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Discussion Starter #1 (Edited)
Found oil on number two yesterday. Wasn't a fresh plug, but was pretty clean when I put it in. Towed up and made a terrible pass ( reference high gear tire shake thread) before clicking it at the stripe. Pumped good, so figured I'd try it again. Plugs looked great the next two passes. I'm pretty comfortable with this tune and feel like it was about two degrees below optimal for the conditions and based on the plugs.

Was it just a fluke thing where it fluttered the rings when I pedaled it and I got lucky? I've pedaled this thing so many times I don't even think twice about it anymore...
 

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How much oil are we talking?
Usually you may get specs from fluttering, but actually oil on it means ring lands are more than likely pinched.
Pedaling it is always a tough deal, we all have done it. But its not a good thing..

Dee
 

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Discussion Starter #3
It wasn't soaked. It just had a little glisten too it that was definetely oil. After it sat around a little while it sort of dried off and really didn't look that bad. I showed it to the guy that did the machine work and he said it was such a small amount it didn't really bother him. I thought sure it was going to be ash trays on the next pass, but like I said came out perfect. Anybody else ever see that?
 

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I would have to agree with Monte here.. Especially in cars with tunnell rams if you shut them down at the end of the run in some cases a bunch of fuel can splash from the carbs and end up in the front cylinders and wet the plugs ?? Just a thought.. SJ
 

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Discussion Starter #6
Well, no such luck. Pretty sure it was oil now. That piston looks fine, but 1, 3, and 5 are not. Thinking the crankcase pressure just happened to push a little oil into #2. Something I didn't mention is that it was pushing some oil out of the distributor gasket and the valve cover breather grommet.

Finally got around to leaking the whole motor, and number 2 and 7 were the only ones that didn't look bad on the checker. Decided to pull the head and found:

#1. Slight erosion at 12 oclock between the piston deck and the top ring. Top ring does not appear stuck. Piston looks sealed up.

#3. Top ring obviously stuck. Erosion at 12 oclock like #1.

#5. Looks just like #3. Leaked about the same but still pumped good. Guess second ring is also affected on number 3 but not this one.

I have a few ideas about what caused it, but want some input. On the first 3 passes on this engine, it was blackening #3 plug. Not oil, just extreme excess fuel. Finally found a little piece of trash in the metering block. There was also a slight restriction in the high speed air bleed passage for #1, but that plug hadn't been showing anything wrong.

I also massacred the rev limiter about 6 passes ago (probably 12 passes total on this) when a dead battery and slipping alternator belt caused the electric shifter not to function. It closed up either #3 or #5 plug when it did this.

I think the oil out of the breathers deal started after the rev limiter incident, but I'm wondering if the excess fuel in 3 was spreading to 1 and 5. Seems like it would have gotten to 4 easier than 5, but 4 doesn't look bad (so far).

I guess I'm just trying to retain confidence in my tuneups, hoping it wasnt them but rather the abuse I put this thing through.
 

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The nitrous guy
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If it is taking alum off the piston at the 12 oclock position..........that is rattling it, HARD. Now the question is, was it simply overtimed, or did it tighten up the second rings first, which results in loss of seal and allows it to rattle.

A dead give away though, is pushing oil out.........so the rings were DONE, but still need to determine what happened to cause it to kill the rings. I am betting it tightened up the second rings first

Monte
 

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Discussion Starter #8
Holy scrap metal batman! Not one good slug left. 4 of them have just very slight darkening at 12 o'clock. A couple have pronounced melt from the edge of the piston deck down towards the top ring at 12 o'clock with no other problems. #5 has the same thing but top ring is stuck at this location.

#3 makes me question my eyesight because I never saw anything but a little black speckling that I thought was overfuel/under timed. Top ring stuck, second ring broke, oil ring stuck.

So what's the chances that #3 second ring butted from the excess fuel and started this whole deal?
 

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The nitrous guy
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You sure that is a melted spot, on the side of the piston, above the top ring, or a "smear", where the piston actually "touched" the cylinder wall, because of piston rock. Measure the skirts, they are probably mashed in pretty bad, allowing the pistons to rock in the bore. The skirts can be collapsed, for various reasons. One, just not a good enough forging. Two, the motor just got loose or three, a rich tune, killed the rings, allowed oil in and then the detonation hammered the skirts.

Doubt seriously, you butted the rings and caused this. Stuck oil rings, is usually rich and broken rings anywhere, is the motor hammering.

Monte
 

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Discussion Starter #11 (Edited)
I guess the pics are a little big, but that is #1 close up, #s 1/3/5, # 3 close up. Final picture is #8. I wouldn't have thought anything about the dark spot at 12 oclock on this one, except it looks just like 1/3/5 only not nearly as bad. There are no corresponding scuff marks at 12 oclock in the block (although there is scuffing in 3). I don't have a mic for the pistons, but with a set of dial calipers, I don't see any collapsing of the skirt. The rock also seemed right before I pulled the short block down. Only 12 runs on hone/piston/rings.

I think its obvious by the pics, but its definetely melt because the aluminum that used to be on the piston is on the cylinder wall.

Oh, and the skirts are coated, just in case anybody is wondering.
 

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The nitrous guy
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That piston has touched, the cylinder wall. Thats a drag mark. If it had been hot enough, to actually melt the piston, the top corner would not be that sharp. Detonation, or too much timing, takes off edges first. Like around spark plugs, valve pockets and edges of pistons. Your edge is still sharp. You said fresh hone, pistons and rings. If you put new pistons in it, were they the same size as before, or did you go up on piston size, because you honed it.

Monte
 

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Discussion Starter #14
Final bore was 4.607. Wiseco said that was too big for a 4.600 piston. Spec sheet doesn't list actual size, but I think they are 4.602. I'm having trouble seeing rubbing, don't see how that would cause the erosion look. Maybe a combo of contact and melt? I should find out today new finish bore. Was planning on going with the same piston at whatever size is necessary? Funny thing is I ran this same tuneup on a set of Ross pistons for awhile that Ross said would only handle 150 shot. I abused those pretty good too and they looked fine except for where a windage tray bolt went thru one.
 

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Discussion Starter #15
I guess the fact that 1/3/5/7 look about the same (bad) and 2/4/6/8 look about the same (barely marked) sure seems to support the rocking explanation.
 
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