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Adjusting valves on 454 mercruiser

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  • Adjusting valves on 454 mercruiser

    Going back together with the 454 mercruiser. Need to adjust the hydraulic valves, with the motor not running. Once the exhaust manifold back on cannot get valve cover off. Head on and intake still off. Was thinking install the intake. Bring the piston up to firing position by watching the firing order at the distributor, tighten the rocker till play out of rod plus ½ turn. Will this work or are there better ways?

  • #2
    Re: Adjusting valves on 454 mercruiser

    scamper,That's how I'd do it, but of course making darn sure you're on the firing position.

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    • #3
      Re: Adjusting valves on 454 mercruiser

      Thanks Top.

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      • #4
        Re: Adjusting valves on 454 mercruiser

        Hello scamper rotate the engine in its direction of normal rotation. watch the intake valve for the cylinder you wish to adjust close, after the intake closes it is on compression stroke with both valves closed. adjust the nut until all play is removed then 3/4 to 1 turn more. the object is to preload the lifter plunger. should depress the plunger about .100" do that with each affected cylinder and it will work fine. I usually do this before installing the intake or distributer. good luck and keep posting
        no tech questions by PM, they wont get answered.
        you have to be trusted by the people that you lie to .

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        • #5
          Re: Adjusting valves on 454 mercruiser

          rodbolt, then rotate the engine to one of the effected cylinder firing position, put the intake on and drop the distributor firing the corresponding cylinder?

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          • #6
            Re: Adjusting valves on 454 mercruiser

            hello scamper after the valves are adjusted and checked.and just before intake manifold installation. continue rotating the engine in its normal direction and watch the intake lifter for # 1 cylinder go down. now continue rotating the crank until the TDC mark on the timing tab is lined up with the slot on the balancer. now install the intake as per the service manual. here is one of the few times silicone is permissable. after thougholy cleaning all gasket surfaces wipe them off with paper towels and rubbing alchohol.then place a 1/8 bead across each block end. use OMC adhesive M or equivalent to adhere the side gaskets to the head. after torqueing all bolts as per service manual this is the easy way to set the distributor. in the service manual it will show how to orient the cap to the dist body. place a mark on the body inline with the # 1 cap tower. install the gasket on the dist shaft. install the dist in the hole with the dist body oreiented correctly. when the dist gear is almost engaged with the cam gear move the rotor so it is almost pointing to the mark made previously on the body. while holding light downward pressue on the dist body rotate the engine 2 complete turns., now you have the crank at TDC compression stroke again. while you were rotating the engine the dist should have droped some indicating the oil pump drive tag has engaged the oil pump shaft. if the flage on the dist housing is not on the manifold DO NOT try to pull it down with the hold down. repeat the installation . if all is well and the rotor now points to the proper cyl/cap tower then install the hold down lightly and continue to assemble the engine. if not it missed by one tooth for or aft as the rotor turned while dropping into the oil pump. if its not aligned lift the dist and rotate the rotor one tooth as required and rotate the engine 2 complete revolutions to bring up #1 cyl TDC compression stroke again. now that the dist is all in place and the engine is all reassembled here is how to set the timing for a no back fire start. install a spark tester on # 1 plug wire. a spark plug on the block will do. turn the key to ignition on. with the engine still at TDC compression stroke and the rotor pointing at #1 cyl cap tower rotate the body back and forth noting when the plug fires. you will note a point where it fires while rotating both ways. now rotate it slightly to the counter-clockwise of where the spark occurs. tighten lock down bolt to keep dist from turning while doing initial start up. remember turn the dist CCW to advance the spark and CW to retard. if over advanced it will backfire or the starter will stall . good luck and keep posting . its very simple if you remember your trying to time the spark to the piston position. no worries
            no tech questions by PM, they wont get answered.
            you have to be trusted by the people that you lie to .

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            • #7
              Re: Adjusting valves on 454 mercruiser

              Rodbolt. A profound thank you for the time and effort you have given me. Your instructions were very clear and concise. I do appreciate it.

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              • #8
                Re: Adjusting valves on 454 mercruiser

                There is no valve ajustment on a 454 GMengine. The heads do not have studs -just rocker bolts.

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                • #9
                  Re: Adjusting valves on 454 mercruiser

                  Hello elpaso. I must beg to differ. on the late style 7.4 you are correct. I belive scamper has a early 80's 454 not a 7.4. the 454 used studs and nuts. good luck and keep postingthat is why a service manual is so important. it will tell you if the engine you think you have is actually what you have.
                  no tech questions by PM, they wont get answered.
                  you have to be trusted by the people that you lie to .

                  Comment


                  • #10
                    Re: Adjusting valves on 454 mercruiser

                    There 86’s. Followed your advice. Bumped it around to firing no.1. Installed the intake. Market no.1 on the cap, dropped it in sure enough didn’t go all the way down. Bumped it around two times (doing all this bumping cause I’m by myself) and it dropped right in. Will do the timing next week. Guess will have to bring binoculars so I can tell when the plug sparks.

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                    • #11
                      Re: Adjusting valves on 454 mercruiser

                      Quickest way. Bring the adjusting nut flush with the stud. Five full turns down for new lifters. Four and half for used lifters. Make sure you put them in the same hole with used ones. Ten minutes your done.

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                      • #12
                        Re: Adjusting valves on 454 mercruiser

                        Originally posted by BRIAN03 View Post
                        Quickest way. Bring the adjusting nut flush with the stud. Five full turns down for new lifters. Four and half for used lifters. Make sure you put them in the same hole with used ones. Ten minutes your done.
                        briano3, could you tell me how you figured 5 turns on nut as i am about to ajust valves on my 454. do type iv @type v heads have the same stud height? i made a mistake the first time i ajusted valves as they where to tight ended up with low compression.engine was re built and heads rebuilt seperate thank you for input

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                        • #13
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                          Re: Adjusting valves on 454 mercruiser

                          Welcome to iboats freon2, might want to look at the date of a post before you reply to it, this one is from 2003. I'm sure the original poster has the problem figured out by now, or sold the boat.
                          Don S.


                          Please, no PM's (Private Messages) regarding boat/engine problems.
                          That is what the forums are for.
                          Only forum/moderator issues will be answered in PM's.

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