Home › Forum › Ask A Member › Beginning a CD-12 adventure › Re: Beginning a CD-12 adventure
OK, I see the brown streak in the upper cylinder. The brown streak probably is due to blow by caused by a problem with the upper piston/rings. The good news is that the walls don’t appear to be scored/scuffed, but your pictures aren’t "close up enough" for these old eyes I’m afraid. Unfortunately, the CD series does NOT have intake bypass covers, so there is no way of inspecting that area without pulling the pistons out. I can’t really see much in the exhaust manifold pictures for similar reason, the good news is that you got the exhaust cover off with no problems.
That looks like a nice fresh water CD engine, I’m assuming there are no broken/castings, the engine looks to be in nice cosmetic condition as well. You might want to drain the gearcase lube to make sure it is in good shape before going much further.
So, at this point, you have a decision to make. You could try to soak those pistons/rings in engine tuner/seafoam, perhaps the brown streak is due to stuck rings, although I’m not seeing evidence of this in the exhaust manifold. Did you try to poke the rings in their grooves with a tiny screwdriver to see if they are stuck?
You mention wanting to work on a larger engine, this engine would be a great one to get experience on, like Chinewalker says! Let us know what direction you want to head in, we will help. I’m thinking this engine could be back on track with a new set of rings and gaskets, perhaps with a donor piston/rod from one of your other powerheads that you mention. The 56 powerhead you mention isn’t really compatible with the 55 spring mount engine series.
The first step in dissembling/rebuilding this engine is finding a decent manual, which I’m sure one of us can provide. Let us know how much OMC powerhead work you have done previously so we don’t bore you with basics or leave out important details. These engines are fairly simple to work on, no needle bearings or complex assembly procedures. But, like anything else, there are some simple mistakes to make that will ruin the project for you.
Don