4.3 LX water in the oil...

[Scott06]

Well I did the acetone test on the exhaust manifolds and they were okay. I'm definitely going to have to replace them at some point though as the rust is getting pretty bad. I tried to do a pressure test on the block but I couldn't get the right parts to get a good seal to pressurize it. I am pretty confident that it's fine though as, like I've said before, It's closed cooled and I had it wrapped in heat trace every winter.

Here's a shot of the Port side after the exhaust manifold was removed. #4 Cylinder is definitely wet.
View attachment 398469

This video gives a better look: VIDEO

Here's the Starboard side, and the #3 Cylinder is also wet.
View attachment 398470

Starboard side video: VIDEO

I next pulled the intake...
View attachment 398471

Here's a better video of the intake sides and valley: VIDEO

One more shot of the underside of the Intake:
View attachment 398472

And subsequent video: VIDEO

Anyway, I will be doing a leak down test in the next few days (now that the tool arrived), and then go from there. So what do you guys think? Anything obvious!

Rust in several
Exhaust ports is sign water is getting into exhaust

May be from head cracks
Or exhaust system leaks

Is there a crack in bottom of intake thermostat housing ?

 

[Swedefj40]

Rust in several
Exhaust ports is sign water is getting into exhaust

May be from head cracks
Or exhaust system leaks

Is there a crack in bottom of intake thermostat housing ?

I didn't notice any anything in the bottom of the thermostat housing. Are you meaning inside where the thermostat is or underneath the intake manifold?

I also noticed the area around both middle coolant runners on the underside of the intake manifold looks quite black. Is that normal?

 

[Scott06]

I didn't notice any anything in the bottom of the thermostat housing. Are you meaning inside where the thermostat is or underneath the intake manifold?

I also noticed the area around both middle coolant runners on the underside of the intake manifold looks quite black. Is that normal?

On underside of thermostat housing /water cross over underside of intake

There are no middle coolant runners this is an exhaust crossover to heat choke stoves and intake. So you are seeing exhaust soot

 

[Swedefj40]

On underside of thermostat housing /water cross over underside of intake

There are no middle coolant runners this is an exhaust crossover to heat choke stoves and intake. So you are seeing exhaust soot

I'll have a look at the thermostat housing tomorrow. The previous owner had an issue with a stripped housing bolt and had the shop retap it. May be an issue there? I'm not sure that, if I have a leak there, how it would show up as a wet exhaust port?

Thanks for the clarity on the cross over runner. I guess that's why the divorced choke heater is mounted on it LOL.

 

[dubs283]

Those heads are toast. Might get lucky with a reman but based on pics it's doubtful

No clue where the water is coming from but a cracked head wouldn't surprise me along with manifold/riser issues

 

[Swedefj40]

I'm going to do a leak down test tomorrow and see if that'll shed some light on things.

 

[Swedefj40]

Updates... leakdown tests confirm the valves aren't sealing, but rings are good. Dropping off the heads at the speed shop to be fluxed and rebuilt. Hopefully back together in a few weeks.

 

[Lou C]

Did this engine have those one piece batwing manifolds on them? I know you said the passed the acetone test but I wonder if they leaked when they got hot? Those manifolds were known to be troublesome, I think they were used from 96-99. There is a Merc conversion kit to change it to the normal 2 piece system & I think Barr makes an aftermarket version of the same thing.

 

[Swedefj40]

Did this engine have those one piece batwing manifolds on them? I know you said the passed the acetone test but I wonder if they leaked when they got hot? Those manifolds were known to be troublesome, I think they were used from 96-99. There is a Merc conversion kit to change it to the normal 2 piece system & I think Barr makes an aftermarket version of the same thing.

They're the 2 piece manifolds/elbows style exhaust.

 

[Lou C]

Ah yep thought it had the Merc Batwings based on the year range but someone already up dated it. Then you did say you had full closed cooling. Your heads & block look good but I guess the machine shop will tell the tale. The block deck you’ll be able to judge when you get all the gasket material off. When you pull off the head gaskets look at where the fire rings connect to the rest of the gasket material. Mine had slits in them right near a water passage. The heads had cracks in the center cyl exhaust valve seat. So replaced both.

 

[Swedefj40]

I'm learning as I go with regards to this engine and how to read the gaskets. That said, Cyl#'s 5 & 6 both look to me like there's rust stains on the head gaskets at the "Fire Rings"(?) I also noticed the lip at the back of the intake/block, where you apply sealant, and right around the sensor, wasn't sealed very good. It was showing rust stains on the block surface.

Anyway, before I order new head bolts, do I need TTY or TTA bolts for my engine? Seems to me that my year of engine is a transition year for GM/Mercruiser engines.

 

[Swedefj40]

I found it...

 

[Lou C]

Even before you get to that point...
get a thread chaser (not a tap) and clean out all the cyl head bolt threads in the block and make sure that the new bolts will fully thread all the way in. Your engine is closed cooled so they will probably be pretty clean but on a raw water cooled engine they are loaded with crud.
Now those I am guessing are the procedure if using GM or Merc gaskets, if you use other brands (like Fel Pro or other) check with them, to see if they advise the same. I used Fel Pro Marine (blue) head gaskets and they sealed well, with the new ARP head bolts I used.

 

[Scott06]

I'm learning as I go with regards to this engine and how to read the gaskets. That said, Cyl#'s 5 & 6 both look to me like there's rust stains on the head gaskets at the "Fire Rings"(?) I also noticed the lip at the back of the intake/block, where you apply sealant, and right around the sensor, wasn't sealed very good. It was showing rust stains on the block surface.

Anyway, before I order new head bolts, do I need TTY or TTA bolts for my engine? Seems to me that my year of engine is a transition year for GM/Mercruiser engines.

Gen plus is the newer true Vortec head engines with 8 bolt intakes. Bolts are vertical two in each corner of intake

 

[Lou C]

Also:
On the Gen + true Vortec keep in mind that the intake manifold bolts take much lower torque than the pre Vortec, IIRC pre Vortec is like 30-35 ft lbs whereas the Vortec is like 15 ft lbs.
I think there was a mistake in the Mercruiser shop manual when the Gen + first came out that used the old torque spec but was later corrected maybe in a service bulletin….

 

[nola mike]

Also:
On the Gen + true Vortec keep in mind that the intake manifold bolts take much lower torque than the pre Vortec, IIRC pre Vortec is like 30-35 ft lbs whereas the Vortec is like 15 ft lbs.
I think there was a mistake in the Mercruiser shop manual when the Gen + first came out that used the old torque spec but was later corrected maybe in a service bulletin….

Yes, I snapped a bolt on the intake using the values in the manual

 

[Lou C]

The Vortec intake gaskets are kinda delicate too. I actually prefer the pre Vortec. Those never had intake gaskets leaking coolant into the cam valley like on many GM cars the first few years of production till they changed the gaskets and publicized the change in the torque specs

 

[Swedefj40]

Dropped the heads off at the speed shop. They're going to flux them and deck them and do the valves, plus a bunch of other stuff. They'll let me know if there's any issues with them.

 

[Swedefj40]

Dropped the heads off at the speed shop. They're going to flux them and deck them and do the valves, plus a bunch of other stuff. They'll let me know if there's any issues with them.

Heads are good, no cracks, exhaust seats are hammered though and will be replaced. I also ordered new exhaust manifolds just to be on the safe side. Old ones were pretty rusty. Should start to put things back together next week.

 

[Lou C]

I’d wonder why the exhaust seats were hammered?
Low octane fuel?
Lean fuel mix?
Too much spark advance?
Boat is not reaching specified max rpm with current prop?
All those should be investigated to avoid a recurrence….

BTW I know some think that 87 octane fuel is fine but my old OMC Cobra has a sticker on the flame arrestor indicating that 89 octane fuel must be used or else the timing should be retarded a few degrees. Our gas dock sells only 93!
Anyway never had pinging or detonation running on 89 or higher octane. Marine engines are highly loaded all the time…