How to adjust valve lash?

[liesight]

I have a 1986 3.0Liter 4 cylinder OMC.<br /><br />My question is this, <br />I am rebuilding the top end of my motor, it was running perfectly except for a very minor gasket leak, My head was professionally rebuilt and I am putting the top end back together. Here is my question, I am about to adjust valve lash, and according to places I've looked and my engine manual it says to make sure the #1 cylinder or piston is at TDC, to me this means at the highest point at which the piston travels...<br />But sites and my manual also say that when the rotor on the distributer is pointing to piston #1 that the GAP should be wide open....how is this possible, I've been trying to figure out all day. When my piston is at TDC the points are closed (there is no gap)...now before the points close, they are open but at that time the piston is still traveling on the up or compression stroke...PLEASE HELP..<br />By wide open (does that mean CLOSE) or am I just a guy who should'nt be working on motors? <br />Thanx ahead of time.

 

[DJ]

Re: How to adjust valve lash?

liesight,<br /><br />Are you sure you're on #1 compression?<br /><br />Did you remove the distributor? Do you have it in 180 degrees off?

 

[liesight]

Re: How to adjust valve lash?

I hav'nt touched the distributor but to remove the dist. cap in order to see the rotor, and I knew what the piston was doing (up or down) because I did not have the head on yet, but now I do!

 

[Boatist]

Re: How to adjust valve lash?

Liesight<br />If you did not remove the distributer, cam shaft or timing gear and only had the head off should be quite simple. Remember this is a four cycle so piston comes up twice for each power stroke. When the piston comes up the rotor cap will either be pointed to number one wire or the other side. The points will actually open 4 degrees before top dead center if it is timed right. as long as the piston is at the top and roter is pointed to the number one spark plug you can adjust. Does not have to be right on TDC as no valve action anywhere near TDC. Adjust for zero lash then down one turn to center lifter. Then go on to number 2. Turn engine until number 2 piston is at top and rotor points to number 2 wire on cap. Next 3 and 4 same way.<br />If your lifter have not been replaced I might suggest a little different way to adjust. Do the same as above but only adjust to zero clearance but not add the one turn down. Reason for this is may have a lifter or two that is bad or not 100 percent. May be stuck in the down postion as spring has not pushed it back up so if adjust down one turn could be forcing the valve down into the piston. At this point can set cover on and start up engine until it warms up. Turn off the engine and double check zero lash. If you think all lifter are good go down one turn on each lifter. <br />The way I do it you will get some oil splash and make a mess but I think safer for engine. I take the valve cover off and start engine. Very slowely turn the adjustment down until the engine misses, slowely back up until run with no miss then up one turn. Then on to next valve until have done all eight.<br />If all lifter are ok either way works and the lifter ends up centered but if have a bad or sticking lifter valve end up too loose and noisy instead of to tight and burnt. Last thing I do is a compression check and retorque the head bolts.<br />If you have trouble finding the compression stroke and top dead center for each here is another way. Turn engine and watch first valve until it opens then comes back up turn engine another 1/4 turn and then adjust valve. Do same for next valve till have all 8 done.<br />Take an old spark plug and break out the center porcelain. Make sure nothing loose inside that could fall into cylinder and then put a balloon over the old spark plug and use a rubber band to hold it on. Screw the spark plug into cylinder one and turn engine until balloon blows up to it largest. Now you can adjust both valves for that cylinder. Move it to number 2 and do same thing.<br />Baloon will only blow up on the compression stroke.

 

[MGuckin]

Re: How to adjust valve lash?

Boatist running method is what I do on all my motors. <br />Just would like to add a few hints.<br />Motor should be warmed up first. <br />I have valve covers with the tops removed so oil doesn't splash all over everything. Granted most people would not have access to a spare set just a thought.<br />Making adjustments with the motor running is dangerous but it is more accurate with used components. Be carefull!!!<br />BTW Boatist, I like the balloon trick.

 

[liesight]

Re: How to adjust valve lash?

So on the rotor shouldnt be on the most flat spot when making adjustments? When you say the points should be open 4 degrees of pointing to the specific piston, does that mean I should see a GAP, I just want to make sure I understand completely.<br />Thank You

 

[Boatist]

Re: How to adjust valve lash?

Liesight<br />I would not worry about the the points when making the adjustment. All you really need to do is make sure the pistion is near the top on the compression stroke. It really can be a 1/4 turn off and make no difference. Remember on the compression stroke both valves are closed while piston is near the bottom. Piston then travels to the top to compress air and fuel. Spark plug fires for the power stroke but both valves are still closed until piston reaches near the bottom. So both valves are closed for almost a full revolution of engine but to be safe and sure better to adjust while piston is near the top.

 

[Boatist]

Re: How to adjust valve lash?

MG Mike<br />I always set to zero clearance put cover on and start up and let warm up then take cover off and adjust slowly down until misses then back up until miss stops then up one turn. Do you do the same or go to zero and down one turn.<br />The top cut out is a good idea. My Dad had a valve cover with the top cut out for that same reason.<br />The balloon works very good, is simple and fool pruff as long as get a big enough ballone. A small balloon will blow up and pop before piston reaches top. I normally just watch intake valve then turn with finger in hole until stops trying to blow finger out and starts to suck then adjust, or just watch until valve closes then go 1/4 turn set to zero. Start up and warm up with the cover on then remove and adjust while running.

 

[MGuckin]

Re: How to adjust valve lash?

Boatist,<br />I crank motor by hand while setting "not quite" zero clearance to center the lifter. <br />Turning in will add more pre-load to an already worn lifter and cam lobe. Back off on used rods & lifters. <br />I "kinda sorta" listen to the motor.

 

[liesight]

Re: How to adjust valve lash?

Thanx all of you for helping out, it really does make perfect sense now, I just wanted to make sure I did it right before starting it up, it runs great.<br />This board is great too.<br /><br />thanx again