Pelican Parts Forums - Hatch..should hatch be of same number all the way down the inner barrel?

Pelican Parts Forums (http://forums.pelicanparts.com/)

- 911 Engine Rebuilding Forum (http://forums.pelicanparts.com/911-engine-rebuilding-forum/)

- - Hatch..should hatch be of same number all the way down the inner barrel? (http://forums.pelicanparts.com/911-engine-rebuilding-forum/196014-hatch-should-hatch-same-number-all-way-down-inner-barrel.html)

Hatch..should hatch be of same number all the way down the inner barrel?

I have hatch in all 6 cylinder barrels. But the hatch is more numerous on the upper non-finned inner narrow part of the barrels. Is this normal?

Thanks

The cross hashing on the cylinders starts out the same all over. As the cylinder wears the hashing begins to dissappear. The greatest wear is near the top of the cylinder where the upper compression ring lives. If you can feel a ridge with your fingernail at the top of the cylinder where the hash marks have thined and then gets thick again you have too much wear to use the cylinders without honing them. If your cylinders are biral (they should be) then you can hone them easily. They don't have a coating to go through.

-Andy

If, for example, your hatching is pefect all the way up and down the bores, how can you have a cylinder that's out of spec?

Quote:

Do you mean by "top of cylinder" the part which mates to the heads?

Thanks

Yes the top is where it mates to the heads. The greatest wear is were the top ring is during the first part of the power stroke.

Chris,

If the cross hash marks are perfect all the way up and down the cylinder it will be in spec. unless it was damaged by dropping or warped in some manner. I've never seen a worn out Nickasil cylinder on my engines. (not a very big sample however)

-Andy

Quote:

Originally posted by Eagledriver
The cross hashing on the cylinders starts out the same all over. As the cylinder wears the hashing begins to dissappear. The greatest wear is near the top of the cylinder where the upper compression ring lives. If you can feel a ridge with your fingernail at the top of the cylinder where the hash marks have thined and then gets thick again you have too much wear to use the cylinders without honing them. If your cylinders are biral (they should be) then you can hone them easily. They don't have a coating to go through.

-Andy

OK Andy, I looked and felt the cylinders. I can see the dark circular circumfrence "line" at the very top of the cylinders where for a few millimeters the cylinder extends beyond the fins. But the "dark top" seems to only denote where the cylinder circumfrence extends just beyond the fins. So I can see a darker line circle, but can't feel any ridge with fingernail at this inner circle.

When you say "hone" are you referring to a grape hone?

Thanks for the information.

Quote:

Originally posted by echrisconnor
If, for example, your hatching is pefect all the way up and down the bores, how can you have a cylinder that's out of spec?

Good question. Sometimes they can heat cycle and become warped, although that will typically show up on hatch wear patterns as well.

-Wayne

HGP,

When I say hone I mean just a standard stone hone. I assume you have Biral cylinders and you can use a standard stone hone to prep the surface for the new rings. You don't want to take off much metal just rough up the surface abit and take off any carbon build up (the dark part you see at the top).

-Andy

Quote:

Originally posted by Eagledriver
HGP,

When I say hone I mean just a standard stone hone. I assume you have Biral cylinders and you can use a standard stone hone to prep the surface for the new rings. You don't want to take off much metal just rough up the surface abit and take off any carbon build up (the dark part you see at the top).

-Andy

Thanks!