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> Piston Slap?, Advice Please
solex
post Apr 19 2009, 05:52 PM
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I recently performed a top end rebuild on my engine with:
  • NOS Mahle pistons and cylinders
  • rebuild heads from HAM
  • Rebuild Raby rods
  • New Rod Bearings
During the break-in period everything was going well, using Brad Penn break-in oil, performed a tune up with new oil at 100 miles.

At about 150 miles I started to hear a knock at idle, sounded like it was coming from #2. The sound seemed to be some what reduced when the plug wire was disconnected.

At 200 miles I decided to do some more investigation; during oil change I noticed that there was a sludge / silvery substance on the oil strainer plate and decided to tear it down, thinking that there was a problem with a rod bearing.

The first thing I noticed was some rubbing on the #4 exhaust push rod.

I removed the heads and noticed that there was cylinder scoring on the tops and bottoms, remove the cylinders and saw the tops and bottom were worn... this must be the source of the silvery sludge. Attached are some pictures.

No what do I do? Any advice would be greatly appreciated... (IMG:style_emoticons/default/sad.gif) (IMG:style_emoticons/default/sad.gif)

Dan


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Jake Raby
post Apr 19 2009, 06:13 PM
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Looks like the cylinder/ piston wasn't cleaned well enough prior to assembly. That looks like a lot of wear for only 150 miles... Did you check the cylinder/piston clearance before assembly?
I have heard some complaints that the new Mahle sets are too tight out of the box, but since we don't use these I have not experienced it.

It takes quite a bit of an issue to create an audible slap from a piston/cylinder....

Those case through bolts don't look like they have been removed in a looooong time.. I would imagine that you snuck in a set of rods and rod bearings without splitting the case, based on your post and the pics.

This is quite risky, as you can't mic the rod journals for size or ovality..

I'd be puling those rod bearings, especially #2... I'd be willing to bet thats where the sludge came from and where the noise is coming from.. I have seen instances when a rod bearing was going south and fed dirty oil up the bore, resulting in the type of wear that you have pictured.
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r_towle
post Apr 19 2009, 06:21 PM
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are there any markings on these "NOS" pistons...on the top face?
If no...how do you ensure that you did not possibly put the piston in 180 off?

Rich
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solex
post Apr 19 2009, 06:30 PM
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Yes Jake I take a number of short cuts and am now paying for it... I have the original pistons that probably have 30k on them and they do not show any wear... and yes I did "sneak in the rod bearings and no I did not check the piston to cylinder clearance. (IMG:style_emoticons/default/sad.gif)

I will pulling it all apart shortly and will update.

Rich, the pistons were installed correctly, they have an actual diagram engraved on the pistons showing a crank and flywheel.
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r_towle
post Apr 19 2009, 06:32 PM
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QUOTE(solex @ Apr 19 2009, 08:30 PM) *

Yes Jake I take a number of short cuts and am now paying for it... I have the original pistons that probably have 30k on them and they do not show any wear... and yes I did "sneak in the rod bearings and no I did not check the piston to cylinder clearance. (IMG:style_emoticons/default/sad.gif)

I will pulling it all apart shortly and will update.

Rich, the pistons were installed correctly, they have an actual diagram engraved on the pistons showing a crank and flywheel.

Cool, just checking.

RIch
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Jake Raby
post Apr 19 2009, 06:39 PM
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Yep.. Most every time that people try to "get away with" not splitting the case, this happens... You could do partial builds before these engines were 30+ years old..

I haven't even attempted to do this in the last 15 years, back when I did I had a 50% success rate at best.

The more you go out of your way to avoid a problem the more problems are created!

I bet the issue is the rod bearing/ crank...

How tight were the wrist pins in the piston/rod?? did you install them with your fingers only, or did they need persuasion?
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solex
post Apr 19 2009, 06:59 PM
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As you can imagine I'm kicking myself. (IMG:style_emoticons/default/headbang.gif)

Here are some shots of the #2 bearings and the wrist pin. I do not think I had to apply to much pressure to install the pins, but this one has some very visible wear that I can feel. The original pins did not have this wear...

The first shot is the cap bearing and the wrist pin. The second and third are shots of the rod bearing.


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Jake Raby
post Apr 19 2009, 07:08 PM
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The pics aren't showing anything notable... Feel free to send me the parts for a free observation..

That pin looks like it was stuck in the rod. was it hard to remove?
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solex
post Apr 19 2009, 07:17 PM
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QUOTE(Jake Raby @ Apr 19 2009, 09:08 PM) *

That pin looks like it was stuck in the rod. was it hard to remove?


Not at all, light tapping with a PVC tube and hammer...

Can I call you tomorrow to discuss?
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Jake Raby
post Apr 19 2009, 07:24 PM
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Not tomorrow.. I am scheduled on the dyno all day and have a car coming from out of state for some magic tuning..

I can talk to you on my way home tomorrow night, but that might be late.. Tuesday I have to assemble a Boxster engine..wednesday back on the dyno to tune another one from out of state....
crazy week... they all are!
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r_towle
post Apr 19 2009, 07:28 PM
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It looks like the rod bearing spun...or is that just funky lighting.

Did you keep track of the proper orientation of the rod caps....and rods for that matter...note when you are taking them apart.

Rich
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solex
post Apr 19 2009, 07:30 PM
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QUOTE(Jake Raby @ Apr 19 2009, 09:24 PM) *

I can talk to you on my way home tomorrow night, but that might be late..


That would be great thank you. Just let me know what time...
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solex
post Apr 19 2009, 07:33 PM
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QUOTE(r_towle @ Apr 19 2009, 09:28 PM) *

It looks like the rod bearing spun...or is that just funky lighting.

Did you keep track of the proper orientation of the rod caps....and rods for that matter...note when you are taking them apart.

Rich



Rich I believe it is the lighting, I questioned it before I posted but the other side is a more accurate representation, I did make sure they were installed correctly.

As a point of curiosity would a spun bearing show more wear on the outer side of the bearing?

Thank you for replying...
Dan
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Jake Raby
post Apr 19 2009, 07:40 PM
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I thought the bearing had spun as well, but only one insert looks like that.. t must be the camera..

In probably won't be able to call till 2100 tomorrow night, unless I break the car on the dyno and get a chance to call earlier-
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solex
post Apr 19 2009, 07:44 PM
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QUOTE(Jake Raby @ Apr 19 2009, 09:40 PM) *

I thought the bearing had spun as well, but only one insert looks like that.. t must be the camera..

In probably won't be able to call till 2100 tomorrow night, unless I break the car on the dyno and get a chance to call earlier-



2100 is good for me I PM'd my phone number. Thank you
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jmill
post Apr 20 2009, 07:23 AM
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Did you change the lifters out? Wonder if you swapped a couple around and smoked your cam sending junk through your engine.
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solex
post Apr 20 2009, 07:37 AM
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QUOTE(jmill @ Apr 20 2009, 09:23 AM) *

Did you change the lifters out? Wonder if you swapped a couple around and smoked your cam sending junk through your engine.


The lifters were not swapped out...

Thank you,
Dan
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solex
post Apr 22 2009, 07:53 PM
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After splitting the case, looks like I have some crank bearing failure, actual pieces of the bearings are missing.

The lifters did not look that great as well, some wear on in the middle of the lifter body across the board.


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r_towle
post Apr 22 2009, 07:56 PM
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looks like possibly the case did not close correctly...maybe one of the dowel pins was not lined up correctly.

That might explain the spum bearing and the cam shaft bearing wearing like that.

Rich
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solex
post Apr 22 2009, 08:33 PM
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Rich,
I think the dowels and bearings were all lined up as the indents on the bearings for the pins were perfect. I think that the previous builder used too much sealant (looks like Indian Head, it was hard as a rock) causing the case halves to not mated perfectly. Just my guess

Dan
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