75 280z manifolds

[siteunseen]

You beat me Jim!

 

[Dave WM]

10 minutes ago, S30Driver said:

Dave,  I did this job about 4 years ago on the same studs and had great success with a good set of left hand drill bits.  You of course need a reversible drill.   I started with a very small bit and worked my way up 3 or 4 sizes and the stud just backed out with the bit.   Going slow is the key here.   I replaced the studs with higher grade Nissan turbo studs I got from the dealer.

Good to know I just bought a kit of those recently.

[Dave WM]

was I right about pulling the distributer? need to remove and easy to figure out how to re install?

[rcb280z]

The Dizzy will only go in the way it came out so you are safe to pull it.

[Dave WM]

roger that rcb280z

[Dave WM]

Wow that was easy (the back one anyway) Used a right angle air drill to start the pilot hole using a drill bit that fit snuggly (a tiny bit larger than the hole) after I established a good dimple I hit it again with a punch for a deeper sharper point right in the center of the dimple from the drill bit. Put in a small (1/8) reverse drill and started about 1/4" max checking by eye for square to head. Upped the bit to a couple sizes larger, opened up the hole a bit, then one more increase and the drill get stuck (air drill has low torque it seems) so I switch out to the electric VSR drill. Much harder to get in position so I am glad I had the small air drill to start and get squared up. a couple hits of the bit, it bites hard and out comes the stud just a pretty as you please. Taking a break (have to get back to work, only work on lunch hour during work days) will savor the success before moving on the front one. Will clean up the hole prob leave it at 8mm since its in such good shape. Dropped of the exh mani at the machine shop, they could not get to it for a week, so I asked about just welding on a nut and giving that a try, said they could do that today so will get it back later, then hit up JSM for his big torch to heat up mani to cherry red (no way my punk a$$ map/oxy can do that). Hopefully the guy at the shop will just take pity on me and do it while there.

Edited April 17, 2017 by Dave WM

[Zed Head]

Check your local yards and craigslist for manifolds.  I took my first one to a shop to have a stud removed and have it ground and the guy charged me the very top of his estimate,even though I told him if it didn't look like it was going to come out to just stop.  He looked at it and said it wouldn't be a problem and should cost at the low end.  He seemed sincere.  I think that he just enjoyed the challenge of removing it, at my expense, when it turned out difficult.  

My fault for not resetting the upper end of the estimate, but I found junk yard manifolds later that I could have bought and used right away for 1/3 of what I ended up paying.

[Dave WM]

something to think about on the manifold studs exp the end ones. Perhaps over tightening them esp cold could contribute to the failure mode of spontaneous breaking?

Expansion and contraction on the ends of the manifold would cause repeated stretching. So maybe under tighten them just a bit or at least on the low side of the torque settings?

as too why the ends, guessing less mass out there so more rapid expansion and contraction?

 

Edited April 17, 2017 by Dave WM

[Dave WM]

1 minute ago, Zed Head said:

Check your local yards and craigslist for manifolds.  I took my first one to a shop to have a stud removed and have it ground and the guy charged me the very top of his estimate,even though I told him if it didn't look like it was going to come out to just stop.  He looked at it and said it wouldn't be a problem and should cost at the low end.  He seemed sincere.  I think that he just enjoyed the challenge of removing it, at my expense, when it turned out difficult.  

My fault for not resetting the upper end of the estimate, but I found junk yard manifolds later that I could have bought and used right away for 1/3 of what I ended up paying.

there was one at the JY not that long ago I passed on figuring I would never need it (gone now). Will see how this ends up.

[siteunseen]

I've tightened mine down from the center outward. I don't know if that's right or wrong but something to think about before reinstalling. 

[Dave WM]

don't buy the pictured gasket sold by Advance Auto parts for a 75/76 Z. I did and they shipped (could only get it shipped to home, not in store pickup) something that has round ports for the exhaust, not the square ones on a N42 head. Looks like a P79 head manifold gasket.

[ensys]

This is an interesting topic for me as I am at the point of re-assembly of the manifolds/plumbing after my rebuild of the quite original engine (with 200K mi.) on my ’77 280Z.

I too find the business of sheared fasteners at the ends of the exhaust manifold (the front on mine, quite some time ago) intreguing. Having verified that the “cold” mating faces are all in the same plane, I am forced to other conclusions about possible causes of what appears to be a common problem.

My theory involves recognizing that the two end branches are long and of considerably less mass than the center, which may contribute to an uneven pattern of expansion, which I couple to a suspicion that there may have been something about the casting process (uneven wall thickness, etc.?) that encourages the ends to pull away from the head. At any rate, there is something going on there.

I found dealing with this was easier with the head off, making the drill-out less… encumbered, if not less stressful.

Incidentally, I too learned that linear manifolds like to be torqued from the center, out.

Lastly, it’s clearly an issue of personal preference, but I figure if the intake has to come off anyway, one might as well take the opportunity to refurbish the plumbing and bench-test the injectors/various elec. valves, and just generally check/clean/replace everything. Unless, of course, all of it is in pristine and fully functional condition…

But again, it’s a personal thing. When I leave a work area well preserved, it makes it easier to tell where I was working.

 

Edited April 20, 2017 by ensys