Hydraulic lifter or rocker problem? 496 HO

Hi everyone have a strange problem with my 496 HO..

Having stripped it down to its last nut and bolt and completely rebuilding started and ran fine but only at idle due to not being in the boat, after fitting I took it out for a sea trial and everything seemed to be fine then there was a slight tapping noise and I returned to port..
First thought it was a fuel issue but after further inspection I found that two rockers had jumped off the push rods, or the nuts worked themselves loose then the rocker was moved.
My questions are my engine is 2001 with very few hours I purchased it from someone who blow up one of his engines and then the boat wasn't used but had some slight moisture issues hence why I rebuilt the engine.
I have to confess I didn't change the valve springs nor the hydraulic lifter as I dismantled them and cleaned them and looked to be fine. The push rods are new and NOT bent so now I'm thinking it may be a oil delivery issue with the lifters or maybe bad valve springs or poor nuts holding the rockers..
On re setting them today I moved the nuts to another place to see if I could see if its the nuts or something else..
Took the boat out and after a short time the noise returned (slight taping) so I went back to port..

Any suggestions would be really appreciated..

Tomorrow I will again take off the rocker covers and find out if the nuts have moved from where I put them or the same cylinder as it was today (with different nuts) has come loose again..

I have tightened the rockers up removing the back lash then a further three quarter turns on each nut to nip them up..
Does anyone know if I'm being correct using these settings??

Re: Hydraulic lifter or rocker problem? 496 HO

Welcome to iboats

What is the serial number of the engine your working on?

Re: Hydraulic lifter or rocker problem? 496 HO

More info: According to service manual 30, you take them all the way down once both valves are closed to 19ftlb, no snug and then 3/4 turn
Here is what is listed in the manual

IMPORTANT: When installing rocker arms and rocker arm balls, coat bearing surfaces
of rocker arms and rocker arm balls with engine oil.
1. Install push rods in their original locations. Be sure push rods seat in lifter socket.
2. Install rocker arm assemblies in their original locations.
3. Ensure cylinder is at TDC and both valves are closed. Torque to 19 lb-ft (25 Nm).

Valve Adjustment
No adjustment is required. Valve lash is automatically set when rocker arm bolts are torqued
to 19 lb-ft (25 Nm).

Re: Hydraulic lifter or rocker problem? 496 HO

AllDodge said:

Welcome to iboats

What is the serial number of the engine your working on?

Click to expand...

Thank you

There isn't a plate with an engine number or sticker.. however the number stamped on the block itself on a square on one side is

T10417
0205XA

Re: Hydraulic lifter or rocker problem? 496 HO

AllDodge said:

More info: According to service manual 30, you take them all the way down once both valves are closed to 19ftlb, no snug and then 3/4 turn
Here is what is listed in the manual

IMPORTANT: When installing rocker arms and rocker arm balls, coat bearing surfaces
of rocker arms and rocker arm balls with engine oil.
1. Install push rods in their original locations. Be sure push rods seat in lifter socket.
2. Install rocker arm assemblies in their original locations.
3. Ensure cylinder is at TDC and both valves are closed. Torque to 19 lb-ft (25 Nm).

Valve Adjustment
No adjustment is required. Valve lash is automatically set when rocker arm bolts are torqued
to 19 lb-ft (25 Nm).

Click to expand...

I saw this and asked around as I have seen two methods of tightening the valves and on asking a friend who had just built a 496 he informed me that it didn't apply to my engine... So I followed the other method..
If I'm correct on probing this method I found that the valves were opening on tightening to 19 lb-ft

Re: Hydraulic lifter or rocker problem? 496 HO

sh4dive said:

Thank you

There isn't a plate with an engine number or sticker.. however the number stamped on the block itself on a square on one side is

T10417
0205XA

Click to expand...

This is a date code. The serial number is located on a tag, starboard side above the starter. I'm figuring it was removed by someone so we will go with a 2001 8.1 (496) HO

sh4dive said:

I saw this and asked around as I have seen two methods of tightening the valves and on asking a friend who had just built a 496 he informed me that it didn't apply to my engine... So I followed the other method..

Click to expand...

Merc service manual 30 covers All 8.1L (496) HO, MAG from 2001-present
Who ever is telling you it doesn't apply needs to tell you why. It is recommend to replace the selflocking nuts on a rebuild. Here is the link to the service manual which you can download in PDF.
Maxum Owners Club - News - #30 - MerCruiser GM 8.1L (2001 - present) Service Manual

Re: Hydraulic lifter or rocker problem? 496 HO

AllDodge said:

This is a date code. The serial number is located on a tag, starboard side above the starter. I'm figuring it was removed by someone so we will go with a 2001 8.1 (496) HO



Merc service manual 30 covers All 8.1L (496) HO, MAG from 2001-present
Who ever is telling you it doesn't apply needs to tell you why. It is recommend to replace the selflocking nuts on a rebuild. Here is the link to the service manual which you can download in PDF.
Maxum Owners Club - News - #30 - MerCruiser GM 8.1L (2001 - present) Service Manual

Click to expand...

Hi thank you so much, it could be the answer to my nightmare.. the engine has loads of torque and runs really well till it starts tapping and as it is two of the inlet valves the chamber is filling with fuel and not going anywhere..
on re connection and the valve opens I get fuel rushing in the cylinder...
And yes I need to find out what is going on with the advice I have been given...

Re: Hydraulic lifter or rocker problem? 496 HO

sh4dive said:

The push rods are new and NOT bent.

Click to expand...

I know their new but I'm reminded about this service bulletin while reading your thread.

http://www.boatfix.com/merc/Bullet/01/01_06.pdf

Re: Hydraulic lifter or rocker problem? 496 HO

Fun Times said:

I know their new but I'm reminded about this service bulletin while reading your thread.

http://www.boatfix.com/merc/Bullet/01/01_06.pdf

Click to expand...

Hi I purchased new both sets of push rods when building the engine..

Thank you for bringing it to my attention

Re: Hydraulic lifter or rocker problem? 496 HO

Did you reface the rockers? Did you re-install the rockers in their original positions? Did the rocker end of the valve stems get refaced, and re-installed in their original position?

Chris.....

Re: Hydraulic lifter or rocker problem? 496 HO

Hi Chris I didn't reface the rockers. I changed for new the push rods and the valves, reseated the valves as normal and returned the rockers to their original positions.
Today I will be torquing down the rockers and hopefully this could be the end of this problem for me as I've had three days of not understanding what was wrong... :/ will post later how I get on..

Re: Hydraulic lifter or rocker problem? 496 HO

If you've put new valves in, you MUST reface the rockers, or they will slide off to the side... Had it happen years ago on an in-line 6 (Merc 165). Took the rockers off, refaced them, never had anymore trouble... And since that time (about 1987) I've always re-faced rockers, every time... Never had any problems.

When you take your rockers off (to re-face them ) you'll see a distinct wear pattern... That's what you need to remove.

If you'd used the old valves and rockers in their original positions, you'd have been ok... But the new valves have a different (rocker end) face, so the rockers need to be re-faced so they can bed in correctly....

Chris......

Re: Hydraulic lifter or rocker problem? 496 HO

achris said:

If you've put new valves in, you MUST reface the rockers, or they will slide off to the side... Had it happen years ago on an in-line 6 (Merc 165). Took the rockers off, refaced them, never had anymore trouble... And since that time (about 1987) I've always re-faced rockers, every time... Never had any problems.

When you take your rockers off (to re-face them ) you'll see a distinct wear pattern... That's what you need to remove.

If you'd used the old valves and rockers in their original positions, you'd have been ok... But the new valves have a different (rocker end) face, so the rockers need to be re-faced so they can bed in correctly....

Chris......

Click to expand...

Hi Chris am today removing them, so I can inspect them before setting the torque setting, the engine I have rebuilt had originally done only ten hours, was part of a pair they were new and one put a piston through the block and the boat was sold without being repaired and I was lucky to get the engine. I'm only rebuilding it as the engine sat around un attended for 5 yrs and I wanted to be sure whatever I fitted in my boat was like the rest of it. I've restored it for the last year and half so obviously want it perfect.
Thanks for your help I'm quietly confident that today will see the difference. Good or bad!!

Re: Hydraulic lifter or rocker problem? 496 HO



Hydrolift S-24

Re: Hydraulic lifter or rocker problem? 496 HO

Had one the nuts were wore out,kept coning loose. Replaced with new-problem solved. Just a thought...
Grub

Re: Hydraulic lifter or rocker problem? 496 HO

Today set the valves @ correct torque setting then went out, all was fine for a while then it died as I was coming off throttle to check. Restarted went a bit then died wouldn't get me back and was towed in.
Far back right cylinder no compression then removed the rocker cover to find this time the back right inlet valve had worked itself off and then as it wasn't letting in fuel to the cylinder I guess it was then filling up the intake manifold with fuel causing other issues..
I NEED HELP!! my local mercruiser dealer is too busy to look at it for two weeks!!! OMG

Re: Hydraulic lifter or rocker problem? 496 HO

sh4dive said:

Today set the valves @ correct torque setting then went out, all was fine for a while then it died as I was coming off throttle to check. Restarted went a bit then died wouldn't get me back and was towed in.
Far back right cylinder no compression then removed the rocker cover to find this time the back right inlet valve had worked itself off and then as it wasn't letting in fuel to the cylinder I guess it was then filling up the intake manifold with fuel causing other issues..
I NEED HELP!! my local mercruiser dealer is too busy to look at it for two weeks!!! OMG

Click to expand...

Sounds like the rocker arm came off. If the intake rocker arm came off the fuel injector would keep pushing fuel into the intake manifold, and without the valvle opening it could fill up, so to speak. Did the nut back it's way off? If it did, then did you replace the nuts with new self lcking nuts? If not this appears to be the problem as mentioned by Grub.

Re: Hydraulic lifter or rocker problem? 496 HO

HI after inspecting the rockers it appeared the third cylinder on the right bank (where I put one of the nuts from the rocker that had jumped) I moved the nuts only to see if it was the nuts or the cylinder with the problem.. So am now going to get new nuts before seeing how it goes.. Although now it would appear the low pressure fuel pump has stopped working as when I'm switching on the ignition to prime the fuel rail I'm only getting a few spoons full of fuel coming out and no pressure to make it pass the filter..
Do you think the issue with the valves and rockers has ultimately damaged the low pressure fuel pump?

Re: Hydraulic lifter or rocker problem? 496 HO

I could see how the lock nuts could loose their strength and become loose if they are put on and off too many times.

I can't see how the rocker issue could effect the fuel pump.

Re: Hydraulic lifter or rocker problem? 496 HO

sh4dive said:

HI after inspecting the rockers it appeared the third cylinder on the right bank (where I put one of the nuts from the rocker that had jumped) I moved the nuts only to see if it was the nuts or the cylinder with the problem.. So am now going to get new nuts before seeing how it goes.. Although now it would appear the low pressure fuel pump has stopped working as when I'm switching on the ignition to prime the fuel rail I'm only getting a few spoons full of fuel coming out and no pressure to make it pass the filter..Do you think the issue with the valves and rockers has ultimately damaged the low pressure fuel pump?

Click to expand...

Agree with Eric on the rocker issue.

What caused lead you to think of the low pressure fuel pump, is it not starting or something else? The key is turned on and the pump runs to prime the system. It's my understanding (no expert, Need Fun Times for that) the key is turned to run and the ECM turns the pumps on for 3 seconds. When engine starts cranking the pumps will start running, and if the ECM receives signal that spark is being delivered, then the ECM will pulse the injectors.