head gasket bore size vs bore size

grumpyvette · Dec 31, 2009

when your assembling your engine one mistake thats fairly common it use of a head gasket that has a bore that is too small,
Your head gasket needs to be flush with or better yet , a bit larger than the blocks bore; maybe .020" .030-(ideal) to even .040" over bore size might be close too ideal, as the edge of the gasket needs to be even with or ideally a bit recessed far enough back into the recess between the block and heads to maintain effective cooling and not stick out enough into the engines bore, to provide a potential hot edge that would promote detonation The edge of the gasket sealing ring needs to be far enough recessed from the edge of the bore to get some effective heat transfer cooling, without being recessed enough to effect the compression or provide a dead air space for carbon residue to collect, effectively reducing too much compression or allowing volume of fuel/air mix to remain unburnt out around the edge of the upper cylinder that won't ignite due to, its being effectively cooled by the close contact with the cooler surfaces much like the quench area.
try to find a gasket that in that .020-.030 (ideal) up to .060 over bore size range, if you must go larger thats preferable too going smaller but far from ideal.
If you take the time to call and ask, most head manufacturers will be able to recommend the correct head gaskets for their cylinder heads

http://www.jegs.com/i/SCE-Gaskets/829/T ... tId=753475

when installing almost any head gasket, but especially with a copper head gasket be sure to put on two wet even coats on both sides of the head gasket and install and torque while the copper coat sprays still damp, the spray fills in micro flaws in the machined surface
http://www.goodvibesracing.com/SBC_Head_Gaskets.htm

grumpyvette · Jan 8, 2011

http://www.aa1car.com/library/gasket_failure.htm

http://www.arrowheadradiator.com/head_g ... ailure.htm

http://www.aa1car.com/library/2005/ic010532.htm

viewtopic.php?f=50&t=6931&p=22695#p22695

Head Gasket Failure Symptoms
By an eHow Contributor

Head gaskets seal the cylinders of the engine in your car, and can fail for a variety of reasons. From overheating to cracks in the gasket, symptoms of gasket failure can give indicators as to the condition of your head gaskets.

Head Gasket Leaks
1. Head gasket leaks are the hardest to diagnose, especially if they are small. Lost or leaking engine coolant can often result in leaks, a strong indicator of head gasket failure.
Heat Problems
2. Lost or leaking coolant can cause heating issues, such as a lack of heat or the heat of the engine fluctuating oddly. The idle may fluctuate as well, another symptom.
Severe Cases
3. Drastic cases of head gasket failure are more obvious, such as white steam coming from the tailpipe in the morning and the odor of burning coolant. The cylinders of the engine might also flood with coolant, preventing the car from starting.
Leaking Fluids
4. Fluids may leak from a blown head gasket as well, such as black oil pooling under the car. Leaking red transmission fluid can also be a strong indicator.
Bubbles in the Coolant
5. If the engine is running, remove the radiator cap and look for bubbles in the coolant. Bubbles may indicate either head gasket failure or cracks in the cylinder heads or cylinder walls.

http://www.thomasnet.com/articles/hardw ... et-failure
Preventing Head Gasket Failure
Car Engine Although gaskets are used to support a vast number of industrial applications, from plumbing and heat exchange systems to machinery components, they are especially significant in the transportation industry. In particular, the head gasket, which creates a seal between cylinder heads, is crucial to the central functioning of most combustion engines. If this gasket malfunctions or fails, it can result in severe damage to a vehicleâ€™s engine and may necessitate extensive repairs or an outright overhaul.

A head gasket is designed to maximize the compression force in a cylinder array and to form a barrier against coolant, lubricant, and oil leakage. It can be made of rubber, copper, multi-layered steel, or composite materials. Since it is housed in the fuel-burning section of the engine block, this gasket is a critical component in most automobiles, making it all the more valuable to understand why head gaskets break down and how to prevent them from doing so.

Reasons for Head Gasket Failure

The degree of pressure within an engine combustion chamber can be a frequent cause of head gasket malfunctions. An excessive amount or an accidental application of pressure can damage the head gasket, as well as other components in the engine block. The two main causes for pressure problems are mistimed ignition sequences and detonation.

â€¢ Mistimed Ignition: If a component inside the combustion chamber, such as an exhaust valve or a metal surface, becomes overheated it can cause accidental ignition before the proper ignition spark is activated. When the fuel is ignited too soon, pressure peaks at the wrong stage of the piston cycle, causing cooling problems, a low air-to-fuel ratio, and impeded exhaust flow.

â€¢ Detonation: Octane refers to the ease with which fuel can be ignited. Sporadic combustion, or detonation, may occur in an engine producing too much compression without a high enough level of octane. This excess compression can cause fuel to spontaneously ignite, producing sharp, damaging strikes against the head gasket and pistons. Repeated or prolonged detonation can eventually damage or break the head gasket, resulting in leakage and poor engine performance.

Coolant Levels and Excess Heat

Like compression problems, overheating is a very common source of head gasket failure. Some newer or lightweight cars have relatively modest cooling systems intended to reduce the vehicleâ€™s overall bulk, but this can result in the engine overheating. When a vehicleâ€™s engine becomes too hot, it causes the cylinder head to expand in size. Since the head gasket is located between the cylinders, this expansion can damage or break the gasket, resulting in coolant leakage and additional overheating. Low coolant levels, calcium buildup, surplus antifreeze, or a malfunctioning fan mechanism can further aggravate the heating problem and require frequent gasket replacements.

Engine Surface Finish

For a head gasket to be properly inserted into an engine, both the cylinder head and the engine block surface need to be relatively smooth and flat. Installing a gasket against a rough engine surface can cause wear that degrades the seal until it cracks. Milling machines or similar resurfacing equipment can provide the level of high-quality finish needed on cast-iron and composite metal engines. Employing a rubber-based gasket may be a viable alternative if resurfacing is not an option, because rubber models can generally withstand rougher exteriors than other types of gaskets.

Bolt Tightening

The head bolts used to secure a gasket are important in maintaining the cylinder seal. A deformed thread in the engine block surface can destabilize the gasketâ€™s placement. Similarly, the bolt itself must be in good shape to increase the chance of a reliable seal. Dirt, corrosion, deformation, cuts, and nicks can all compromise a head boltâ€™s efficacy. The head gasket seal may also suffer if an improper bolt tightening procedure is applied. Bolt specifications and installation methods are periodically revised, making it important to remain up-to-date on the latest techniques.

Reducing the Risk of Head Gasket Failure

Ensuring that a head gasket remains functional lowers the chances of fluid leakage and drops in compression pressure, as well as reducing the need for engine repair and part replacement. Keeping an eye out for some of the common causes of gasket malfunction can help in maintaining the deviceâ€™s efficiency, but there are several preemptive steps that can be taken to reduce the potential for damage in the first place. Some of these steps include:

â€¢ Resurfacing Cylinders: The smoothness requirements for engine cylinder heads have generally been increasing since the days of cast-iron parts. Now, lighter and more flexible cylinders need a higher degree of surface finish to install a gasket. Resurfacing a cylinder head or engine block facing to provide a smoother, flatter plane in which to insert a head gasket can increase the strength and reliability of the seal.

â€¢ Torquing: In order to maintain a leak-proof seal, the head gasket must be compressed between two surfaces and conform to their particular shape. However, if the head bolts holding the gasket in place are not torqued in a uniform or predetermined sequence, the compression will be lighter on some parts of gasket, destabilizing the seal and increasing the likelihood of leakage. The head bolts should be tightened in a specific order and to an exact degree of pressure to ensure the proper distribution of compressive force.

â€¢ Flattening: In addition to smoothness, the level of flatness along a cylinder head and engine block can also be important for effective gasket installation. Surface deformations, such as warping, scratches, roughness, gouges, pits, or sloping can create an uneven surface poorly-suited for a seal. An irregular cylinder head can be returned to flatness through milling or the application of wedge, also known as a â€œshim.â€
btw Ive used these head gaskets on several 383 builds, installed without the ringed block and wire , installed with both sides sprayed wet with copper coat spray and installed and torqued in place while damp, and while thats NOT, the recommended procedure I have NOT had a head gasket failure in over 20 years doing that

Keep in mind there are solid copper head gaskets , Ive used for decades that you simply spray with copper coat and install damp and torque in place, and the TITAN style with a steel fire ring, sandwiched between to layers of copper, Ive never used the titan style but have used the solid copper gaskets extensively with good results, in both cases the head gasket must be slightly recessed between the head and block ,not sticking out into the edge of the combustion chamber

http://www.scegaskets.com/Chevrolet/283 ... 98121.html

when installing a copper head gasket be sure to put on two wet even coats on both sides of the head gasket and install and torque while the copper coat sprays still damp
the slight miss alignment on the coolant ports has no effect

viewtopic.php?f=50&t=1222
if you don,t have a particular engines torque sequence its a safe bet that you start with the center head bolts and tighten each , in stages in a spiral outward pattern, then repeat the sequence with each increased torque setting moving in that same spiral increasing diam spiral moving from the center to outer bolt locations.

SBC HEADS

Big Chevy

grumpyvette · Feb 14, 2013

" strokerboats posted this bit of info
If you want a big surprise put a head on the block, attach it with a couple bolts without the crank and flip the block over. When you look up the bore to the head you will be shocked at the shrouding that takes place up there. Yes, notching the block, both intake and exhaust will help with flow and unshrouding. Use a headgasket as a guide, scribe (with a sharpie) around the gasket perimeter and use that as a template where to remove metal. If you cut at an approximate 45* angle it will be a plus. Just cut down about 2oo thousandths but pay attention to where your top ring land depth is on your piston. You can actually use the top ring land as a guide on how deep you wish to cut."

now obviously you don,t want to grind clearance or un-shroud the bore down as far as the contact point in the bore surface area the compression ring actually contacts , but some minor bevel and rounding of the area new the valve tangential edge can,t help but very slightly increase air flow, yet the amount of improvement will most likely be minimal at best, so its up to you to make a call on if its worth doing

head gasket bore size vs bore size

grumpyvette

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grumpyvette

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grumpyvette

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