Head gasket?
 

I've got one motor putting more steam out of the exhaust that the other. Been doing it all season, no obvious problems, good water flow, good compression, no signs of corrosion in the manifold/riser.
Could a head gasket have such a slight leak that it wouldn't affect the compression reading?
Any other thoughts, or am I over-reacting to nothing? Dont want to pull the heads for nothing.
Gary

Re: Head gasket?
 

Are both banks on this engine putting out the same amount of steam?

BT

Re: Head gasket?
 

I have full water jacketed headers. One side always seem to have more steam. If one header flows more. Water will exit with the least resistance.
My setup has run like this at Idle for years.

Hope that helps
Gerry

Re: Head gasket?
 

Unfortunately, it's a single exhaust on the motor. Wet exhausts going into a Y pipe, single outlet, so I cant say if one bank is hotter than the other.
I'm going to look for low firing voltage, chack the compression again if I find anything. Then check exhaust manifold temps with an IR gun. Anything else?
Would a leakdown test show anything more than a compression test in this case?
Gary

Re: Head gasket?
 

Leakdown is the way to go.
You can buy one for less then 100.00 bucks.
Record your readings . Then lator you have something to compare.
Im betting you are ok.

Good Luck
Gerry

Re: Head gasket?
 

Plug reading should tell the story if you are getting water into the combustion chamber. I would do the leak and listen test too... after the plug reading.

BT

Re: Head gasket?
 

Followup:
Only steams after warm up, lightly at idle, increases A LOT at increased rpm.
I've got 1 plug that looks steam cleaned. Compression on all cylinders is 180-185 psi and leakdown is less than 15%. All that sounded like it was going past the rings.
20psi to the cooling system, btw, it's a pre heat so that included exhaust manifolds, (water still in it) did not show bleed down.
The lack of steam till warm (140 degrees) and good compression + little leakdown makes me think it's not the head or head gasket. Although the clean plug sure looks like a head gasket problem.
Could I have a small crack in the exhaust manifold allowing for reversion, and that's cleaning that one plug?
Cam specs 282 duration, 104 intake center, 107 exhaust.
HEP, before I waste a good engine.
Gary

Re: Head gasket?
 

Hey Gary:

Is that duration at .050"? (Reversion on only one cylinder??) Is there no water flow through exhaust manifolds until T-stat opens?

If exhaust manifolds are only pressurized when the T-stat opens, then I vote for a cracked manifold at the clean spark plug. Gotta check them before the head comes off the valve. Maybe it's cracked BECAUSE there is only flow after the T-stat opens.

P.S. Were you at the LOTO Shootout?

Re: Head gasket?
 

I'm assuming that's at 0.050, but doesnt say on the TSB.
There is water flow (drilled 2 1/8" holes in thermostat) and pressure in the block/exhaust manifold at all times. There's also a 10psi bypass if thermostat is closed, goes to the risers after the bypass.
When I pressure checked the block + manifolds, the engine was cool, but got no leakage that I could find.

Oh yeah, definitely was at the shootout. Saw your intercooler at the booth. Very nice work.
Gary

Re: Head gasket?
 

What number plug is clean and what for exhaust, center rise merc?

BT

Re: Head gasket?
 

BT,
Log exhaust, second from rear. Unlikely to be reversion from a cracked riser.
Gary

Re: Head gasket?
 

I've never owned a boat with log manifolds. How far back does the water/exhaust gas mix? When ever I've had water problems from leaking exhaust it has been the center 2 cylinders 3,4,5,6 on either side. That was with center rise manifolds though and not being able to keep riser gaskets in.

Another question, are you getting milky oil? Leaking exhaust will drain into the crankcase through open exhaust valves when let sit for a few days. Have you ever serviced this exhaust?

BT

Re: Head gasket?
 

Log style enters at back (cylinder 8), that plug is fine, it's the one forward of 8 that looks clean.
No, on the milky oil. No signs of contamination at all.
I know what you mean about leaking risers with center rise, always the center 2 cylinders.
Looks like the exhaust is coming off.
Does everyone agree that with those symptoms & compression/leakdown numbers, I can rule out head gasket and crack in cylinder head?
Gary

Re: Head gasket?
 

If you have serviced the manifold in recent past and feel they are clear, I say you need to collect more facts before tearing into it. That of course depends some on how tough a job getting the manifold off will be. Mine are very difficult with engines in the boat. Generally if you are getting water from exhaust cracks it will be worse in the combustion chamber or above the valve after sitting some. After it sits, remove the suspect plug and while holding a paper towel in front of the plug hole, have someone crank the engine (kill switch out). If water flies out and wets the towel, you have to remove the exhaust. If it remains dry, I would run it until I have more facts. Hopefully those facts would not be a valve head coming off. Is this spark plug getting rusty too?

BT :cool:

Re: Head gasket?
 

Gary- This sounds like a tough one. If one plug looks like it's steam cleaned, you've got water getting in that cylinder. You said the manifold and block were pressure tested and passed. Did you pressure test the head? You could have a leaking head gasket or a cracked head. Once had steam coming out the exhaust. Couldn't find anything until I pulled the head. The engine was still warm. Saw a dark line in the combustion chamber between the intake and exhaust valves that was leaking water. Pulled those valves to find a crack between the seats. My experience is that a compression test won't show something like this. 15% leakdown isn't the greatest. Was the "steam cleaned" cylinder out of line with the other cylinders? This could be nothing at all or a problem in the making. How many hours since the motor was apart? Keep us posted. Lou