350/5.7 Exhaust valve seal leak + low compression

[roos]

Hi,

I have an Indmar Assualt 5.7 / 350 TBI from 2002. Engine very similar to a Mercruiser, hopefully it is ok to post in this part of the forum, didn't find Indmar.

Background:
Last year my exhaust valve spring on #7 cylinder broke, it just snapped. I didn't run the engine and got towed to dock. I replaced the spring and the valve stem seal (which was damaged). Luckily everything seemed fine after that. Compression was good (190 PSI) and engine ran great.

This season I have been experiencing some intermittent hard starts (not very, but needed to give a bit of throttle) combined with some blue smoke at start up, that quickly disappeared.
Late in the season once or twice I heard what I think was sticking valve(s) that faded and disappeared once engine was warm.

I did a compression test yesterday and found that all cylinders show 180-200 PSI except #7 that reads 100 PSI. I don't have the equipment to perform a leak-down test, but blew air into the cylinder (at TDC) with my compressor. I could hear the air leaking out the exhaust.
As I had already winterized my engine and the ambient temperature is right around freezing now I performed these tests on a (very) cold engine.

After pulling the exhaust manifold I can see that the #7 exhaust port is wet or rather oily. The valve stem is covered in what I believe is oil, but even the walls look wet. The other ones all look about the same, not pretty, but dry carbon a some rust spots that I guess is due to condensation in the exhaust.

Since I had to pull my heads a few years back at that time I bought a fel pro 17232 gasket set and included in that I got 16 valve stem seals in a bag stamped 70817B.
They don't look the same as the ones originally on there. These have a steel spring instead of a steel "jacket" around them. But from what I understand they should be the correct replacement. This is what I put on #7 exhaust valve anyways.

So questions are:
Why is the #7 exhaust wet with oil? Leaking valve seal?
Can this explain the low compression?
Will it then get better if I start the engine and run a hot test, thinking that maybe the excessive oil will be burned from the engine running and then the valve might seal better?
Is this the wrong seal or did I mess up installation? Or does it rather indicate a damaged valve guide?


Thanks for any help!
I am attaching pictures of the oily (I smudged the oil a bit with my finger before snapping the pic) and "normal" exhaust ports.

 

[alldodge]

The valve seals will keep oil out IF the valve stem and guide are within spec. With it only being on 7 I'm thinking the guide and/or valve need replacing.

The 180 to 200 psi on the other cylinders is to high unless the motor is designed to run with high compression, meaning it requires 93 octane (Would be specified by Indmar). Could also be your gauge is defective or your getting water in the cylinders.

There is oil but also shows signs of water is there.
The gasket set is for a pre-vortec motor but is a marine set

 

[nola mike]

The valve seals will keep oil out IF the valve stem and guide are within spec. With it only being on 7 I'm thinking the guide and/or valve need replacing.

The 180 to 200 psi on the other cylinders is to high unless the motor is designed to run with high compression, meaning it requires 93 octane (Would be specified by Indmar). Could also be your gauge is defective or your getting water in the cylinders.

There is oil but also shows signs of water is there.
The gasket set is for a pre-vortec motor but is a marine set

Either way, the seal wouldn't affect compression. That means your valve isn't seating correctly for whatever reason. As AD said, that would be valve, guide, or seat.

 

[Rick Stephens]

A leak down test would tell you. A vacuum gauge will also show a loose or leaky valve guide with a needle twitch.

 

[Scott Danforth]

check your pressure gauge. at between 180 and 200 you are reading between 30 and 50 psi higher than when the motor left the factory. that is usually oil in the cylinders or a faulty gauge

a rusty valve or seat would give you at least one hole reading low. do a leak-down test as suggested.

 

[roos]

Thanks for all the input.

I am pretty sure the 17232 gasket set is the correct one, it is stated to be Vortec. "FEL-PRO 17232 HEAD SET, GM 5.7 LITER, VORTEC ENGINES, 8-BOLT INTAKE MANIFOLD". And the intake gaskets did fit.

Maybe you were referring to the Valve Seals 70817B. And those are not the correct ones, I have now figured out. I didn't know better and used that one last year when replacing the valve seal for for #7 exhaust. There are some info out there on the internet that makes it seem to be interchangeable with the mercruiser original ones, I don't know what is correct really. And I also didn't know it was supposed to be used together with a little o-ring on the valve stem, so I have been running without it and it didn't properly fit on the valve guide so I guess it has been leaking pretty bad on that one exhaust valve.
The fel pro kit also included 16-72861 valve stem seals which looks to be the right ones, at least same kind as was on there before.

The compression tester is likely not accurate, but at least it is consistent. I have been having around 190 PSI on all cylinders since 2015 when I had to pull the heads (first and only time so far). So let's assume it is reading 15-20 % high. Regardless it is consistently saying that compression is significantly lower on #7 and I can feel the pressure escaping the exhaust valve. All other cylinders when pushing compressed air into them seem to hold the pressure. The force from the air turns the engine over unless I hold the engine from being able to turn over. And pressure seem to stay in the cylinder until I release the rubber bushing I use around my air gun. I understand this is far less accurate than an actual leak down test, but it at least tells me that all other cylinders seem far better than #7.

I am going to start the engine and hope that running the engine will burn off all the oil-sludge that is in #7 exhaust port and on the valve in hopes that it will then seal. If it doesn't I guess the valve seal leak have caused a sticking valve or less than ideal valve sealing for enough time to let the exhaust valve burn and that I need a new valve or at least a valve lapping on that one.

Is there anything I can use to clean the valve while the head is still on? Carburator or break cleaner? But I guess it will seep into the cylinder, not sure if that is ok. (I will of course change my oil afterwards).

 

[Scott Danforth]

Is there anything I can use to clean the valve while the head is still on?

No, head needs to come off and go to a machine shop. you cant clean rust with carb cleaner.

 

[Lou C]

The heads have to come off. Both pics show evidence of water leaking in from the exhaust or other sources and you have either bad valve seals and/or guides.
Here’s a pic of my old engine when I had the manifolds off to change them. At the time the engine was 23 years old used in salt approx half of that...

 

[roos]

Hi,

Now the (so far) one head is off. And I removed the exhaust valve that isn't sealing.

Now I will try to find a machine shop that can fix this. (I am located in Sweden, Europe, so you probably don't have any nice suggestions...)

Thanks for the input.

 

[Lou C]

Find one that caters to American muscle cars.

 

[Scott Danforth]

Or order a new set of heads for $850 and ship from the US (about $125)

 

[roos]

On top of price + shipping it would be 30 % VAT and Customs when importing to Sweden. So Roughly $1270. I have found a machine shop that will grind the seats and valves for $300-350 locally.
Not sure if it is worth it spending the extra on new heads as the engine is already 19 years old with somewhere around 1200 hours. Most of it in salt water.

 

[Lou C]

I did the same thing on my engine when it was about 29 years old used 15+ years in salt water. Due to an overheat both heads were cracked in the valve seat area in the center cyls on the V6 head. The machine shop I took them to felt the cooling passages were getting too eroded for them to seal well against the new head gaskets. And I’d heard of cyl heads rusting through behind the valve seats causing a hydrolock. So I took their advice and installed a set of remanufactured heads. Three years later still running well. The heads seem to rust through much sooner than the block in salt water. Don’t forget to replace your exhaust system since you had water getting in.

 

[Lou C]

here's what the intake port looks like on an older raw water cooled engine. who knows how close to rust thru they were.....