Complete Misfire on Three Cylinders

[Captain Obvious]

So here's a question for today... What do I want to use for exhaust manifold nuts?

I'm looking ahead and I want to use something better than the mix-n-match of nuts my PO used. Of the eleven nuts I took off the exhaust... Ten of them were 1/2 inch, and one (just one) was 9/16. In addition, two of them were stainless (really really bad idea to mix stainless on stainless) and the rest were carbon steel.

Anyone got a part number for something self locking? Distorted thread? I would really like something 12mm instead of the 1/2 inch nuts I took off.

I would really like a set of matched, 12mm wrench, self locking nuts.

And BTW, I discovered that my intake manifold is thicker than my header flange, so that might help explain all the exhaust leaks. Another thread popped up here:
https://www.classiczcars.com/forums/topic/62535-thick-manifold-washers-notched-wanted/?

I'm soliciting input along with the original poster over there.

 

[S30Driver]

This could be what you are looking for Bruce.   Zcardepot   https://zcardepot.com/collections/exhaust/products/copper-exhaust-manifold-nut-set-240z-260z-280z

[siteunseen]

Here's my answer for today's question.  The one on the left came with my header but I didn't like them so I bought the bigger ones from Nissan.  The first and last holes on my N42 were wallered out so tapping to the bigger size was easy.  I have that invoice at home if you can't make out the p/ns.  

Edited July 22, 2019 by siteunseen

[Zed Head]

If you use self-locking nuts they'll probably pull the studs out on the next removal.  Nissan did not even use lock washers.  Actually, they didn't even use flat washers, where the yoke was used.  Stud, yoke, nut was all of it.

The mismatched flange thickness is the standard problem with headers.  John Coffey suggested cutting flat washers in half and tacking the pieces on to the header flange as a fix.  Requires a welder of course, but it was a simple and effective solution.

http://www.carpartsmanual.com/datsuns30/Datsun-Z-Index/Engine-280Z/Manifold-Egr/From-Aug-76

[Patcon]

I woulg with s30's suggestion.  Copper coated, no issue getting them off in the future

[Captain Obvious]

Yeah, I know if I use self locking, it's likely that it will pull the studs out next time. Don't care. I'll deal with that next time.

Thanks guys. Two votes for copper.

[Zed Head]

I bought a 280ZX engine and it had bolts instead of studs.  They looked factory.  

Seems like the basic question hasn't been defined.  What are you trying to accomplish by changing from the factory setup?  If you don't care about the studs getting pulled out why not just use thread locker?

[Dave WM]

same here on the maxima head, all bolts, looked factory. I still like the after market studs with the hex head ends, but as ZH mentioned IIRC mine came with the 13mm  head and locking nuts, did not like those at all, ended up using regular nuts (12mm hex) on them.

Edited July 22, 2019 by Dave WM

[Captain Obvious]

Yes, the stock system used bolts everywhere. I found that same thing on the 83 motor I'm working on in parallel with my blowed up one from my 77.

My PO already deviated from stock by installing stainless studs instead of the stock all bolt system. And ignoring the questionable length of the studs he had in there, it worked and I am (at this time) satisfied with that concept. I am NOT, however, satisfied with his choice of nuts that he used on the aforementioned studs.

[240260280]

"CO's Stud Service Thread" giggle, snort

[Captain Obvious]

  Yeah man. Never seize.

[siteunseen]