to overhaul - or not to overhaul... that is the question.

[CruiserHopeful]

I am at the point in disassembly where I decide whether or not to take the block apart. Head is off, valves are all pulled.

The main reason I did this was because I was getting a TON of smoke at operating temperature just POURING out of the oil fill cap (and my temporary fix involved getting a rubber stopper and about 15' of 1" hose, and just ran it out the port side head porthole while running the engine, so all the smoke wouldn't fill up the cabin). It was one of two things: cylinder blowby or valve guide blowby.

The first thing I did was a compression test, at operating temperature, even before the engine came out of the boat.

Results were basically 90-90-90-90 for each cylinder dry. (that is good - I think)

then I did a wet compression test and got approximately 97-110 for them.

But the smoke kept coming. Coming and coming and coming. I got fed up with it and decided that I was going to start taking the thing apart to try and see if there was any obvious maladies with the engine (scratched cylinders or something). So I took the head off and looked at each cylinder wall - they looked pretty darn good except for the following:



The red areas are barely visible in just the right angle of light and not even feelable unless you REALLY focus and use your fingernail to scratch it... light vertical scratches.

I am also able to wiggle the piston around in the cylinder at TDC, so I know for a fact that the rings are not frozen.



These things are telling me that maybe I was wrong all along? maybe its NOT the cylinders that are the problem?? Could it be the valve guides? and if so - then how hard is it to size/install new ones? What about lapping the valves and the seats?

I guess my main question is: how do I know for CERTAIN that the blowby is occurring at the valve guides OR the cylinders? I've done basically everything test-wise to determine

[SailorT]

First thoughts

My first thoughts, for what they're worth ...

You say that you can "wiggle" the piston inside the cylinder at TDC ... what kind of "wiggle" are you talking about and how much? Is it up and down or side to side? I don't think the pistons should wiggle in the cylinders - they should be set in there with only enough room between the piston and cylinder wall so the piston can move up and down, and the rings are supposed to make the pistons fit air tight.

Your compression sounds solid, both the numbers and the fact that they're consistent. If the compression is sound then the valve guides are suspect. Since the valve guides are not in the compression cycle, their soundness is not measured by the compression test.

One idea you could do is plug the oil fill cap to prevent the smoke from coming out and see what happens. Does the smoke build up pressue? Does it come out somewhere else, such as through the PCV? Does the performance of the engine change when you prevent the smoke from coming out the oil fill cap?

Also, since I'm assuming you're sure that this is exhaust smoke, what kind of exhaust and cooling systems do you have, fresh water or raw water? Is the discharge from those systems normal?

[CruiserHopeful]

My first thoughts, for what they're worth ...

You say that you can "wiggle" the piston inside the cylinder at TDC ... what kind of "wiggle" are you talking about and how much? Is it up and down or side to side? I don't think the pistons should wiggle in the cylinders - they should be set in there with only enough room between the piston and cylinder wall so the piston can move up and down, and the rings are supposed to make the pistons fit air tight.

Your compression sounds solid, both the numbers and the fact that they're consistent. If the compression is sound then the valve guides are suspect. Since the valve guides are not in the compression cycle, their soundness is not measured by the compression test.

One idea you could do is plug the oil fill cap to prevent the smoke from coming out and see what happens. Does the smoke build up pressue? Does it come out somewhere else, such as through the PCV? Does the performance of the engine change when you prevent the smoke from coming out the oil fill cap?

Also, since I'm assuming you're sure that this is exhaust smoke, what kind of exhaust and cooling systems do you have, fresh water or raw water? Is the discharge from those systems normal?

I asked a fried who works on car motors what he thought about my problem, and he told me "put each cylinder to TDC and then with your fingers, try to wiggle the piston around in the cylinder. If it can move around freely then the rings are not frozen. If you are unable to wiggle them around, then the rings are bound up inside the piston and they are frozen. Every engine is supposed to have a little play in the pistons/rings like this. The rings are free floating entities". It made sense, and is a quick and free diagnostic tool.

There was a lot of pressure coming out of the oil fill cap, and no I never DID plug it up 100% for longer than like 30 seconds to try and see what would happen for fear of what that might do to the rest of the engine - I figured that if burning oil wanted to come out of my engine, it would come out any way possible... or something . After the 30 seconds though, the smoke would POUR out of that PCV hose and would inundate the carb to the point of very very bad performance.

By the way, I'm actually not entirely sure if it was exhaust or burning oil. I figured it was oil burning because it didnt smell like exhaust fumes (they are distinct, I couldn't smell fuel)

Cooling is raw water, and everything SEEMED normal as far as exhaust fumes/exhaust water coming out the back in my opinion.

[Marian Claire]

My understanding is that blowby is a piston/cylinder/rings issue. Your compression #s are on the lower end of the OK range and indicate an evenly worn engine. But it sounds like a lot of smoke. What is your oil usage? What do your plugs look like? Judging by your name I would be thinking rebuild. Dan S/V Marian Claire
Edit: Welcome to the forum.

[ndutton]

Another thought. I tend to approach these things aggressively so being this far into the engine already, why not go a little farther and do a full rebuild, (bearings, rings, the works)? That way no matter what the issue you're covered.

One of Don's short blocks or long blocks may be an attractive adoption.

[CruiserHopeful]

Another thought. I tend to approach these things aggressively so being this far into the engine already, why not go a little farther and do a full rebuild, (bearings, rings, the works)? That way no matter what the issue you're covered.

One of Don's short blocks or long blocks may be an attractive adoption.

While I agree with this philosophy - I have a hard time swallowing that cost. I found this boat for a steal when I bought it a year ago, and have already spent 10k on it (that includes the purchase price of the boat by the way). So to spend about the SAME amount of money that I spent buying the entire boat - on fixing the ENGINE? It hurts.

I do have another option though: I have an opportunity to purchase a good running a-4 closeby for about 2k, and I could then just drop it right in and not even worry about this. A mechanic told me that if I had him fix this up for me (certified for atomic 4's) that it would cost either 2k or even upwards of that.

I hate spending money, and I HATE spending money on things that don't - for 100% - need that work done.

If you know what I mean.

[ndutton]

I didn't mean to be insensitive. It's easy to spend someone else's money. It may help explain why the price was so good.

I'm somewhat of a veteran of the unbelievable price backlash. I bought my boat so cheap that my marina of choice wouldn't even accept my application until their dockmaster made a personal inspection and signed off. Based on price alone they were certain it was half sunk. Similar problem getting insurance.

[Dave Neptune]

Smoke?????

CruiserHopeful, here's another thought. Since you know the rings are free and the compression is very good I wouldn't be to excited about doing a rebuild. Your compression is much better than mine was 26 years ago when I had the same problem (and she's still running well). I purchased an oil fil cap that had a vent tube on it and hooked a piece of hose to it and ran it into the exhaust fan (I use muine whenever the motor is running) to evacuate the fumes from my cabin. Since then about 6~8 years ago I installed the Indigo PCV kit. This vertually eliminated the fumes and I have now been running for 26 years since I had the head off.
With your good compression and the fact that the valves are seating fine if you have that much compression I would explore two other things first!!!
First I would go ahead and reinstall the head (2 gaskets) and install the PCV kit. The valve-guides in a flat head engine are not as prone to getting oil into the cylinders as an overhaed engine!
Second I would look at and evaluate the oil you are using IE how old is the oil and what type and viscosity are you using? As the oil breaks down it will get by the rings much easier and increase oil consumption. How is the consumption not the smoke with fresh 30wt oil?
How do you use your blower, for starting or fulltime? Also do you keep a vent or forward hatch cracked open while motoring? These to can be factors in fumes building up in the cabin.

Dave Neptune
1970 E-35MKII original A-$ still ticking!!!

[CalebD]

I found this boat for a steal when I bought it a year ago, and have already spent 10k on it (that includes the purchase price of the boat by the way).
...

Still a good price for a Catalina 30' even if the engine is not running flawlessly.

Since you have only had this boat for about a year I have to ask this question: Has the engine ALWAYS been problematic in this manner or is this a symptom that suddenly or gradually appeared?
If this has ALWAYS been a problem with your engine I will stick with my original assertion that I posted on CF that you very well MAY have a blockage in your exhaust system. A complete blockage is a fairly rare occurrence but partial blockages are fairly common. The hoses may look fine on the outside but the inside these hoses can collapse and restrict the flow, creating a back pressure to the engine.
I couldn't find a very scary picture of a collapsed exhaust hose that I have seen here in an older thread but I did find this: http://www.moyermarine.com/forums/sh...+back+pressure

Good luck.

[Marian Claire]

The intended use should be considered in this conversation. Is this a boat you will cruise in? Is this a step before the next boat? Is it for getting out of the marina then up with the sails? When faced with this same decision two years ago I chose, after much inner turmoil, to rebuild it myself. I planed to continue cruising in this boat and using my A-4 for extended runs. For fighting currents and maneuvering around bridges I wanted all the A-4 could give. I am not a mechanic by any stretch. The rebuilding taught me allot about the engine and I have a complete maintenance history since the rebuild. Good luck with which ever way you go. Dan S/V Marian Claire