3.0 Valve Adjustment

[kjhowayeck]

I have 1987 3.0 Mercruiser 4cyl 140 hp, Found out that I had a blown head gasket and I decided to go into it myself with help, but have run into a few problems getting the motor to run correctly. After we put the head back on we adjusted the head bolts in the pattern and then adjuster the lifters as well. Started the engine ran rough. Took the valve cover back off and adjusted the lifters as the Manual said by finding zero lash and turn a half turn tighter. The boat starter idled okay and decided to put into the water for a test. When we did the boat shuttered and idled hard. Disengaged The engine the engined reved good and sounded great, but engaged the engine struggled and had no power. We thought to take it apart again and try to adjust the valves again by the advice of a boat mechanic. This time we tryed to go 3/4 a turn past the zero lash. After this the boat turner over and over again before it backfired to times in a row. Seems we are missing something. Does anyone have any suggestions about the valve adjustment, turn pash zero lash, or special tools that would make it easier to do. I just can't understand how so much engine can have no power now.

 

[Don S]

Re: 3.0 Valve Adjustment

Not sure what manual you are using for adjusting the valves, but the Mercruiser manual says noting about 1/2 or even 3/4 turn. It says to turn 1 turn.<br />If that was wrong, what about the rest of the procedure? Also, what about the timing, did you get it adjusted correctly?<br /><br />

 

[Northern Eclipse]

Re: 3.0 Valve Adjustment

The non-running adjustment is good for getting it to run, but in my past with several engine jobs, including a Merc 3.0 I found it best to pull valve cover have plenty of old rags and run engine at slow idle back off rocker until is clacks then turn back down until quiet and 1/2 a turn after , be sure pushrods will rotate but not have play up and down, its messy but works well when dealing with old valve trains and lifters... oh ya don't run her out of oil.

 

[Reel Poor]

Re: 3.0 Valve Adjustment

Welcome to iboats Artie 21<br />Each cylinder has to be on the compression stroke to adjust the valves for that cylinder. Starting with #1 cylinder and working your way back to #4 cylinder. <br />STEP 1...With valve cover off and watching rocker arms turn engine in direction of rotation[manually] till the intake valve opens and then FULLY closes + an aditional 30 but not more than 45 degrees. Now adjust the intake and exhaust valves for this cylinder. then repeat step 1 for each cylinder. <br />Back off adjusting nut till loose. Then check for zero lash by spinning push rod with your fingers while slowly tightening rocker nut [pushrod should spin freely until point of zero lash] then tighten an additional turn.<br />Valve arrangement from front to rear should be<br />ex-in-ex-in-ex-in-ex-in I THINK If im wrong someone will correct it. good luck

 

[waterone1@aol.com]

Re: 3.0 Valve Adjustment

I respect service manuals...most of the time. Today was prime example of Merc factory manual being way off base...had to replace "cool fuel" fuel pump (electric) the manual said I should remove air plenum and fuel rail, and injectors..to disconnect fuel line from pump...what the he11 for ? I disconnected fuel lines and water line from front of unit and left "output" side alone, pulled unit from under engine, replaced pump and Orings (with unit laying on top of engine, re-installed, worked perfect....saved a few hours and several gaskets and seals. In this case,while the manual may get it running, it will not (in my opinion) give you a real world way of adjusting the valves for used components. If you had installed a new cam and new lifters, 3/4 to 1 turn may work. With a 1987 engine and normal average hours per year, those lifters have been operating at the end of their adjustment range for a few years now. I'm thinking more like 1/4-1/2 turn past zero lash while running would be the answer.

 

[Boatist]

Re: 3.0 Valve Adjustment

What Don said is in the manual and should work.<br />I personaly like to do it different but it is more work. I like to adjust each cylinder when the piston is at the top on the compression stroke. Lots of ways to determine this. As Don said mark the base of the distributor where each plug wire lines up. Pull the cap and turn until rotor point to Number 1 wire and points open. Adjust # 1 to zero lash. Mow turn until rotor points to # 3 wire and points open. Adjust both valves on number 3. Next turn to number 4 and point open then adjust 4. Last turn till number 2 lines up with rotor and adjust both valves for number 2 to nero lash.<br /><br />I do it a little different, I pull all the plugs and turn engine in the right direction slowly. I watch for exhaust to open and close on # 1, then intake to open and close. Then I put my thum in the #1 spark plug hole and continue turning engine at first your thum will be blow out of the hole. When the piston reaches the top it will then try and suck your thum in so you know piston is at the top. adjust that cylinder. Do same for 3,4,2. <br /><br />Now that all are set to zero lash turn on the water and start engine. Let it warm up then turn it off and remove valve cover. Start at the lowest idel you can run. Then I adjust each valve slowly slowly down until starts to miss. This should be about 2 turns down so keep track. Then I bring valve up slowly until runs smooth and then continue up 1 turn. I do all 8 vlaves this way then shut it down and do a compression check.<br /><br />Here is the reason I do it this messy way. When the lifter are new going to zero lash and then down 1 turn will center the lifter in it travel and that is where it should run. However used old lifters may not have the full 2 turns of travel. It may stick down or have something in the bottom of the lifter that prevents it from going all the way down. Either way zero lash and down the normal 1 turn may leave the valve open but if you go down until open then up until seated then up one turn the valve will not stay open and do damage. If the lifter is good as new it will be adjusted the same as zero and down 1 turn. If the lifter sticks or has reduced travel the worst that can happen is a noisy tappett but it will run good. <br /><br />The compression check at the end should be done either way just to make sure. If compression is low then you still have a problem.

 

[trog100]

Re: 3.0 Valve Adjustment

years ago when gm first came out with hydraulic lifters they used to say when resusing them u had to "unprime" them.. get some oil out.. they said put them in a vice and sqeeze up tight for a while till oil started oozing out.. then start from there.. this made sure that none were "overprimed" and all the valves were closing at first start up..<br /><br />trog100

 

[rodbolt]

Re: 3.0 Valve Adjustment

no reason to adjust valves with the engine running. have not done it that way on a chebby motor since the mid seventies. by the 1 turn past zero lash you set the lifter plunger preload. does not matter running or not. if the lifters are full of nasty oil or the plunger is stuck its time for removal,dissasembly and cleaning or replacement. but its just to mesy to do running and its totally unnessasary. I do usually do the adjust ment one at a time. if not I use pieces of tape on the ones that I need to adjust before rotating the engine. of the thousands of 4,6 and 8 cyl chevies I have built in the past 30 years I have set the valves on the engine stand and never taken the covers off again since the mid seventies.

 

[kjhowayeck]

Re: 3.0 Valve Adjustment

I am planing on adjusting the valves again today, I have one more question . Once you adjusted the valves and they have bleed down and become loose again how do you check the adjustment.

 

[olbuddyjack]

Re: 3.0 Valve Adjustment

You have to back off to zero lash again. Zero lash is with the lifter fully extended internally. When you make the extra 1/2 to 1 turn the inner plunger collapses into the lifter body. There is no solid contact within a properly adjusted hydralic lifter so with the engine off your adjustment is going to feel "loose"

 

[sea wolf]

Re: 3.0 Valve Adjustment

I adjusted the valves on my 3.0 omc after head gasket replacement a couple years ago the same way Don S posted. Never had a problem & I only did it once. Yea, i'm bragging.

 

[rodbolt]

Re: 3.0 Valve Adjustment

cool<br /> see the service manuals actually work, mostly <br /> if ya really wanna get picky you can always set the lifter plunger preload with a dial indicator to insure all are equal.

 

[kjhowayeck]

Re: 3.0 Valve Adjustment

I just wanted to thank everyone for thier advice. We took it all in and decided to try again with the engine running and it worked very well. I think that it may eb stronger than before the head gasket blew. I really appreciate everyone's help and attention to detail.

 

[Boatist]

Re: 3.0 Valve Adjustment

Artie 21<br />Thanks for comeing back and letting us know you got it going. So many Never come back. <br />Great Job. Hoping you finsihed the job with a compression check.

 

[Northern Eclipse]

Re: 3.0 Valve Adjustment

Good stuff Artie21 hope you have good boating season... Thanks for replying back with your results.

 

[kjhowayeck]

Re: 3.0 Valve Adjustment

I have taken the engine back apart, found two cracks in the head. Can not seem to find another one. I have been throughing the idea around about replacing the engine. Do you know of another bolt up engine swap other than another 3.0 and 2.5. Maybe something with more power. Thanks again

 

[olbuddyjack]

Re: 3.0 Valve Adjustment

The 4.3 and 5.7 should "bolt up" but it might get a little more involved than that...How much boat have you got?

 

[Don S]

Re: 3.0 Valve Adjustment

You will need to change the gear ratio in the drive, and install a Y exhaust pipe, plus find all the exhaust manifolds and risers needed for a V8. It would be cheaper to just replace the present engine.

 

[kjhowayeck]

Re: 3.0 Valve Adjustment

Thanks again we put the remanned head back in last night instead of engine upgrade. Decided new engine be too much money for "how much boat I got" We are testing it this weekend in the water.

 

[kjhowayeck]

Re: 3.0 Valve Adjustment

One more questions for you mechanical masterminds. Getting great compression now with rebuilt head but the engine not putting out any power in the water top speed maybe 5mph. Sounds great in idle but not under a load. I tried to check timing, noticed the number 1,3 plugs are getting no fire. However the engine starts, wires are tested good, new dist cap, new rotor. Does this mean the distributor is gone, or are there other problems that may occur. I am lost on this another new one for me.