"Vic Smith" wrote in message
...
On Wed, 23 Jul 2008 08:28:39 -0700, JR North
wrote:

As you will recall, In our last episode, I was preparing to install the
new starter in my Merc. 5.0. I did a compression test with the old
starter in place, 150 all around. After sitting 2 weeks, the new starter
is in; I cranked it with the plugs out (no manifolds installed yet) And
it spun 3 revolutions with a *Clack* every 360?. I thought in this brief
time that possibly a tooth was sheared on the flywheel ring, but after 3
revolutions the engine locked and would not turn. ****. I was thinking
maybe a socket I had holding the Qjet choke open had somehow fallen into
the intake manifold and wedged an intake valve open. Ok. I put a chain
wrench on the balancer and found I could rotate the engine backwards,
but would lock at the same point forwards. I pulled the valve covers,
expecting to find an offending intake valve hung open, with slop in the
rocker arm as a result. Found it, alright, but an exhaust valve, not
intake. Feeling up the #4 exhaust port with my finger, I can feel the
broken end of the exhaust valve stem. The valve head is loose in the
combustion chamber, preventing the piston from reaching TDC. DOUBLE
****. In the 2 weeks since the compression test, the #4 exhaust valve
seized in the guide, and on cranking, because the valve is at an angle
with the piston, was broken off. Now I get to pull the heads......
Oh well, the engine is 18 years old, has 495 Hrs on it, and with all
that down time, a seized valve is not unusual.
JR

That's weird, since you were cranking it 2 weeks ago.
What do you suppose caused it to seize?
I've never heard of that happening on a 305, but you say that's
not unusual.
I'd like to hear the autopsy report after the stem is driven from the
guide.
This boating stuff is starting to scare me.

--Vic

Salt water in the valve guides.
Rebuilders won't touch heads from sal****er boats.

On Wed, 23 Jul 2008 15:46:59 -0400, "Jim" wrote:



Salt water in the valve guides.
Rebuilders won't touch heads from sal****er boats.

That sort of cuts down your options, don't it?
But why is that? I can see how the SW cooled heads might have
more of the passages eaten away, but they could grind, revalve,
respring, and reguide with no problem. Just make it clear future
cracks aren't warranteed, same as any head rebuild.
Anyway, I'm only batting .500 with shop work on heads.
I don't know anything about those boat engine manifolds, but I guess
that's how the salt got in the guides.
The other thing that doesn't make sense to me is how the piston hit
the valve, because I thought that engine was non-interference.
Couldn't find that's a fact anywhere though, so maybe I'm missing
something.
Seems like there's big differences between car and boat engines.
Think I'll get an O/B.

--Vic

On Jul 23, 5:56 pm, Vic Smith wrote:
On Wed, 23 Jul 2008 15:46:59 -0400, "Jim" wrote:

Salt water in the valve guides.
Rebuilders won't touch heads from sal****er boats.

That sort of cuts down your options, don't it?
But why is that? I can see how the SW cooled heads might have
more of the passages eaten away, but they could grind, revalve,
respring, and reguide with no problem. Just make it clear future
cracks aren't warranteed, same as any head rebuild.
Anyway, I'm only batting .500 with shop work on heads.
I don't know anything about those boat engine manifolds, but I guess
that's how the salt got in the guides.
The other thing that doesn't make sense to me is how the piston hit
the valve, because I thought that engine was non-interference.
Couldn't find that's a fact anywhere though, so maybe I'm missing
something.
Seems like there's big differences between car and boat engines.
Think I'll get an O/B.

--Vic

Well, one thing is that engine heads are sort of a soft cast iron and
after years of salt water exposure, the minerals of said water
actually impregnate into the heads and cause the cast iron to break
down. just like an old rusty iron water pipe that's laid bare to the
elements over several years.

So quality machine work is next to impossible

On Jul 24, 1:20 am, Tim wrote:
On Jul 23, 5:56 pm, Vic Smith wrote:



On Wed, 23 Jul 2008 15:46:59 -0400, "Jim" wrote:

Salt water in the valve guides.
Rebuilders won't touch heads from sal****er boats.

That sort of cuts down your options, don't it?
But why is that? I can see how the SW cooled heads might have
more of the passages eaten away, but they could grind, revalve,
respring, and reguide with no problem. Just make it clear future
cracks aren't warranteed, same as any head rebuild.
Anyway, I'm only batting .500 with shop work on heads.
I don't know anything about those boat engine manifolds, but I guess
that's how the salt got in the guides.
The other thing that doesn't make sense to me is how the piston hit
the valve, because I thought that engine was non-interference.
Couldn't find that's a fact anywhere though, so maybe I'm missing
something.
Seems like there's big differences between car and boat engines.
Think I'll get an O/B.

--Vic

Well, one thing is that engine heads are sort of a soft cast iron and
after years of salt water exposure, the minerals of said water
actually impregnate into the heads and cause the cast iron to break
down. just like an old rusty iron water pipe that's laid bare to the
elements over several years.

So quality machine work is next to impossible

Not to mention that it's a whole other volume to get into the
electrolysis issue of salt water and engines.....

On Wed, 23 Jul 2008 23:20:03 -0700 (PDT), Tim
wrote:

Well, one thing is that engine heads are sort of a soft cast iron and
after years of salt water exposure, the minerals of said water
actually impregnate into the heads and cause the cast iron to break
down. just like an old rusty iron water pipe that's laid bare to the
elements over several years.

So quality machine work is next to impossible

Never thought of that. Thanks, Tim.

--Vic

On Jul 24, 2:20*am, Tim wrote:
On Jul 23, 5:56 pm, Vic Smith wrote:





On Wed, 23 Jul 2008 15:46:59 -0400, "Jim" wrote:

Salt water in the valve guides.
Rebuilders won't touch heads from sal****er boats.

That sort of cuts down your options, don't it?
But why is that? *I can see how the SW cooled heads might have
more of the passages eaten away, but they could grind, revalve,
respring, and reguide with no problem. *Just make it clear future
cracks aren't warranteed, same as any head rebuild.
Anyway, I'm only batting .500 with shop work on heads.
I don't know anything about those boat engine manifolds, but I guess
that's how the salt got in the guides.
The other thing that doesn't make sense to me is how the piston hit
the valve, because I thought that engine was non-interference.
Couldn't find that's a fact anywhere though, so maybe I'm missing
something.
Seems like there's big differences between car and boat engines.
Think I'll get an O/B.

--Vic

Well, one thing is that engine heads are sort of a soft cast iron and
after years of salt water exposure, the minerals of said water
actually impregnate into the heads and cause the cast iron to break
down. just like an old rusty iron water pipe that's laid bare to the
elements over several years.

So quality machine work is next to impossible- Hide quoted text -

- Show quoted text -

Sounds a bit like an urban legend. Guides are either knurled or bored
and inserts added. Knurled is quick and easy but won't last as long.
The salt water is not really going to affect either option. The seats
are hardened. Have been ever since they went to unleaded gas.
Besides, how does the machine shop know where the head has been
anyway?

As someone else mentioned, I too thought this engine was supposed to
be non-interfering. The other 305s I've seen from the boating world
have had seriously dished pistons, no way a valve would hit them. We
need more facts from the autopsy after the head is removed :-) I'd
also suggest removing a few other springs and checking those valves
for wobble.

On Jul 24, 11:47*am, wrote:
On Jul 24, 2:20*am, Tim wrote:





On Jul 23, 5:56 pm, Vic Smith wrote:

On Wed, 23 Jul 2008 15:46:59 -0400, "Jim" wrote:

Salt water in the valve guides.
Rebuilders won't touch heads from sal****er boats.

That sort of cuts down your options, don't it?
But why is that? *I can see how the SW cooled heads might have
more of the passages eaten away, but they could grind, revalve,
respring, and reguide with no problem. *Just make it clear future
cracks aren't warranteed, same as any head rebuild.
Anyway, I'm only batting .500 with shop work on heads.
I don't know anything about those boat engine manifolds, but I guess
that's how the salt got in the guides.
The other thing that doesn't make sense to me is how the piston hit
the valve, because I thought that engine was non-interference.
Couldn't find that's a fact anywhere though, so maybe I'm missing
something.
Seems like there's big differences between car and boat engines.
Think I'll get an O/B.

--Vic

Well, one thing is that engine heads are sort of a soft cast iron and
after years of salt water exposure, the minerals of said water
actually impregnate into the heads and cause the cast iron to break
down. just like an old rusty iron water pipe that's laid bare to the
elements over several years.

So quality machine work is next to impossible- Hide quoted text -

- Show quoted text -

Sounds a bit like an urban legend. *Guides are either knurled or bored
and inserts added. *Knurled is quick and easy but won't last as long.
The salt water is not really going to affect either option. *The seats
are hardened. *Have been ever since they went to unleaded gas.
Besides, how does the machine shop know where the head has been
anyway?

As someone else mentioned, I too thought this engine was supposed to
be non-interfering. *The other 305s I've seen from the boating world
have had seriously dished pistons, no way a valve would hit them. *We
need more facts from the autopsy after the head is removed :-) *I'd
also suggest removing a few other springs and checking those valves
for wobble.- Hide quoted text -

- Show quoted text -

Interference vs. non interference only applies to out of time. etc.
Like if the timing chain breaks, timing belt or chain slips, etc. If a
valve breaks and sits on the piston it'll punch holes in the piston,
or lock up even on a non-interference engine.

On Jul 24, 1:09*pm, wrote:
On Jul 24, 11:47*am, wrote:





On Jul 24, 2:20*am, Tim wrote:

On Jul 23, 5:56 pm, Vic Smith wrote:

On Wed, 23 Jul 2008 15:46:59 -0400, "Jim" wrote:

Salt water in the valve guides.
Rebuilders won't touch heads from sal****er boats.

That sort of cuts down your options, don't it?
But why is that? *I can see how the SW cooled heads might have
more of the passages eaten away, but they could grind, revalve,
respring, and reguide with no problem. *Just make it clear future
cracks aren't warranteed, same as any head rebuild.
Anyway, I'm only batting .500 with shop work on heads.
I don't know anything about those boat engine manifolds, but I guess
that's how the salt got in the guides.
The other thing that doesn't make sense to me is how the piston hit
the valve, because I thought that engine was non-interference.
Couldn't find that's a fact anywhere though, so maybe I'm missing
something.
Seems like there's big differences between car and boat engines.
Think I'll get an O/B.

--Vic

Well, one thing is that engine heads are sort of a soft cast iron and
after years of salt water exposure, the minerals of said water
actually impregnate into the heads and cause the cast iron to break
down. just like an old rusty iron water pipe that's laid bare to the
elements over several years.

So quality machine work is next to impossible- Hide quoted text -

- Show quoted text -

Sounds a bit like an urban legend. *Guides are either knurled or bored
and inserts added. *Knurled is quick and easy but won't last as long.
The salt water is not really going to affect either option. *The seats
are hardened. *Have been ever since they went to unleaded gas.
Besides, how does the machine shop know where the head has been
anyway?

As someone else mentioned, I too thought this engine was supposed to
be non-interfering. *The other 305s I've seen from the boating world
have had seriously dished pistons, no way a valve would hit them. *We
need more facts from the autopsy after the head is removed :-) *I'd
also suggest removing a few other springs and checking those valves
for wobble.- Hide quoted text -

- Show quoted text -

Interference vs. non interference only applies to out of time. etc.
Like if the timing chain breaks, timing belt or chain slips, etc. If a
valve breaks and sits on the piston it'll punch holes in the piston,
or lock up even on a non-interference engine.- Hide quoted text -

- Show quoted text -

Yes, but typically valve heads break off in the first place because
the piston hits them. In a non-interference engine that's not
possible. And while valve heads do break off for other reasons, it's
not usually while cranking. Some missing pieces in this story yet to
be filled in I think.

On Jul 24, 10:47*am, wrote:
On Jul 24, 2:20*am, Tim wrote:





On Jul 23, 5:56 pm, Vic Smith wrote:

On Wed, 23 Jul 2008 15:46:59 -0400, "Jim" wrote:

Salt water in the valve guides.
Rebuilders won't touch heads from sal****er boats.

That sort of cuts down your options, don't it?
But why is that? *I can see how the SW cooled heads might have
more of the passages eaten away, but they could grind, revalve,
respring, and reguide with no problem. *Just make it clear future
cracks aren't warranteed, same as any head rebuild.
Anyway, I'm only batting .500 with shop work on heads.
I don't know anything about those boat engine manifolds, but I guess
that's how the salt got in the guides.
The other thing that doesn't make sense to me is how the piston hit
the valve, because I thought that engine was non-interference.
Couldn't find that's a fact anywhere though, so maybe I'm missing
something.
Seems like there's big differences between car and boat engines.
Think I'll get an O/B.

--Vic

Well, one thing is that engine heads are sort of a soft cast iron and
after years of salt water exposure, the minerals of said water
actually impregnate into the heads and cause the cast iron to break
down. just like an old rusty iron water pipe that's laid bare to the
elements over several years.

So quality machine work is next to impossible- Hide quoted text -

- Show quoted text -

Sounds a bit like an urban legend. *Guides are either knurled or bored
and inserts added. *Knurled is quick and easy but won't last as long.
The salt water is not really going to affect either option. *The seats
are hardened. *Have been ever since they went to unleaded gas.
Besides, how does the machine shop know where the head has been
anyway?

As someone else mentioned, I too thought this engine was supposed to
be non-interfering. *The other 305s I've seen from the boating world
have had seriously dished pistons, no way a valve would hit them. *We
need more facts from the autopsy after the head is removed :-) *I'd
also suggest removing a few other springs and checking those valves
for wobble.- Hide quoted text -

- Show quoted text -

Not necessarily "urban legend", though. Around here we don't run
boats in salt water, but there are salt water pumps that have been run
in the "oil patch" for years. and find out that "mineral saturation"
can and does take a toll on various cast iron components, to the point
that the integrity of the metal is compromised, and machining (boring,
honing, resurfacing) is , or to the least, can be rather limited. I
agree with what you're saying about guides being preswsed and/or
knurled, but they still are fit and pressed into the cast iron core
of the head. So......

Bingo. First prize to Jim. It's FWC, just salt water from the failed
manifold(s) in the exhaust ports. That was why I oiled it when I pulled
the manifolds. Didn't work....
JR





Salt water in the valve guides.
Rebuilders won't touch heads from sal****er boats.

--
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Home Page: http://www.seanet.com/~jasonrnorth