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Head cavitation repair or replace?


Jbone32

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Erosion not cavitation.

 

As long as none of it is inside the chamber and as long as you do not block coolant flow from the block into the head. You may have to build it up in layers so it doesn't slump. Hand file it down.

 

I see the fire rings left an impression or is it just a stain? If an impression then corrosion? Are you running water or water anti freeze? Maybe a sheet of glass and some sand paper. Drag the head over it 15 or 20 times to true it up.

 

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Tell the truth I checked every 20 or so back and forth passes but easy to forget how many sets altogether

 

60 is way too coarse for the gasket. I don't think a fine mirror polish is good either. Some texture allows the gasket to grip it. I pulled mine down fast with 180 and a slight polish with 220, although 180 is plenty fine enough.

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1 hour ago, datzenmike said:

Tell the truth I checked every 20 or so back and forth passes but easy to forget how many sets altogether

 

60 is way too coarse for the gasket. I don't think a fine mirror polish is good either. Some texture allows the gasket to grip it. I pulled mine down fast with 180 and a slight polish with 220, although 180 is plenty fine enough.

I plan on finishing it up with the 180..i shit you not im at probably 5000 pulls. At this point this is an experiment to figure out if you can sand a head that was so warped i could get a popsicle stick in between a level in the center..my bidy is done pulling..

Ive been keeping track after every 100 pulls i use a sharpie to tell how far in getting...ill beat this devil 😂

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See of the cam spins freely by hand. If tight or seized that's going to need the tower bases milled down level. Head probably isn't worth the trouble. Number one and four combustion chambers will be smaller than the middle two. OK for a stock driver.

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6 minutes ago, datzenmike said:

See of the cam spins freely by hand. If tight or seized that's going to need the tower bases milled down level. Head probably isn't worth the trouble. Number one and four combustion chambers will be smaller than the middle two. OK for a stock driver.

Damn..never thought about that..cam moves with a wrench but not by hand..damit..im probably wasting my body away with this..but i intend to beat this bastard..i have advanced RA so its hard enough to grab a wrench let alone ponder how tired i am for doing it..should it spin freely?

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29 minutes ago, datzenmike said:

Grrrrrow!

 

Make sure you are not pressing down on the ends. Just push and pull, let's own weight do the work, and clean the powder regularly.

Yes you are right it took me a while to figure this out.. its all about stance and not to grab it but push and pull from ports without making downward force so it goes even if not very small downwards pressure males it go uneaven ....now i expend more energy but im only pushing and pulling and letting the weight cut through..im almost there..im concerned about cam but it ran until i took it apart so i feel like im saving one more head at this point. I love these trucks but they need to be owned yny people with money not like me. But im trying. I guarantee it will run when im done because its a Datsun.

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Checking to see if the cam spins freely should be done without the rockers in place. Since some of your valves look to be open in the pics, I would say your rockers need to be removed before you can check the see how the cam spins. Not super important, but keep the rockers and lash pads in order, so they can go back in the same spots (lash pads more important, if they are different thickness).

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A closed chamber head has areas, at TDC, is where the piston and head has only the head gasket thickness separating them. An open chamber head has a combustion chamber that extends over the entire piston top when at TDC. Closed chamber L series heads have a slightly smaller 41cc of volume. The open chamber head is 45.2cc volume. Closed chamber heads only work properly if they are used with flattop pistons to maximize the pinch or squish area where piston top and head surface are largest. At TDC the air is violently pinched out and into the combustion chamber increasing turbulence and mixing of the gas and air as it burns. Hot spots are reduced, the mixture is homogenized and the smaller combustion chamber area absorbs less heat so more is available to push down on the piston, combustion efficiency is increased. They were terrible for emissions. A piston top with any dish defeats this.

 

Any L20B head will work U67 or later W58. These are open chamber heads as no closed chamber heads came on Datsuns imported into N America. You'll find the odd closed chamber heads floating around from low mileage import engines that were cheaper to buy than rebuild the originals. 

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Thanks for the info.. i dont know much about all that. I do know my pistons are flat 🤣. Im going to try to have in machined and salvage it. Otherwise if i cant find one from maybe one of the forum members or ebay I might debate selling it. Got a little 720 camper for it too. Cause now im dumping all my time and money into my ambulance camper

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It's not impossible that you have an L18SSS import engine.

 

Look behind the oil dipstick. The engine displacement is stamped on the flat space. Confirm it's an L16 or L18. Or simply measure the bore. 83mm is L16 and 85mm is L18

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Look on the bottom ledge of the head between #1 and #2 spark plugs for the head ID. May be 219 or A87. Look also on the front left near the distributor for a small 219 cast there.

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