Are Fel Pro head bolts torque to yield?
T-T-Y (TORQUE-TO-YIELD) HEAD BOLTS T-T-Y head bolts are engineered to stretch within a controlled yield zone. Once they reach this zone they spring back to provide a precise level of clamping force.
Can you reuse bolts that have been torqued?
Many of the bolts used in machine assembly, such as the automotive industry, used what are called “torque-to-yield” (TTY) bolts. And since there is no way to tell how many times a bolt has been reused, it doesn’t make any sense to reused TTY bolts – the risk far outweighs the replacement cost of used bolts.
What kind of head gaskets do I need for a late model engine?
Consequently, late model engines with TTY head bolts typically require less torque on the head bolts than older engines with conventional head bolts and composition or graphite head gaskets. MLS head gaskets are usually made of three, four or five layers of embossed stainless steel, although some OEM gaskets use more layers.
What kind of bolts to use on MLS headgasket?
Typically, the OEM’s use torque-to-yield head bolts to clamp the cylinder heads to the block. Torque-to-yield bolts are one-time use only. So once you pull them off, throw them away. Usually, these bolts can be identified because they will have a flat gray surface coating, but if you aren’t sure, always play it safe and buy new head bolts.
How are head bolts and head gaskets related?
The relationship between head gaskets and head bolts is an intimate one. The clamping load applied by the head bolts is what allows the head gasket to maintain its seal. For this marriage to last, there has to be constant tension – not too much, otherwise the bolts may stretch or break, and not too little, otherwise the gasket may lose its seal.
How big should aluminum head gaskets be for performance?
Aluminum heads and performance applications, on the other hand, should have no more than .002 in. (.05 mm) out-of-flat in any direction. The maximum amount of out-of-flat should not exceed .001 inches within three inches in any direction in a stock engine, so even less is best for a performance build.