Cylinder wall problems ( never seen anything like it)

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Thank you for all the response guys :cheers:
The engine lost more power for every run, from 12.2 to 12.8.( about 0.1 sec /run). That the reason why I tore it down.

No noise and It never took any water.

The dents line up with the groove in the piston at bdc.
This engine has been raced for over 8 years and tore down every year at the end of the season and the bores have always looked good.

This is soooo strange but I will mesure the cylinder walls and pistons today and get back to you
thanks again!
 
Cudafever said:
In the 1st and 2nt pic, at the bottom of the bore were the two oval ....stains? are. is this the area that you say is indented?

If so then i would GUESS, and say that the cyl wall is very Thin in that area. You only bored it .030 over?
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That´s correct. If the piston to wall clerance were to big the dents would be at 9 o´clock right??
 
you cannot run E-85 at 12:1 or 12.5:1. E-85 has 85% alchohol (supposedly). I do not know the exact number but I seem to remember about 7:1 at WOT. 12:1 would be ok for E-15 or E 10. (maybe?) this is your problem too lean.
 
Okey just got back from my shop and I measured the bores and pistons.

piston skirt : 3.9377 - 3.9382

bores : 3.9401 - 3.9425 ( Some of the bores was out of round 0.0015 )

Ring gap average: 0.019 - 0.023 ( both first and second ring )

So the clearance is between 0.0019 and 0.0048

the clearance appears to be a tad to big but should be okey, Kb says 0.0015 to 0.0045. I still think it has something to do with the fuel, It´s almost like the fuel has destroyed or washed the oil film away from the cylinder walls???
 
some more picures:

This has to be detonations just over the ridges that was caused by the top ring but I can be wrong :scratch:

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annother one

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And one more on the piston


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Looks like the cylinder walls are too thin. What I see looks like water stains as stated many times in this thread. I have seen these type stains many times and water was always the issue. Toss the block or have it sleeved are your only options.
 
Oldmanmopar said:
Don't let the same shop do another motor for you. And that block is junk
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It was like 8 years ago the block was bored and it has only been honed once after that, The cylinder walls did not look like this the last teardown(one year ago and only a couple of races and I know the block is junk, I just trying to figure out what caused the discoulor and the wierd big dents at bdc just under the top ring.
 
Oklacarcollecto said:
Looks like the cylinder walls are too thin. What I see looks like water stains as stated many times in this thread. I have seen these type stains many times and water was always the issue. Toss the block or have it sleeved are your only options.
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I agree with you, It´s almost like the cylinder walls has been "flexing" under full load or something if you now what I mean.
 
Do you guys think to much rpm could do this. The last run at the stip was the worst, the engine was very hard to start before I was going to warm the tires ( has never been hard to start before ) I started in 2 gear and reved it to 7000rpm as usual and after the burnout the engine started to run like a bag of nuts, shut down on cylinders and so on.

But when I lined up against the tree it started to go on all 8 again so I thought what the h# and ripped of a bad 12.88 @ 103.1 but a decent 7.98@1/8
After that I got home and made a Leakdown and compression test And the readings were all over the place so I took it apart and found the discoulor and dents.
 
what year is this engine block. Mid eighties 318 we bad for core shift AND porosity.
(for some reason the 360's were ok though). maybe a crack or two in the bore of a thin wall on that side. Under pressure....problems.
 
omahamoparguy said:
what year is this engine block. Mid eighties 318 we bad for core shift AND porosity.
(for some reason the 360's were ok though). maybe a crack or two in the bore of a thin wall on that side. Under pressure....problems.
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Produced in 1983, hmm I gona see if I can get a hold of an ultrasonic tester,
I´m very curious, so I have to go to the bottom of this issue :toothy7:
 
You say the ring gaps were .019-.023 for first and second ring. Those look like hypereutectic pistons to me and they require a larger top ring gap than a regular cast piston. Were you running these pistons before or did you just change to them?
 
That tattoing in the cylinders is standing-water corrosion. If this thing is seeing only short trips, that oil is going to be FULL of moisture from condensation on cool-down, because the motor never gets hot enough long enough to boil it off.

Add in some water-saturated alcohol and it won't help, but that's moisture-based corrosion for sure.
 
Looks to me like rings never seated and been sucking oil. With the short amount of miles that is why top of the piston look like that. If it had sucked water in the top of the pistons would look like brand new. You didn't say if it was smoking bad when you pulled it apart.
 
mischiefdart said:
You say the ring gaps were .019-.023 for first and second ring. Those look like hypereutectic pistons to me and they require a larger top ring gap than a regular cast piston. Were you running these pistons before or did you just change to them?
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Yes, has been running them for 8 years but the engine has only gone about 4 competitions since last hone and only 5 runs since last time I looked at the bores
 
67cudafb said:
Looks to me like rings never seated and been sucking oil. With the short amount of miles that is why top of the piston look like that. If it had sucked water in the top of the pistons would look like brand new. You didn't say if it was smoking bad when you pulled it apart.
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No smoke, no noise, no moisture in oil. Inside of valve covers look like new, just started to run bad times at the last race
 
The last photo of your piston looks like the area just below the oil ring has a lip between the oil ring and the skirt. The only way a lip can be there is if the skirt is a more narrow diameter that the piston head where the oil ring is. Maybe it is an optical illusion.

I hope you can get a sonic check so we can know. I'm betting on the block being porous. GL!
 
68gtxman said:
The last photo of your piston looks like the area just below the oil ring has a lip between the oil ring and the skirt. The only way a lip can be there is if the skirt is a more narrow diameter that the piston head where the oil ring is. Maybe it is an optical illusion.

I hope you can get a sonic check so we can know. I'm betting on the block being porous. GL!
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Yes it´s an illusion :lol:
 
Perhaps the last guy to hone and rering the motor did not know the equation for figuring the top ring gap. My instructios for the kb hypers in my motor had me fitting the top rings a fair amount wider than the second ring.
 
did u sonic test the cyl. walls before it was bored? looks like the walls are to thin. the walls need to be .080 to.100 thick. Or this kind of thing well happen. bet the motor ran hot.
 
block is scrap metal. you won't clean those bores up with a hone. never seal.
looks like the bores were rust pitted before the last trip to the boring bar.
didn't cleanup then, won't now.
 
mischiefdart said:
Perhaps the last guy to hone and rering the motor did not know the equation for figuring the top ring gap. My instructios for the kb hypers in my motor had me fitting the top rings a fair amount wider than the second ring.
Click to expand...

No my instructions says it should be the same, it also says so on kb:s homepage.
 
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