Can this be repaired?

Engine, Transmission and related drivetrain.
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abisel
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Can this be repaired?

Post by abisel » 30 May 2015 06:32

And by whom? The dropped seat did not damage the piston. Lucky for sure.
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This is an A87 head from an L20B and the intake ports had been opened to 1.5". Although the intake runners still neck down to the 1.25" of which should be corrected.
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510wizard
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Re: Can this be repaired?

Post by 510wizard » 30 May 2015 07:32

Yes, and replace the brass seats with steel. Any automotive machine shop could do this.

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Byron510
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Re: Can this be repaired?

Post by Byron510 » 30 May 2015 12:03

The U67 heads with brass seats were famous for dropping out after about 100K miles - personally had it happen on a motor that had never been torn down, but had just over 100K on it.

As noted - it's a standard and strait forward replacement, but you should be doing all 4 intake seats at once. And if performance is part of the picture, upgrade to the larger 280ZX intake valves at the same time for better breathing.

The brass seats were meant for leaded gas, and don’t last well with today’s dry fuel anyways.

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OUTthere
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Re: Can this be repaired?

Post by OUTthere » 30 May 2015 13:53

That should be a easy valve seat repair. Would also recommend upgrading the valves as stated especially since it sounds like you will finish up the port work.

Anyway, check out my beauty.
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abisel
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Re: Can this be repaired?

Post by abisel » 31 May 2015 09:21

Thanks for the replies.

I may just send the head to a Datsun engine person to do the work since they would be a lot more familiar than the machine shop around the corner. That way it gets done right the first time. There isn't much room to install the larger 280ZX valves but then they would know how to do it, and the one intake valve seat area may have to be welded up and machined before installing new seats. Then flowing the intake runners could be completed as well.

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defdes
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Re: Can this be repaired?

Post by defdes » 31 May 2015 10:26

If you are going all in and are looking for power, deshroud the valves and cc the head while he's at it.

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Re: Can this be repaired?

Post by okayfine » 31 May 2015 16:39

Mods would depend on what else has been done to the engine and what you want out of it. For street stuff, you can have too much of a good thing.

Intake ports at the manifold, for instance, were likely ported out to match the manifold ID. But you noticed they still neck down in the bowl to 1.25", and it probably would have been better to taper the manifold to 1.25 than open the head to 1.5.
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Byron510
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Re: Can this be repaired?

Post by Byron510 » 31 May 2015 21:46

abisel wrote:Thanks for the replies.
... There isn't much room to install the larger 280ZX valves but then they would know how to do it, and the one intake valve seat area may have to be welded up and machined before installing new seats.
Unless you are tuning the head on an l16 bore and running big lift, you'll be alright with the 280ZX valve size. They all cost the same, you might as well go bigger.

Regarding the welding up, it's likely not nessesary as the head will need to be machined out for the larger at stellite seats anyways. If you have the chance, get the machine shop to install the seats and rough in the seat ID. Take the head home, do all your port and chamber work and then take the head back to have the valve faces finished. This way if you nick a valve seat, you won't have to redo the vale job.

This is how I did my last few heads.

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Re: Can this be repaired?

Post by Dave Patten » 01 Jun 2015 13:56

This head was repaired to race again. If you can find a good head shop, its not undoable.

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510wizard
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Re: Can this be repaired?

Post by 510wizard » 02 Jun 2015 07:34

Dave Patten wrote:This head was repaired to race again. If you can find a good head shop, its not undoable.

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Ok Dave, I want to see the matching piston :)

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Re: Can this be repaired?

Post by bertvorgon » 03 Jun 2015 07:56

While this is not from the picture above, it does give you an idea of what happens when a valve/seat has an issue.

In this case, it is from a NISSAN IRL motor, when they had problems with valves dropping at very high rpm.
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Re: Can this be repaired?

Post by okayfine » 03 Jun 2015 08:01

Nom nom nom.
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

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mell00510
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Re: Can this be repaired?

Post by mell00510 » 03 Jun 2015 12:24

Close- but I think teeth were involved......
datzenmike wrote:Too bad about the fire wall. What does the V8 weigh?

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abisel
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Re: Can this be repaired?

Post by abisel » 22 Jun 2015 04:51

I have experienced another dropped seat.

Not on the subject head of this thread, but the U60 head that replaced the A87. It was running fine after a valve adjustment then I shut it off. Came back after 10 minutes or so and started it up. Right away a very loud valve noise and misfire. I figured a jamb nut came loose from the valve adjustment so I took off the valve cover and discovered the rocker lash pad for intake valve for #2 was lying next to the spring and the height of the spring not as high as other intake valves. Took out the spark plug and could see the valve seat. Poo!!. Sure hope the piston didn't get damaged. I'll know later this week.

So now I am looking for a U67 head (open design with larger intake ports).

I know of a rebuilt head that still has the brass seats and wonder if I should take a chance. Maybe go ahead and get the head and relace the brass with steel.

Thoughts?

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Re: Can this be repaired?

Post by okayfine » 22 Jun 2015 05:43

Any head that's been rebuilt in modern times that didn't have the seats replaced is a head I'd avoid, since who knows what other shortcuts were also taken at the same time. That said, if you're going to go through it anyway and have it all done right, that doesn't really matter.
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

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