Sounds like you cracked a ring... ouch! maybe worse.
Chris
On Mon, 21 Aug 1995, John M. Trindle wrote:
> OK... here's the Puzzler:
>
> The Car: '73 MGB, twin HIF4 carbs, crankcase breather connected directly
> to front carb.
>
> The Chronology: Engine rebuilt in February, no oil consumption after
> break-in period, switched to synthetic oil 750 miles after rebuild. 3500
> miles on first batch of synthetic, due for oil change. Oil is dark but
> not opaque.
>
> Friday afternoon: Thinking about my friend with the '72, complaining
> about having blow-by already 2 years after his rebuild. Pull breather
> hose to check blow-by... WOW! lots. Plug it all back up and meet family
> for dinner. As I'm driving my mother around I notice an oil smell... her
> husband (following in the diesel) notices puffs of oil smoke out the
> tailpipe when I switch gears.
>
> Saturday morning: Car is working fine around town. When I go onto
> interstate on-ramp, billowing clouds of oil smoke stream out the back,
> and I can smell oil burning. This lasts about 30 seconds and quits. 5
> minutes go by. More oil smoke for a few seconds, then the smoke quits.
> This happens a couple more times on the way down... each time the smoke
> is billowing I also hear a clatter or pinging from up front.
>
> I suspect oil being burned external to the engine since I can smell it at
> 60 mph. I check plugs at my destination: The first two show a moderate
> lean condition with granularity (evidence of pinging??) with the rear
> plugs slightly sooty but smooth. Compression check shows 160, 165, 170,
> and 90 for cylinders 4-3-2-1! This was with the engine cooled down.
>
> I richen the front carb 1/2 turn, and check the valve adjusters on #1
> cylinder. They are slightly loose but no big deal. I drive back home with a
> few more smoke incidents.
>
> Next morning: I check the oil and buy a couple quarts. I'm low on oil!
> I drive the 65 miles again, with more smoke / clatter incidences. It's
> happening more often but is still intermittant.
>
> I race the car in an autocross. The oil smoke is evident only in the
> first run in once corner (but it's an enormous cloud). I check the plugs
> after the run, and the rear plugs are the same as before. The front two
> show an EXTREME lean condition and granularity. I also fracture the
> ceramic on #1 plug when removing it. Compression check shows (engine hot
> from race) 150-155-160-35 !!
>
> Trip home: Continuous oil smoke now. I have to stop every few miles and
> add oil. I finally wise up and 1) Disconnect breather from carb, plug
> carb inlet 2) disconnect carb 1 from throttle linkage, and 3) leave oil
> filler cap off (to vent pressure). Oil consumption drops significantly,
> and in fact the oil level seems to rise a half-quart or so over 20
> miles. Naturally since I have to drive slower at this point I am taking
> a round-about route on back country roads.
>
> I'll start tearing things down tonight, but would appreciate any
> guidelines for what to look for:
>
> Summary:
> 1) blow-by increased dramatically in a few days
> 2) Compression in #1 cylinder has dropped quite a bit.
> 3) #1 and #2 have been running lean, perhaps because of blow-by. Clattering
> while smoking could have been pinging due to excessively lean mixture?
> 4) Problem was intermittant for a 1 1/2 days and then continuous.
> 5) Most of the oil consumption seems to have been via the breather system,
> forced back into #1 and #2 cylinders. When pressure was relieved, oil
> level seemed to climb slightly (1/4 to 1/2 quart).
> 6) Radiator fluid level is good, pressure is held, and no oil is seen in
> coolant.
>
> John M. Trindle | jtrindle@tsquare.com | Tidewater Sports Car Club
> '73 MGB DSP | '69 Spitfire E Stock | '88 RX-7 C Stock
> Home Page: http://www.widomaker.com/~trindle
> "Anthony's Law of Force
> Don't force it - get a bigger hammer."
>
>
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