Cometic Falure with Pics

[jhanson1750]

I have been running the GN for about a year and a half now with the current set-up (see sig). I went to the track last Friday and made a pass all was going well but at about the 1000' the car didn't "feel" right so I lifted. It didn't want to run right (very slight miss) and running hotter that it ever has 205-215. Took it home and pulled it apart. I got the driver side head pulled last night and found this? Has anyone had this happen to them? I am going to pull the pass head this evening and see what it looks like. Let me know what you think. I did log the run but will have to post the log this evening when I get home. I was kinda bummed and havn't even looked at the PL file yet.:frown: All 3 layers of the Cometic are "broken" on the #1 hole in the area near the lifter valley. The head looks to have lifted and then I'm not sure? The piston crowns have no signs of detonation. Just neet to be cleaned off.

 

[WINDMILL]

i was wondering if you was running a power plate and what hat was you useing? just wondering..... this dont mean nothing,,, thanks
also who ported the intake and heads.....

 

[SPOOLFOOL2]

Yep.

I've seen it on engines that were overheated, and had detonation. How did the plugs look?

Mike Barnard

 

[jhanson1750]

WINDMILL i was wondering if you was running a power plate and what hat was you useing? just wondering..... this dont mean nothing,,, thanks
also who ported the intake and heads.....

I bought the head off the board already ported and I ported the intake. Yes running a power plate.

SPOOLFOOL2 Yep.

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I've seen it on engines that were overheated, and had detonation. How did the plugs look?

Mike Barnard

The car never ran above @ 170 while just driving typicaly 165. When I would run it I would leave at 165 and when I would turn off the track it would be @180 but back down to 165 by the time I picked up my time slip. The only time it ever saw 200 what last friday. I have had an issue about a year ago with detonation (Cheep alky kit) but started using race fuel and then got an Alkycontrol kit and have not had any issues sence. The plugs look great just a nice even brownish color. I will post more pics this evening of the combustion chambers with the plugs still in them. thanks for the replys. Jon

 

[jpratt]

I had the exact thing happen to me, twice.

 

[bison]

Those look like at least 4" bore gaskets and detonation/lean out occurred. Imo if you are running a big bore gasket you really need the extra clamping force of the extra head bolts or you have a weaker head gasket that is more prone to heat induced and detonation failure. Whenever #1 goes lean id look into fuel delivery

 

[Scott231]

Could very well be a lack of fuel from the pump not spinning hard enough. Did you log the battery voltage? How hard were you running it?

Don't be surprised when #1 goes, as it is the 'last' to receive fuel from the rail. could have also been an unevenly torqued head fastener that 'gave' when the cylinder pressure got too high.

 

[jhanson1750]

I will let you know once I look at the PL file. I log the FP on my PL and I have my pressure sender where the schrader should be so being that it is the last point on the rail past the regulator I should see any fluctuations on pressure. I will be checking that this evening.

On the head studs, I went thru an extensive retorque. I torqued and waited 2 days then retorqued waited 2 days and checked again. Then heat cycled it about 3 times and retorqued again. then just ran it.

We'll see once I get the logs posted up.
thanks for all the responces. Jon

 

[bison]

I will let you know once I look at the PL file. I log the FP on my PL and I have my pressure sender where the schrader should be so being that it is the last point on the rail past the regulator I should see any fluctuations on pressure. I will be checking that this evening.

On the head studs, I went thru an extensive retorque. I torqued and waited 2 days then retorqued waited 2 days and checked again. Then heat cycled it about 3 times and retorqued again. then just ran it.

We'll see once I get the logs posted up.
thanks for all the responces. Jon

Next time put it under some pressure not just heat cycles and re-torque cold. Typically ill re-torque 3 times before i stop getting movement. This does not seem to be a torque issue though.

 

[1987]

stud torque

What are you torquing the heads down to as far as ft. lbs, also have you checked your torque wrench to make sure it is accurate?

 

[bison]

What are you torquing the heads down to as far as ft. lbs, also have you checked your torque wrench to make sure it is accurate?

Ive had equal success with 75 to 90 ft lbs. Ive tried everything in between in 5 lb increments and there was no difference. I havent had my torque wrench calibrated for a while but im the only one who uses it and i only use my half inch drive one to torque head bolts and mains. Its never been used in reverse. I torque at least 3 times after chasing the threads to be sure the threads are polished on the fasteners and the block. I use ARP thread sealant.