Cylinder wall problems ( never seen anything like it)

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65SignetSweden

65SignetSweden

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Well hello everybody! Have been along time since I posted on Fabo, I need some help with this odd problem. The cylinder walls are all discoloured and 3 cylinders has dents just over bdc, you can feel it. 3 cylinders also has ridges at tdc towards the ( ground). The Engine has only run 4 competitions ( about 15 runs and 100 miles street ) since the last rebuilt. The engine has never overheated.

Here´s some info on the Engine :
318 cui (.030 over)
kb pistons 167
eagle H-rods
Edelbrock heads
mp 4120094 camshaft (.577 lift)
AF:ratio low 12 to 12.5 wot

Please help me figure this thing out, has anybody had this problem?











 
All of your pics are not showing up for me, but that second pic is from water sitting in the bore and rusting the culinder.
 
RustyRatRod said:
that second pic is from water sitting in the bore and rusting the culinder.
Click to expand...

That's what I thought too! I tore down a boat motor that water got into and it looked very similar. Don't know about the "dents" in the bores though.
 
X2 on the water action. The dents?.....I dunno. My only guess would be pinging or you ran a 250 H.P. nitrous shot and lugged the engine.
 
No nitros and no water in the cylinders, The dark spots is not rust and the engine was fully warmed up and had run for almost 45 minutes before tear down .
In the first picture you can see the 2 round dark marks at 7 and 11 o´clock at bdc, that is big inwards dents that is shallow and in the second picture you can see the ridge at tdc. I talked to a friend about this and he had a similar problem with his car that runs on E 85. All the cylinders look like this and I think it has something to do with oil or fuel that caused the discouloration.

The pistons has big V groves(gas port) in them between top and second piston ring that I think collects fuel, and when you turn the engine off the fuel discoulor the cylinder walls, that is my theory
 
Pic of the kb 167 and the V-groove

IMG_0253.jpg
 
I'm not familiar with these pistons, but it looks like the skirt has been made narrower than the bore, therefore the entire piston can potentially rock in the bore. That would definitely explain the dents and the grooves below the top.

Can you post two side photos of the piston (one from front side view and one from left to right side view)?

Did the engine make a lot of noise before you tore it down? Why did you tear down such a low mileage engine in the first place?
 
I agree w 68GTX, It looks like the skirts are smacking the cylinder walls. The third.image shows some.cloudy spots, that looks a lot like cavitation. What's your piston to wall clearance? By the looks f those pistons ,its gotta be crazy big. I think my biggest concern would be the potential cavitation/water intrusion.
 
It looks to me like the ring seal is gone. Way too much carbon below the top ring. I've seen bores stained like that - it was water that did it. The walls might feel smooth but in reality the honing process tears the metal on a microscopic level. Rust can form below the level that the rings ride on. It can form from condensation - when you run E-85 or methanol it holds water - gasoline does not. I wouldn't sweat the marks. The ridge tells me the 2nd ring is messed up which might also be a part of the sealing problem.
 
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?
 
In the third to the last picture, that piston appears to be in backwards.
 
15 runs and 100 street miles??? Man, i've been in a lot of engines, but I have never see anything like that. I'll be watching, but I have no advice. Lots of carbon, funky looking crosshatch, stains, dents.....i'm still shakin, my head!

:happy1:
 
OldmanRick said:
15 runs and 100 street miles??? Man, i've been in a lot of engines, but I have never see anything like that. I'll be watching, but I have no advice. Lots of carbon, funky looking crosshatch, stains, dents.....i'm still shakin, my head!

:happy1:
Click to expand...

I am with you there.

I will bring the drinks to go with the popcorn.

:drinkers:
:drinkers:
 
Mic the piston and mic the bore.Any intake leaks or head gasket leaks.Have you lost any coolant?
 
Sorry bigger picture helped. See the second ring now.
 
I am building a 440 six pack motor now that had those same cylinder stains & indentions. Motor was factory stock,low miles & was just planning to freshen up. I attributed it to unburned fuel + condensation = acid. Needless to say ,its getting a full rebuild!
 
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