Lifters

[reavesga]

I have a 1974 OMC 3.0L motor that I have since converted to mercruiser. Over the years it developed a clicking sound that was very much like a lifter so I decided to replace the lifters. Now, assuming that all of the 3.0 motors are pretty much the same I went to the mercruiser book and found that the lifter part number is 46744 replaced by Siera part number 18-1402. I ordered 8 of them and when they got here I installed them. Now I noticed that these were squishy as I would expect from a hydraulic lifter. however the ones I took out looked the same but I could not press the top of them in at all. Anyway, I put the motor together, adjusted the valves, and tried to start her up. All I get is the random backfire or the random cough through the carb. I am assuming the problem is in the valves, but before I go crazy adjusting the valves, are the lifters just the wrong part for the OMC 3.0 motor? They physically look identical I just can not push the tops down where the rod goes and I can push it down, albeit with some effort on the new ones.

The other thing I noticed is that as I was adjusting the valves, I never could seem to get the push rod to quit turning. I have always just use the push rod stopping rotation as the place that the valve is adjusted. Should I just keep cranking till the rod quit turning. Any experience here is greatly appreciated.

 

[reavesga]

Update: out of frustration I backed all the adjusting nuts off 1 full turn. motor started and ran for about 3 minutes then started bucking and coughing and shut down. I backed the nuts off another full turn to see if that made it better, ie should a loose valve adjustment. nope, same behavior. So not sure now if the issue is the valves or if something else has gone south.

 

[alldodge]

Need to adjust the valves for Zero lash and then 3/4 turn. Zero lash is when all up/down movement has been removed NOT when the push rod stops rotating.

This can also be done with engine running. Back off nut until clatter is heard, then crank down slowly until clatter stops (this is Zero lash). Now turn nut 1/4 turn and wait 10 seconds, then turn another 1/4 turn. Repeat one more time for a 3/4 down from Zero lash.

 

[reavesga]

Thanks. Fresh eyes on it this morning and some sleep and realized that on one of the reassembles last night I crossed numbers 3 and 4 plug wires at the distributor. So that is probably why it is acting as if the timing just went wonky because, well it did just go wonky due to my error. Re-read the manual and watched a couple of videos and realized that I am determining zero lash wrong. So after some errands this morning back go adjusting valves. Several places around the web says 3/4 turn my selco manual says 1 turn. Think I am going to go with the 3/4 as that seems to be the consensus or maybe I am just reading the manual wrong.

 

[kenny nunez]

2 Xs on the 3/4 setting that has never failed me. The way I always set the valves on the in line engines is using the respective firing order method. With the spark plugs removed, turn the engine by hand, start from #1 at tdc then turn the engine to the next firing cylinder and so on.

 

[reavesga]

Got the valves adjusted. fired the motor up with the valve cover off and let it run for a little bit. All seemed ok. Motor was a little rough at first but smoothed out. just for fun I thought I would feel each of the push rods while it was running, I have never done that. So starting at the front and working down the motor I tried to rotate or wiggle each rod with the motor running. they were all the same except the last one, #4 Exhaust. The first 7 I could not wiggle or twist them. However, the last one was rotating. Each time it actuated the valve push rod would rotate a little bit. I could not hold it to keep it from rotating. Is this rotation ok? Why is it doing that?

 

[kenny nunez]

If you ever look closely at a cam shaft lobe you will notice that one side of the lobe has more wear , cams are ground that way to cause the lifter to spin which designed to rotate the pushrod to prevent excessive wear in one spot. Of course with the current engines that have roller cams and push rods that no longer happens.

 

[alldodge]

I would readjust with the motor running, all warmed up using the method above

 

[Lou C]

I would not worry so much if you can still rotate it; it's more important that there is no up and down play in the pushrod. Sometimes you can still rotate the pushrod even though you are at zero lash....

 

[fishrdan]

Replied to your other thread. Basically, run the engine at 1500-2500RPm for 15-25 minutes, to break in the lifters.

I wouldn't worry more about adjusting the lifters (unless they are ticking bad or engine running poor) until you get the lifters broken in. Then you can go back and adjust the lifters if needed.

Since you have the valve cover off, just run through all of them (once the break-in is finished) with the engine running. Use the procedure AD posted.

 

[reavesga]

thanks for the info. On the subject of oil right now I am running mercruiser brand 20W50. Based on recommendations I am guessing I should switch to a Lucas ZDDP 30W high zinc oil or a rotella high zinc.

 

[fishrdan]

Mercruiser brand oil is perfect, the good stuff. Most of us are too cheap to buy it and opt for something close to Mercruiser oil specs. I'm running 15W40 Rotella.

Not sure if you know, but, modern engine oils have done away with zinc as it's not needed with roller cam engines and can cause catalytic converters to fail. OK for modern engines, but not good for flat tappet cam engines.

 

[reavesga]

Thanks for the info. I completed the break in run today.30 minutes varying the RPM between 1500 and 3000. made a change about every 5 minutes. All went well. Billows re back in as well so time to check drive alignment and then put the drive back on and take to the lake.

 

[gm280]

reavesg, sounds like you got your experience with hydraulic lifters now. The reason you could push the top of the new lifters down some was because they were not yet pumped up. The reason they went to hydraulic lifters verse solid, was because the hydraulic lifters will pump up to take the valve lash out and never need to be readjusted again. Solid lifters have to be adjusted initially and if wear takes place, you have to readjust them over their life span. And some people installing hydraulic lifters think that they have to keep turning down the rocker arm nuts until they take out all the push rod movement (engine not running). But that is never going to work. You merely tighten down the rocker arm nuts until you just feel some resistance in spinning the push rods. That is it. They will pump up to zero valve lash. Neat isn't it.

 

[reavesga]

Well to write the epilog to this story. On the next start the motor was sounding good warming up when suddenly I heard a knock knock knock knock. No it can not be a rod bearing. Yes it is. Followed the standard test of pull the plug wire and sure enough number one plug wire on knock knock knock, number on plug off sound is gone. I gave up and pulled the motor. Ordered a crate motor and dropped it in the past weekend. 9 hours start to finish including reinstallation of the drive. Motor sounds like silk. I will rebuild the other motor when I get a chance. Thanks for all the help.