Exhaust Smoke

[AN6-TX]

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...

 

[Deleted member 8987]

Ah. So. Now go back and start undoing things that he did to see where the change occurs.
It's a 67...you have emissions testing in Colorado?
Pull the hose off, cap the PCV temporarily and see.
First thing. Was the canister cleaned out before re-plumbing?

 

[ChrisS]

I'd have someone follow you and tell you what the smoke looks and smells like. White smoke is usually coolant and has a sweet smell, blue is oil and most people know what that shells like, black is a fuel rich mixture and will tend to irritate the eyes. There was carb work done but there is no mention of black smoke so the smoke and the carb work may not be related.

As far as the temperature goes, ask the mechanic if they adjusted your ignition timing. If he retarded the ignition timing this could explain the increased temperature.

 

[AN6-TX]

Thanks, TOC. I plan to do some further investigation throughout the week. In regards to whether or not the canister was "cleaned", I am guessing not as you have to clear a path to get to it, and subsequently pull it out for cleaning. I could be wrong and plan to verify with the mechanic tomorrow.

I appreciate the response, Chris, and the suggestion to have someone follow me. On a related note, the coolant level did not appear to drop after today's drive so I am hopeful that its not coolant causing the smoke...as that would mean bad things.

 

[Deleted member 8987]

In will say this based upon many decades of professional auto repair. Just read it and think about it.

When we had a smoker, we would walk through the cloud and inhale through our mouth.

If it's anti-freeze, you will taste a slightly sweet smell. If rich mixture, you will taste petrol. Then in through your nose...oil you know the smell of...then get out of the cloud.

Gave us a quick direction of where to look.

On the smoke, if you had a road draught tube or hose, any blowby would vent externally. With a PCV, yes, emissions-wise it's better, but now you are sucking any blowby into the inlet manifolds.
I know there are issues with some rocker covers and PCV valves....if the baffle is gone, or the rockers are worn enough oil is gushing out, you'd never notice with a road draught tube, but with suction continuously on that source, could be a big problem.
Been a lot of years since I had my hands on a 67 Sprite, but isn't there a high and low port on the canister? Isn't suction off the fumes on top, breather line to rocker cover on the bottom?
If backwards, oil will suck right into the inlet.
Just disconnect the hose at the rocker cover, plug it with a bolt or old spark plug, and see what you have for smoke. Cheap, quick, won't hurt anything (you may notice the idle will change a bit without the forced vaccuum leak of the PCV Valve).

 

[Bayless]

I agree. The logical starting point is the crankcase venting system. That was the change made that is most likely to cause smoke.

 

[dklawson]

Per the above, suspect the PCV system you added. As a quick test, restore the old draft tube configuration and make sure you plug the disconnected ports of the PCV valve. Put the draft tube end into a catch jar instead of leaving it open to the road. If the smoke goes away you know you need to re-think the PCV system. They can be problematic.

 

[nomad]

I'm curious as to whether it got the factory PCV or a home made set up. Like the others I suspect that.

Kurt.

 

[AN6-TX]

I'm curious as to whether it got the factory PCV or a home made set up.

Based on some research I did last night, I believe the PCV that was installed was the later version (say 1968 and after) rather than the appropriate one for my engine (looks like a mushroom - bulbous head and skinny stalk). That said, I spoke with the mechanic today over lunch and he knew what the (most likely) cause was before I finished my description. Offered to reverse it at no cost and promised to get me in and out at my convenience in 30 minutes or less.

 

[AN6-TX]

Put the draft tube end into a catch jar instead of leaving it open to the road.

I haven't Googled any home remedies but whats the easiest why to make/install a catch jar without drilling holes? Any suggestions?

I know Moss sells an option but is somewhat pricey IMHO.

 

[dklawson]

I haven't Googled any home remedies but whats the easiest why to make/install a catch jar without drilling holes? Any suggestions?IMHO.

I have seen items ranging from old Coke bottles, bicycle water bottles, and anodized aluminum water bottles used as catch jars. I've seen them mounted with homemade brackets, windshield wiper bottle brackets, and tied to convenient locations with zip ties or even tape. It's largely a question of how you want things to look and what is at hand. The only advice I offer is that if you choose a wide mouth bottle for the catch jar, fill it with Chore Boy scrubbing pads or similar to increase the surface area, then insert the draft tube about 1/2 way down the depth of the jar. This will help collect some of the oil fumes that would otherwise escape.

 

[nomad]

Baling wire and an old quart oil can!:friendly_wink:

Kurt

 

[SaxMan]

I don't want to jinx it either, but white smoke and increased operating temperatures seems to point to the beginning of an issue that rhymes with "red masket".

That being said, I once switched my original stock air cleaner on my '69 Sprite with one of those "Open" air cleaner types, and the car produced a huge smokescreen. I don't know what the difference was, but when I put the stock air cleaner back on -- no more problems. I'm guessing it was a vacuum related issue.

 

[AN6-TX]

Final update:
I finally found the time to reverse the PCV installation. As suspected, this did the trick - no smoke. Put a good 20 miles on the car yesterday without issue. I appreciate the guidance (and support).

 

[Bayless]

I love it when a plan comes together.

 

[Boink]

Per the above, suspect the PCV system you added. As a quick test, restore the old draft tube configuration and make sure you plug the disconnected ports of the PCV valve. Put the draft tube end into a catch jar instead of leaving it open to the road. If the smoke goes away you know you need to re-think the PCV system. They can be problematic.

Had this problem. The intake would occasionally gulp oil from the oil-separator... and, man, does that produce a HECK of a lot of white smoke. If you added or messed with the PCV system, I'd disconnect it. I went back to old-school venting to ground. :rolleye: