I hadn't been driving the Maxima almost at all since Halloween, and decided to start replacing the worn out parts over the weekend. I put in a new P/S pump, radiator and replaced the noisy aftermarket timing belt tensioner with an OEM unit (a bit pricey). I started the car to make sure everything was functioning properly before putting it all back together. In retrospect, I should have put the crank pulley back on before doing this. The crank sprocket started working its way off the crank and spit the woodruff key out...Pretty sure I won't ever forget the noise it made - it IS after all an interference motor. After getting the timing back in alignment I started the motor and it has a miss.

Did a compression test, two of the cylinders in the rear bank are a little bit down and one (cylinder 3) has no compression at all. So now I am going to spend the next month researching what I have to do, buying parts, and finding a storage unit to rent so I can throw the car in there and work on it in my spare time. Once I have found a place to put it I need to pull the heads, replace the valves, etc. and I would like to have the heads ported and polished if I can find someone to do it for a reasonable price.

This isn't the best way to start off a new year...

 

fortunately, it's a gxe. find a junkyard motor, with good heads, and swap 'em out.

at least it still runs?

 

I would think it's easier (and cheaper) to replace the valves as opposed to pulling an additional set of heads.

It still runs (albeit on five cylinders). I had to drive it from the courtyard of my building into the parking garage after unloading it from the tow truck.

 

Westside performance did the heads on my VE. plan more than a month though if you want that kind of work done.
The porting and valve job on my heads was ~$900 IIRC. yours will be a little less since there's 1/2 the valves, but you'll still have to replace that bent valve too. if they're working the heads over, might as well go ahead and have them replace that valve guide and maybe the seat so there's no worries about lingering damage.

With all of that, you might as well install a set of cams as well. porting the heads won't do you much without cams and ECU to make it work right.

 

i really have no worthwhile advice for you and for that i apologize but seriously; nissans are so hard to kill

 

If it costs that much for port / polish work and I need to mess with the ECU and get different cams I think I will just keep it stock. I want to keep this as cheap as possible (without cutting corners) and I already have a go-fast car.

 

I can refer you to a really good machine shop I've used since 1978...(Kent Machine Shop-7134337261) and (Engine Logics-2819332262) High Tech shop that can flow your heads , port and polish, fab intakes, etc...I would go with Isky or JWT cams and a reflashed ECU if possible...sorry about the mishap!

 

IMO your best bet is get a used VG30E cheap, just replace the whole thing.

 

If you want to just get it running on the cheap, then a fel-pro head gasket kit is $160 and a replacement valve is about $10. springs, seats, retainers, etc are about $10 each as well.
pull the head off, scrape the head gasket, buy a replacement valve and possibly spring + retainer +rocker just for grins so you have all the parts on hand when you tear it down.

lap the new valve in and reassemble. clean the gasket surface on the head with a 600 grit sanding block and reassemble.

You can probably do it in a day, but I'd plan a full weekend just for grins.. R&R the intake manifold and vacuum tubes is what will take the longest of any other part of the job.

 

True that!!!!

 

That's too bad man, trying to give the ride some TLC and end up bending bending valves Good luck with whatever you decide to do with it.

 

I have heard that felpro head gaskets are the worst there is, second only to chinese no name stuff. something about the design, or something. For the price, OEM is supposed to be the best bang for the buck
This is generally true for the vg, anyway. I have never heard of felpro having issues on an American V8

 

I've never seen issues on a Fel Pro gasket- most of the ones Fel Pro doesn't make themselves are done by the same as OEM suppliers (and Fel Pro is an OEM for many carmakers.).

The only issue I've seen on them is the water passages aren't large enough, which is easy to fix with a Dremel if you want to spend the time on it. I've used Fel Pro for 15 years now and done a couple VG HGs and never had problems just bolting them on and going.

 

After thinking about the situation a bit more I came up with something else that might be a concern:

How likely is it that when the valve bent it caused some kind of damage to the camshaft?

 

Possible, but more likely that you just bent a valve. considering the car is still running OK otherwise, I would suspect the cams are okay.

can't really tell until you pull off a valve cover and look, but I haven't yet seen a cam destroyed on a VG by what happened to your car. I personally wouldn't worry about it. If it did get damaged, call up Bakke at Awesome Z and see if they have some spares laying around from a Z31 or an old Maxima engine they have. they usually keep resuable (and regrindable) parts like cams and cranks.

 

Cool, Matt...

IYO, should I replace all the valves in the motor (or at least the rear bank)? The front bank gave me ~150 PSI in two cylinders, and the other one slowly worked its way up from 90 to 120 PSI.

The rear bank gave me ~90-100 PSI in two cylinders and 0 in the other one.

Would the 90-100 readings indicate slight damage?
Have you ever seen damage to the lifters in this situation?
How does one adjust the valves in an OHC engine?

 

you don't adjust these valves. they have a self-adjusting hydraulic thingy, similar to the chain tensioners on cars with timing chains.

only lifter damage I've seen was during a catastrphic engine failure. not what you're talking about.
the lower readings than expected on compression could be many things... age, engine being cold, rings not seating well, valves not sealing 100% (slightly bent), etc etc etc.

Ideally when testing compression, you want the engine at operating temps so the piston-wall clearance is proper and the rings are all well lubricated and sealing properly.

another thing to check would be to redo the compression test and put a teaspoon or so of oil into each plug hole just before checking (try to check it on a warm engine too)..
if the pressure goes up to normal with the oil, then you have old rings that aren't sealing well. If they stay low, then you have a valve problem or aren't pushing the gas pedal all the way down while cranking the engine.

 

I don't think anything has been mentioned yet about the valve guides. Thoughts on the likelihood they are ok or will need replacing?

They look to be only a couple of bucks a piece, but how difficult are they to replace?

 

i havent had any problem with the gaskets i changed out, and theyre felpro.. maybe the oil pan and valve cover gaskets dont rele take that much stress tho. lol..

 

It's possible but unlikely that it was damaged, you won't know until you pull it apart. You can change them, but they're not exactly easy. I would leave that up to a machine shop if you have to change a guide.

 

I personally would change all the damaged valves only if you aren't a super high mileage vehicle..... If you are a super high mileage (200,000+) I'd feel better changing them all and getng a good 3 angle valve job! Call Kent machine shop for a head swap versus a rebuilt head it's a quicker turn around, unless you've got headwork on your heads!

 

186K miles...I have good compression in the other cylinders though, and I want to fix it for as little money as possible.

 

I'm sure for most everyone who has posted this is a no brainer......but for Newbies, when doing a timing belt, there are several "never do-its!"
Never start the car without the crank pulley; thread makes point.
Never use the starter to rotate the engine. Always, once the belt is in place and has proper tension upon it, rotate the engine slowly with a breaker bar. You can do this by sliding a large socket onto the crank snout and running the crank pulley bolt onto it (holds crank sprocket in place), then slowly turning the engine clockwise. If timing is off for any reason, you will only lightly bump the piston against the valve and avoiding any damage. I always rotate my engine this way at least x6 revolutions by hand just to make sure everything is in place and the belt is not traveling off the sprockets.

We can go on and on. Never over/under tighten the pressure on the timing belt from the tensionor pulley.
Never use an AutoZone woodruff key...etc, etc.

 

Chris-

Matt thinks my piston should be fine - this obviously happened while the car was idling...do you concur?

Although it's impossible to tell for certain until I remove the head.

As far as the tension goes - I used the feeler gauge as is recommended in the FSM, but the belt seemed WAY too loose. At that point I tightened it using my better judgement. BTW, the tensioner spring is brand spankin' new.

 

I do want to be clear, my post was directed at Newbies reading, not ripping you....seems you've already learned what you need to do the job next time!

I absolutely agree that the pistons are likely fine. In my experience, the pistons can take a heck of a beating. Personal experience, I had a timing belt go on my at about 3-4k rpm accelerating. Definate "marks/scores" on pistons, but nothing where replacement was needed. Absolutely though, check them out. Nothing else, post some images and get some opinions from guys on the forums. BTW, taking an image of the inside of the cylinder might be tricky depending upon the amount of deposits inside the cylinder. If it's really clean, you will get the flash reflected and be unable to distinguish any marks/damage otherwise visable to the naked eye.

I've found that the tensioner spring can be tricky when first learning it. You have to rotate it quite a bit, and make sure it will be adding pressure on the crank sprocket end of the belt. Meaning the tensioner pulley should want to rotate counter clockwise when released.

I agree, the belt seems loose at what the factory indicates. I DO NOT recommend going against Nissan. But, I will say I go just a tad tighter than what it seems Nissan indicates. I also suggest you make sure you have the right washers for the tensioner. There are two as I recall, one appears bent. This specifically helps keep the tensioner nut from vibrating off and helps the tensioner do it's job and maintain proper tension on the belt for the duration of it's life.

I think too, it's already been said, go ahead and replace the valve guides and seals. Simply too cheap of parts to simply not do it. It is very likely the guides and/or seals were damaged....particularly on the valves which were bent.

FYI: My timing belt went becuase I got into too big a hurry and let someone who was supposedly a Nissan certified tech to my timing belt install when building my turbo. He ended up installing the tensioner upside down. If that doesn't make sense, don't worry, he did it. Needless to say, I rebuilt my engine myself!

 

Update: I have finally found a suitable garage to have the car moved to, so I can work on it...I will be having it transported today.

Seeing as it is a 3-day weekend, I will have plenty of time to remove the head(s). I hope to drop them off at a machine shop for a valve job early next week.

 

Work begins tomorrow...wish me luck!

I will post pics of the damage...

 

Depending on how much the job is going to cost, I would consider getting another engine if the head job is too expensive.

 

Be patient with all of the hex indented bolts (allen) and use plenty of PB. If you haven't already, pick up the 12mm hex key socket from any parts store/ tool store, it's worth its weight in gold. Not to mention a good breaker bar with a decent weight soft faced hammer......... Just my 2 pennies, good luck, and have fun!

 

Obviously, I will have to unbolt the y-pipe, but do the exhaust manifolds need to be removed before pulling the heads? Any tips / tricks on doing this?

 

No, your should be able to pull the heads with the exhaust manifolds attached...gl, But usaully folks remove the exhaust manifold from the head and leave the Ypipe...

 

Hmm...I wonder which way is easier.

I could sure use some of the OG's advice about now...

I also had another thought: For the last 30K miles or so I get some lifter tick on cold startup. This is characteristic of old engines and one would think this is due to a well-worn lubrication system since the only other option would be to adjust the valves / lifters - which I don't think is possible on these cars.

I was thinking if it would be beneficial to replace the oil pump while I am at it...thoughts?

 

I would leave the manifolds on the heads; pita to get the rear studs, anyway. you could easily pull the front manifold off with it in the car, but not so easy for the rear.

 

actually i can see how removing the heads with the manifolds attached could simplify things. you don't have to pry the manifolds off the studs and plus it's alot easier to unbolt the rear flange of the ypipe than it is to unbolt the rear manifold.

 

You are probably right on that...That is most likely what I will do. Besides, after thinking about it, wouldn't the weight of those heavy cast manifolds bend the y-pipe? They wouldn't be suspended by anything else.

 

Do you anticipate to pull the the oil pan, crank pulley, and alternator off anyways? If so, you would have a clear path of access, besides the timing belt sprocket behind the crank pulley (which is a PITA to remove BTW), but the need of replacement is not something I would be able to tell you about.

The manual describes the process of dis assembly, they aren't expensive items, but if you were having issues with oil not lubricating the lifters: there may have been blockage in the small channels throughout the head. If you took the head to a machine shop, they more than likely would wash em out with an acidic solution and degreaser which would clean out all of the channels. I recommend that , even if done at home in a bath tub, as it surely makes a difference in the longevity of their performance.

I have a working oil pump if you want it, perhaps to tear down and see what it is going on, in case you want to replace yours. I replaced mine, and imagine you could get a good idea of what 170K miles does to an oil pump by looking at this one, so as to encourage you towards leaving the one you have on there or not............ random thoughts, hope they help!

 

I also removed my heads with the exhaust manifolds on them for simplicity sake. Not to mention the studs appeared to be "one" with the nuts with all the rust action taking over..... I highly recommend replacing those too, for ease and appearance. Have fun getting the bolt holding the cam shaft in the head without air tools, it can be a bit tricky to hold the cam in place while trying to reverse thread the fairly large bolt, but you may have gorilla grip and strength.

 

isn't there a spot on the cam that has a hex shape that you can fit a wrench around to hold it still? maybe i'm thinking of VQ cams but i thought the VG cam had a spot you could put a wrench on

 

I suppose the oil pump is only one possibility. You are right though, it could be blocked passages in the heads, or maybe leaky lifter seals. Whatever the case, I am going to pay a reputable local machine shop do both heads.

The exhaust manifolds shouldn't be too difficult to get off either way tho...about 3 years ago I had all the original studs replaced with turbo Z31 units.

Maybe a dumb question, but: will the cam still be in the head when you remove it or does the cam need to come out before the head comes off? (I know, I know...I am working my way through the FSM, but it helps to hear an answer from an actual person.)

 

There isn't a hex shaped portion, but more of a square shaped spot where one can fit a 21mm wrench onto, but still, it's just tricky...........

I guess it was silly of me to mention the cams coming out seeing as you won't need to remove them to get the heads off. I thought you were going to tear them down your self. I took mine to the local machinist, but still thought I would measure everything as a preemptive measure for my own encouragement........... Have fun!