How to change your head gasket

[joe]

How to change your head gasket:

Its usually pretty easy to tell when you have done the head gasket, the engine will be running rough, if its blown near the water jacket the oil can be a milky colour from being contaminated with water, it can have bubbles in the radiator, lots of steam/water coming out at the exhaust pipe, the engine may not even turn over as a cylinder could be full of water or there may be a very loud pinging/knocking sound coming from the engine which can be caused by the gasket blowing between two cylinders (usually 3&4) as a result of cylinder 3 firing and also detonating the mixture in cylinder 4. This noise should stop if you take one of the spark plugs off. If you have any doubt, take it past a mechanics and it should take about 3 seconds for them to tell you if it’s a problem with the gasket or if its something else.

Ok, so its rooted. Should I just take it to a mechanic and pay them $300 labor to change it plus the cost of having the head reconditioned?
No. Save your money. Its pretty easy to change and probably takes only about 40mins to remove.
What tools do I need?
A flathead/Philips head screwdriver, a 10mm allen key socket, torque wrench, 10mm spanner or socket, 12mm spanner/socket, 17 (maybe 19)mm socket, ratchet and extension bar and probably a large shifter for the EGR pipe if you have one and a set of feeler gauges.

Im just going from memory here so If I forget anything.. im sure you will find out:
Start by having a beer and using those screwdrivers to loosen off the hose clamps to drain the radiator, also same goes for the engine oil - the sump plug is on the bottom of the sump if you get under the car on the drivers side you should see it, it’s the only bolt there. If you have any difficulty so far then maybe it is best to take it to a mechanic after all. If the sump is full of water too then there’s going to be quite a lot of fluid in there so you may need a pretty big bucket to empty it all into. This is of course unless you’re doing it at a mates place, then just empty it on his drive way or garage floor.

If you are still running with the stock carby/airfilter then the first thing your probably going to have to do is take that air filter off, a few 12mm bolts connecting it to the rocker cover and it should lift off. Get one of your mates to go to work with a 12mm to take off the exhaust manifold/extractors whilst you have another beer. If you have a pollution model engine then you will have a Exhaust Gas Recirculation (EGR) pipe that you will probably need to take off. This is the pipe that runs from your exhaust manifold to the underside of the intake manifold. Have a bash at it with a big shifter or the right sized spanner but usually there on there pretty tight and can be a bit of a bitch to take off, try spraying it with some wd40 or similar.

Its been so long since I have had and pollution gear on my engine I cant remember exactly what’s needed to remove it but just remember/mark where all the connections go and rip all the crap off. Not that hard. Personally I would not put any of the pollution crap back on, just get 4 bolts with the same thread as the air injection pipe and screw them into the head. Just remember though that technically your car is not road worthy with out it, but you will get a little more power and fuel economy.

Usually I take the head off with the intake manifold attached as I find it easier to remove the manifold when the heads off the car. Up to you if you want to do it this way or not, just means you need to take off all the connections to the manifold/carby (pretty easy)

Remove the heater hoses coming from the fire wall to the inlet manifold, just remember or mark which ones top/bottom. There is also a wire going to the temperature sender unit located just underneath the thermostat housing on the underside of the intake manifold that just unclips. Take off the fuel lines and mark which one goes where. Take off the spark plug leads and the tube going to the rocker cover from the manifold.

Take off the 4 bolts on the rocker cover with a 10mm spanner or socket and remove it. Turn the engine over by hand until it reaches top dead center (TDC) This is marked on the crankshaft pulley. There will be a notch in the pulley that you line up with the ‘T’ timing case. If you look at the cam shaft then there should also be some valve timing marks also lining which are located near the timing chain.



If you have a mechanical fuel pump (usually found on later model gemini’s) then there will be a pump cam attached to the camshaft sprocket. You may need to take the fuel pump off so you have more room to work, just 2x12mm nuts. The distributor will probably prevent you taking the pump completely out but just as long as you can get the pump arm out of the way then you wont need to remove the distributor as well.

Put a lint free rag or plastic bag down the timing chain orifice to prevent any bolts etc falling down there. If they do then you will be just creating more work for yourself because you may have to pull your sump off to get it out. This could mean pulling the whole engine out to do so…but don’t let that deter you (can also try using a strong magnet to fish it out).

Probably time for another beer about now, then get some wire or string and tie the timing chain to the camshaft sprocket to stop it falling off. Get a 17mm (or maybe its 19mm) socket and take off the bolt that holds the camshaft sprocket in place. Release the tension on the timing chain by pressing down the slide pin of the automatic chain tensioner (white thing on the left hand side of the timing chain) then turn it 90 deg clockwise to lock it in the released position. You will probably need to use the extension bar and a 12 mm socket to take the two bolts retaining the cylinder head to the timing case. Try putting a bit of blutak or similar in the end of the socket so the bolt can be easily lifted out. Take the sprocket off the camshaft and now you should be ready to deal with the head bolts. Using the 10mm allen hex bolt slowly ‘crack’ all the bolts in the order:

3 4
7 8
10 9
6 5
2 1

Just release the tension off each bolt in that order a little at a time. This decreases the chance of you warping the head when you take it off which with a bit of luck did not happen when the gasket blew. Once all the bolts are out just do a final check that nothing is still attached to the head or manifold that will prevent it from being lifted off, eg. The accelerator cable to the carby, take that off as well as the vacuum line that attaches to the intake manifold from the brake booster. Now it should be ready to lift off. Once its off then you can admire what a big chunk you managed to blow out of the gasket. If there’s no chunk missing then you may have a crack in the head or block. If this is the case then it would suck, so get stuck into a few more beers. If not - may as well have a few more anyway.

Once the head is removed from the engine take off the intake manifold (if you haven’t already) and take the head down to your local head reconditioner. You will probably want them check the condition of it, most places wont charge to have a quick look over it to tell if its gone soft, warped or other obvious things..an easy indication that the head has gone soft is there will be indent marks from the head bolts, usually caused from the engine overheating and will probably be prone to continually blowing caskets and warping.

It may be necessary to go the a wreckers or similar and get another head to use. If this is the case then get an early model tx head as they had bigger valves in them (42mm I think).

What you will probably want to do then is to pressure test it ($40-50) which will ensure theres no crack in it, depending on the heads condition you may need to get it rebuilt and a surface grind so theres a good flat surface for the gasket to seal. While the heads are off, it might be a good time to look into a bit of performance work. Eg. Mild/hot cam, port work or have a fair bit shaved off the head for more compression or maybe even get a thick copper head gasket for lower compression and put a turbo on. If you have taken the head to a decent place just tell them your plans and they should be able to work out what would give you the best value for money.

If your in Melbourne try Head 2 Head in Oakleigh (95627276) really helpful blokes there and wont rip you off, they used to race buggies with Gemini engines in them so they know a fair bit about them. If you go here then you may as well take a few beers with you and expect to be there for a while because Peter really likes to talk. Some of his stories are pretty good though, and if you don’t know much about heads then he will probably explain a fair bit about their operation and physics to you.

If you are going to have a lot shaved off the head you will want to measure the distance between the valves and the piston. Just put some placticine on the piston spray it with cooking oil, wd40 or similar so it wont stick to the valves, and using your old pre-crushed head gasket, put the head back on the engine and turn the engine around by hand. Take the head off again and cut the placticine down the middle so you can see the deepest part of the valve imprint and measure how much room you have left before the valve hits the piston with a set of verniers or something. This will then help determine how much you can have safely machined off the head or how much lift the cam can have. Or of course you can go to the full extent of pulling the pistons out of the engine and having them fly cut so the valves wont hit at all.

Ok, so now you have your head back from the machine shop and a head gasket kit (should be about $50-60 for head gasket, intake/exhaust gaskets etc) just do everything pretty much in reverse order. Make sure that the top of the engine block is clean and place the gasket on top of it. Bolt the manifold back onto the head and put the head back on the engine. Grab another beer and your torque wrench and start torquing. The head gasket should come with some specs on how tight to torque it, will be something along the lines of:

Stage Nm Lb.ft
1 68 50
2 81 60
3 98 72

And if you have changed the cam or the head shop hasn’t completely tightened the nuts then the rocker shaft bracket nuts should be around 24Nm I think. Just make sure the cam shaft has some lube on it and the timing mark on the camshaft is inline with the mark on the front of the support bracket, and the crankshaft pulley is still pointing to TDC. To tighten the head bolts again, start in the middle and work your way out so the head wont warp when you put it back on like sequence:




(note: to remove head sequence is in reverse order)

Put the 12mm timing case bolts back in and be careful not to over tighten them as its pretty easy to strip the thread which sucks, I think they need about 25Nm. Put the camshaft sprocket back on the camshaft and bolt it back on with the mechanical fuel pump cam if you need one. Use a flat head to release the timing chain tensioner by turning 90deg anti-clockwise.

Rotate the engine by hand to make sure it turns over ok and that the pistons are not hitting the valves. Also check your valve clearances. If you have a reground cam then adjust it to those specifications if not, the stock clearances when cold are Inlet - 0.15mm, exhaust -
.25mm. To do this rotate the engine until the cam lobe is pointing straight down (towards the ground) and use a feeler gage between the valve stem and adjusting screw. To adjust the clearance loosen the 12mm nut and then using a flat head screwdriver adjust it until you can feel a sight drag on the feeler gauge then tighten the nut up again.

You may also need some gasket goo for the two end seals (the black semi circle things that fit into each end of the head) Reconnect all the manifolds/rocker cover/hoses/fuel lines/temp sender/accelerator cable/vacuum hoses/spark plug leads etc..

If you had water in the sump then flush a bit more oil through it and get a new oil filter. Fill the engine with oil and the radiator with water, grab another beer, pray and turn the key to start…

…Listen to that baby purr. You may need to re-torque the head again after the engine has full warmed up and cooled down again (maybe do it the next day). Everything should be running fine and dandy and if not…well.. umm.. I guess you should have listened to me in the first place when I told you to take it to a mechanic.

Anyway, Good luck.

[Turbo_Gem]

have struck problems with these engines after the head has been shaved, the locating dowels on the block end up interfering on the recesses in the head,this is easily cured by taking an appropriate amount off the dowels using a bench grinder, measure the amount of recess in the block & head, then measure ur dowel and cut it down to the same height.the head gasket will provide enough clearance..

[TUF TF]

I cracked my head gasket about 3 weeks ago and pulled it off last week, i didnt find this tip till today but i wish i found it earlier, everything i did was identical and in the same order as it is here!! GOOD TIP

[HONES]

when the gasket has time to settle in etc

can u give us the re-tensioning details?