wrote in message
oups.com...


Bill McKee wrote:
Head. Gasket or valve.

"nate" wrote in message
. ..
I have a 8 cylinder 350 (I think GM..it's in a boat)

Engine back fires and sputters. Engine does not leak oil that I know
of.
(or at least not very much)Compression test revealed 0 compression in 1
cylinder and all others were ok. Based off these symptoms, Is it
likely
that I will have to do work on the engine block or will the problem be
likely in the Head (gaskets or other)


Why? It could very well be a hole burnt in a piston, or a valve broke
off and pounded a hole in the piston. Usually if it's the head gasket,
you'll show a little compression, but will leak down easily. Same with
a burnt exhaust valve.


When the valve breaks off there is not a little hole in the piston.
Normally the piston splits and the rod breaks. And the cylinder can crack
also. Makes a little tapping sound before a single big bang sound. Been
there, done that. Pistons rarely have a hole burned through them, unless
you are running really hard and lean. Then you see aluminum on the
sparkplug when you pull the plug. And depending on the size of the head
gasket hole, and the speed of the engine turning, you get so little
compression, it will not register on the gauge. Takes a couple of PSI to
move the gauge. You have to overcome the Schrader valve spring in the
tester. Same for a burned valve. And if the rocker for the intake is
broken, you also get a zero to very low reading on the compression gauge.

nate wrote:

I have a 8 cylinder 350 (I think GM..it's in a boat)

Engine back fires and sputters. Engine does not leak oil that I know of.
(or at least not very much)Compression test revealed 0 compression in 1
cylinder and all others were ok. Based off these symptoms, Is it likely
that I will have to do work on the engine block or will the problem be
likely in the Head (gaskets or other)



A hole in a cylinder top? A bad valve? Stuck open? A broken ring?

Not likely a bad gasket, but you will need one anyway. Yank the head.

Terry K

When I pulled mine (1986 350) heads for a stuck valve. Both Heads had
cracks in the Exhaust Seats, clar thru to the water jacket. This is
apparently not uncommon for GM small block engines running with a high
load.

Get a cylinder leak down test done. This test wil tell you the condition of
the rings, valves, and where the problem is! Any "good" auto shop should be
able to do the test in under 2 hours.

"nate" wrote in message
. ..
I have a 8 cylinder 350 (I think GM..it's in a boat)

Engine back fires and sputters. Engine does not leak oil that I know of.
(or at least not very much)Compression test revealed 0 compression in 1
cylinder and all others were ok. Based off these symptoms, Is it likely
that I will have to do work on the engine block or will the problem be
likely in the Head (gaskets or other)

Bill McKee wrote:

When the valve breaks off there is not a little hole in the piston.
Normally the piston splits and the rod breaks. And the cylinder can crack
also. Makes a little tapping sound before a single big bang sound. Been
there, done that.


Pistons rarely have a hole burned through them, unless
you are running really hard and lean. Then you see aluminum on the
sparkplug when you pull the plug. And depending on the size of the head
gasket hole, and the speed of the engine turning, you get so little
compression, it will not register on the gauge. Takes a couple of PSI to
move the gauge. You have to overcome the Schrader valve spring in the
tester. Same for a burned valve. And if the rocker for the intake is
broken, you also get a zero to very low reading on the compression gauge.

I've changed Several head gaskets that showed SOME compression on the
gauge. I've never, ever seen a head gasket that would blow a chunk of
it out that it wouldn't read anything, seeing how the valve in the
tester keeps the pressure reading. Same with an burned exhaust valve.
The thing being, in your reply, you acted definitive. You could VERY
EASILY be wrong.

Here's my story...
http://groups-beta.google.com/group/...099392c5fc37df

I agree with the guy's that indicated it's an intake valve issue. Pull
the valve covers first, see if the rocker or push rod is the problem. I
have seen cases where the rocker stud pulled out, but that would keep
the valve closed. The valve could be stuck open, in which case the
rocker will be real loose.

I read each post and appreciate everyone taking the time to reply. I'm
going to tear into it this weekend and will post the results.


"Capt John" wrote in message
oups.com...
I agree with the guy's that indicated it's an intake valve issue. Pull
the valve covers first, see if the rocker or push rod is the problem. I
have seen cases where the rocker stud pulled out, but that would keep
the valve closed. The valve could be stuck open, in which case the
rocker will be real loose.

wrote in message
oups.com...


Bill McKee wrote:

When the valve breaks off there is not a little hole in the piston.
Normally the piston splits and the rod breaks. And the cylinder can
crack
also. Makes a little tapping sound before a single big bang sound. Been
there, done that.


Pistons rarely have a hole burned through them, unless
you are running really hard and lean. Then you see aluminum on the
sparkplug when you pull the plug. And depending on the size of the head
gasket hole, and the speed of the engine turning, you get so little
compression, it will not register on the gauge. Takes a couple of PSI to
move the gauge. You have to overcome the Schrader valve spring in the
tester. Same for a burned valve. And if the rocker for the intake is
broken, you also get a zero to very low reading on the compression gauge.

I've changed Several head gaskets that showed SOME compression on the
gauge. I've never, ever seen a head gasket that would blow a chunk of
it out that it wouldn't read anything, seeing how the valve in the
tester keeps the pressure reading. Same with an burned exhaust valve.
The thing being, in your reply, you acted definitive. You could VERY
EASILY be wrong.


I could be wrong about what is wrong, but I have seen several head gaskets
without compression. And my daughters Explorer broke the intake rocker and
zero compression reading.

Bill McKee wrote:
.. And my daughters Explorer broke the intake rocker and
zero compression reading.

How? Intake valve ALWAYS closed that way. So, when the piston comes up
on the compression stroke, both valves would be closed JUST EXACTLY
like they would be if the intake rocker wasn't broke.