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Discussion Starter #1
Disclaimer: This is NOT a post about performance gains.

When I change the manifold gasket, I was thinking I might as well also change the manifold. IF the manifold was cracked I'll definitely change it but if not I'm still interested in changing it out with an aftermarket header. Is there any positives to gain with going with the aftermarket header or should I just stick with the manifold if it's not cracked?

Here's an example of what I would be looking at: Header Racing Exhaust Black L28 280Z 280ZX 75-83
 

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Weight reduction will be noticeable. Stock manifold is cast iron and is heavy. Overall HP gain might be small, but you will both reduce the weight and get more power. Win-win.
 

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Discussion Starter #3
The fact that it's cast iron makes me think it's probably not cracked at least haha. Have any personal recommendations or was my linked header sufficient?
 

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The stock manifolds warp like a banana to cause the #1 and #6 exhaust studs in the head to shear off. New factory manifolds do not exist anymore, We bought he last couple 280 Z manifolds in recent years and all before them have
been gone for decades. Headers are your almost only option for a new part. Hp increase in a stock engine is a falicy
as proven on the dyno however if you are open to mods and want to run it above 6k rpm's, then there is a few percent there.
 

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1983 280ZX Turbo
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A 280Z is not a drag racer. If the stock manifold is still in good shape, I recommend using it. You avoid problems with non-stock parts, you don't have to adapt the exhaust system, and you know exactly what you have. Less expense, less technical complexity, and a difference of a few pounds really doesn't matter.
 

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1983 280ZX Turbo
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For testing for warpage, should I just stick a ruler on top?
You could have a machine shop check it for you, or use a good straight edge..but I'm not sure you can check it both vertically and lengthwise. I think that if all I had was a straight edge, I'd also check it on a slab of stone to see if it's flush in every dimension. But...given the amount of work required to get at it, I'd have a machine shop check it.
 

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Discussion Starter #8
UPDATE:

So I decided to do this entire thing a little at a time (within 1 week). Let me tell you, if you aren't even intermediately mechanically inclined, don't try this. I had to dig in my stash of never used tools and getting those heat shields off was a real PITA. So as of now I have the entire intake manifold off. The exhaust manifold is coming off tomorrow and will be going to a local machine shop. I noticed though that there were no studs, all were bolts and came out quite nicely. So nicely in fact, that I think that this was part of the exhaust leak problem. I'm not talking "pretty easy" to get the bolts off, I'm talking literally turning the 1/8th inch wrench with one hand easy, WITHOUT penetrant. Same thing with the 4 top intake manifold bolts. I'm wondering if these bolts are even correct for the purpose that they are being used for. I have a full stud and nuts kit coming in so before I keep going I have a few questions so I don't have to do this whole nightmare again in the future....

1. Should I use the studs coming in over the existing bolts? Is there a problem using these bolts anyway?
2. If I use the studs, where should they even go? There's a lot of 12mm bolts on the manifolds and I don't know which ones need studs vs bolts.
3. Torque specs and tightening techniques to make it where it has the least chance of working its way loose?

Thanks guys! Help is much appreciated. Pics of current status are below.
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106604
 

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Discussion Starter #9
BUMP: I plan on doing this on this coming weekend so if possible please help me out on those last few questions! Also.... I found the exhaust leak culprit. An entire missing bolt on the cylinder 1 flange, which explains why I heard it most prominently by the distributor. I think whoever rebuilt it most have forgotten to tighten that one, because I couldn't imagine it just falling off by working its way ALL the way out. I actually found it laying on top of the AC compressor bracket. The cylinder one part of the exhaust gasket was torched as well since it pretty much took the full force of the hot fumes rather than it going down into the manifold. At least nothing broke so far...

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The exhaust ports use the studs (including the shared intake/exhaust). The intake only use the bolts. Probably more for ease of assembly than anything.
 

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Discussion Starter #11
Thanks for the help guys. Driveability has improved and sound is definitely down. Longest week ever but it's done!
106621
 

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Congrats! Good move to order the bolt and stud kit, and finding that missing stud was a great discovery to explain the leak. Hope it runs great for you.
 

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Discussion Starter #14
Congrats! Good move to order the bolt and stud kit, and finding that missing stud was a great discovery to explain the leak. Hope it runs great for you.
Yeah, it would have been much easier to spot if I had known what I was looking for! lol It was definitely apparent once I took the intake off and saw the soot around the thermostat housing. Better to order the studs and do it right the first time around.
 
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