Lake test, Not fun...

[Sea Raider I]

Gentlemen,

I recently had my heads rebuilt (5.7 Mercuruiser 260) and went out for the first lake test today.

On the muffs, she fired up and ran great I tuned her and got the timing set correctly. She ran for an hour with no issues, very smooth throttle response.

On the lake however; she fired up and ran just fine. Took her up to plane with no problems. She ran great for about an hour UNTIL, the loud knocking noise that slowly starts up. Back off throttle and knocking continues with rpm range.

Anticipating trouble, I remove the valve cover on the lake and find #2 exhaust rocker very loose. BTW I followed the valve lash adjustment procedure to the tee...
I tightend down the loose rocker and started her up, noise gone.

Hoping for the best, we got her up on plane once again and within 10 min KNOCK< KNOCK etc....

Pissed.... I removed both covers and tightend em all down a little bit. Went to fire her back up and of course she wants to runs terrible ..... I figured I mis adjusted or overtightened some valves causing the rough running motor. We limped her back in.

My question is this: Is it unheard of to use locktite on these rocker nuts? Why would it persistantly spin loose?

I have already replaced the slightly bent push rods....

All Opinions Appriciated!!!

 

[mthieme]

Re: Lake test, Not fun...

I agree, you overtightened the valves. But I understand the circumstances and frustration.
I suspect a flat lifter. Could have picked up some trash from having the motor apart (piece of gasket, carbon, sludge, etc). I like to soak them in oil for a while before putting everything back together too.
Did you pull them and inspect the bottoms for wear?
I'm assuming the springs and keepers (etc.) were okay.

 

[Mkos1980]

Re: Lake test, Not fun...

I'm betting your pressed in stud is slowly coming out. Make sure the rocker stud is level with the rest of them.

 

[Don S]

Re: Lake test, Not fun...

They are self locking nuts on the rockers. Did they come loose, or is the stud pulling out. You normally see about the same number of threads above the nut when the lifters are all working properly. If you have too many, could mean the stud is pulling loose, or the lifter is collapsing (faulty lifter).

 

[Sea Raider I]

Re: Lake test, Not fun...

Thank you for the quick responses!!

Tomorrow I planned to go through the procedure again, I will pull the rockers and check for wear. As far as the springs and valves go, they were just rebuilt so I can assume that is all solid.

I am leaning toward the stud pulling, any suggestions on this repair. Are these pressed in?

Don, I see you suggesting tossing out my original seloc and downloading the new manual - Could you help me out with this link?

Could the lock nut possibly wear, causing it to spin out? I'm sure you will all suggest getting new nuts in that case, but would medium str locktite work just the same?

Thanks again!!

 

[Big Boat Bay Buster]

Re: Lake test, Not fun...

"I have already replaced the slightly bent push rods...."

To me, thats a clue. Whatever force bent the rod, also might have also pulled the rocker stud up. I had a similair problem on an old Pontiac motor. A sized rocker pulled up the stud. I gently hammered the stud back down, never had a problem since. I would buy a new set of stock rockers, since they would probably have new lock nuts. Should be real cheap for a Chevy motor, don't need to go marine. Change over to screw in studs might be an option, don't know if the head needs to be removed for this.

 

[Don S]

Re: Lake test, Not fun...

As far as the springs and valves go, they were just rebuilt so I can assume that is all solid.

You know what happens when you ASSUME something don't you ...........

I am leaning toward the stud pulling, any suggestions on this repair.

Let's go thru that if necessary, LOOK first.

Could the lock nut possibly wear, causing it to spin out? I'm sure you will all suggest getting new nuts in that case,

If you can turn them by hand without a ratched, yea, they are worn out. Highly unlikely, but possible. Forget locktite, things will be way too oily, if the locknuts are loose, replace them.

Don, I see you suggesting tossing out my original seloc and downloading the new manual

?????????????? Where did I say that in this thread???????????

But, yes, get rid of the seloc. Look at the links in the Adults Only sticky at the top of the forum.



Just a general question and not directied at you personally, but WHY don't people ever look at the stickies in forums????? They are there for a reason, and in many cases would answers many of the questions.

 

[Sea Raider I]

Re: Lake test, Not fun...

Don,

You didnt direct that to me, but I see you suggesting it to others on many different threads.

I did go to the sticky, when I click on the link nothing comes up....

I will go through this tomorrow and look at everything, but the lifters - I just dont want to pull the dang intake again.

Thanks.

 

[Don S]

Re: Lake test, Not fun...

I did go to the sticky, when I click on the link nothing comes up....

The manuals have to download. They may take a very long time to download, depending on which one you are trying to get.

 

[Sea Raider I]

Re: Lake test, Not fun...

This is the link/Manual I am trying to get:

Service Manual #3 1978 - 1984 All engines (1.36GB)
http://www-alt.mercurymarine.com/mne...l/03/cover.pdf

I have had the screen open for more than 10 minutes now, on several occasions. Its 1.36 Gig, I should be able to download that in no time at all.

Please help.....

 

[fishrdan]

Re: Lake test, Not fun...

If the stud is pulling there are a few options. Screw in studs are best, but should be installed at a machine shop so it's done properly, every thing at the proper angle. You can also "pin" the rocker studs where a 1/8" hole is drilled through the stud boss and stud (about 1/2" down the stud boss) and then hammer in a 1/8" split or roll pin. Make sure not to drill completely through the stud boss and use the proper length pins. The pinning removes some metal and could weaken the stud boss, but I've never heard of this causing a problem.

If it's just 1 stud you are pinning, and there's room, and you are very meticulous and clean, and keep all the metal shavings out of the engine,,, you could pin the stud with the head on the engine. But if it were me I'd pull the heads and do all of them on a work bench. I've done several sets of heads and the process was easy, but I watched a machinist do it the first time around...

Then again, maybe I'm jumping the gun...

 

[fishrdan]

Re: Lake test, Not fun...

This is the link/Manual I am trying to get:

Service Manual #3 1978 - 1984 All engines (1.36GB)
http://www-alt.mercurymarine.com/mne...l/03/cover.pdf

I have had the screen open for more than 10 minutes now, on several occasions. Its 1.36 Gig, I should be able to download that in no time at all.

Please help.....

Click on link and go to bed,,, it will be there in the morning Think it took me 2-3 hours to get some of the larger manuals...

 

[Sea Raider I]

Re: Lake test, Not fun...

With all due respect to all, I am on high speed cable internet - 1.36G is nothing really....

Fisher, Excellent repair idea- I will find out more in the morning on if it is the stud or not- probably is.

Im not pulling these dang heads again, so I will tape off any areas where any potental shavings may go. I will be very careful!!

Thanks for the ideas!!!

 

[Mkos1980]

Re: Lake test, Not fun...

I used a stud tapping / puller tool and a tap to do all of mine on my Vortecs. They all came out stright as an arrow. To do one should take you no more then 10 minutes with the guide and tap. Any auto store sells single rocker studs.

 

[Sea Raider I]

Re: Lake test, Not fun...

I had to save the manual link to favorites, restart my comp and BANG there it is!!

Anyway, thanks for all the tips- Keep em coming!!

 

[Don S]

Re: Lake test, Not fun...

Just click the link in the post. If you just do a copy and past, you only get part of the link.
Make it easy on yourself and just CLICK HERE and the manual will download.

 

[Sea Raider I]

Re: Lake test, Not fun...

Boy, I must say I am not by any means computer illiterate.. but - even when I click on the link the explorer comes up but downloads nothing. It just sits there, with no indication of downloading anything....

Now, when I got the manual to come up using aforementioned method I cannot find my particular motor - just the 454 502??

I feel bad for wasting your time on this one.

 

[Maclin]

Re: Lake test, Not fun...

Regarding your resolve to not pulling the heads again while doing some drilling or other work like that, I would ask you to reconsider. Compare head removal to engine removal, engine removal becoming necessary due to oiling problems caused by debris introduced by the on-engine head work.

You know the engine will run fine once the valvetrain issue is solved, so if head work is indicated just pull them again to have it done. That way you will not be limited to what you can do on the boat. Also eliminates the chances for chasing other more serious problems later that could be induced by the on-engine head work.

 

[Don S]

Re: Lake test, Not fun...

Boy, I must say I am not by any means computer illiterate.. but - even when I click on the link the explorer comes up but downloads nothing.

When you click on the link, it doesn't "Download" so to speak, it Opens the file which you then have to save to your computer. If you just open it, you will not see any download screens, just a blank screen till the file does open, which takes a while.

If all you see is 454 and 502, then for some reason, you downloaded manual #16, since there were no 502's in the #3 manual.


You can right click the link for #3 and "save target as" and save it to your desktop, it's also a lot quicker than opening and saving. Give it a try on a smaller manual, like #24 to see how it works first before going for the biggest one.

 

[Sea Raider I]

Re: Lake test, Not fun...

First off< Don - Thanks, right click and save as worked like a charm!!

RESULTS:

While removing the rocker nuts I noticed quite a bit of them were fairly easy to turn by hand while threaded through the top of the nut. I also noticed several different nuts being used....

I put a straight edge along the studs and noticed them all to be even, no stud pulling issue at hand. I figured the nuts were bad, went to the store and bought a complete new set.

Went through the valve adjustment procedure per the manual, She fired right up and ran strong and smooth.

Hoping for the best, I cranked her up to 2500 RPM and let her go for it. She ran for 40 minutes at this RPM straight with no issues at all!!!

Next lake test this weekend, I have my fingers crossed
but I am pretty sure that was the issue. Will Post further results after the test

Thanks again to all for the quick responses and great advice!!!