Broken Value Spring

[Gary_Stokes@email.com]

I have a 1997 215 Express Crusier with a 5.7 Mercruiser. I have a broken value spring which I am in the process of replacing. My question is how do I adjust the values as I have to put the value cover on before I can put the exhaust manifold back on, whihc needs to be done before I start the engine.

On a car I would start the motor with the value covers off and do a final adjustment with a vacuum guage attached. This is not an option on a marine engine.

 

[aqua*holic]

I have a 1997 215 Express Crusier with a 5.7 Mercruiser. I have a broken value spring which I am in the process of replacing. My question is how do I adjust the values as I have to put the value cover on before I can put the exhaust manifold back on, whihc needs to be done before I start the engine.

On a car I would start the motor with the value covers off and do a final adjustment with a vacuum guage attached. This is not an option on a marine engine.

Wow. Never heard of doing that. I'll bet that is a pretty messy process. I just rotate the push rod and tighten the rocker untill there is slight drag on the rod. Then I believe it is a 1/4 or 1/2 turn tighter.

You could do your adjustment and then pull the manifolds back off to put the covers back on. I know that is double work and wastes a few gaskets but it could be done.

 

[Gary_Stokes@email.com]

It is not really that messy. I was fully expecting to have to pull the head so I was pleasantly surprised when I saw the broken spring. You are right, it is not something you see all that often anymore. Thanks for your advice.

 

[aqua*holic]

That would be a nice surprise. Hope that your repair goes well.

On the vacuum reading, I would think that if only one valve is slightly out of adjustment it wouldn't make that much of a difference on overall vacuum. Maybe if you are building a race motor and need every 1/4 horse out of it to gain that 0.01 second it would be worth it. Probably not in a boat motor. Good luck.

 

[docofthebay]

If that engine has hydraulic lifters, then I believe you don't adjust the valves, you tighten the rocker arm nut all the way down and you're ready to go.
Confirm that with a mechanic first before you overtighten and burn a valve but all the small block ford and chevy engines I worked on years ago had hydraulic lifters and the valves were not adjustable.

 

[Gunn]

Do a quick search on valve adjustment and you'll find the exact steps. But in summary, you have to get the engine at top dead center (TDC). Then you can adjust half of the valves (exact ones I can't recall). Usually you tighten the rocker arm stud bolt until there's drag on the pushrod, and then between 1/4 and 1/2 turn more with the wrench, if you have hydraulic lifters... Then you spin the engine one revolution and do the other half.

I haven't done it in a few years, so verify what I've described before actually doing it and to figure out which values can you can adjust at each crank position.

Tom

 

[aqua*holic]

NO! Hydraulic lifters are adjusted by drag on the push rod. Most certainly do not tighten the nut all the way down.

You are correct that hydraulic lifters do not require perodic adjustment like flat tappet, but they still require an initial setting.

 

[docofthebay]

Ok, thanks for the update to my knowledge base. Sorry for the bad advise.
I'll stick to adjusting human valves in the future.

 

[aqua*holic]

Ok, thanks for the update to my knowledge base. Sorry for the bad advise.
I'll stick to adjusting human valves in the future.

I think I will stick to engines. At least with them, I am pretty sure if I don't get it right the first time, I just re-do it. Not sure I would have that luxury with a human!

 

[ardeprint]

I have a 1997 215 Express Crusier with a 5.7 Mercruiser. I have a broken value spring which I am in the process of replacing. My question is how do I adjust the values as I have to put the value cover on before I can put the exhaust manifold back on, whihc needs to be done before I start the engine.

On a car I would start the motor with the value covers off and do a final adjustment with a vacuum guage attached. This is not an option on a marine engine.

If I may ask, what symptoms did you have prior to you discovering the broken spring?

 

[Dick Whetstone]

If I may ask, what symptoms did you have prior to you discovering the broken spring?

A broken valve spring first manifests itself by losing power in the effected cylinder usually followed by popping back (backfiring) through the carb or air filter. Which one or both depends whether it is an intake valve or an exhaust valve.

Very bad (expensive) things happen if the valve drops down into the cylinder. STOP the engine before that happens.

 

[skibum]

That's what I was wondering. Did that valve happen to bounce off of the piston before he found it?