c5mtl

iTrader: (3)

Just looking to get some advice..pushed water all summer but got really bad at the end of season...so I pulled the passenger side head and found this ....what caused this? Check out the torching at the bottom of cylinders between the bottom bolts ...Is it head lifting from tune being off or is it block flex..I read somewhere if the black marks are at the bottom of the head it's the block stretching ....if the darkening is everywhere including around the studs it's head lift.....car ran 8.82 @157 at 3650pounds and gaskets were cometic Mls .071 thickness
22 psi ysi iron 408 trick flow 225 heads



Am kind of going of what I'm reading here

LASTLS1

iTrader: (7)

What fuel and timing at peak boost?

c5mtl

iTrader: (3)

Oops......I figured I missed some important info
straight c16 with 2 m15 nozzles ....18-19 timing at top 22psi air temps were reading about 90 at end of run did not see any knock on logs but plugs looked like timing was at egde of glory
Afr was in the mid 11
HP tuner Logs available

soundengineer

iTrader: (16)

on c16 its really not necessary to use the meth.....
we do way more power on c16 with zero meth and no issues...

sounds like you found the limits of your block.

the superchargers take quite a bit of power to turn...you easily eat up 100-150 HP (or more) just turning the blower...
so you figure you are likely 750 to the tire, after 30% driveline loss and having to turn the blower....so maybe 1200 at the crank..you are well past what the 4 bolt blocks really like to do...

also
if you push water once...its done... take the heads off and change the gasket...and go try again
if it continues to push water....figure out why and solve the issue....
create a better seal(o-ring and receiver groove)


I'm not saying it was or was not caused by detonation....as we cant tell without looking at a whole lot more pieces...but it is possible to get Rich detonation...and a little bit of detonation at that level can cause the block to stretch and the head to lift
what was Air fuel ratio on most of those passes
people like to go overly rich for no reason with forced induction...
as 22psi... you dont need to be any richer than 11.8:1~12.0:1

another thought....Block distortion is also caused by the motor mounts...
if you are in the 8's, its time to start thinking about a change to a Motor plate/mid plate setup
motor mounts will pull on the cylinder walls and distort the block causing the block stretch/head lifting scenario

LASTLS1

iTrader: (7)

I would think your at the limit. Right around 940 rwhp I was lifting heads like crazy. So with a blower I would stay below 800 maybe 18 psi. I also never used meth, just C16. I would back the timing off a couple degrees too.

Bob@BruteSpeed

iTrader: (16)

http://www.cometic.com/technical.aspx
A surface finish of 50 RA (roughness average) or finer, is recommended for a proper gasket seal. Anything rougher may conflict with the gasket design.

If you haven't already, you might try a set of GM head gaskets instead of the Cometic's to see if they last longer. Bob

OldGold

iTrader: (1)

Mine are like this as well. I also have a 408, but with a turbo. 408 stroke is an elevator. I just went ahead and installed a one gallon catch can in the trunk, and I now bleed pressure off between passes. I don't push a ton, but it is definitely there.

Mike