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Birdy426

Surface head when replacing head gasket?

11 posts in this topic

The nut on the back side of my cylinder head backed off, and resulted in a leak between the cylinder and water jacket. I have pulled the head and have a new gasket on order. I checked the head for flatness using a straight edge as described in the manual and as is standard practice), and all is good. If this were a car motor, however, I would still "kiss" the head to be absolutely sure I had a good sealing surface.

What say the experts here: Is it necessary to surface a 426 head? I have a big bore (444) kit and am running 13.5:1 compression.

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I checked both cylinder and head on my 2000 wr 400f and they were both good like yours, I'm not doing anything to it, the gasket will help seal any minor discrepancies anyways - if you do the head, you should do the cylinder, this will lead to even higher compression, you're already at 13.5:1, your valves won't like you much if it gets any higher.

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A little valve grinding compound on a thick sheet of glass, a beer and practice making figure 'Eights'. Swirl a little, wipe and look, swirl some more. The amount you will be taking off will be insignificant.

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A little valve grinding compound on a thick sheet of glass, a beer and practice making figure 'Eights'. Swirl a little, wipe and look, swirl some more.

I believe you missed a step, It should read:

A little valve grinding compound on a thick sheet of glass, a beer and practice making figure 'Eights'. Swirl a little, swig a little, wipe and look, swirl and swig some more.

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I believe you missed a step, It should read:

A little valve grinding compound on a thick sheet of glass, a beer and practice making figure 'Eights'. Swirl a little, swig a little, wipe and look, swirl and swig some more.

Looks like he missed TWO steps to me! lol.... :thumbsup:

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Hey, the instructions I gave are for an experienced wrench. The swigging part is normal operating procedure, like which way to loosen a bolt and therefore not required to be defined.

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If your Cylinder head is flat. Then I would turn my concentration to surface finish. Obviously clean is important but a fine finish on the head gasket surface will give the Head something to "Hang on to".

A Scotchcbrite pad on a sanding block would leave a nice clean finish without taking off too much material. maybe light passes of wet 400 sanding paper on a flat surface like plate glass or a surface plate would be good just enough to shine the surface. The oem Head gasket has a coating on it which (I believe) reacts to heat to form a better seal after running the engine.

You could make a few passes over it with a wet stone, You get the idea:thumbsup:

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On a side note:

when installing the head "Think Clamping force" Torquing the nuts to a certian consistant torque is great but clean threads with lube will give more clamping force for a given torque value.

The additional clamping force will also hold the nuts tight longer.

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The additional clamping force will also hold the nuts tight longer.

hmmm.....interesting......this can be applied elsewhere in life.....

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I coat all sides of my head gaskets with 'Copper Coat'. It is a semi tacky sealant that supposedly contains fine copper particles, Sprays on clear. Let sit over night and assemble. Just did a big bore (4.5 mm over) stroker engine (5 mm), sealed like a champ

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