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Well, as much fun as a 92 TDC in a pontiac Fiero can be over a summer, all good things must come to an end.
The motor was a 190k-km donor out of a 92 Olds Cut/Sup/Int Auto donor and mated to an M19 Muncie 4.10 4-speed stick in an '84 Fiero.
I did the wiring myself, and save for a few minor gremlins, it ran strong, and it ran HARD.
So, the story goes like this:
Since I had bought the motor, there was a bit of lifter tick coming from around piston #1. Nothing major. Plenty of power, no burning oil, oil was clean. Slight leak from the distro plug (surprised aren't you
). Oil pressure was a steady 30psi at idle when warm (with 10w30)
After about a week of driving, I became aware of a louder tick(more of a tap) that coincided PERFECTLY with an exhaust pulse (in a fairly open exhaust, you know that musical throb you get at cruise? Well, it was matched up beautifully with it), but ONLY while accelerating from cruise, and between 2000 and 2200rpm. It was much louder than what I'd normally associate with a valve tick or lifter clatter... I was pretty much convinced that I had an exhaust leak in my front manifold (which btw is about 3" away from the firewall in a Fiero) and that It was just exhaust noise.
This continued for about 2-3 months... The weather turned cold, I switched to 5w30 (from 10w30) and the valve tick got a hair louder once the car warmed up. Oil pressure dropped a hair to ~25psi at idle warm.
Of course, with the icy roads, there were no more hard starts or high-speed runs. Glare Ice and packed snow (even with my totally awesome winter tires) make for gentle if not paranoid driving habits. The car ran better than before (my theory was that it was idling rich, and the cold air was softening this), but the ticking was a bit louder than before. Then again, EVERYTHING was louder than before. I associate this with all the bushings icing up and transmitting more noise....
And then, on a particularly mild sunday (12º below freezing) I changed the oil. The oil had been in for just over a month (I'm neurotic about oil-changes. Once every 2 months TOPS, once per month favorably) and was if not squeeky clean, only just starting to darken (was the color of dark honey). No sparklies or milky-way galaxies in the oil pan. I topped it up, spun on the new filter, started it up, checked the oil, and resumed the commuting routine.
Two days later, I'm on the freeway to work, cruising at 50mph (~80kph) and I hear what sounded like an explosion in the back. The car lurched, and then continued on... Only now it sounded like someone had put a coffee can of bolts in the spin-cycle of a washing machine.
I pulled over, and popped the decklid. It was definitely lifter noise. It was WAY too slow to be bottom end... But holy frijoles.... It sounded like some mad bastard was smacking the head with a ballpeen hammer. It wasn't a knock so much as a gunshot.
Well, to hell with that. Limped the car home (already wrote off the engine by this point. no WAY that something big isn't broked). drove it into a snowbank in the back 40, and dusted off my new Dodge Colt Winter Beater.
So, Does anyone have any theories? I'm a little attached to the ends of my fingers, and I don't have a heated garage, so I won't be tearing into the motor until spring.
MY question to you folks is this:
WTF happened, and WTF can I do to make sure it don't happen again.
I've pinpointed the location of the "break" to be just over Piston #2 (that's the one on the rear bank closest to acc. pulleys... Unless I'm flipped). If I yank the plug wire (what I'd do to check bottom end noise) the noise changes and becomes a solid thump rather than a more metallic SMACK!
There's no metal in the oil (at least, what I can see on the dipstick), and oil-pressure is still good. More amazingly, the car still had smooth power (didn't try past 3000rpm obviously)... So it's still FIRING at least on all cans...
Other than that, I'm not going to open that can o worms until spring. Any thoughts?
The motor was a 190k-km donor out of a 92 Olds Cut/Sup/Int Auto donor and mated to an M19 Muncie 4.10 4-speed stick in an '84 Fiero.
I did the wiring myself, and save for a few minor gremlins, it ran strong, and it ran HARD.
So, the story goes like this:
Since I had bought the motor, there was a bit of lifter tick coming from around piston #1. Nothing major. Plenty of power, no burning oil, oil was clean. Slight leak from the distro plug (surprised aren't you
). Oil pressure was a steady 30psi at idle when warm (with 10w30)After about a week of driving, I became aware of a louder tick(more of a tap) that coincided PERFECTLY with an exhaust pulse (in a fairly open exhaust, you know that musical throb you get at cruise? Well, it was matched up beautifully with it), but ONLY while accelerating from cruise, and between 2000 and 2200rpm. It was much louder than what I'd normally associate with a valve tick or lifter clatter... I was pretty much convinced that I had an exhaust leak in my front manifold (which btw is about 3" away from the firewall in a Fiero) and that It was just exhaust noise.
This continued for about 2-3 months... The weather turned cold, I switched to 5w30 (from 10w30) and the valve tick got a hair louder once the car warmed up. Oil pressure dropped a hair to ~25psi at idle warm.
Of course, with the icy roads, there were no more hard starts or high-speed runs. Glare Ice and packed snow (even with my totally awesome winter tires) make for gentle if not paranoid driving habits. The car ran better than before (my theory was that it was idling rich, and the cold air was softening this), but the ticking was a bit louder than before. Then again, EVERYTHING was louder than before. I associate this with all the bushings icing up and transmitting more noise....
And then, on a particularly mild sunday (12º below freezing) I changed the oil. The oil had been in for just over a month (I'm neurotic about oil-changes. Once every 2 months TOPS, once per month favorably) and was if not squeeky clean, only just starting to darken (was the color of dark honey). No sparklies or milky-way galaxies in the oil pan. I topped it up, spun on the new filter, started it up, checked the oil, and resumed the commuting routine.
Two days later, I'm on the freeway to work, cruising at 50mph (~80kph) and I hear what sounded like an explosion in the back. The car lurched, and then continued on... Only now it sounded like someone had put a coffee can of bolts in the spin-cycle of a washing machine.
I pulled over, and popped the decklid. It was definitely lifter noise. It was WAY too slow to be bottom end... But holy frijoles.... It sounded like some mad bastard was smacking the head with a ballpeen hammer. It wasn't a knock so much as a gunshot.
Well, to hell with that. Limped the car home (already wrote off the engine by this point. no WAY that something big isn't broked). drove it into a snowbank in the back 40, and dusted off my new Dodge Colt Winter Beater.
So, Does anyone have any theories? I'm a little attached to the ends of my fingers, and I don't have a heated garage, so I won't be tearing into the motor until spring.
MY question to you folks is this:
WTF happened, and WTF can I do to make sure it don't happen again.
I've pinpointed the location of the "break" to be just over Piston #2 (that's the one on the rear bank closest to acc. pulleys... Unless I'm flipped). If I yank the plug wire (what I'd do to check bottom end noise) the noise changes and becomes a solid thump rather than a more metallic SMACK!
There's no metal in the oil (at least, what I can see on the dipstick), and oil-pressure is still good. More amazingly, the car still had smooth power (didn't try past 3000rpm obviously)... So it's still FIRING at least on all cans...
Other than that, I'm not going to open that can o worms until spring. Any thoughts?
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