Jump to content

Head cavitation repair or replace?


Jbone32

Recommended Posts

  • Replies 23
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

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.

 

yz0S5ca.jpg

 

aPly8lR.jpg

 

58T2nP2.jpg

  • Like 1
Link to comment

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.

  • Like 1
Link to comment
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 😂

IMG_20210915_195731339.jpg

IMG_20210915_201015023.jpg

  • Like 1
Link to comment

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.

  • Like 1
Link to comment
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?

  • Like 1
Link to comment
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.

  • Like 2
Link to comment

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).

  • Like 2
Link to comment

as stoff said

I would pull the rockers out and mark where they go to and see if the cam spins freely otherwise you have to get the top flat also.

 

I had a shop did mine years ago and while at it get the head welded for thet hole.  Might be more that you can afford but thats a closed chamber head. I would save it myself, or least not throw it away yet

  • Like 1
Link to comment
On 9/16/2021 at 10:58 AM, banzai510(hainz) said:

thats a closed chamber head.

Whats a closed chamber head? Going to try to see if machine shop can fix it. But if they say no go, where should i try to find another one. Pretty sure scrap yards are a no go.

  • Like 1
Link to comment

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. 

  • Like 1
Link to comment

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

IMG_20210407_184135275.jpg

Link to comment

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

fb9yF51.jpg

 

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.

yp5uytu.jpg

 

 

 

  • Like 1
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.