Hope i don't get acussed of giving to much info....
this is a great how to with pics....
Head Gasket Replacement
this has all of the HCI stuff but you can skip the cam swapping and other misc. info. Good pictures
http://www.allfordmustangs.com/techa...intakeswap.pdf
and here is a play by play how
same procedure as if you were replacing the heads
Hope this helps you....
Cylinder head removal & replacement
Plan on 3 days to do the job if you haven't done it before.
Day one gets the heads off in 4-6 hours. Remove the A/C compressor mount bolts and move the compressor out of the way. The A/C compressor swings out of the way without disconnecting any of the lines or losing any refrigerant. Mark all the electrical, smog and vacuum lines with tags to help you remember where to re-connect them.
Day two gets all the gasket surfaces scraped off extra clean and the heads dropped off at the machine shop if you are going to have them reconditioned. Time here is another 4-6 hours. Whatever you do, don't skimp on cleaning the gasket surfaces. New gaskets need to seat against bare metal and not the residue left from the old gaskets in order to seal leak free. This is the most time consuming and tiresome part of the job. Look for little things that need to be replaced like the short hose from the thermostat hosing to the water pump, damaged vacuum lines and hose clamps that are rusted or broken.
Day three starts when you get the heads back from the machine shop. This is the time to pick up all the little odd pieces you found needing replacement on your day two inspection/cleanup. Plan on 6-8 hours to reinstall the heads and reconnect everything. Plan on an additional 2 hours to troubleshoot/adjust everything.
Now for some practical tips:
Plan on cutting the thermostat to water pump hose, or removing the thermostat housing. Also plan on removing the distributor to get clearance to remove the
intake manifold. Remove #1 spark plug, stick your finger in the spark plug hole and crank. When your finger gets air moving past it, stop cranking. Turn the
engine until the timing marks line up with the pointer. Make a scribe mark on the distributor base and engine block. Now you can pull the distributor out. When you re-install the distributor back in the engine, make sure you are still on TDC compression for #1 and then line up the scribe mark on the distributor and engine. You will be very close to where the engine was timed when you took out the distributor.
You'll need new head bolts - get ARP bolts ($40) or studs ($93, maybe more). All the bolts get antiseize under the bolt heads, and everything but the short head bolts get it on the threads. You need Teflon pipe dope or ARP sealant to coat the threads of the short head bolts. The short bolts go into the water jacket and will seep coolant if you don't use the sealant.
Note: The ARP cylinder head bolts have a radius under the bolt head. The washer has a matching relief. Make sure that the bolt head radius mates up to the relief in the washer. If you don’t, the bolts will never torque down properly.
My favorite trick that saves time and effort is the stay in place gasket. Be sure that you scrape (don't use a wire brush) all the old gasket material off, then clean all the surfaces with acetone or MEK.
When the surfaces are clean, use weather strip adhesive on the head to manifold surface, and on the side of the gasket that mates to the head. Follow the instructions on the tube or can and when it gets tacky, press the gasket down on the head.
Clean the area where the rubber rails mount to the block in front and in the rear with more acetone or MEK and do the same trick with the weather strip adhesive that you did to the heads.
Coat the rubber seals and the gasket area around the water passages with lots of Blue Silicone gasket sealer and put it together. Walla! No leaks and no gaskets that shifted out of place.
If you reuse the injectors from your old setup, a repair kit is available from most
auto parts stores if needed. Coat the injector body "O" rings with oil before you use them and everything will slide back together.
For iron heads, clean the combustion chambers with a wire brush in an air or electric drill. I used a scraper for the pistons. I don't like to use the wire brush on pistons because it will remove metal very easily.
Change the oil once you get everything back together. Once the engine is up & running, run it for 1-2 hours and change the oil.
Tools: a good torque wrench is a must have item. A razor blade scraper that holds a single edge razor blade from Home Depot or Ace hardware is another handy thing. Get a Chilton or Haynes shop manual - you'll need it for the bolt torques and patterns. The intake manifold has an especially odd pattern. You'll need access to a timing light to set the timing after you re-stab the distributor.
Consumable parts:
Fuel injector seal kits with 2 O rings and a pintle cap (Borg-Warner P/N 274081) are available at Pep Boys auto parts. Cost is about $2.74 per kit. The pintle caps fit either injectors with a pin sticking out the injector end or 4 with more tiny holes in the injector end.
Parts list.......
Head gaskets
upper manifold gasket
lower manifold gasket set.
Exhaust manifold gasket set
Rocker cover gaskets - look for the rubber ones with the steel bushings - Summit has them
Short formed hose between thermostat hosing and intake manifold
6 ft 7/64" or 1/8" vacuum hose
2 ft 1/2" heater hose
1 1/2 ft 5/8" heater hose
Blue Silicone sealer
ARP antiseize or equal for the bolts
ARP thread sealer or Teflon pipe dope for the short bolts.
4 each 3/4" hose clamps (spare item in case the old ones are bad)
4 each 1/2" hose clamps (spare item)
Suggestions for changing out the head gasket on a 1989 Mustang GT 
