Hello, I am rebuilding an L28. I have an N42 block with an N47 head that I bought a couple months ago. I noticed one of the exhaust liners on the head pretty much fell out. I am wondering if I will run into any issues if I go head and remove the rest of the exhaust liners and if that will effect passing smog in any way or if I will run into any issues with how the car performs.

That’s a crap shoot . Not sure if you’ll pass smog because that will probably change the way it runs . And be ready for a fight . One might have fell out , but I bet the others won’t 🙂 . 

My understanding is that removing the exhaust liners ruins the flow of the head. Without them the exhaust ports are too big and/or the wrong shape for ideal flow characteristics.

I've always read it's not a good move to remove. Here's some threads on them.

https://www.google.com/search?q=removing+exhaust+liners+n47+classiczcars.com+&client=ms-android-americamovil-us-revc&source=android-home&source=hp&ei=siN5ZKrvMZzcptQPmryb0AE&oq=removing+exhaust+liners+n47+classiczcars.com+&gs_lcp=ChFtb2JpbGUtZ3dzLXdpei1ocBADMgUIIRCgATIFCCEQqwI6CAgAEIAEELEDOgsILhCKBRCxAxCDAToLCC4QgAQQxwEQ0QM6CwguEIAEELEDEIMBOhEILhCABBCxAxCDARDHARDRAzoOCC4QgAQQsQMQxwEQ0QM6EQguEIMBEMcBELEDENEDEIAEOgsIABCABBCxAxCDAToFCAAQgAQ6CAguEIAEELEDOg4IABCABBCxAxCDARDJAzoICAAQgAQQkgM6CAgAEIoFEJIDOggIABCKBRCxAzoGCAAQFhAeOggIABAWEB4QDzoICCEQFhAeEB06CgghEBYQHhAPEB06CQgAEBYQHhCLAzoLCAAQFhAeEA8QiwM6CwgAEIoFEIYDEIsDOggIABCJBRCiBDoFCAAQogRQxw9YtbgBYP7CAWgBcAB4AIAB6QGIAeIpkgEGMC4yOC40mAEAoAEBsAEAuAEC&sclient=mobile-gws-wiz-hp

2 hours ago, madkaw said:

That’s a crap shoot . Not sure if you’ll pass smog because that will probably change the way it runs . And be ready for a fight . One might have fell out , but I bet the others won’t 🙂 . 

Yeah the others seem pretty on there. I know people have ran without them and people have ran with some that are missing, however I haven't heard of anyone confirming if they can't pass smog or if the car runs better or worse with one or all of them gone.

2 hours ago, rturbo 930 said:

My understanding is that removing the exhaust liners ruins the flow of the head. Without them the exhaust ports are too big and/or the wrong shape for ideal flow characteristics.

I can see the flow being ruined due to the shape of the ports without the liners so a lot of grinding would need to be done I know that much.

11 minutes ago, siteunseen said:

I've always read it's not a good move to remove. Here's some threads on them.

https://www.google.com/search?q=removing+exhaust+liners+n47+classiczcars.com+&client=ms-android-americamovil-us-revc&source=android-home&source=hp&ei=siN5ZKrvMZzcptQPmryb0AE&oq=removing+exhaust+liners+n47+classiczcars.com+&gs_lcp=ChFtb2JpbGUtZ3dzLXdpei1ocBADMgUIIRCgATIFCCEQqwI6CAgAEIAEELEDOgsILhCKBRCxAxCDAToLCC4QgAQQxwEQ0QM6CwguEIAEELEDEIMBOhEILhCABBCxAxCDARDHARDRAzoOCC4QgAQQsQMQxwEQ0QM6EQguEIMBEMcBELEDENEDEIAEOgsIABCABBCxAxCDAToFCAAQgAQ6CAguEIAEELEDOg4IABCABBCxAxCDARDJAzoICAAQgAQQkgM6CAgAEIoFEJIDOggIABCKBRCxAzoGCAAQFhAeOggIABAWEB4QDzoICCEQFhAeEB06CgghEBYQHhAPEB06CQgAEBYQHhCLAzoLCAAQFhAeEA8QiwM6CwgAEIoFEIYDEIsDOggIABCJBRCiBDoFCAAQogRQxw9YtbgBYP7CAWgBcAB4AIAB6QGIAeIpkgEGMC4yOC40mAEAoAEBsAEAuAEC&sclient=mobile-gws-wiz-hp

Yeah, I did as much research as I could before posting but no one that has had them removed and ran their car with one missing or all of them missing have reported if it actually makes a difference to the way the car drives or if it'll effect smog etc... Trying to avoid getting another head as I haven't found any around me at the moment and money is tight.

It probably won't have a huge effect.  My impression has been that it just isn't worth doing. 

What kind of testing does "Canyon Country" do?  Most only do idle and 2500 RPM.  Does the car have a catalytic converter?  

What does "pretty much fell out" mean?  Do you still have it?  You could probably reattach it, depending on the failure mode.

10 minutes ago, Zed Head said:

It probably won't have a huge effect.  My impression has been that it just isn't worth doing. 

What kind of testing does "Canyon Country" do?  Most only do idle and 2500 RPM.  Does the car have a catalytic converter?  

What does "pretty much fell out" mean?  Do you still have it?  You could probably reattach it, depending on the failure mode.

Would it be better to run the head as is with the one liner then?

Basically LA county, 2500 and idle testing to my knowledge. Yes, I have two catalytic converters on hand to try, I'm also ordering a new EGR.

No I do not have it. It was missing when me and my friend removed the manifold. Sorry bad wording.

If you break it down to the basics, the whole point of the liners is to stay red hot and complete combustion of anything uncombusted.  So, the action in the cylinder should not change.  The 280Z exhaust manifolds are pretty primitive if you take a close look.  The exhaust ports basically dump in to a large common chamber.  I can't see a reason that the missing liner would do anything more than make one cylinder dirtier, emissions-wise, than the others.  The EFI and emissions systems were advanced for the time, but pretty primitive today. 

This is just me, but I'd run it.  Probably won't see a measurable difference.  The converter will absorb one cylinder out of six's extra hydrocarbons.  That's probably the only real effect.  75 and 76 didn't even have liners.

You could try that junkyard search engine and see if there's a p79 close by.

The n47 is the least desirable head. Mine had a spray bar and an oiler cam, 0 oil pressure. I robbed the valve train components and scrapped the aluminum head.

16 minutes ago, Zed Head said:

If you break it down to the basics, the whole point of the liners is to stay red hot and complete combustion of anything uncombusted.  So, the action in the cylinder should not change.  The 280Z exhaust manifolds are pretty primitive if you take a close look.  The exhaust ports basically dump in to a large common chamber.  I can't see a reason that the missing liner would do anything more than make one cylinder dirtier, emissions-wise, than the others.  The EFI and emissions systems were advanced for the time, but pretty primitive today. 

This is just me, but I'd run it.  Probably won't see a measurable difference.  The converter will absorb one cylinder out of six's extra hydrocarbons.  That's probably the only real effect.  75 and 76 didn't even have liners.

Thanks for the explanation and breaking it down, I kept reading too many different responses to what these things are for etc. Hopefully the one missing liner does not get me into any trouble when I smog after the rebuild. I will leave it as is and run it with the missing liner. I did read one post someone ran their car like that and he said the car was very fast so shouldn't cause any big issues performance wise at least.

21 minutes ago, siteunseen said:

You could try that junkyard search engine and see if there's a p79 close by.

The n47 is the least desirable head. Mine had a spray bar and an oiler cam, 0 oil pressure. I robbed the valve train components and scrapped the aluminum head.

I was considering a P79, but I would not want to loose the higher compression of the N47 since this is a mostly stock internals rebuild and I had a P79 in a previous build with an N42 block and it was definitely one of the slowest setups I've had. I already have an oil pump upgrade so hopefully 0 oil pressure won't be an issue because I had that in the past with my e88 head.

6 hours ago, siteunseen said:

Mine had a spray bar and an oiler cam, 0 oil pressure.

Never heard of that! It's one or the other never both! (I think your cars previous owner didn't know what he was doing?) 

It could work iff you installed the special oilpump.. but you solved the problem already! 🤠

On topic..

I got a reserve N47 from a 280zx USA. does that have the same exhaust ports as the N47 from the older 280z's?  (I'm asking because there are also old and new E88's that are totally different! ) 

My N47 does have the steel inlays/linings in the exhaust so it must have come from a US 280zx as our 280zx's never had a cath..

I always thought that they were there (Those linings) to keep the exhaustgasses hotter for the catalitic converter, so it chemical reaction's start earlier?

Isn't it possible to make the outlet's better ( get rid of the linings and make them a lot bigger for a good flow)?  The valves are big enough i think.

18 hours ago, Ownallday said:

I was considering a P79, but I would not want to loose the higher compression of the N47 since this is a mostly stock internals rebuild and I had a P79 in a previous build with an N42 block and it was definitely one of the slowest setups I've had. I already have an oil pump upgrade so hopefully 0 oil pressure won't be an issue because I had that in the past with my e88 head.

If you use a P79 head on a standard N42 block that had a N42 or N47 head it will kill your CR and serverly reduce the performance.

You can modify the P79 but shaving it 80 thou (2mm) use the valves from the N47 head (N42 & N47 vavles are two mm longer) and shim the cam towers.

That will compensate for the 10.9cc dish in the pistons.

If the aluminum stakes/posts/pins are still in the port I'd bet somebody might scavenge an old head for a liner and send it to you.  Maybe.  Post a picture of the linerless port anyway, if you can, just for viewing.  Maybe it's fixable.