Late last year, I started developing an exhaust leak from the number 6 port which was... of course, broken off flush with the head. Probably has been broken for many years before I got the car. With the nice summer weather, I decided to replace the gasket & install all new high grade studs & bolts. Let PB Blaster go to work for a few days and went to work.

I removed the manifolds and used left hand drill bits to extract the broken studs. (number 1 was also broken off - discovered when i removed the manifolds) Number 1 backed out by the time I got up to about a 3/16th bit. Number 6 refused to comply, so I drilled it out and re-tapped for the stud.

Patience is definitely the key - accurate center punch mark, slow drill speed, cutting oil, don't overheat the small bit sizes.

Chased all the threads and prepped the head for the new gasket. All is looking very good so far.

Tomorrow, or the next day, will pick up the new stud & bolt hardware. Going to try and get grade 10.9 for the studs and 3 middle exhaust bolts. Grade 8 at least.

Also, have the main heat shield and some other stuff at Performance Coatings for ceramic exhaust coating - Chromex. Should be ready in 3 or 4 days.

Will be interesting if it has any impact on the minor heat soak issue I experience occasionally.... Will report back on that.

In other news... if you look at my 2nd picture, you can see that the liner is missing from the #2 exhaust port (N47 head). I actually found some pieces of it hung up in the downpipe area - hopefully the rest made its way thru the system to the muffler.

I am wondering if this has any impact on the motor - good or bad. Is it possible to remove the other liners? Any thoughts....

Apparently you can remove the liners. Some do, for the general bigger-is-better concept. But the remaining hole is probably not good for flow over the normal RPM range. It has no shape. Somebody did some flow-testing on a variety of heads and found that the liners didn't hinder flow, on a stock N47 head.

I would be concerned about an imbalance between cylinders. May not be a real issue. I've never heard of anyone using a head after they discovered a liner fell out. Pretty sure that they're cast-in. Maybe someone could weld the broken aluminum piece back in, if that's why it fell out.

Thanks for the info Zed, I share your concern. However, I will live with it for now. maybe address it at some point in time when I have to remove the head.

Too bad I can't get #4 liner out to give it some balance.

Did a piece of the head casting break off or did the liner just work its way out if its slots? A closeup of the damage would be interesting. Your problem is the reason that some people recommend avoiding the N47 or P79 for use with turbos.

For what its worth, here is a pix of the number 2 exhaust port with the missing liner. Need to get better lighting and a better cam to show more detail.

The 2 pieces I found in the down pipe flange area were rounded steel from the liner.

After much searching for the holy grail of exhaust studs, I ended up taking Zed's advice and a Nissan dealer parts guy put me onto a set of M8 upgraded studs for the 300zx turbo & pathfinder. They are grade 8.8.

Turns out that in the world of double ended studs, it is very hard to match the A & B lengths that Nissan used. The A length needs to be 14mm (the short side that goes into the manifold) and every stud I found in M8 was 10mm on the A side. I did not want to sacrifice the other 4mm of thread into the head.

The Nissan part number for the studs is 14065-V5004

Here is my kit I assembled for the manifolds, now just waiting for my heat shield & other stuff to come back from Performance Coatings ....

Parts finally ready at the coater's today, so stopped & picked them up on the way home.

Started putting everything back together.

The chromex on the heat shield looks nice. Probably should have looked for one that was less pitted where it is visible. I'm guessing rain and dirt coming in thru the hood vent and collecting on it, causes the rust and decay.

But not now!

Mostly complete, runs much quieter & fairly well. Changed the oil & coolant as a treat for the beloved Z car.

Need to check ign. timing & see if I can get the vacuum up from 15 or 16 in hg. Also idle is low - around 650 rpm which might account for the low vacuum.

The intake & exhaust looks like they are sealed up well from the new gasket.

Need to clean up the wiring a bit.

See what tomorrow brings....

That looks really good.

Thanks Steve

Now I'll have to get the pass side of the engine bay a little cleaner to match the work I did on the driver side....

(my back is hurting from all the leaning over the fender)

I know how you feel. I took off the intake an exhaust a week ago. Fortunately for me, a friend did most of the leaning over work putting it back in.