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What made this engine get piston slap?

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KarmaKannon1
I think I'll order a "tab"
I think I'll order a "tab"
Posts: 44
Joined: May 21st, 2020, 10:13 am
Stroker Displacement: 4.7
Vehicle Year: 2000
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Utah

What made this engine get piston slap?

Post by KarmaKannon1 » June 9th, 2020, 3:19 am

Just curious what the stroker experts have to say. I purchased this jeep with the piston slap and obviously the engine was recently rebuilt. I got into it knowing I would be putting a new engine in, but after trying to find a decent donor engine for under $1k I decided to rebuild what I have. Like most of my projects, this one cascaded a little and now I'm doing a 4.2 crank with a diy ported head, and most likely bishop Buhl pistons and rods.

The engine sounded like a diesel and I could tell #5 and #6 were the worst using a long pipe for identification. Engine temperature didn't seem to matter much. All bearings looked pretty good besides the thrust was down to copper. There was obviously some aluminum kicking around in there. The pistons are .03 over and the bore seems to be matching by the book numbers for .03 over. I'm wondering if this was just an inconsistent bore that led to piston slap after what looks like under 5000 miles on a rebuilt engine.

So what do you think caused this so quickly?
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KarmaKannon1
I think I'll order a "tab"
I think I'll order a "tab"
Posts: 44
Joined: May 21st, 2020, 10:13 am
Stroker Displacement: 4.7
Vehicle Year: 2000
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Utah

Re: What made this engine get piston slap?

Post by KarmaKannon1 » June 9th, 2020, 3:22 am

Thread is mostly for curiosity's sake. I don't know how changing the crank, boring the block, and using new pistons/rods wouldn't "fix" any issue that would have led to the pistons doing the mad clap dance. Well I always wanted a diesel jeep and for a few weeks I had one!

XJOverland
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Posts: 19
Joined: May 14th, 2020, 8:46 pm
Vehicle Year: 1997
Vehicle Make: Jeep
Vehicle Model: Cherokee

Re: What made this engine get piston slap?

Post by XJOverland » June 10th, 2020, 6:01 pm

Bad tolerance on cylinder bore
Bent rod
Too tight of a gap on piston rings

There a far more qualified people on here that could add a lot of reasons to that list.

Good luck!

KarmaKannon1
I think I'll order a "tab"
I think I'll order a "tab"
Posts: 44
Joined: May 21st, 2020, 10:13 am
Stroker Displacement: 4.7
Vehicle Year: 2000
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Utah

Re: What made this engine get piston slap?

Post by KarmaKannon1 » June 11th, 2020, 3:04 am

XJOverland wrote:
June 10th, 2020, 6:01 pm
Bad tolerance on cylinder bore
Bent rod
Too tight of a gap on piston rings

There a far more qualified people on here that could add a lot of reasons to that list.

Good luck!
I'm leaning towards bad tolerance or inconsistent bore for the following reasons. All cylinders were doing the same things even though 5 and 6 were the worst. When I checked the bore with a gauge I was getting some tight and loose spots. Granted the bore is beaten up now, but it still seemed to have been inconsistent when checking with my cave man methods.

The rings are also a possibility. I'll look into that one.

Russ Pottenger
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Posts: 792
Joined: August 15th, 2009, 1:27 am
Stroker Displacement: 4.7
Vehicle Year: 2000
Vehicle Make: Jeep
Vehicle Model: Cherokee

Re: What made this engine get piston slap?

Post by Russ Pottenger » August 1st, 2020, 9:57 am

Don’t rule out oil dilution.
Did you smell or sense there was fuel in the oil?

KarmaKannon1
I think I'll order a "tab"
I think I'll order a "tab"
Posts: 44
Joined: May 21st, 2020, 10:13 am
Stroker Displacement: 4.7
Vehicle Year: 2000
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Utah

Re: What made this engine get piston slap?

Post by KarmaKannon1 » August 3rd, 2020, 3:38 am

Russ Pottenger wrote:
August 1st, 2020, 9:57 am
Don’t rule out oil dilution.
Did you smell or sense there was fuel in the oil?
I didn't notice any fuel smell from the oil. That's a good point though. I pulled a 258 apart recently that had oil that smelled like two stroke gas. The rod bearing were completely toast on that engine. Hardly any silver left.

How rich would be enough to get past the rings and dilute the oil? I think I'm currently hitting the high 10s on my aem right about 4500rpm at wot. Up until that it's 14.5-13. just seems to richen up quite a bit around 4000rpm at wide open throttle.

Anyway, my new engine has been running for a couple hundred miles now and seems good. Hopefully it stays that way so I can build another head and get a bigger cam in it later on.

Russ Pottenger
Strong Poster
Strong Poster
Posts: 792
Joined: August 15th, 2009, 1:27 am
Stroker Displacement: 4.7
Vehicle Year: 2000
Vehicle Make: Jeep
Vehicle Model: Cherokee

Re: What made this engine get piston slap?

Post by Russ Pottenger » August 3rd, 2020, 12:46 pm

Just be mindful what the spark plugs are lookin like, AFR’s, and oil.

Good luck.

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