Cody's advice (above) is
REAL GOOD advice. The two different goals are like oil and water - they do not mix!
Don't want people to get mis lead on the torque specs. The most you want to torque aluminum heads to aluminum block is 85ft lbs. Anything more can lead to stress cracks. What you don't want is "stretching". Even John M torques his motor to 85ftlbs.
Somehow I missed that 125 ft/lb TQ spec recommendation Russ, thanks for catching it! Just as Russ has already indicated this is a big time no-no! Both blocks have been shown to crack when the studs go over 100 ft/lbs. There is a growing body of evidence that the 100 ft/lb TQ spec for the 2000 steel studs exceeds what many blocks can reliably be torqued to. The 125 ft/lb figure will crack virtually all blocks out there and will also be well above the torque spec ARP has for the 2000 steel studs.
If you are experiencing head gasket leakage at 85 ft/lbs you probably have a PD blower and a fairly impressive amount of torque from down low in the rpm range. The PD blowers strain MLS gaskets to their failure thresholds in these types of environments. The other thing that will push out a gasket is blowing the tires off, back pedaling, letting the tires hook and then getting back on the throttle. When you do this you will exceed the MLS style gasket's ability to seal the engine up (at any torque) and push out the head gasket.
When you push out a head gasket under these circumstances you will damage the head and the block. That jet of fiery combustion gasses is just like an acetylene cutting torch. It will cut through anything and everything in its path. The pic below shows what mild damage will look like on the block deck. This particular driver lifted when he felt the engine start to fade away. If he had not, the damage would have torched out a half inch wide trough that would be around 3/16 of an inch deep through the liner, cylinder block and also head material.
And this is what the corresponding damage to the head will look like. Same comment about lifting. Had the driver not lifted the damage would have become irreparable turning an expensive head into scrap aluminum.
There is only one fix for this problem and that is dead soft copper head gaskets and stainless wire o-rings in the heads. To get a corresponding receiver groove in the block surface you need to use flanged sleeves. The sleeves are available from LA Sleeve and will provide adequate flange material to machine an appropriate receiver groove for a stainless wire o-ring that is installed in the head. This is what two of the sleeves look like side by side on 100 mm bore centers like we use;
Right about now Cody's earlier words should be ringing in everyone's ears. This kind of an engine is not even close to a dual purpose motor. It has crossed a line into race motor country and needs to be managed and operated as a supercharged race engine. BTW in case you haven't guessed by now, the other excellent operating practice is to kill the run if you loose traction. Attempting recovery and continuing to race will not give you a win, or any good tuning data and guaranteed, it will damage your engine.
Here are a couple of real good guidelines for PD blown race engines;
Driver's rule #1 when racing a high powered PD blown car;
If you blow the tires off, shut the run down - you've already lost the race no need to loose the engine!
Driver's rule #2 when racing a high powered PD blown car
No matter how robust your PD blown engine feels down low, do not lug the engine - you will kill it!
The reason the turbo cars can run the boost they do with gaskets the PD blown crowd can not is the way the blower boosts the engine at the hit. With a PD blown engine it gets everything the blower has, literally instantly. With turbo race engine's there is a very fast but smooth build up of boost as the engine comes up through the engine speed. The difference is how heavily the head gasket and other parts of the engine are loaded.
Next time you watch FS1 and see an NHRA T/F or Funny Car race watch what the driver does if he strikes the tires down track - 9 time out of 10 times he will shut off unless the other car is in trouble also and he thinks he can win a pedal-fest. When he puts his foot back in the throttle, he delivers a death sentence to most of the rotating assembly's pieces and sometimes the car. Those operations carry the equivalent of ten engines worth of spare parts in the trailer and a couple of bodies. None of us have that kind of back up in our trailers.
Be prudent there is no good reason to unnecessarily use up engine parts this way at our level of racing. Remember if you strike the tires, that he who lifts and drives away has an engine that lives to race another day. Don't race dumb!
Ed