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PostPosted: April 16, 2018, 9:46 am 
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Good morning Team Slotus!
I spent some quality time in the shop over the weekend, when not accompanying TWWTFM's daughter and our grandson to the ER for what turned out to be an ear infection/strep throat. Story for another forum...

I got the rear suspension re-assembled with the new br@ckets and bushings and such. It goes Bouncy-Bouncy much better now. Further testing will be required.

Then on to the real fun part... I pulled the motor and began the teardown. Got the big piece out of the frame on onto the motor stand, began some cleanup and gasket scraping, then flipped it over and looked at the rods, crank and pistons. Earl came by and assisted with the inspection. Nothing waved any red flags at us, but more teardown/inspection is needed. I did pull the #1 rod/piston out of the block (OK, Earl did most of that, but he ain't here, I'm taking credit...)

Here's the weird part... Y'all knew there was gonna be a weird part, right? When I did the leakdown test correctly that second time around, most of the obviously leaks were audible at one valve or another, usually the exhaust valve. However, the #1 cylinder was one of the ones that appeared to be leaking air around the piston itself and blowing it into the crankcase. We assumed "burnt piston" at the time. OK, yesterday, we pulled #1 and it ain't burnt. Rings look good, no "erosion" around the edges of the piston, no real tell-tales of any defect at all, except a small mark on top where something (piece of a metal?) hit it. So, why did it appear to be leaking into the crankcase instead of around a valve? Anybody???
Attachment:
04 15 18 Piston.jpg
04 15 18 Piston.jpg [ 812.74 KiB | Viewed 501 times ]
Here's a picture of the #1 piston, taken to record that part number, but you can see the "ding" in the surface. Doesn't show the nice, clean edge around the perimeter, but take my word for it. Oh... No??? OK, FINE, I'll take another picture later... :mrgreen:

So, what do y'all think? Was it just at the bottom of the stroke and the rings weren't sealing due when I tested it? (It hadn't run in quite a while.) Or was it Aliens? Or Sharpies? Or Alien Sharpies?

Peace, Love and Aliens-
JDK

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PostPosted: April 16, 2018, 10:56 am 
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I'm not the most expert engine guy, JD, but I'd be tempted to put a very bright light up under the piston in a dark area of your shop and see if any light shows through that larger "ding." It looks pretty serious to me. Are you sure it doesn't go all the way through the piston top?

Cheers,

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PostPosted: April 16, 2018, 11:15 am 
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That "ding" doesn't look serious to me. At least not in and of itself. I would be more concerned about what made it. It looks like somebody put a drift punch to it at a angle. A nice, clean circular tool mark, pushing the displaced material ahead of it. I know that didn't happen, but that is what it looks like. Without any other observation, there is no telling if it was there before assembly or not.

I would mic out the piston and the rings. Make sure they are what they say they are. Were the rings installed correctly? Right side up and in the right location? If everything else checks out, I'd put the piston back in the engine about midway, along with another like-positioned piston Then put in some mineral spirits in both and compare the 2 drain rates.

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PostPosted: April 16, 2018, 9:43 pm 
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If everything else checks out, I'd put the piston back in the engine about midway, along with another like-positioned piston Then put in some mineral spirits in both and compare the 2 drain rates.
Hi Chuck! A friend of mine who is a professional mechanic that specializes in mechanical restorations on older Jags and Triumphs and such (even Morgans!) suggested that same trick.

I'm going to measure (With my new Horrible Freight caliper!) the #1 piston against a couple of others and then try the "Drainage Rate" trick. Stay tuned...

Thanks to you and Lonnie for your input, wisdom and moral support.

:cheers:
JDK

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"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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PostPosted: April 17, 2018, 12:05 am 
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GonzoRacer wrote:
Thanks to you and Lonnie for your input, wisdom and moral support.


Glad they stepped up to the plate, all I have to offer is immoral support :ack:

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PostPosted: April 17, 2018, 1:17 am 
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I had something similar on an old Cortina GT engine I had. Had a heck of a time figuring out what was making the tapping sound when the engine was running! Finally pulled the head, and found a tiny piece of compression ring pounded into the crown of the piston. An examination of the rings on that piston revealed that about a 3 mm piece broke off the gap end of one of the rings & worked its way up to the top of the piston.

We pried that piece of ring out of the piston, rotated the ring so its gap didn't line up with that of the other rings, put it back together, and raced that engine for another 5 years without any trouble. Strangely enough, the compression on that cylinder was absolutely identical to that of the other 3 cylinders, even with the oversized gap in that one ring :roll:

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PostPosted: April 17, 2018, 7:07 am 
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horchoha wrote:
GonzoRacer wrote:
Thanks to you and Lonnie for your input, wisdom and moral support.

Glad they stepped up to the plate, all I have to offer is immoral support :ack:
Yep, good thing they did, because God knows my morals won't support anything... They can barely support themselves. :mrgreen:

Other'n that, how the heck are ya? Thawed out yet, up there in the Great Frozen Northland?

:cheers:
JDK

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Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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PostPosted: April 17, 2018, 7:10 am 
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found a tiny piece of compression ring pounded into the crown of the piston
Wow... That's pretty amazing... The "ding" in my piston looks like something hard (like part of a ring) scraped up a divot in it, but there doesn't appear to be anything embedded in it. I'll look over the rings again and see if I'm missing part of one. (Of course, if I am, the question becomes "Where is it?")

Good hearing from ya, Bro!
:cheers:
JDK

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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PostPosted: April 17, 2018, 7:53 am 
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Cylinder leakage checks.

Check the cylinder for an out of round condition. The new SBF motors have a LOT less metal in the cylinder walls. With a .030" over piston you may have cylinder wall distortion.

Check piston land clearance and possible piston ring up-side down.

Check the actual piston ring for a flat spot on the sealing surface, and end gap.
DaveW


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PostPosted: April 17, 2018, 11:17 am 
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GonzoRacer wrote:
Other'n that, how the heck are ya? Thawed out yet, up there in the Great Frozen Northland?


Old man Winter just won't let go this year for some reason.

About the mark on the piston - is there a mark in the head also? Considering the location where it is I'm thinking the shrapnel must have been considerable size (even being small). Where is it? My bet is that it went past your ex valve and is sitting in the muffler.
You may want to check all the pistons and rings. I've seen pieces travel from one cylinder to another on engines (in extreme cases when things start to go sideways).

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'If man built it, man can fix it'
"No one ever told me I couldn't do it."

Perry's Locost Super Che7enette Build
Perry's TBird Based 5.0L Super 7 L.S.O.
Perry's S10 Super 7 The 3rd
Perry's 4th Build, The Topolino 500 (Little Mouse) Altered


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PostPosted: April 17, 2018, 11:22 am 
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horchoha wrote:
GonzoRacer wrote:
Thanks to you and Lonnie for your input, wisdom and moral support.


Glad they stepped up to the plate, all I have to offer is immoral support :ack:


I wish I could've said that :cheers:

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PostPosted: April 17, 2018, 1:05 pm 
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Parts ingested will definitely travel from one cylinder to another. We recently had an air cleaner bolt bounce around 4 of 6 cylinders in a Slant 6 at a Lemons race.


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PostPosted: April 17, 2018, 4:30 pm 
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rx7locost wrote:
I wish I could've said that :cheers:
You can, Chuck! Go for it! I mean, it ain't like I've never told the same joke twice, or stolen a good one from somebody else... :mrgreen:

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"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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PostPosted: April 17, 2018, 6:53 pm 
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The first time I blew an engine (Big block Chevy) in my dirt track car, I started to dismantle it, and the first thing I did was to remove the carb. When I looked into the intake manifold and saw a 3/4" piece of piston ring laying there, I knew it wasn't gonna be good. My fears were confirmed when I pulled the intake manifold and found the piston in the lifter gallery with a big chunk of con-rod still attached! :shock:

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PostPosted: April 22, 2018, 11:35 am 
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Good story, Mike... But you haven't lived until you've blown an engine and scattered pieces along the highway... :ack:
Attachment:
04 21 18 Rebuild#3.jpg
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Speaking of :ack: ...
Here's the block and most of the rotating assembly, out of the car. #1 Piston is removed and you can see a piston ring and feeler gauges sitting on the block. What I did, based on Dave W's advice (amongst others!), was to run that piston ring up and down the cylinder. I found a PVC coupler that jussst fits the bore and used that to square up the ring with the cylinder walls and then check the ring gap with the feelers. I found that most of the way down the cylinder the .021 gauge fit the ring gap just fine. On a couple of locations, the .020 would go in, but barely. On a couple near the base of the cylinder I could likewise jam the .022 in, barely. According to James, that's likely due to the honing process being less than perfect. He also says a variance of .001 or even .002 isn't enough to worry about.

I will be removing the rest of the pistons/rods in a bit and while I'm there I'll probably remove the main caps and crank. I'll do similar piston ring gap measurements on the other 7 cylinders then. Stay tuned!

:cheers:
Peace, Love and Ring Gaps-
JDK

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"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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