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DIY: Valve Adjustment

 
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Old 12-03-2011, 11:33 AM
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DIY: Valve Adjustment

VALVE LASH ADJUSTMENT

-*-Explanation: As part of every major tune-up or service interval, the valve clearance should be checked and ajusted if necessary. If the valve clearance is too large, part of the lift of the camshaft will be used up in removing the excessive clearance, thus the valves will not be opened far enough. This condition makes the vlave train noisy as they take up the excessive clearance. The engine will perform poorly, since a smaller amoung of air/fuel mixture will be admitted to the cylinders. The exhuast valves will not open far enough to ven t the cylinder completely; retained pressure (back pressure) will restrict the entry of the next air/fuel charge.
If the valve clearance is too small, the intake and exhuast valves will not fully seat on the clinder head when they close. This causes internal cylinder leakage and prevents the hot valve from transferring some heat to the head and cooling off. Therefore, the engine will run poorly (due to less gases escaping from the combustion chamber), and the valves will overheat and burn (since they cannon transfer heat unless they are firmly touching the seat in the cylinder head).

-*-Before Beginning: Valve lash must always be adjusted with the engine cold. The head temperature must be below 100 degrees F. Generally, this means allowing the engine to cool for at le ast 3 hours without driving. Overnight cold is best. If the valve adjustment is being performed as part of a routine amintenance or mileage service regimen, do it before the engine is warmed up to check timing or idle.
Valve location will vary with the type of engine. As a guide, the intake valves always are aligned with the ports or runners of the intake manifold. The exhaust valves align with the tubes of the exhuast manifold.
Adjusting the valves requires positioning the No. 1 cylinder at TDC, then rotating the engine to certain other precise positions. Rotate the engine with a socket on the crankshaft pulley or just roll your car forward with the shifter in 5th gear. Rotation is made easier by removing the spark plugs first. This elminates compression. Always rotate the engine in a counterclockwise (or pushing forward with it in 5th gear) direction.
If you miss a mark during the rotation keep going in the same direction until it comes around again. Turning the engine backwards may cause the timing belt to jump a tooth or slacken, riisking engine damage when restarted. Remember that cylinder No.1 is the one closest to the pulley end of the engine.
The engine is at TDC No. 1 if ALL of the following are true:
-The TDC mark on the flywheel or flexplate is aligned with the pointer in the timing inspection window at the rear or fthe engine. The TDC mark is generally white. It is never red.
-The distributor rotor is point at cap terminal or plug wire No. 1. Mark the cap with the correspoinding wire numbers, then lift the cap and check the rotor position.
-The alignment marks on the camshaft pulley are positioned as indicated in the individual procedure.
-The rocker arms for at least one of the valves on cylinder No. 1 is loose; the points or lobes of the cam are not putting pressure on the rocker arms.

-*-Procedure:These engines employ Dual Overhead Camshafts and use 4 valves per cylinder. The intake valves are operated by one cam and the exhuast valves by the other. Each camshaft pulley has UP or arrow marks and grooves; when the engine is rotated during the adjustment, the marks must be aligned both with the cylinder head and with each other.

Valve Clearances for 1992 Preludes are:
Intake: 0.004-0.005 in. (.09-.13mm)
Exhaust: 0.006-.0007 in. (.15-.19mm)

Valve Clearance for 1993-1995 Preludes w/o VTEC
Intake: 0.003-0.004 in. (.07-.11mm)
Exhuast 0.006-0.007 in. (.15-.19mm)

Valve Clearance for 1993-1995 Preludes w/ VTEC
Intake: 0.006-0.007 in. (.15-.19mm)
Exhaust: 0.007-0.008 in. (.17-.21mm)

1. With the engine OFF, remove the valve cover.
2. Set the No. 1 piston at top dead center. The UP or arrow marks on the pulley should be at the top, and the TDC grooves on the edge or side of the pulley should align with the cylinder head surface. The distributor rotor should be pointing towards the No. 1 spark plug wire.
3. Check the clearance on all the valves for cylinder No. 1 with a feeler gauge. The gauge should pass the gap with a slight drag.
4. If the guage passes with no drag or cannon be inserted, adjust as follows:
a. Loosen the adjusting screw locknut.
b. Turn the adjusting screw to obtain the proper clearance.
c. Hold the adjusting screw in position and tighten the locknut. Correct locknut torque is 20 ft. lbs on models without VTEC and 14 ft lbs. on models with VTEC. After the locknut is tightened, recheck the clearance and readjust as necessary.
5. Rotate the cranksahft 180 degrees counterclockwise (the cam pulley will turn 90 degrees). The UP or arrow marks should be at the exhuast side. The distributor rotor should point to the number three spark plug wire. At this point the valves on NO. 3 cylinder can be checked. Repeat the adjusting steps previously described as necessary.
6. Rotate the crankshaft 180 degrees counterclockwise to bring the No. 4 piston up to TDC. Both UP or arrow marks should be at the bottom and the distributorrotor should point to the number four spark plug wire. The grooves on the pulley align with the cylinder head surface and with each other. Check the valves for cylinder No. 4. Repeat the adjusting steps previously described as necessary.
7. Rotate the crankshaft 180 degrees counterclockwise to bring the No. 2 cylinder up to TDC. The UP or arrow marks should be at the intake side. The distributor rotor should point at the number two spark plug wire. Check all the valves for cylinder No. 2, repeating the adjustment steps previosuly
described as necessary


link Prelude Tech Guide - Honda Forum : Honda and Acura Car Forums
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Old 12-10-2011, 11:43 PM
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Re: DIY: Valve Adjustment

Not sure if that's you on that other forum or not - i'm going to assume it's not.



Relaying someone else's information does not count as a DIY - nice try but you did nothing here.

There is already a writeup with pictures included in the DIY section.
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Old 12-11-2011, 05:07 AM
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Re: DIY: Valve Adjustment

Quote:
Originally Posted by wing8806 View Post
Not sure if that's you on that other forum or not - i'm going to assume it's not.



Relaying someone else's information does not count as a DIY - nice try but you did nothing here.

There is already a writeup with pictures included in the DIY section.
damm i suppose you were born an expert on adjusting valves.
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Old 12-11-2011, 07:16 AM
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Re: DIY: Valve Adjustment

he isn't trying to be an expert on valve adjustment, he's explaining our forum rules. Don't worry I'm sure this thread will be deleted soon enough by a mod because you copied it from someone else and there is already an excellent valve adjustment diy on this forum.

EDIT: Oh yeah, and you posted it in the wrong section
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SHdriver once told me that some preludes lose vtec after a while. I think you need to take it to Honda and RE-Vtec-a-lize it. Just my .02
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