Y...pipe.

First new (thickwalled?) Y-pipe. Later broken studs... --->Is it so?

Does that new Y-stuff have different heat expansion properties & forces than the original y-pipe - corking those studs out?


bhunter
I don't know of a correlation, but the y-pipe bolts on to the the manifold, not directly to the studs that break.

tripleGmax
anyway about wikings remark. After i installed my warpspeed y-pipe my exhaust studs decided to break more. they were already slightly weak, but the new y-pipe seemed to make em break (4 in all before i replaced all of the exhaust manifold studs)

Cut/paste from http://forums.maxima.org/showthread.php?t=380403

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The engine is V. Both blocks live 'their own life' if heat expansion is considered. Now these blocks are connected with a third [here unknown] heat expansion element: the y-pipe.

1. Std Nissan with a 'straight' engine never blows these bolts. Just plain NEVER.

2. Cannot beleive that Nissan went shopping some bad quality studs for maxima.

1 + 2 = there is something better in the stupid original pipe [flexibility?] if u need a new y-pipe to start blowing studs.

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Q.2. Are the y-pipes thichker material, or is the Nissan original curve bent juts to lessen the forces acting on these blocks?

Q.3. How about other V-engines...

(Stainless steel at least has very different characteristics to std steel.)

 

Having had broken studs twice now (on the same manifold), And this is with the Nissan Y-pipe, I often thought about what causes this and here's my $0.02 worth.

I really think the studs themselves just aren't that good. A lot of people have this problem.

On Toyota's, I noticed they use extra long studs At first, you wonder why they used such long ones with a lot of threads exposed, but they use the extra threads to dissipate more heat. Those extra threads, if you think about, it make good heat exchangers.

Also I think I think how you drive and the state of the engine tune is a big factor in the life of the studs.

Heat and heat cycling is what kills these things, especially if the cycling is more rapid. If you suddenly floor your engine, or like to take off quickly from a stone cold engine, that doesn't help.

Also, if you advance your ignition timing (like most of us do, I did in the past), that raises the combustion temp higher, which doesn't help.

If you have fuel injector(s) that are going out, that can lean your air-fuel mixture, again making your combustion temp higher, which doesn't help

When you remove and replace the original Y-pipe, you're likely inducing some extra loads/stress on the studs that they don't normally see, which doesn't help and likely contributing to their demise.

The studs are a pain, but I much rather replace them than head gaskets like on the early Toyota V6 engines.

 

Sounds reasonable.

Then the next mod is to get stud coolers?

edit: ...or flex parts on y-pipe?

 

So if I get this right Tom has broken studs on a VG with stock y-pipe, correct? From what I read it seems this happens more on VG's than VE's. Is that wrong or not? On my three VE's I have not had a single broken stud--106k,145k,166k. I think wiking has raised an interesting point. Broken studs--new y-pipe or not?? We could probably get a pretty good poll here.

 

I had broken studs on both manifolds with a stock y-pipe and 75k miles when I got the car. My weather is similar is to Wiking's. I believe one injector was dying for a while, too.

 

75k ...I am there now. scary. Then original pipe is none better [if even any correlation].

Do u know about car history; how was it used? Lots of short drives...

 

there's a flex pipe in the Y section so that "should" take the vibrations out.

i believe a lot of the older VGs has weaker studs hence why nissan upgraded the part and now it's the same studs as the Z32. also i've seen newer heads w/ bigger studs..so nissan probably figured their wimpy 8mm (i think it's 8) stud is too weak for the motor.

use a lot of anti sieze in the studs when you do the job...makes pulling them out again a bit less stressful.

 

What do u suggest. Just wait until it happens, or try to replace 'em before it?

Is there certain year when this better stud (=less complaints) implementation started.

 

my studs broke shortly after i puta new warpspeed y pipe on..

 

it's always better to replace them BEFORE they break. only down side is that sometimes when you make the attempt to take them out they snap...so you end up drilling it out anyway.

 

I've repaired broken studs on at least half a dozen cars, and seen many more with the problem- almost all of them bone stock.


You have several things going against you on these studs.
1. weak, small diameter studs
2. soft engine mounts that allow a lot of engine movement
3. front and rear manifolds tie together with a rigid pipe. the Z31 doesn't have many of these problems, and they have a very small flex section between manifolds.


the first time I ever broke a stud on my old GXE was when I was sitting at a light waiting to make a left turn in heavy traffic. I had been driving for 30+ minutes on the highway, so it was definitely at operating temps.. studs nice and soft from the heat I'm sure. I saw an opening in traffic, gunned the engine, and HEARD the thing break when the engine torqued up.. exhaust suddenly got louder, and I could hear something bouncing around the engine bay and then under my car.
When I got home, I let it cool down and checked- sure enough.. front exhaust stud-- the one behind the AC compressor-- was gone.

Notice these studs always start at the ends of the head and work their way to the middle. All of the ones I've ever had to drill out were on the ends, and I've snapped a fwe more off at the next spot in once I started taking them apart.. One one car, I ended up drilling out SEVEN studs..
This car was a bone stock 91 SE 5 spd, driven by a 40 something man and it had about 150k miles on it with the original engine mounts.

 

Not the Y, it's the weak studs as Matt said. Stock manifolds are cast iron. Heads are cast aluminum. Expand/contract a diff rates. Bends stud like a wire. Bend a wire too many times = break. Need stronger upgraded Z31 turbo studs. Problems solved.

 

From that text I am figuring that the manifolds tend to bend from heat. (?) If so, they had already a problem in the mold design phase.

...no problems yet. Should I get new y-pipe and install an extra flex on front pipe...

 

Ok, went ahead and ordered the y-pipe from Warpspeed. Mentioned Maxima.org and got the discount. Nice lady. So the VE has better studs?

 

VE might have better studs, but they still snap. I've had a broken one on my car for years but I'm too lazy to rip apart the front half of the engine to fix it.

 

VE's have the same crappy studs. AMHIK

 

I was gonna ask that!

so should an extra flex section be added?
I'm probably gonna do a custom y anyhow, so any suggested upgrades to be done to the pipe at the same time, besides adding the turbo to it?

 

You can add flex pipes up the ying/yang, if you don't replace the studs, they will break.

 

10983274

 

From people with experience with stud replacment. What would be the best way to fix this problem.. pull the engine out and do all of them at once or do them as they break.?

 

there's no need to pull the engine. that's 20 hours of work to remove and replace the engine, but it only takes about 6 hours to do the stud replacement on the car.

just pull the manifolds off and replace all the studs at once.. make a weekend project out of it and you're done. never have to mess with it again.

 

When I do it I'll probably unbolt the crossmember from the car and lower the engine as much as I can without having to disconnect anything except maybe radiator hoses. I can barely fscking see the rear manifold as is.

 

How can I drill out the studs for the rear manifold without removing the engine? It looks seriously tight in there.

And yes, I noticed my studs started breaking from the ends too. Both times, it started with the one nearest the A/C compressor.

 

I have a 94 VE with almost 280,000 on it and have not had one manifold stud break yet. I am wondering if nissan used stonger studs in the last year of the 3rd gens?

 

so whats the verdict, is it easier to pull out the engine and drill freely or to leave it the engine in place and drill on your back..(this is for all the studs)
Is there a benifit of having the engine out - i.e. timming belt replacment..

 

hey green, just hit 200 in my girls ve 93se and blamoooo all studs break in front half of engine.....expect yours soon.....


take care
kevin the fish