|Head Sealing Tips|
Scott Simpson - Scott231@Juno.com
|I'd like to start by stating that any head gasket will usually work fine IF you keep detonation under control. More often than not, a head gasket failure is due to excessive detonation. The extreme forces present during detonation can actually cause the gasket material to weaken or disintegrate allowing either water into the cylinders or exhaust gasses to leak out into the atmosphere, between cylinders or into the lifter valley. Atmospheric air can also leak into the cylinder during the intake stroke if the gaskets blow out to the atmospheric side.
The bolts or studs used to hold the cylinder head can also play a large part in sealing the cylinder heads. The head fasteners are usually not the main topic of discussion when changing heads, but the incorrect use of the bolts you have can lead to disaster. The most frequent problem that occurs, due to improperly torqued head bolts (studs,) is an occurrence of the head lifting up off the block momentarily. Some installation tricks are listed at the end of this page.
|First, let's look at some of the options for head gaskets...
Installed on more Turbo Regals than anything else, obviously, yet this also includes many 11-second cars that have never had the motor opened. Made of a composite material these gaskets are not very forgiving when detonation occurs (unless factory installed,) but lots of people have gone tens with these gaskets. The gaskets installed by the factory were done with much more sophisticated tools than you are going to find at Sears.
Fel-Pro Gaskets (p/n 1000)
These gaskets are more detonation resistant than stock thanks to a stainless steel fire ring. According to a listmember that spoke with Fel-Pro, the new fire rings are a little too thick for use on a stock-configuration head bolt arrangement and the rest of the gasket tends to "come apart" in areas other than the fire ring. This allows water to eventually get past the fire ring and you've got problems. Gaskets are blue in color and have a stainless steel fire ring that goes around the combustion chamber. These gaskets have the extra 6 boltholes for use on the Stage II engines. Whereas these holes are unused on a stock block/head configuration, it is the use of these extra bolt holes that provides the necessary clamping force to get the thick fire ring to seal properly on the Stage blocks. Then again, we've got a listmember who has run 10.74 with these gaskets on a stock block/head configuration and has had no problems.
Stacked Steel Shim Gaskets
Due to their thickness being about half of the stock gaskets, you should use two of these gaskets on each side of the motor when installing. When properly sealed with some strong sealant, these provide one of the strongest, most detonation resistant gasket setups available. The installation sounds a little tricky, but they don't blow, and they will be your cheapest option (as of 1997 these gaskets are about $9 a piece.) Unfortunately, if the motor is detonating heavily, they won't blow...something else might.
Copper Head Gaskets
Require an O-ring groove be cut into the block (you add the O-rings) and will provide great detonation resistance just like the Stacked Steel gaskets...with one less mating surface to worry about. The O-rings cut into the copper, leaving a fingerprint if you will, to provide their strength. These are becoming harder to find as a major distributor has recently decided to stop making these gaskets. Once again, if the motor is detonating heavily, they won't blow...something else might.
Fel Pro p/n 1007 Wire-Loc Gaskets
Require an O-ring groove be cut into the head. These gaskets look just like the 1000 but already has the O-ring "built into" the gasket surface for superior sealing abilities. However, several people have found problems with getting the groove cut 100% correctly and the gaskets eventually leak. Then again, many of the top TR engine builders use these (Duttweiler, Precision Turbo) with much success.
|Next, let's look at some of the options for head fasteners...
Stock Torque-to-Yield (TTY) Bolts
These work fine up to 22psi of boost. Beyond that you are pretty lucky if they stay together. These bolts MUST be replaced every time the heads are removed. They reportedly "stretch" under boost easier than aftermarket fasteners, mostly because they are designed to stretch or yield a little bit when torqued into place.
Stronger than stock and are NOT torque to yield, thus they are not designed to stretch. These bolts are reusable, but should be retorqued after a couple warm-up cycles. They come in two different strengths, which I believe are 80,000 psi and 120,000 psi breaking points.
Strongest clamping force for the turbo Buick cylinder heads. Their superior clamping force comes from the fact that the strain placed on the fastener is distributed along two surfaces instead of one. The studs are threaded into the block, the heads on placed on the block and nuts are then threaded onto the studs. These should be also retorqued after a couple warm-up cycles. If you retain the Air Conditioner/heater blower core, you have to remove the engine to remove the heads as the heads now have to be lifted up over the studs to get them off.
There are GNTTYPE listmembers that have run in the 28-30 psi range with stock gaskets and studs. Others have hit the same boost with the Fel-Pro 1000's and studs. Similar results have been achieved with stacked steel gaskets and studs.
|Finally there is the head fastener torque sequence. First, make sure that both the threads of the bolt (stud) and the underside of the bolt (or washer and nut if using studs) are properly lubricated. The threads require some sort of Teflon sealer as the bolts/studs protrude into the water jackets of the block. The other end needs to be fully lubricated with engine assembly lube to reduce friction. The factory manual shows a pattern which is basically a criss-cross pattern starting in the middle and working outwards. The proper way to install the fasteners is in 10-pound increments. (This is much easier if you have a clicker style torque wrench with a dial adjuster.) Check with your gasket or cylinder head supplier for the best pattern and their recommended torque values... don't forget to tell them if you are using head studs, bolts or TTY bolts which have a specialized installation procedure.|
|Tricks and Tips|
|Last but not least, there are several tricks that people use to install head gaskets. These include torqueing the fasteners down, waiting an hour, breaking the bolts loose and re-torqueing (assuming you are not using TTYs) one bolt at a time. Some people actually like to run the motor without the headers attached for a short stint and then re-torque. Another trick is to install the head fasteners finger tight, install the intake manifold, fully torque down the manifold and then fully torque the head fasteners to the desired torque spec. This will draw the heads up closer to the intake if there is any slack in the head pins. This helps to eliminate the possibility of the heads shifting later, like at the track. ;-)
To summarize, you need to follow a recipe for your specific cylinder head, head gasket and fastener combination. There are other gaskets (for both aluminum and iron heads) and other fasteners, but the above should cover a majority of questions and/or get you up to speed for discussing the proper head gasket recipe for your combination. And if you are a GNTTYPE mailing list subscriber, you can always ask your questions on that list for further opinions.