I've been thinking all along that it's gas, from running rich. But then I find that when I'm getting combustion in my tailpipe, it's caused by running lean? When I coast at higher rpms, I get popping out of my exhaust. Doesn't happen as long as my foot is on the gas.

Anyway, what I notice is that after I've been driving for a bit, usually at highway speeds, when I pull into a campsite and start trying to level my camper, I get a TON of smoke out the tailpipe. This is really the only time it happens.

For some reason I'm having a hard time telling if it's unburnt fuel or oil I'm burning. But it happens after driving for awhile, then pull into a spot, idle for a little bit, then give it a lot of gas to get up on my leveling blocks. It wasn't happening before, but now I've got a pretty good plume of smoke I send out when I do this. Getting a little embarrassing...

This is a 20R, desmogged with a Weber.

If it turns out to be oil, is there a way to narrow it down to rings or valve seals based on when it happens?

 

oil smoke is not black. it ould be white or blueish white. black sounds like flooding to me

 

Oil would be a blueish color. Black is unburnt fuel. Checked the condition of your plugs? That should tell you

 

Well, I should say "dark" smoke. Having a hard time telling if it's more black or blue. I'll check my plugs. Last I looked at them, they agreed with the backfiring out of my exhaust. If anything, I'm running lean.

 

Well a friend confirmed it for me. It's blue smoke. So...what are the easier ways to tell whether it's rings or valves?

 

Dry and wet compression tests

 

You'll need to do a compression test and leak down test. First, for the compression test, when the engine is warm, make sure you disconect your coil from the plugs at the base of the coil, block fuel entry to the carb, and do the test with the throttle open, write down your numbers. Then drop a bit of oil in the cylinders and do the test again, check the difference in number. If there is a significant difference, rings are shot. For the leak down you can have someone hold the pedal down and try to listen for a loud hissing noise coming from the intake (valves) or through the block from the dipstick tube (rings but mainly compression rings)

All the specs on % of leak and compression number service limit are in the fsm. Rule of thumb is if you are smoking at startup it is valve seals from the oil dripping when the engine is turned off. If there is smoke at acceleration or when you press the gas after letting it decelerate it is usually stuck or worn rings.

My rings are shot and I used a bottle of lucas additive it helped a little...

 

Usually if you get smoke on start up it's the valve seats leaking but after driving and it still smokes it's the rings normally

 

Ok, thanks. I'll get to those tests at some point when I'm not on the road.

It happens a little at startup, but mostly like I mentioned above. I notice it most when I've been driving for a bit, pull into a camp and idle for a little while, then hit the gas. Big plume of smoke.

 

It really sounds like valve seals, time for a refresh! In the mean time I suggest your next oil change to be done with shell rotella diesel 15w40 oil and half a bottle of lucas additive (you don't have to use the brands I use I just really like them and always run diesel oil for their high zinc content) it will help with the smoke.

 

^x2 Rotella diesel oil can do wonders for an old engine in need of a rebuild. It doesn't completely fix the problem, but it does prolong the life of the engine until a rebuild can be performed. Rotella has additives and cleansing agents that help seal rings, clean valves and lubricate seals thus reducing blow by and oil consumption. I had REEEEEALLY bad blow by and oil consumption on my 83 22R, but it was summer time and I didn't have time to rebuild it. I was going through about a quart and a half of oil per each fill-up (about 250 miles) until I put some 15W-40 Rotella in the crank case. After that, I was only consuming about a half a quart per fill-up and my fuel economy event went up a little. But like I said, it's a fix to prolong the life of the engine for a little bit; it's not the solution to your problem.

 

I will do that, thanks!

 

Just an update.

Had the head rebuilt over the winter. Put it together early this spring, and have driven it about 2,000 miles. No big plumes of smoke, and I don't notice any smoke when I get started from a light or stop sign.

I can smell a little burning, but I'm sure that after 35 years there's some making its way past the rings. But the big plumes of blue smoke seem to have been the head.

Thanks.