AN6-TX
Jedi Hopeful
Offline
I've recently developed "exhaust smoke" following a tune-up by a reputable mechanic here in CO (note - recently moved here from TX). The car is a '67 Sprite (1275) with an oil cooler, roller rockers, and a mild cam. I use synthetic, high-mileage motor oil (10W-40) per the PO. The car rarely ran hotter than 160F (in TX) regardless of the ambient temperature. Details of what was done and what I am experiencing are as follows:
Background:
PO had the car setup to run "rich" (no choke needed to start car). Also, had a "road draft" setup whereby the crankcase was venting to the to atmosphere rather than to the canister. Turns out, there were some carb mods as well - a series of washers on the front float that caused it to sit "lower" than the rear.
Car went in for brakes and to troubleshoot a very low idle.
What was done:
- carb cleaning, balancing, and adjustments (removed the washers, ensure the SUs were functioning as they should; choke now needed to start).
- re-plumbed crankcase through the canister and back to the manifold, added a pcv valve.
- added an exhaust tip to bring the muffler out just beyond the rear bumper.
The issue:
I've driven the car twice since the repairs - 30 miles or so home from the garage (mostly interstate), 16 miles this morning on "open road". The car smokes. But not all the time. The puff at start up is blue - there has always been a start-up puff, so I'm not overly concerned aboutit.
I should note that it was first noticed on the interstate (and because someone was yelling at me). The smoke is thick/heavy and is more white than blue although I swear there's some blue in it. As I was on the interstate during the starting phases of Friday-afternoon rush hour I wasn't able to pay close attention to what I saw (to avoid getting mashed by SUVs). I happened to notice, however, that the temp gauge was higher (a lot higher) than I ever recall seeing it. Ambient air temp was +/- 90-95F and the gauge was reading 195-ish. I chalked this up to traffic but the smoke was perplexing. Took the rural way home after I got off the freeway and the temp came down and the smoke dimished but was still present at times.
Had the car out this morning (16 mile drive). Blue puff on start up and shortly after take-off but then it went away. I was on open road this morning with the occassional traffic light (no traffic to speak of). The smoke, however, returned. I observed that the thick/heavy smoke was only present when the engine temp >120 degrees and the engine was below 3,000 rpm. Once I was above 3K rpm, there was no smoke. I mention that it is heavy because I can see the cloud lingering from several hundred yards away.
I've inspected the engine compartment and do not see any oozing, leaks, or otherwise suspicious fluids. Popped the bonnet as soon as I got back this morning to inspect for oddities and I saw nothing. Yesterday, I checked the oil and the level was normal. Coolant appeared to be low yesterday so I topped it off. This, in my mind, may be a clue. I plan to check again today once the engine has cooled.
Unfortunately, I know what *could* be the culprit (I won't say it for fear of jinxing it) but the intermittency of it all has me perplexed. Is it possible that the smoke is caused by the "new" exhaust tip? That is, as the exahust heats up, when there is blow-by, it is burning off at the muffler tip? I would have thought the replumbing of the crankcase ventilation would have fixed this.Any thoughts? As luck would have it there is a rally/Brit car show in 3 weeks and I really want to participate in my car...
Background:
PO had the car setup to run "rich" (no choke needed to start car). Also, had a "road draft" setup whereby the crankcase was venting to the to atmosphere rather than to the canister. Turns out, there were some carb mods as well - a series of washers on the front float that caused it to sit "lower" than the rear.
Car went in for brakes and to troubleshoot a very low idle.
What was done:
- carb cleaning, balancing, and adjustments (removed the washers, ensure the SUs were functioning as they should; choke now needed to start).
- re-plumbed crankcase through the canister and back to the manifold, added a pcv valve.
- added an exhaust tip to bring the muffler out just beyond the rear bumper.
The issue:
I've driven the car twice since the repairs - 30 miles or so home from the garage (mostly interstate), 16 miles this morning on "open road". The car smokes. But not all the time. The puff at start up is blue - there has always been a start-up puff, so I'm not overly concerned aboutit.
I should note that it was first noticed on the interstate (and because someone was yelling at me). The smoke is thick/heavy and is more white than blue although I swear there's some blue in it. As I was on the interstate during the starting phases of Friday-afternoon rush hour I wasn't able to pay close attention to what I saw (to avoid getting mashed by SUVs). I happened to notice, however, that the temp gauge was higher (a lot higher) than I ever recall seeing it. Ambient air temp was +/- 90-95F and the gauge was reading 195-ish. I chalked this up to traffic but the smoke was perplexing. Took the rural way home after I got off the freeway and the temp came down and the smoke dimished but was still present at times.
Had the car out this morning (16 mile drive). Blue puff on start up and shortly after take-off but then it went away. I was on open road this morning with the occassional traffic light (no traffic to speak of). The smoke, however, returned. I observed that the thick/heavy smoke was only present when the engine temp >120 degrees and the engine was below 3,000 rpm. Once I was above 3K rpm, there was no smoke. I mention that it is heavy because I can see the cloud lingering from several hundred yards away.
I've inspected the engine compartment and do not see any oozing, leaks, or otherwise suspicious fluids. Popped the bonnet as soon as I got back this morning to inspect for oddities and I saw nothing. Yesterday, I checked the oil and the level was normal. Coolant appeared to be low yesterday so I topped it off. This, in my mind, may be a clue. I plan to check again today once the engine has cooled.
Unfortunately, I know what *could* be the culprit (I won't say it for fear of jinxing it) but the intermittency of it all has me perplexed. Is it possible that the smoke is caused by the "new" exhaust tip? That is, as the exahust heats up, when there is blow-by, it is burning off at the muffler tip? I would have thought the replumbing of the crankcase ventilation would have fixed this.Any thoughts? As luck would have it there is a rally/Brit car show in 3 weeks and I really want to participate in my car...