If you overtighten the valves, it causes them to stay open, reducing the compression. It may also cause the valves to strike the piston as the engine turns.
Remove all the spark plugs and turn the engine over with a breaker bar & a 15/16" socket on the harmonic balancer bolt. If you hit a hard sport as you hand turn the engine, you have mechanical problems. Either a piston is striking a valve or there is something loose in the cylinder between the piston top and the cylinder head. If the engine does not have any place where the resistance to turning increases, then proceed to the next checklist.
Cranks Ok but no start for carb’d cars.
Updated 17-Jun-2008 to include firing order diagram
Carb'd cars require an old time approach to troubleshooting.
1.) Remove push on connector from starter solenoid and turn ignition switch on. Place car in neutral or Park. Remove coil wire from distributor & and hold 3/8” away from engine block. Jumper the screw with the red wire to the big bolt on the starter solenoid that has the battery wire connected to it. You should get a nice fat blue spark.
Most of the items are electrical in nature, so a test light, or even better, a voltmeter, is helpful to be sure they have power to them.
No spark, possible failed items in order of their probability:
A.) Coil
B.) Distributor PIP sensor or points & condenser
C.) Bad ignition Box or Duraspark unit
D.) No power to ignition system wiring or ignition box (if used)
E.) Bad ignition switch
F.) Bad fuse links.
AutoZone wiring diagrams
http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model Mustangs
http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model Mustangs
http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model Mustangs
2.) Spark at coil wire, pull #1 plug wire off at the spark plug and check to see spark. No spark, possible failed items in order of their probability:
A.) Moisture inside distributor – remove cap, dry off & spray with WD40
B.) Distributor cap
C.) Rotor
D.) Spark Plug wires
E.) Coil weak or intermittent - you should see 3/8" fat blue spark with a good coil
3.) Spark at spark plug, but no start.
4.) Pull the air cleaner and sniff for fuel vapor - look for signs of flooding. If so, then press the accelerator to the floor and crank for a while – if the engine is flooded, this will clear it out. You may want to have a jumper battery & cables handy.
5.) Electric fuel pump if you have one, is it getting power? Use a volt meter or test light to probe the wires at the pump.
Don't see any evidence of flooding? Then pump the throttle - does the accelerator pump squirt fuel? If so then you should have enough fuel to start the engine. If not look for fuel delivery problems. Check the fuel pump, and fuel filter. Remember that most carbs have a fuel inlet filter that protects the float needle valve from trash.
Next, get a can of starting fluid (ether) from your local auto parts store: costs a $1.30 or so. Then pull the air cleaner, open the throttle, and spray the ether in it. Reinstall the air cleaner and try to start the car. Do not try to start the car without reinstalling the air cleaner. If it backfires, the chance for a serious fire is increased. If the engine starts now, you have a fuel delivery problem.
A warning about backfires: Holley carbs may have damaged power valves as the result of a backfire. The engine may be hard to start. Other symptoms are that it may seem to load up on fuel and be slow to accelerate until it clears out a bit.
6.) Fuel & ignition OK:
The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8