2007-01-08 23:00:27 · 11 answers · asked by Debbie M 1 in Cars & Transportation ➔ Maintenance & Repairs
So as not to damage the gasket.
2007-01-08 23:03:26 · answer #1 · answered by Anonymous · 0⤊ 1⤋
I'm an engine builder, and a machinist/machine builder. The reason this is done in sequence is; No two parts are machined exact, therefore in order to insure a near perfect seal around each cylinder, the head is torqued from the inside bolts to the outside bolts. Lets suppose you have an air bubble in the middle of a piece of window tint you are putting on a glass. Common sense tells you, in order to work the air bubble out from under the plastic tint, you must work from the inside to the outside applying pressure in order to move the air bubble out from under the tint. The same thing applies to a head. In order to work the gasket to its flatest position, you must apply pressure from the inside to the outside. If you tighten the bolts from the outside to the inside, you have the air bubble effect on the gasket, and this will allow the combustion to blow hot gases up into the pockets, thus burning the gasket, and eventually blowing a hole to the outside of the gasket. As an example; use a piece of paper (letter size), and soak it in water. Now lay the paper onto a piece of glass such as a mirror. Use something like a credit card, and see which way you have to squeege the paper to make it lay down without having bubbles trapped between the paper and the glass.
As you can see, if you start in the center and work your way to the edges, it will remove all wrinkles and bubbles from between the two.
Glad I could help you, Good Luck!!!
2007-01-09 00:07:57 · answer #2 · answered by Anonymous · 0⤊ 1⤋
You tighten the nuts in the order that best allows the stresses in the block and cylinder head, that are imposed when the nuts are tightened, to distribute themselves evenly. This avoids distortion, particularly in the cylinder head. Distortion can lead to cracking of the cylinder head and also to uneven pressure on the gasket which in turn could give rise to gas and/or water leaks.
2007-01-08 23:11:48 · answer #3 · answered by David S 2 · 1⤊ 1⤋
THE TIGHTENING OF CYLINDER HEADS BOLTS ARE DONE IN SEQUENCE TO MAKE SURE THAT THE HEAD DO NOT WARP, WHICH IN TURN WOULD ALLOW THE GASKET TO BLOW
2007-01-08 23:34:34 · answer #4 · answered by alan t 1 · 0⤊ 1⤋
Yes, it must be.... this will prevent warping of the head. Also check in a haynes manual, it will show you the order of the bolts to torque down.
2007-01-08 23:27:05 · answer #5 · answered by Anonymous · 0⤊ 1⤋
to clamp the head down onto the block evenly and with equal pressure on the head gasket all around
2007-01-08 23:07:30 · answer #6 · answered by Goanna Dundee 4 · 2⤊ 1⤋
Yep its because it will leak if you don't. You need even torque over the gasket to make a good seal.
2007-01-08 23:06:22 · answer #7 · answered by lemans81 3 · 0⤊ 1⤋
Because if you tighten from the outside in it bows in the middle and will not close ,when you tighten down from the middle it flattens from the middle outwards , leaving no gaps
2007-01-09 03:21:00 · answer #8 · answered by ? 7 · 0⤊ 1⤋
To ensure the mating surfaces remain perfectly parallel.
2007-01-09 08:02:52 · answer #9 · answered by Bandit600 5 · 0⤊ 1⤋
For even displacement on the gasket.
2007-01-08 23:05:13 · answer #10 · answered by Laird John Meredith 3 · 0⤊ 1⤋