Cylinder head removal hex nut stuck need to remove to replace bent valves

you will need to remove the cylinder head because it sounds like you have a bent valve in the cylinder that has less compresion that would make the engine run rough. That cylinders piston has made contact with a valve so the bent valve wont seat properly

For the four cylinder engine:

1. Remove and label all electrical wiring, connectors and vacuum hoses necessary to gain removal clearance.
2. Remove the spark plug wires. Disconnect the PCV hose.
3. Remove the four nuts and grommets located on top of the cylinder head cover.

1. Remove the cylinder head cover and the cover gasket from the cylinder head.
2. Discard the gasket and replace with a new one.

To install:

1. With a wire brush or gasket scraper, remove all the old gasket material from the cylinder head and the cylinder head cover gasket surfaces.
2. When the cylinder head surfaces are free and clean, apply beads of sealant to the cylinder head in the locations shown in the accompanying illustrations.
3. Install the new cylinder head gasket in the cover. Make sure that the gasket seats evenly.
4. Place the cylinder head cover with the gasket onto the cylinder head.
5. Install the four grommets and nuts. Uniformly tighten the nuts in several passes to 17 ft. lbs. (23 Nm).
6. Connect the PCV hose. Connect all removed vacuum hoses, connectors and electrical wiring. Connect the negative battery cable.
7. Start the engine and inspect for oil leaks.
8. Repair any leaks as necessary.

For the V-6 (3.0L) engine:

1. Drain and recycle the engine coolant.
2. Disconnect the radiator inlet hose.
3. Disconnect the throttle and accelerator cables.
4. Remove the air cleaner cap assembly.
5. Remove the V-bank cover. Use a hexagon wrench to loosen the nuts.
6. Label and remove all emission control valve hoses. Disconnect any wiring interfering with the valve cover removal.
7. Remove the air intake chamber. This will gain you access to the back valve cover.
8. Disconnect the engine wire from the left hand side, No. 3 timing belt cover, rear side and right hand side. Most of the wiring is secured by nuts and or bolts to the body of the vehicle.
9. Remove the ignition coils, make sure the place them in order on a table so not to mix them up.
10. Remove the 8 bolts retaining the valve covers and gasket.
11. Clean the mating area of the valve cover and cylinder heads well. If necessary, scrape any left gasket from either surface.
12. Apply seal packing to the cylinder heads and place new gaskets into position.
13. Attach the valve covers. Uniformly tighten the bolts in several passes to 69 inch lbs. (8 Nm).
14. Install the spark plugs in their proper locations, then place the ignition coils into place and secure.
15. Attach all engine wiring be sure to secure each harness properly.
16. Install the air intake chamber. Refer to Fuel System .
17. Attach all emission hoses and wiring.
18. Attach the V-bank cover.

If you are sure you have no compression in that cylinder you need to remove the cylinder head and check for a burnt or bent or stuck valve.

Think about this for a moment....You already know you have a few bent valves. Valves are serviced by removing the cylinder head. That single fact tells you that the head needs to come off to do the repair.
Once you remove the head, you will be more able to inspect the remaining valves and piston tops, then with that information, decide if you can rebuild it. A compression test requires spinning the engine and risking further damage.

get a repair manual, youll need to remove the head and replace the bent valves.

the big brain

Hello jim slaughter: My name is Roger and I will help with your question. The answer is not likely. You must remove the object before cranking the engine. If you crank the engine over with the object in the cylinder. Major damage will occur. You will impact the piston and cylinder head with the object.If you have aluminumn cylinder heads the object will most likely become implanted in the head and bend valves. It could severly damage the piston and crack the edge of the oil land. If the heads are cast iron. figure bent valves and damaged piston.You will destroy the spark plug also. The best way to remove the object is to remove thhe cylinder head. If this is a late model vehicle you will also need a new set of head bolts. Do not reuse the old bolts. They stretch when tightend and will break. Should you need further help please just ask. Please rate the answer. This way I know it was useful. Thank You for using Fix Ya. Roger

You didn't say what kind of car is, but but if they have a hex nut with Allen screw inside it. Remove the nut and screw the screw back. Remove their old rocker and put the new one on. Put the nut on but not too tight. Now turn the motor slowly until the other valve for that cylinder opens. Now a just and nut down. If it's a hydraulic tighten the nut down snug thing go 3/4 turn more. If its mechanical use a feeler gauge and go with the proper clearance. Then tighten the Allen screw back down very tight. Try to figure out what went wrong. Because it could happen again. Remove the push rods and roll them on a flat surface to see if they are straight don't use bent push rods. Then check for spring bind, with the valve all the way open there should be no spring bind use a feeler gauge to check for this. Also look at the rocker to make sure it's not restricted in any way, also no interference with the pushrod. Without seeing it that's about the best I can do. Good luck.

60,000 Miles also your van is an interference engine which means if timing belt breaks will cause major engine damage ( bent cylinder head valves ) and cylinder heads will have to be remove to replace bent valves.

REMOVAL & INSTALLATION

1C-LTC and 2CL-TC Engines
(see Figures 1 and 2)

1. Disconnect the negative battery cable. Remove and label all electrical wiring, connectors and vacuum hoses necessary to gain removal clearance.

Fig. 1: Loosen and remove the cylinder head cover retaining nuts

1. Disconnect the PCV hose.
2. Remove the six nuts and seal washers from the cylinder head cover. Loosen them in a crisscross pattern.
3. Remove the cylinder head cover and the cover gasket from the cylinder head. Discard the gasket and replace with a new one.
   

To install:

1. With a wire brush or gasket scraper, remove all the old gasket material from the cylinder head and the cylinder head cover gasket surfaces.
2. When the cylinder head surfaces are free and clean, apply beads of sealant to the cylinder head in the locations shown in the accompanying illustration.

Fig. 2: Be sure to apply sealant on the cylinder head prior to cover installation

1. Install the new gasket in the cover. Make sure that the gasket seats evenly.
2. Place the cover with the gasket onto the cylinder head.
3. Install the six nuts and seal washers. Tighten the nuts to 65 inch lbs. (8 Nm).
4. Connect the PCV hose. Connect all removed vacuum hoses, connectors and electrical wiring. Connect the negative battery cable.
5. Start the engine and inspect for oil leaks. Repair any leaks as necessary.

Hope this help (remember comment and rated this).

If you are referring to an intake or exhaust valve, cylinder head must be removed (and likely replaced if valve is broken) Also if that's the case, pistons may be badly damaged and not even worth tearing down. If another valve (tire, egr etc, just remove & replace)