Rear Cam bearing of L6 head.

[Joeoski]

The camshaft in this head i bought on ebay would not turn to good so i took the cam out to get a better look and here is a few pictures on what was going on, 

 

Would this have happened do to some thing getting in to the bearing area or is the head warped?

 

[datzenmike]

Check the head for warp. When milling it, the cam bearing surface must be ground down too. This should bring them into better alignment. I think that scored one will be fine but if you have another one you could swap it. Check that it spins freely before adding the rockers.

[banzai510(hainz)]

As Mike said but you might get away with it if oil up and loosely put the tower back on.

Last time this happen to me my head was Warped as mike said. It was so bad the machines milled the top and the bottom of the head.

[Joeoski]

Thanks for the info you two, I will have this head checked for straightness before i use it , On another forum a member said that the damage might have been caused do to some thing being in one of the oil galleries but will still get this cylinder head check for warping and for twisting.

[Driftease]

You can check the bore alignment just as you would for main bearings using a strait edge and round feeler guage (wire type) be aware of shops that say they can mill your head it is better to starighten it if possible. Milling a warped head causes your combustion chamber volume to vary across the head and can further the warping. The book how to modify your nissan and datsun OHC engine explaines how to sraighten the head on page 54

[Driftease]

As Mike said but you might get away with it if oil up and loosely put the tower back on.

Last time this happen to me my head was Warped as mike said. It was so bad the machines milled the top and the bottom of the head.

it is generally a bad idea to leave parts loose in an engine, you can replace the bearing and have it allign honed or polish the originalbearing with 1000 grit paper then 2000 grit and clean the debris out that caused the problem in the first place if on a budget

[datzenmike]

You can check the bore alignment just as you would for main bearings using a strait edge and round feeler guage (wire type) be aware of shops that say they can mill your head it is better to starighten it if possible. Milling a warped head causes your combustion chamber volume to vary across the head and can further the warping. The book how to modify your nissan and datsun OHC engine explaines how to sraighten the head on page 54

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Page 54 is about pistons. I didn't find anything on straightening a warped head on any page.

 

 The increase in compression from a few thou shave is minimal on a street car.

[Driftease]

I'll check the page # again lol it may be 154 there are strange greasy marks all over the pages for some reason. I realize that slight compression difference across the cylinders will be acceptable, I just have crippling attention to detail.     

[Driftease]

it is in the head section just after the topic of welding the head for repair or compression gain

[datzenmike]

I'll check the page # again lol it may be 154 there are strange greasy marks all over the pages for some reason. I realize that slight compression difference across the cylinders will be acceptable, I just have crippling attention to detail.     

.

Ha ha ...say no more.

 

it is in the head section just after the topic of welding the head for repair or compression gain

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I'll check when I get home. It may have an older/newer edition.

[Driftease]

It is on page 54 in my book.

[datzenmike]

Very curious is all.

[Driftease]

the book does not have an edition num it said nissan p/n 99996-M8012 so it is probably just a different book than yours. It is a good read i would suggest it to anyone who is into zs even if they are not capable of building an engine!