75 280z manifolds

[Dave WM]

I have been contemplating a trans swap, well that involved removing the exhaust, which I have managed to break two of the 3 down pipe nuts on the studs. figuring I will need to remove the exhaust manifold to repair, I decided to tackle removing the various bolts that hold the intake/exhaust on. I assume both should come off since again I assume it will need a new gasket there as well.

I PB blasted and smacked the 4 intake nuts and the one easy to get at exhaust nut with a 1/2 ext and a BFH to shock them, then used a 14 and 12 mm box to remove. so far so good, after backing them completely out I replaced with some anti-seize compound snug.

Was curious about the use of bolts vs the studs and nuts as per the FSM? perhaps someone has been here before? any one else know if OE was ever bolts on a 75?

Also note the exhaust stud was broken on the back of the engine, it actually broke in place, I just noticed the engine hoist bracket hanging at an odd angle. Now here there was a stud and nut.

Seem weird that if the manifold was removed before and bolts used to replace studs why mixing of parts? Now I know the center top exhaust used a bolt but could not see the other two on the side of the center mount so maybe I will find studs there.

Anyway finally some success with removing stuff and not breaking parts. After the thermostat housing (top nut) and the down pipe I was about to throw in the towel.

I can fix the broken stud (I hope) where the hoist mount is as well this way, will have to see what I am dealing with AFTER I get the manifolds off. It looks like I can leave the fuel injectors on the intake, or will I run into an issue if I do that?.

 

anyway the goal is:

remove and fix broken exhaust manifold stud on rear of engine.

remove exhaust manifold to take to shop so they can remove broken studs on down pipe.

replace with new studs and brass nuts.

while at it will see if I can get the EGR bottom connection loosened up. Top is ok and I know I can leave it attached on the bottom, but if I can get it out would be nice to get some anti-seize there as well.

get it all buttoned up so I can get started on the trans swap.

 

fyi I got some quotes on the above (the manifold bold and the down pipe fix) they said would need to pull manifold (just as I described) to make the fixes listed, 700$ min ouch...

If the remaining bolts (3 on the exahaust and common ones used to clamp) come off as easy as the ones done so far, then I will be happy to do the work myself.

I plan to borrow a torch for the one remaining down pipe nut.

Thx to JSR who advised me that the ones on the head were generally not a problem.

 

 

 

 

 

 

 

[siteunseen]

I've pulled the injectors with the fuel rail, not the intake. Right or wrong I dunno?

[Dave WM]

it looks like I can leave all that attached ( injectors and rail) to the intake manifold, just disconnect the fuel supply and return line. I think I recall someone doing this, and not even disconnecting them just lift the intake up and balance on the valve cover long enough to clean up the gasket surfaces.

Edited April 14, 2017 by Dave WM

[Zed Head]

If you remove the nut or bolt on the front of the head that holds the fuel rail you could probably even leave the rubber hoses connected.  But, if you have old hoses, it's a good opportunity to just cut the hoses to get everything off easily then take your time removing the old hose with the manifold on the bench.  Actually it's a good opportunity to replace all of the old hoses and insulators and injector seals.

[Dave WM]

progress, I decided to try my el-cheapo maf/oxy torch, got the last stud on the down pipe moving, its unscrewing from the manifold (the nut is staying on the stud). got it about 1/4 inch down, I hope it come soon.

[Dave WM]

success! and it was the nut after all that came off. So now I can continue with the manifold removal. I put it back on for now after using some anti seize compound. Now it goes on and comes off easy.

[Dave WM]

Deep into it now, pulled the manifolds off, left the injectors and rail attached, just disconnected the wire harness from the various parts bolted to the intake manifold. Turns out both the first and last exhaust mount studs were broken, below the surface. I found the 1st one just laying there, guess it heat cycled out like the last one. The two broken down pipe studs actually had about 3/16 of the stud sticking out (the non threaded part). I tried heating with the small torch but no joy. I will take to the machine shop tomorrow and see what they say. I tried the vice grips, not working, I don't have a mig to try and weld on a nut and the vice grips will just keep eating up the nub.

On the broken manifold nuts on the head, they are below the surface, which I think may be a good thing since I may try drilling them out, and the hole that is open above them would be a good guide for a pilot drill to center drill a starting point. The one in the back is easy to get at, so I may try it. The on up front would require pulling the thermostat housing (no prob the bolts are NOT stuck) and the dizzy. Never removed a dizzy before, I assume its keyed and should just go in worse case 180 out so if I note the rotor I assume its a no brainer.

I sure would like to have all the studs back in so the exhaust bolts up tight. I don't think I am up to pulling the head just to take to the shop for drilling out the studs, but maybe that is the best way to go. I don't want to goof up the head with a bad drill job.

[siteunseen]

I drilled out the m8 bolts your talking about. Bought m10s from Nissan.  They're for the Titan 8 cylinder. I'll put up the part numbers in the morning. 

The header I bought from msa has the first and last holes already the bigger size. 

[Dave WM]

how hard was it to get a good straight hole drilled? I presume you had to remove the T stat housing and the distributer?

[Dave WM]

will try one of these things

OTC Robinair Bosch OT6982DGS Drilling Guide System

 

 

[EuroDat]

Well Dave. I just went through a similar drama. I needed to remove the down pipe so I could weld a nipple to fit the O2 sensor for my aftermarket ecu. Broke one stud, the second nut screwed off and the last stud screwed out of the manifold. 

I had to remove the manifolds, but was very lucky no broken studs. I didn't remove the injectors or fuel rail and the harness was already removed. I took the manifold to work and used an "easy out" with the oxy torch to get the broken stud out. The three new studs Nissan p/n: 14064-N420A are a little different and a little longer than original. They came with brass nuts so they should not seize as easily.

I don't get to spend much time on the car lately and this "weld M18 nipple in downpipe step" set me back almost three weeks with the extra work and waiting for parts.

[S30Driver]

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.