Originally Posted by lilgreenjeepyj
Well as I was cleaning a LS motor that Im swapping, I noticed 3 broken header bolts and I haven't even put a wrench on them to remove the headers. So based on the good advice Ive gotten here before, what is the best way to avoid breaking the rest of them? How can I get penetrating oil down into the threads in the block? I plan to heat them and give the heads a couple taps with the ball peen, but is that all I can do?
As for the broken bolts, whats the best way to attack them? These are the first bolts I have broken off in aluminum heads. I HATE easy outs so Im not even going to try them, and it looks like the bolts are just about flush with the heads so no room for vise grips.
Since the engine is out and the head can be accessed, the best way is to carefully drill 'em out. Head off the block and bolted to drill press would be best. If not, then using a hand power drill for power, you first need to hit a pretty good center on each bolt with a punch to get the bit started without it walking around. Start with a sharp 1/8 bit and go all the way thru the bolt. then step up in 1/16th increments to 1/4 inch. This, if you're dead on center, should with an 8 mm bolt just leave the threads. Then with probe like that used for spiral locks, dig the threads out. OR!!!!!
Since I will not use those crummy 8 mm bolts, they're like the 5/16s Chrysler tried for years to get them to hold LA manifolds on to no avail, you need to go to a 3/8s or 10mm. Given my hatred for all things metric, I drill these things out and tap them for a 1 inch long, 3/8s x 16 thread stainless steel bolt.
Never put ordinary carbon or low alloy steel into aluminum, regardless of the rated grade of a fastener. A grade 8 will corrode as much as a grade 5. They will always corrode with the aluminum making a bond that usually destroys both on disassembly. Exhaust in particular needs a bolt that is not chemically reactive with the aluminum. This especially is a problem with the exhaust manifolds and headers because of the temperatures involved and water entry from that present under the hood as moisture or wash water. Any bolt or fitting put into aluminum should also use high temp anti-seize on the threads in hot areas like the exhaust or a sealant in cooler areas like plain old plumbers Teflon paste pipe sealant.
For sizing a 5/16th or 8mm will always fail and be more troublesome than a 3/8s or 10mm. The history of this is well documented from those people working on Chrysler engines versus Chevy or Ford. Very surprising how much greater reliability that 1/16th of material diameter makes when you bolt up manifolds and headers. That's not to say larger the larger size doesn't fail, but the rate of occurrence is greatly lessoned by a power factor of more in my experience.
To further reduce corrosion each head should be ground jumpered to the block and all grounded to the chassis or the battery. This helps eliminate structural fasteners from becoming current paths between the castings. Where ever engine parts are separated by non-conductive gaskets, any difference in electrical potential is carried thru the fasteners and or the coolant. The same can be said for the exhaust system. Most exhaust systems float on robber mounts, somewhere the system should also be ground wired back to the chassis so the exhaust manifold/header bolts to the head are not a current path for the exhaust system.