# Replacing head



## XakkGrill (May 23, 2012)

So Im fairly certain my Sentra jumped timing and destroyed the head. My compression is 100, 120, 130, 150. With the oil cap off I can feel air pressure when turning it over. It wont start, but Ive literally replaced everything else on the car.

So I found a head in the junk yard for $28
I found a timing chain kit from rock auto for $60
I found a head gasket for $12
And I found head studs for $22

I bought the car for only $500, so I don't plan on spending a ton of money.

Is there anything I should know before I tear into this? Any chance for a walk though? Ive personally never done a head swap, but Ive done almost everything else there is to do to a motor on my MR2 turbo. I have a couple friends who have done head stuff before that are willing to help, but I want to know if there is any tricky things I need to look out for.


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## jdg (Aug 27, 2009)

If you jumped the chain, and bent a valve, intake or exhaust, even in the slightest, you would have zero compression in that cylinder.
I know this from...(wait for it)...experience...and my own stupidity which caused it.


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## XakkGrill (May 23, 2012)

Zero compression? Your telling me you had zero compression across the board. Well, I had 180psi before this happened, so Im assuming its the head because I would have to have terrible gas to burn the ringlands on all 4 cyclinders. My oil looks fine so I doubt its the head gasket. Also, with the valve cover removed, the cam sprocket is missing teeth and there are scars on the walls of the head where the chain dug in, so I have a feeling I jumped timing. Im just wondering if there is anything that is hard to get to, or requires special tools.


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## jdg (Aug 27, 2009)

No, just zero compression in that particular cylinder that had the bent valve...just barely bent too. The only thing I saw get thru it was light. Water would trickle thru...but that's about it.
Didn't say anything about scars on the walls in the original post. Ya, sounds like you've got major problems and the head is gonna have to come off just to figure out what's what.


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## BeyondBiscuits2 (Jan 18, 2006)

The GA16i is a fairly simple OHC design, so it isn't very complicated in regards to timing components. The intake manifold, however, is another beast of a nightmare to deal with. Go ahead and buy the timing chain tensioner, unless it comes with the aforementioned kit (sometimes they do, sometimes not). Buy the Chilton or Haynes manual for the car. I'd suggest removing the engine from the vehicle entirely, and use this opportunity to fix any leaks or old seals. The most important thing about doing the timing chain on the GA16i is the removal of the lower timing cover. You MUST drop the oil pan. Non-negotiable. Don't even think about trying to pry the cover off with the oil pan on... you are guaranteed to split it in half. Other than that, should be pretty straight forward. Just make sure your crank is set at TDC before you get the started.


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## XakkGrill (May 23, 2012)

I pulled a head out of the junk yard today. It wasnt that bad took about an hour. We didnt have to mess with the lower cover because we werent taking the chain. The head seems to be in good shape. The intake manifold was a pain due to all of the vacuum lines. We tore all of them on the donor car. Once the kit comes in Ill deal with all of that on mine.


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## XakkGrill (May 23, 2012)

So I started this timing chain/head swap project.

Pulled the exhaust manifold, easy.
Pulled the intake manifold, complicated, but not terrible.
Pulled the valve cover.
Pulled the upper timing chain cover.
Pulling out all of my ac because it doesn't work and it's in the way. 
Pulled the egr, difficult for how few parts there are.
Pulled the wiring harness, broke several connectors. 

Then I took the cam sprocket off, then head studs, then the head comes off. 

I managed to break 4 teeth on the cam sprocket and bent all of the exhaust valves. All of my pistons are scared, but that's no big deal. 

At this stage I'm pulling the oil pan (I haven't had to raise the car for anything yet), and then the lower cover comes off and it all goes back together. 

This sounds like a lot of work, because it is, but it's not very hard compared to some of the stuff I do on my 3SGTE. I know y'all don't have a walk through for the timing chain maintenance, so this can kinda serve as a guide.

So far the only tools I've used are:
10mm
12mm
14mm
A big 22mm(not sure) for the cam sprocket
Screw drivers
Crescent wrench for the egr
Pliers 
A T10 for the head studs
And a hammer for breaking stuff

Pic of the fun


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## jdg (Aug 27, 2009)

Scars on the pistons...just file them down smooth so they don't have any sharp edges.
And spray some WD40 or something on the cylinder walls to keep them from rusting...especially with that coolant sitting in #1.

Good times eh?


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## XakkGrill (May 23, 2012)

The coolant is from the intake manifold jacket, it kinda leaks into that cylinder if you dont drain the coolant before hand. Im kinda skipping steps because its so cold outside.

My cylinder walls look good, so Ill probably just do like you said and file down the sharp bits on the pistons.

Its also good to note that if anyone else is doing this job, you will need vacuum hose. While that intake manifold is out its just a good idea to replace all of it. 

The good thing is that this motor is so small that its fairly easy to get to everything. The intake manifold does require creative use of extensions and universal joints, but I think itll be harder to put back on than to take off.

Should also note that if your gonna do the euro cam, now would be the time because of how easy it is to play with the head when it is out of the car.


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## jdg (Aug 27, 2009)

Oh ya, it'll be harder putting back on.
When I took my head off, I had wiped out on the ice, thrown out my back and wrecked my left shoulder a few days before...and just taking it off was a serious P.I.T.A...er...upper body 
I'd venture to guess it took me roughly 5-10 times longer to put the intake back on...finding the right hardware for the right spots, second/third/fourth guessing myself, redoing things, still playing with a rotten shoulder, etc.
In the end, it ran just like before, no better, no worse. Again, good times...


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## BeyondBiscuits2 (Jan 18, 2006)

Have fun getting the new head gasket to seat and seal properly in the cold! I'd suggest moving the vehicle into a heated shop or at least a garage when the time comes to reassemble, if it isn't already in one. I made the mistake of not doing that when I did the head gasket on my GA16DET. Also, while you're down there, mine as well change your front main seal. All the GA-series have a bad habit of leaking from it, so just get the $8+ seal from Nissan and slap 'er in.


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## XakkGrill (May 23, 2012)

I probably will. I have a nice shop to work in, but Im using that space to do a water pump on my MR2, so the sentra will have to sit outside until Im ready to put it back together. I didnt buy a front main seal yet, but I will. Right now Im just taking it all the way apart so I can see what I do and dont have. I just pulled the AC compressor and all of the lines because the compressor is bad and in the way.


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## XakkGrill (May 23, 2012)

I finally finished this project. Got the head installed, 190psi compression in all cylinders. It runs great. Only now, when it warms up it will randomly die if left to its own devices. Only gauge I have that works is speedo, so no real information being passed to me. 

I have fuel, the pump even kicks on. Cold start is fine(a little head rattle from the rebuilt head break in), no warm start though. I dont seem to have spark after it is warm, but the plugs might just be fouled with gas. When it dies it dies quick so it is not running out of fuel and sputtering. It is losing spark or stalling.

To me Im thinking it is either the coolant temp sensor telling the ECU to add to much fuel, the ignitor/coil is over heating and no longer giving spark, or my battery is so dead that it cant sustain the low idle. I have the battery on a trickle charge overnight and Im going to replace the coolant temp sensor asap. I already tried changing out the coil, but it was with a junk yard coil, same exact symptoms between the two coils.

I will add some pictures eventually.


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## Wesleyb12 (Jun 19, 2012)

XakkGrill said:


> Im thinking it is either the *coolant temp sensor telling the ECU to add to much fuel, the ignitor/coil is over heating and no longer giving spark, * Im going to replace the coolant temp sensor asap. I already tried changing out the coil, but it was with a junk yard coil, same exact symptoms between the two coils.
> 
> I will add some pictures eventually.


its not your bat. your car uses the alternator primarily once the vehicle is running. i'd pull out a plug and check how fouled it is with fuel. sounds like you gotta bit of a spark issue or a sensor issue. have you learned how to pull codes on these rusty old ga16i ecu's? How do I Read Computer Codes on a 1989 Nissan Sentra? | eHow.com here is a link. and be careful dont mess around too much. i have really messed an ecu up doing this wrong lol


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## XakkGrill (May 23, 2012)

I fixed the problem. It was a mixture of several things. Bad fuel pump wiring, AAC valve clogged, catalytic converter clogged, stuck piston rings causing good compression but no oil seal fouling spark plugs. I seafoamed the AAC valve, rewired and sealed the fuel pump, and poured some ATF into the cylinders to free up the rings. Runs great now. Will probably need another ATF treatment here soon. Rings dont seal perfectly, but they are way better.

Now I need a new exhaust manifold. I broke two of the studs holding the midpipe on. there are no B12s in the junk yards near me, and even though B13 manifolds will bolt up, the EGR shit doenst line up at all. So I'm going to try to figure that out. Might just make some EGR block off plates. 

Now that the Sentra is reliable Im working on my MR2 turbo again so I wont be on the forums much. However, if anyone needs some info on GA16i's, Ive rebuilt one from the ground up lol. Wouldnt recommend it, just swap it and save the hassle lol


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## BeyondBiscuits2 (Jan 18, 2006)

I'd just take the manifold to an exhaust shop and have them torch the broken studs out. Probably much cheaper than searching for a GA16i exhaust manifold in good shape. You can get replacement studs at any parts store.


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