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Help! 944 Cylinder Wall Scratches

Well,

Long story short.....

Had a "friend" help me rebuild a 944 engine. At some point (I was not around) he put the cam tower on and did not set the cam to TDC. When he attempted to start the engine, it bent valves.

After removing the head, there is noticable scoring on one cylinder. At this point, the "friendship" is over and I need to get my car out of his place.

When the engine did not start, a compression test was done and that cylinder did have decent compression. Also, we put some assembly lube around the top of the bad cylinder's piston, and it did not seep below the rings.

Would anyone attempt to use this engine? I am concerned that if I do not help my friend re-install the engine and subframe, I will not be get all my parts back, (he's got parts from ton's of cars scattered around) yet do I go through an engine re-install with scoring the way it is?

Again would anyone put this engine back in the car and run it? It is a race engine, and a little smoke would not be the worst thing, but could I even get a season out of it????

I think I know the answer, but it makes me ill......

Thanks!!!
Old 01-05-2006, 07:58 AM
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No. Tear it down and have a machine shop bore it.
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Old 01-05-2006, 08:36 AM
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Too expensive too do that....probably cheaper just to get a new block
Old 01-05-2006, 09:58 AM
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Guys, is there not a way this one cylinder can be honed, to remove a light scratch, and keep the car in service without pulling the whole engine?

I know it takes a special tool, but I am wondering if there is a reasonable way to help this guy without pulling the motor.

Just curious.

P
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Old 01-05-2006, 11:38 AM
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A used engine is your cheapest route.

Unfortunately you do not have any other choices...

..P Pulling the engine is the least of his problems. An NA engine can be on a stand fairly quickly. The surface can't be honed.

I would run it with scratches that are maybe a thousand (finger nail catches it). On a turbo probably not.... but thats just me.

If you have pictures it would be nice.
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Old 01-05-2006, 11:50 AM
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Let me clarify...

The engine is out of the car, and that is why I am considering not putting it back in the way it is. The block was used but supposedly "like new". All new pistons, connecting rods, and rings were installed. I am assuming the damage was done when the engine was being started for the first time. This is when the valves were bent.

To complicate things, the car is 5 hours from my home.

As much as I hate to do it, I am thinking of bringing it back with out the engine, get a new block, and swaped everything over...

The alternative is to put it back in the car and see how it runs.....
Old 01-05-2006, 12:47 PM
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Quote:
Originally posted by 944CUPRACER
Let me clarify...

The engine is out of the car, and that is why I am considering not putting it back in the way it is. The block was used but supposedly "like new". All new pistons, connecting rods, and rings were installed. I am assuming the damage was done when the engine was being started for the first time. This is when the valves were bent.

To complicate things, the car is 5 hours from my home.

As much as I hate to do it, I am thinking of bringing it back with out the engine, get a new block, and swaped everything over...

The alternative is to put it back in the car and see how it runs.....
Without actually seeing the damage it is difficult to give you an accurate answer.

New pistons/rods don't mean much to me they are not something that normally fail. Well if they do its game over for the entire assembly.......... but If you decide to rebuild another engine you will still need 500-1000 in new seals/gaskets.

Now you mention that the bore is scorred. Now the only way this happened is if a valve actually broke and caused the damage. Bent valves do not normally cause a ruined block. I would think something else has happened to score the block ?


Sorry can't help much else...
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Old 01-05-2006, 01:06 PM
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ae1969,

I agree, something dropped down to cause that damage, but I was not there when the head was removed, and couldn't find anything upon examination. It just kills me to put a an angine up in a car that has such an issue. It could smoke like a pig and destroy the rings in a couple of months. Or, it could be fine......

Just think I should do it right the first time.
Old 01-05-2006, 01:52 PM
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If you can feel the scratch, it is too deep to leave and not cause more damage.

..P, FYI, no, there really isn't a way to do it in the car, which is unfortunate. You need a sunnen machine to do it correctly.

If you are close to a Porsche dealer, they can or should be able to refer you to a shop that can re-hone the cylinder. If it isn't too deep, they may be able to "buff" it out with the silicium paste. Otherwise, you will be looking at a oversized piston and rings. Fortunately, you only have to change the one that is bad.

AFJ
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Old 01-05-2006, 02:19 PM
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Quote:
Originally posted by AFJuvat
If you can feel the scratch, it is too deep to leave and not cause more damage.

..P, FYI, no, there really isn't a way to do it in the car, which is unfortunate. You need a sunnen machine to do it correctly.

If you are close to a Porsche dealer, they can or should be able to refer you to a shop that can re-hone the cylinder. If it isn't too deep, they may be able to "buff" it out with the silicium paste. Otherwise, you will be looking at a oversized piston and rings. Fortunately, you only have to change the one that is bad.

AFJ
Is it possible to rebore these cylinders? I was under the impression the bores are specially treated for long life but can't be rebored.
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Old 01-05-2006, 02:46 PM
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These cylinders can be bored, but be prepared to spend big bucks. You will then need over-sized pistons, over-sized rings, etc.
It's a very expensive process that I just went through.
IMO if the scratch is barely enough to catch a fingernail on, run it like that. Honestly you won't be able to tell.
Pictures help, but it's probably fine.
Check the depth of it with a fingernail, and report back.
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Old 01-05-2006, 03:53 PM
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