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Just bought a 521


mainer311

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Well, this W58 head just showed up. The steel exhaust liners were previously removed. It also looks like some work was done on the intake runners because they’re very smooth. 
 

Does anyone know what the cam markings mean? There’s a “B,” “DC 93,” and “280” stamped into the end of it.

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I've removed liners before and ground away the bumps. These bumps support the liner in place and hold them away from the wall so they cannot transfer any heat. This way they glow red or yellow hot and with a working air pump pushing oxygen into the exhaust flow it self ignites and burns away any unused hydrocarbons.

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Sorry, didn't answer your question.

 

Aluminum heads need to be heated up first, usually a propane torch will do, but just heat the area slightly.

With the right size hammer, guides generally come out in 15~25 strong, steady blows. 

Make note of any guides that come out looser than others and if you find a stubborn one, not much movement, try using an air hammer.

Take measurements of the guides bore I.D. by using a snap gauge, dial bore gauge or a micrometer.

Not sure of the actual tolerance here but I think you can buy oversized guides if required.

 

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Usually the head is set with the combustion chambers up and filled with kerosene and left over night. In the morning any empty combustion chambers need a valve job.

 

2 hours ago, mainer311 said:

Have any of you guys had luck removing the valve guides on one of these aluminum heads? 

 

With the valve in the head and on it's seat but without the spring, the tip should not rock back and forth more than 0.2mm or 0.0079" in a direction parallel with the rocker arm.This is approved in the FSM for a quick indication of valve guide wear.

 

 

There's a tool like a valve stem that's inserted from the combustion chamber side and you hammer them out or use a 2 ton press. Warming the head in your oven to 300F will make it easier.

 

 

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I definitely need a valve job. I soaked the head in gasoline to clean it, and upon filling the inlets, both intake and exhaust on #4 leaked out. I then filled the inlets with ATF (since it's red and easy to see) and had red leaks coming out the combustion chamber side. See my picture above. The head is hodge-podged together. It has all different valves and valve guides in it: some brass, some cast iron. I want to strip it all apart and put all new in. It looks like Riley (datnissparts) has 35 and 42mm stainless valves in stock. 

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On 11/12/2020 at 12:33 PM, datzenmike said:

That's odd because all '78 and up engines had the W58 head with coolant flow intakes unless someone swapped them. If it had the married intake to exhaust this was from a '75-'77 L20B . The co-joined ones would get hot because of exhaust but also because they are bolted together. The W58 intakes have a heat shield to reduce radiant heat.

These 80s 720s were California emissions trucks.

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I love buying used stuff and discovering PO BS. I just bagged all of my valvetrain components and then filled each one with oven cleaner to let it sit for a couple days. Washed everything off tonight and the wipe pattern on the rockers is off to one side. Whoever rebuilt this head was using a mild cam with stock lash pads. 😧

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Still waiting for my pistons to show up before I can send the block off to get tanked, decked, and bored...so in the meantime I’ve been fitting these stainless valves from SI. Intakes are oversized to 43mm, and exhaust is stock 35mm. Debating on opening up the seats myself with one of those DIY cutters and an 8mm guide. I’m also waiting on my 8mm guide tool to show up so that I can finish replacing those. 2 of the valves have a ton of play, so I’m replacing all 8.

 

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NISSAN OHC......Used on '76 an on L20Bs

 

DATSUN OHC.... L16s after '70, '74 and '75 L20Bs. L18s on '73 610, '74 710 and '74 620

 

DATSUN 1600 OHC Fins over cam sprocket or stop at cam sprocket before '71 on 510 and 521. I think fins over sprocket the earliest. Had them on my '68 510 and put them on the L20B I transplanted into my '71 521 which had fins stop at cam

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