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  #1   IP: 50.255.147.157
Old 07-24-2018, 10:55 AM
TomB TomB is offline
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Diagnosing no compression post water in cylinder

Hello I’m a newbie to the Atomic 4 world and was hoping to get some advice/input from the experts out there. I should first thank this forum for all the information i have gathered up to this point. The moyer manual has been a great help also.
Without going into all the gory details, a friends Pearson 28-1 had flooded with 10 inches of seawater, and unfortunately the other friend who had discovered it bail it out and unsuccessfully tried to start the engine.
I climbed on board the next day, fixed the leak in the boat and took a look at the engine. I took off the drain plug and water came gushing out of the block. Oh boy. I siphoned the rest of the oil out and replaced with 4 fresh quarts and a can of seafoam (I have since replaced with 50/50 sae30/ATF).
I took out the spark plugs and gave the engine a bump, and yep, water fountains. Mostly out of 3 and 4. I pour some mystery oil in the chambers and gave another bump, a little more mystery oil and lightly replaced the spark plugs (it was getting dark).
Eventually i did a compression test. Dry 115,115,85,0. Eeek. Did a wet test with cylinder 4 and it came up to 85. So I concluded most likely a cylinder problem and hopefully a ring.
Next day i proceed to work on getting the head off, the cylinder 4 end came loose rather easy with a few taps. The thermostat corner on the other end, however, was not as compliant. I did a little work on it and went home to let PB Blaster continue the work.
I was still a little wary about the diagnosis. I had read about blowing compressed air in the cylinder to listen where it came out. So the next day I torque the head back down to specs and blew air into the cylinder. I had my ear near the oil fill expecting to hear the air, however, i felt the air coming out of the thermostat housing????, hmmmm… i’m thinking a blown gasket maybe? I was actually somewhat relieved (let’s call it wishful thinking, though). Days later, plenty of pb blaster and tapping on the studs and i get the head off. See the pic below. Explained the air out the thermostat.
Thought i found the problem, however, it started bugging me that the wet test was 85. Would mystery oil really be able to clog even a tiny sliver of a crevice at the top of the cylinder head to bring compression to 85? I looked back at the pics of the block that i had taken when i first removed the head and sure enough there was a gunky area right where the hole was. Perhaps when i loosened the head that piece stuck to the gasket was pulled off the head, but was intact before I loosened the head. And maybe I still have a bad piston ring.
So I decided to pour mystery oil in the cylinders to see if the volumes held. See before pic, and then 2 days later of cylinder 4. Maybe ⅛ inch.
Is MMO too viscous to leak very much? Is there another fluid to better test this cylinder? May 0w30? Any other way of ensuring the ring is good?
Any advice on how to continue would be greatly appreciated. The engine seems in obvious need of an overhaul, but was otherwise running well. We would just like to get the boat running for now and overhaul at the end of the season. The boat is on a mooring and if I have too, I can pull the engine onto a cradle and work on it in the cabin, but of course, would just like to replace the head and gasket, put her back together, flush etc. get her running and finish the season.
Sorry for the lengthy tale, but this is the abridged version.
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  #2   IP: 172.95.97.58
Old 07-24-2018, 05:36 PM
Dave Neptune Dave Neptune is offline
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Tom, welcome to the MMI Afourian Forum.

Don't be so sure of the wet test and the number. As the engine has been flooded the low number on #4 could be a PARTIALLY sticking valve. Zero to 85 is a long stretch for a dry/wet ring comparison.

The head does not look to bad in the pics. Check around the area of the t-stat where you heard the air for metal loss due to corrosion. The head can be easily resurfaced.

If you are a direct drive go for a single gasket as the bump in compression will help SLIGHTLY.

Dave Neptune
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  #3   IP: 24.61.70.122
Old 07-24-2018, 06:33 PM
TomB TomB is offline
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Thanks Dave. 4 weeks ago i had never heard of an atomic 4, but over the last couple of weeks I am finding myself becoming quite attached to this little engine.

I should have pointed out the problem instead of assuming it was easily noticeable. If you look just above the outline of cylinder four you will notice where the water jacket had corroded through. Although most of it was over the gasket area it appears it was just breaching the cylinder chamber. This explains the air coming out the thermostat when i blew air through the chamber.

As i didn't blow air through the chamber until i initially loosened the head, i thought that perhaps the loosening of the head pulled off the corrosion, and that the breach may not have been present when i originally did the compression testing. That's my dilemma. Could i still have a ring problem.

If you think that 0-85 is a stretch for a piston ring than that is reassuring. But it seems a bit of a stretch to me that mmo could have sealed even a small crack at the top of the cylinder during the wet test. but I really don't know.

I am thinking that I will clean up the valves, get a new head/gasket, torque it down, and redo the compression testing. If good, throw her back together.

My friend seems to think this head can be salvaged via some welding/machining. Seems crazy to me, but thought i would drop by a machine shop and ask.

Last edited by TomB; 07-24-2018 at 06:57 PM.
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  #4   IP: 172.95.97.58
Old 07-24-2018, 07:04 PM
Dave Neptune Dave Neptune is offline
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Tom, do any cracks show?

It takes a lot of "opening" to get zero compression. An open valve will do it and if there was a crack in the cylinder it would be a big one and the oil would run out. I'll still bet on the sticky valve.

Get the cylinders dried out and rotate the engine and inspect the bores.

Dave Neptune
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  #5   IP: 24.152.132.140
Old 07-24-2018, 07:16 PM
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ndutton ndutton is offline
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Is this the breach/hole you're talking about? If you opt for repair, why wouldn't the rest of the water passages in the head be just as thin? They're all the same age, all subjected to the same water flow and therefore the same corrosion.

You're buying a new head sooner or later, may as well do it sooner and be done with it.
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  #6   IP: 174.192.4.10
Old 07-24-2018, 07:29 PM
TomB TomB is offline
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Dave: was hard to look for cracks initial inspection(cramped), but didnt see any. Will dry out and take a better look. I have one of those endoscopic cameras, will go over it real well.

Neil: Yes, I agree, would feel more assured with a replacement head.
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  #7   IP: 172.95.97.58
Old 07-24-2018, 07:34 PM
Dave Neptune Dave Neptune is offline
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Good eye Neil! Not really worth the expense of the repair. You may be able to find a used head here, on the net or a new one from our host.

Dave Neptune
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