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Join Date: Feb 2007
Location: Taipei, Taiwan
Posts: 332
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Please help evaluate cylinders
Had a #5 rod failure 3 months ago, probably due to oil starvation or failed rod bolt, and finally got all 6 cylinders out today. The pistons cannot be removed yet because the crank is stuck by debris of the broken big end of the rod. Please help me evaluate the cylinders, thanks a lot!!
1. the #5 cylinder, a small part of the cylinder base is missing, with a reverse L-shaped crack extending upwards. Guess it cannot be used any longer.   2. the #4 and #1 cylinders with carbon deposit along the upper rim, these two cylinders have the best looking spark plugs, almost like new, so they must have been running pretty well but why the carbon deposits not seen in other cylinders not running as well?   3. the #6 cylinder with a fouled plug showed some oil pooling besides the piston when the head was removed.  Cyl #2 and #3 looked like cyl #6, hence not shown here. Please note that all the vertical scratch lines shown on the cylinder walls felt very smooth to the touch.
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'87 3.2 Targa |
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06-21-2009, 06:44 AM
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Location: Nash County, NC.
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If the crank isnt bent, it will be scored big time. Most of the damage is done before the rod breaks loose.
I d get another set of cylinders or P/Cs. If its just cylinders, you need deck height and size, it stamped on the base of the cylinder. Bruce |
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06-21-2009, 06:00 PM
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Location: Cape Vincent, NY
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Bruce is right, crank is probably toast. new piston and cylinders probably good idea too. The difference in carbon deposit could be from adjustment on the carbs. The scratch lines are not abnormal. The busted one is definitely dead, but wear and possible cracks may be in the others too. It is not unheard of to find hairline cracks on cylinders with magnaflux inspection after a rod failure as the sudden change in the engine balance and rotation slam the pistons around, especially on lighter weight engines like Porsche where there is less "hard" material around the cylinder. If you decide to reuse your "good" cylinders double-check the measurements and get them inspected for cracks first.
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1968 911S "Leona" Air goes in and out, blood goes round and round, any variation on this is a bad thing. |
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06-22-2009, 03:04 AM
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Thank you both! Did learn more than had expected. Have to consider a good set of used p/c now.
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'87 3.2 Targa |
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06-22-2009, 04:15 AM
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Air Medal or two
Join Date: Jul 2003
Location: cross roads
Posts: 14,081
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My vote is measure the broken cyl for "round' as a hit like that may have distorted the whole thing
If round..looks like you could just "eyebrow it " like a lot of us do any way. Send it off to your favorite re chrome -nich place, have therm done, and call it good.
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D troop 3/5 Air Cav,( Bastard CAV) and 162 Assult Helicopter Co- (Vultures) South of Saigon, U Minh Forest, Delta, and all parts in between |
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06-22-2009, 11:22 AM
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The "eyebrow" mod you talk about is on the sides, not the top and bottom. Those look like Alusil to me so why not just get a nice used set of Nikasil.
-Andy
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72 Carrera RS replica, Spec 911 racer |
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06-23-2009, 05:28 PM
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The photos don't show the flare of Nikasil because I want to show the scratches clearly.
They are definitely Nikasil.
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'87 3.2 Targa Last edited by alniki; 06-23-2009 at 11:53 PM.. |
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06-23-2009, 08:48 PM
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