[geeteeohguy]

I think Lee is on to something here. Very possible the bolts are too long and bottoming out. These gaskets are leaking along their length, indicative of the heads not being tight enough or seriously out of true. Regardless, the heads must come off, the surfaces and bolt length checked, and NEW gaskets must be installed. There have been incidents involving ARP bolts that are a hair too long, with the same result. Trying to simply re-torque and run is a shortcut and not in the best interest of the newly rebuilt engine.

[chiphead]

In theory, I agree with the "breakaway torque" discussion on a properly torqued fastener without a gasket, like a main journal bolt or something. A clamped joint is held together by the bolt, which is stretched by being torqued to a given value. The amount of rotational torque applied to the bolt gives a predictable amount of stretch, and thus a given clamping force for thread pitch, bolt diameter and bolt material. When a bolt is torqued to X value, it will require more than X value to further turn the bolt against friction in the threads and under the head.

This is why the type of lubricant on the threads is critical when torquing bolts. ARP suggests the use of their lubricant, since the amount of torque with lubed threads will more reliably produce the expected amount of stretch in the fastener.

However, when re-torquing head gaskets, you are RE-tightening fasteners that could have less than the correct torque value when you re-torque them. Torquing to the correct torque (without loosening) should properly stretch the bolts that are at less than rated torque. The loose bolts will be readily apparent by rotating but the tight fasteners will simply "click" when you torque with a clicker style torque wrench.

When retorquing, I watch for bolts that never seem to stop turning, they just keep going and going as you try to reach rated torque. Those bolts are likely stretched beyond yield and may break in half. I remove and replace those.

If you back the bolts off first, you will have no idea if the bolt was near rated torque or not. I do back off head bolts if I suspect that the original installer did not jump around and tighten the head bolts in the correct pattern, which does not evenly clamp the gasket.

If re-torquing does not shut the leaks up, it's time to pull the heads and see what's up. Could be too long bolts, improper deck surface (pits, etc), uneven deck, cheap head gaskets, fatigued bolts, bad install procedure, dowel pin issues, etc.

my .02, anyways......

[charlie66]

Originally Posted by chiphead

In theory, I agree with the "breakaway torque" discussion on a properly torqued fastener without a gasket, like a main journal bolt or something. A clamped joint is held together by the bolt, which is stretched by being torqued to a given value. The amount of rotational torque applied to the bolt gives a predictable amount of stretch, and thus a given clamping force for thread pitch, bolt diameter and bolt material. When a bolt is torqued to X value, it will require more than X value to further turn the bolt against friction in the threads and under the head.

This is why the type of lubricant on the threads is critical when torquing bolts. ARP suggests the use of their lubricant, since the amount of torque with lubed threads will more reliably produce the expected amount of stretch in the fastener.

However, when re-torquing head gaskets, you are RE-tightening fasteners that could have less than the correct torque value when you re-torque them. Torquing to the correct torque (without loosening) should properly stretch the bolts that are at less than rated torque. The loose bolts will be readily apparent by rotating but the tight fasteners will simply "click" when you torque with a clicker style torque wrench.

When retorquing, I watch for bolts that never seem to stop turning, they just keep going and going as you try to reach rated torque. Those bolts are likely stretched beyond yield and may break in half. I remove and replace those.

If you back the bolts off first, you will have no idea if the bolt was near rated torque or not. I do back off head bolts if I suspect that the original installer did not jump around and tighten the head bolts in the correct pattern, which does not evenly clamp the gasket.

If re-torquing does not shut the leaks up, it's time to pull the heads and see what's up. Could be too long bolts, improper deck surface (pits, etc), uneven deck, cheap head gaskets, fatigued bolts, bad install procedure, dowel pin issues, etc.

my .02, anyways......

Very well put.

When I called ARP they told me when re torquing NOT to loosen the bolt and to do it cold....

[FASTGOAT66]

I went to the machine shop today and showed the builder my pics. He looked at the pics and said it looks like the leak is above the front head bolt leaking through the bolt threads down the gasket. He said I could try to retorque the bolts and add those gm seal tablets.

[69Goatee]

I had the exact same leaks on my 1969 GTO. It was the ARP head bolts being too long and bottoming out in the block. I had not run mine yet, so I reused the head gaskets. I read the way to check is to put the bolts in hand tight without the washer and check the clearance. If the bolt head touches the cylinder head, the bolt is fine, if not you need to put two washers on those bolts. I had 7 bolts too long, 4 on the pass, 3 drivers. I put extra grade8 washers on the long bolts and torqued the heads down, broke the cam in, and have about an hour of run time with no leaks so far.