Any hope for this head?

Engine, Transmission and related drivetrain.
Button
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Any hope for this head?

Postby Button » 18 Mar 2017 14:55

Hey guys, it has been awhile. Life has gotten in the way lately and the poor Datusn has been collecting dust in the garage but I am finally back at it.

So after a series of misadventures and increasingly poor decisions on my part I finally have a "rebuilt" long block that I am trying to button up. Against my better judgment I had a place rebuild my L20, which they technically did. They put in new pistons, rings, bearings, freeze plugs, etc. Among what they did they also surfaced the head. Ultimately it's a long story, i have learned some lessons, and I am where I am with this engine now for better or for worse.

So I started installing the timing chain today and there is a ton of slack in the chain. After scratching my head for a minute I pulled out a tape measure and compared the thickness of this head to another head I have in the garage. The old head is ~4.25" thick and the new head on my engine is ~4.125" so they have taken off ~1/8". They surfaced the top of the head as well and didn't put any cam tower shims in.

So at this point I am assuming that the head is junk, would you guys agree? I could put cam tower spacers in but I would imagine that it wouldn't be enough to even get close to the 1/8" of missing material.

You can see how much slack there is and this is with a new timing chain kit.
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datzenmike
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Re: Any hope for this head?

Postby datzenmike » 18 Mar 2017 21:34

First thing... you need to shove that slack side guide over as far to the right as you can to remove as much slack as possible. Open or oval the holes to get as much movement to the right as you can before tightening it.

The head may have already been resurfaced before.... or they are just idiots. Or both. That's way over 3mm removed. A quick calculation.... a stock L20B would have a 10.97 compression with this.

Buy 2 master links for a Mercedes-Benz timing chain (#000997-0598) and remove one or more links and join it together to shorten.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

Button
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Location: Thousand Oaks, CA..

Re: Any hope for this head?

Postby Button » 19 Mar 2017 09:30

Thank you for the response Mike. If I get the chain the right length will this set up be changing the timing at all, or affecting the valve train in a negative way? Do you think in addition to adding the link/s I should also shim the cam towers?

This head is the closed chamber a87 head. I also have a W58 head. Obviously all else being equal the a87 head is the one to use but in this situation should I just put on the W58 and call it a day?

Thanks for the help guys.

datzenmike
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Re: Any hope for this head?

Postby datzenmike » 19 Mar 2017 12:28

Three mm's removed, reduces the combustion chamber by 17cc ... and that's on a open chamber head. A closed will be about 1/3 more. Compression is already 11.

Time to put the W58 head on.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

Three B's Racing
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Re: Any hope for this head?

Postby Three B's Racing » 20 Mar 2017 05:19

.125" yikes!!! Did you tell them or did they tell you the top of the head needed a cut? if they told you did they tell you why like as in an amount of warpage? I can tell you this, your cam geometry will NOT be correct and that will/may require new valve spring retainers for thicker newly needed lash pads to correct the cams wipe pattern/cam geometry.
"Lastnight the wife said oh boy when your dead you can't take nothing with you but your soul oh "Think"
- John Lennon

Button
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Location: Thousand Oaks, CA..

Re: Any hope for this head?

Postby Button » 20 Mar 2017 19:55

This was the head that I mentioned in a previous post that had a snapped camshaft. They were machining the top to flatten it out. I'm not sure how much they took off each side. I do not believe they are a quality machine shop unfortunately and i'm learning a hard lesson.

With that said I am going to just get a new head. The other head I have (W58) is not serviceable either, so tomorrow I am going to meet a guy that has a few used heads I can choose from. Does anyone have any advice on what to look for in a used head, besides what type of head it is? I don't think he has any closed chamber heads so it will be between the less desirable models. Ideally, at this point, I would like to get a head I can just throw on and use for now and that I won't have to do a whole head job but i'm not sure exactly what to look for.

Button
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Re: Any hope for this head?

Postby Button » 21 Mar 2017 11:56

Well I picked up a W53 closed chamber head today for a good price and it appears to be in decent condition. It's a little dirty but i'm not sure if it needs to be rebuilt or just cleaned up. Anyone have any advice on determining if a head needs rebuilding or anything replaced?

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okayfine
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Re: Any hope for this head?

Postby okayfine » 22 Mar 2017 06:30

Post pictures.

If the head's off, remove the cam, turn the head over, and fill the combustion chambers with fluid (water's safest), see if any valves leak.

Straight edge across the bottom to check for flat.

Corrosion in the cooling passages.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

datzenmike
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Re: Any hope for this head?

Postby datzenmike » 22 Mar 2017 16:57

Use diesel fuel water's too thick. Let sit over night. If the valve seal is good they won't leak down.

Without the valve spring on, and using a dial gauge, shift the valve stem end back and forth at right angles to the cam. Valve guide wear should not be above 0.008"

Replace the valve guide seals, they are cheap and easy to do.

Check for broken studs or stripped threads now.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

Button
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Location: Thousand Oaks, CA..

Re: Any hope for this head?

Postby Button » 22 Mar 2017 20:10

Thank you for the feedback guys this is good advice. I ended up decided to bite the bullet and I took the head to a reputable shop this time. They are in the process of cleaning it and checking it out and I should get some info tomorrow. I did bring them the valve guide seals that I got from you Julian so thanks again for that.

Hopefully after this I can finally put the motor back together and get it in the car.


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