My brother made an airboat and has been riding around in it for about a
year. It has a new Chevy 350 300HP "Hi-Po" engine in it, Weiand intake,
Carter 625 carb, and Mallory Unilite distributor. He calls me up and asks
if I would change his head gaskets cause he heard a "ticking noise". I am a
pretty good backyard mechanic. I go over their and just to appease him, I
didn't think the head gasket was blown, I tore into the engine. Immediately
I notice the some of the rocker studs were pulled up, some as much as a 1/4
inch. I took the heads to work and pressed them back down. I asked "does
this thing run hot?" usually heat can pull the studs up, he says "yes, all
the time". I start putting the motor back together and am about to fire it
up. I put the #1 cylinder at top dead to get a good start for the timing
then I notice no timing tabs connected to the timing cover to show where to
time the engine. I say "how did you time this thing?" he says "I just
turned the distributor until it ran good"(that's bad). I noticed a set of
bendable stainless exhaust pipes connected to a set of Headman stainless
mufflers in a pile next to his garage and asked "what happened here?" he
said that they get hot and get ruined, all burned up. He said that when he
drives the boat at night the ENTIRE exhaust from header to muffler glows
cherry red. I am thinking the timing was so far off the combustion cycle
wasn't through and fire was blowing through the exhaust.

So here are the questions: 1.) Has anyone seen an airboat run at night?
Does the entire exhaust normally glow cherry red like that? I could maybe
understand the headers glowing a little but not the entire exhaust.

2.) I saw a plastic holding tank with water in it and asked what's that?
He said it's the coolant catch can/reservoir. I asked why is the water
clear, are you using coolant? He said that it's weird, another person he
knows with an airboat also has that problem. Is this possible? The coolant
was definitely green when I drained the block. He claims it some how
separates and turns clear when it gets to the reservoir. Is this possible?

Might be detonating and that would explain the running hot. Cylinder walls
and piston tops looked ok? You could be right about the timing. Or it's
running too rich. I have seen some pretty hot exhaust. Marine engines run
a lot closer to full tilt that they ever do in a car. Imagine driving your
car 100 miles a hour for 30 minutes. If those stud have already pulled up
once you probably should go ahead and tap them out and put screw in studs.
You don't have to machine the top of the bosses if you're not adding guide
plates. Just get regular studs.

"kevin" wrote in message
...
My brother made an airboat and has been riding around in it for about a
year. It has a new Chevy 350 300HP "Hi-Po" engine in it, Weiand intake,
Carter 625 carb, and Mallory Unilite distributor. He calls me up and asks
if I would change his head gaskets cause he heard a "ticking noise". I am
a
pretty good backyard mechanic. I go over their and just to appease him,
I
didn't think the head gasket was blown, I tore into the engine.
Immediately
I notice the some of the rocker studs were pulled up, some as much as a
1/4
inch. I took the heads to work and pressed them back down. I asked "does
this thing run hot?" usually heat can pull the studs up, he says "yes, all
the time". I start putting the motor back together and am about to fire
it
up. I put the #1 cylinder at top dead to get a good start for the timing
then I notice no timing tabs connected to the timing cover to show where
to
time the engine. I say "how did you time this thing?" he says "I just
turned the distributor until it ran good"(that's bad). I noticed a set of
bendable stainless exhaust pipes connected to a set of Headman stainless
mufflers in a pile next to his garage and asked "what happened here?" he
said that they get hot and get ruined, all burned up. He said that when
he
drives the boat at night the ENTIRE exhaust from header to muffler glows
cherry red. I am thinking the timing was so far off the combustion cycle
wasn't through and fire was blowing through the exhaust.

So here are the questions: 1.) Has anyone seen an airboat run at night?
Does the entire exhaust normally glow cherry red like that? I could maybe
understand the headers glowing a little but not the entire exhaust.

2.) I saw a plastic holding tank with water in it and asked what's that?
He said it's the coolant catch can/reservoir. I asked why is the water
clear, are you using coolant? He said that it's weird, another person he
knows with an airboat also has that problem. Is this possible? The
coolant
was definitely green when I drained the block. He claims it some how
separates and turns clear when it gets to the reservoir. Is this
possible?

Running to lean?
What MAX RPM is the engine turning
Timing
Cooling system?
What is the engine temperature?

"kevin" wrote in message
...
My brother made an airboat and has been riding around in it for about a
year. It has a new Chevy 350 300HP "Hi-Po" engine in it, Weiand intake,
Carter 625 carb, and Mallory Unilite distributor. He calls me up and asks
if I would change his head gaskets cause he heard a "ticking noise". I am
a
pretty good backyard mechanic. I go over their and just to appease him,
I
didn't think the head gasket was blown, I tore into the engine.
Immediately
I notice the some of the rocker studs were pulled up, some as much as a
1/4
inch. I took the heads to work and pressed them back down. I asked "does
this thing run hot?" usually heat can pull the studs up, he says "yes, all
the time". I start putting the motor back together and am about to fire
it
up. I put the #1 cylinder at top dead to get a good start for the timing
then I notice no timing tabs connected to the timing cover to show where
to
time the engine. I say "how did you time this thing?" he says "I just
turned the distributor until it ran good"(that's bad). I noticed a set of
bendable stainless exhaust pipes connected to a set of Headman stainless
mufflers in a pile next to his garage and asked "what happened here?" he
said that they get hot and get ruined, all burned up. He said that when
he
drives the boat at night the ENTIRE exhaust from header to muffler glows
cherry red. I am thinking the timing was so far off the combustion cycle
wasn't through and fire was blowing through the exhaust.

So here are the questions: 1.) Has anyone seen an airboat run at night?
Does the entire exhaust normally glow cherry red like that? I could maybe
understand the headers glowing a little but not the entire exhaust.

2.) I saw a plastic holding tank with water in it and asked what's that?
He said it's the coolant catch can/reservoir. I asked why is the water
clear, are you using coolant? He said that it's weird, another person he
knows with an airboat also has that problem. Is this possible? The
coolant
was definitely green when I drained the block. He claims it some how
separates and turns clear when it gets to the reservoir. Is this
possible?

JamesgangNC wrote:

Might be detonating and that would explain the running hot. Cylinder
walls
and piston tops looked ok? You could be right about the timing. Or it's
running too rich. I have seen some pretty hot exhaust. Marine engines
run
a lot closer to full tilt that they ever do in a car. Imagine driving
your
car 100 miles a hour for 30 minutes. If those stud have already pulled up
once you probably should go ahead and tap them out and put screw in studs.
You don't have to machine the top of the bosses if you're not adding guide
plates. Just get regular studs.

The cylinders, valves, plugs and pistons looked fine that I could tell.
It's too late for the machining of the heads as I put everything back
together. It's just the part about the entire exhaust glowing red that has
me confused and the coolant reservoir tank having clear fluid in it.

Woodchuck wrote:

Running to lean?
What MAX RPM is the engine turning
Timing
Cooling system?
What is the engine temperature?

It could be running to lean, not sure but the carb is box stock but I did
set the idle mixture screws. He keeps it around 4000 rpm but it doesn't
overheat when he is going fast, just going slow. The timing I am not sure
about but I am going to get some timing tabs and run it at 8 degrees before
top dead center. the cooling system is very good, in my opinion. Its an
aluminum Griffin four core with an electric fan and no air in the system
that I could see and the radiator cap looks good as did the thermastat,
plus the fact that the engine just sits out in the open and he also bought
a small "radiator" that straps on to the oil filter. The motor will
definitely peg the 250 degree mark on the temp gauge but comes down once he
gets going at a good speed. I also noticed that the choke was not hooked
up and when I asked why he said cause it detonated. I am almost positive
it was just set up wrong with the timing. But have you ever heard of
coolant seperating? Having green coolant in the block but clear in the
reservoir? If I see it again I am going to see if its water from what he
is boating on.

kevin wrote:
Woodchuck wrote:


Running to lean?
What MAX RPM is the engine turning
Timing
Cooling system?
What is the engine temperature?


It could be running to lean, not sure but the carb is box stock but I did
set the idle mixture screws. He keeps it around 4000 rpm but it doesn't
overheat when he is going fast, just going slow. The timing I am not sure
about but I am going to get some timing tabs and run it at 8 degrees before
top dead center. the cooling system is very good, in my opinion. Its an
aluminum Griffin four core with an electric fan and no air in the system
that I could see and the radiator cap looks good as did the thermastat,
plus the fact that the engine just sits out in the open and he also bought
a small "radiator" that straps on to the oil filter. The motor will
definitely peg the 250 degree mark on the temp gauge but comes down once he
gets going at a good speed. I also noticed that the choke was not hooked
up and when I asked why he said cause it detonated. I am almost positive
it was just set up wrong with the timing. But have you ever heard of
coolant seperating? Having green coolant in the block but clear in the
reservoir? If I see it again I am going to see if its water from what he
is boating on.

We don't have air boats, however we do have plenty of hovercraft around
here, same idea.

The symptoms sound like detonation & as you allude the timing was
definitely suspect, if he just turned it till it ran best then it's
surely over advanced, add heat & detonation is in prospect.

The other less obvious thing is a lean mixture at high power causing
detonation. With some of the hovercraft, the engine is in proximity to
the fans low pressure side, if the carb is the normal top vented type
then the mixture can get leaned, a vent hose to a less effected (normal
atm press) area is the suggestion.

K