Mercruiser 496 proplem
12-29-2020, 04:07 PM
#52
Registered
The 8.1 is not adjusted like in the vid.
From manual 30
Not sure its an exhaust issue. Can pressure test the man by sealing of exit port and apply pressure to intake port
I would lean toward removing the head and have if looked over by a machine shop
From manual 30
Valve Adjustment
No adjustment is required. Valve lash is automatically set when rocker arm bolts are torqued to 19 lb-ft (25 Nm).
No adjustment is required. Valve lash is automatically set when rocker arm bolts are torqued to 19 lb-ft (25 Nm).
I would lean toward removing the head and have if looked over by a machine shop
12-29-2020, 04:19 PM
#53
Johan, I can see you have some bad luck here! I think you have to pull the heads and have your valves done. Thatīs what I did after my CMI misshap, had similar bad numbers but at #7 and 8. Do a new leak down test first as AllDodge wrote to check the rings.
I changed both my low- and high pressure fuel pumps a couple of years ago, I didn`t take the housing of the pump out just took the lid off and then the filter and the pumps. The colour inside my pump was intact, looked like new. It was a little tricky to get the lid back on the pump if I remember right. My engine is a 2005 with 550 hours on it now.
If you have the 425HO standard cam I doubt you have reverison and I have never heard or read here that anyone have had reversion on this engine.
I changed both my low- and high pressure fuel pumps a couple of years ago, I didn`t take the housing of the pump out just took the lid off and then the filter and the pumps. The colour inside my pump was intact, looked like new. It was a little tricky to get the lid back on the pump if I remember right. My engine is a 2005 with 550 hours on it now.
If you have the 425HO standard cam I doubt you have reverison and I have never heard or read here that anyone have had reversion on this engine.
12-30-2020, 03:06 AM
#54
Registered
Thread Starter
Do you mean pressure test it like I trying to describe on the picture below or on a different way?
Feed the intake port with water and stop it after the manifold before the riser?
12-30-2020, 03:16 AM
#55
Registered
Thread Starter
Johan, I can see you have some bad luck here! I think you have to pull the heads and have your valves done. Thatīs what I did after my CMI misshap, had similar bad numbers but at #7 and 8. Do a new leak down test first as AllDodge wrote to check the rings.
I changed both my low- and high pressure fuel pumps a couple of years ago, I didn`t take the housing of the pump out just took the lid off and then the filter and the pumps. The colour inside my pump was intact, looked like new. It was a little tricky to get the lid back on the pump if I remember right. My engine is a 2005 with 550 hours on it now.
If you have the 425HO standard cam I doubt you have reverison and I have never heard or read here that anyone have had reversion on this engine.
I changed both my low- and high pressure fuel pumps a couple of years ago, I didn`t take the housing of the pump out just took the lid off and then the filter and the pumps. The colour inside my pump was intact, looked like new. It was a little tricky to get the lid back on the pump if I remember right. My engine is a 2005 with 550 hours on it now.
If you have the 425HO standard cam I doubt you have reverison and I have never heard or read here that anyone have had reversion on this engine.
Im going to take of the heads.
But first I must take the valves/rockers of right?
And after that the intake manifold before I can take of the headers?
First time im doing this.
Did you also have problems with reversion due to bad valves or did it happen after the cmi leaked?
I have the leak down test tools, but not a compressor. See if I can borrow one.
But I can do a leak down test with the valve covers off right?
Did you manage to get the plastic box off that is surrounding the fuel pump? I have tried but I didnt make it, gonna try again.
It should be the 425 HO cam on it, I hope.
A mechanic shop here in Sweden rebuilded it from a 375 Mag to a 425 HO.
I have also read that it shouldnt cause any reversion with the standard HO cam.
12-30-2020, 07:34 AM
#56
Registered
Oh, thank you. Is the valve adjustment just different on the marine 8.1L or is it 496 in general?
Do you mean pressure test it like I trying to describe on the picture below or on a different way?
Feed the intake port with water and stop it after the manifold before the riser?
Do you mean pressure test it like I trying to describe on the picture below or on a different way?
Feed the intake port with water and stop it after the manifold before the riser?
There are several motors which valves are adjusted by torque to spec.
The vid is good and there are also several which are adjusted to zero lash and then 3/4 to 1 turn more. Just depends on which motor (year, serial number). Always good to have a service manual
12-30-2020, 09:07 AM
#57
Registered
Thread Starter
Yes, pressure test man as shown
There are several motors which valves are adjusted by torque to spec.
The vid is good and there are also several which are adjusted to zero lash and then 3/4 to 1 turn more. Just depends on which motor (year, serial number). Always good to have a service manual
There are several motors which valves are adjusted by torque to spec.
The vid is good and there are also several which are adjusted to zero lash and then 3/4 to 1 turn more. Just depends on which motor (year, serial number). Always good to have a service manual
Just with the garden hose I think/normal garden hose pressure from the house?
Okey, I see
12-30-2020, 09:21 AM
#58
Registered
Best to test with air. Air will leak where water may not when cold. Test around 2 bar
12-30-2020, 10:13 AM
#59
Registered
Thread Starter
12-30-2020, 10:38 AM
#60
Registered
Heads will need to come off, pressure test, cleanup, Valvejob hopefully will fix them. Leakdown test the cylinders to be sure thats your problem.
Your exhaust manifolds see roughly 20-30psi h20 during operation. I would not be afraid to double that number with air psi to test. Use air as mentioned and submerge manifold into tub of water. Bubbles will be very noticeable.
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JohanSweden (12-30-2020)
