
Likes: 52
From: Coral Springs, FL
Yes, at some part of the crank cycle sounded slower and then would speed up, then slow down...repeat.
No sir. Built 416 LS3 through the stock T56.
No sir. Built 416 LS3 through the stock T56.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,562
Likes: 4,034
From: Cape Coral, Florida
up after the bad cylinder since there was no or low compression in that cylinder offering any resistance so that’s why it sounded that way !!...glad you found it !!
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 1,021
Likes: 52
From: Coral Springs, FL
This is a quick way to sometimes tell it’s a mechanical issue...what’s happening in your case is the crank sped
up after the bad cylinder since there was no or low compression in that cylinder offering any resistance so that’s why it sounded that way !!...glad you found it !!
up after the bad cylinder since there was no or low compression in that cylinder offering any resistance so that’s why it sounded that way !!...glad you found it !!
Last edited by slow goat; May 14, 2021 at 06:06 PM.
