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Having a problem with my 77 luv. Idles great, doesnt smoke at idle, drives okay, but when i go about 75% on the throttle it gets real sluggish stutters and then a massive amount of grey almost black smoke will pour out of the exhaust. checked plugs theyre good all fluid levels are good. little help please?

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1977 Stock Luv.

sounds like two things...

valve stem seals/worn piston rings.
do a compression check and see what you are running at.

also could be a carb problem.
get it tuned and see if that helps.

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To the Oquirr hills for awesome thrills! Go-go 4wd, Activate!

Oil problems/wear is usually bluish white smoke and usually goes along with oil fouled plugs.

Usually black smoke is running rich or unburnt fuel.

Sounds like it's running rich under wide open throttle to me. Could be as simple as a really dirty air cleaner?

thats right, sorry ben. i wasnt thinking clearly

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To the Oquirr hills for awesome thrills! Go-go 4wd, Activate!

well my air cleaner is brand new... and sometimes the problem goes away. did a little test driving today to see what was going on. the smoke isnt black it is a greyish color tho. i have played with the carb a few weeks ago because it was idling funny. turned the screw with the spring on it a few times to the left and it started idling right. i do not have a muffler on the engine and currently no thermostat. i thought that white/greyish smoke was usually coolant? is it possible i have a blown head gasket and its only blowing by at that high rpm and not doing it when the engine is cold?

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1977 Stock Luv.

yeah, thats the mixture screw. you need to set it according to the method described under the hood

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To the Oquirr hills for awesome thrills! Go-go 4wd, Activate!

First you said it was gray, almost black. Now it's white?

yes. thats my fault it was at night when it first started.
However, i set the carb to the settings stated under the hood. And, the hesitation is gone but the high rpm/high mph smoking is still there. its not a steady stream of smoke. Just one huge puff of smoke. Starting to scare me. Really do not want to replace this engine.

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1977 Stock Luv.

Keep an eye on your coolant and see if you are losing any, do a compression check, by all means put a muffler on your vehicle, engines NEED back pressure. Unless you pulled your thermostat for a reason you need to put one of those in as well. Thermostats help maintain pressure and while maintaining coolant temp also keep your oil at the right viscosity.

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In life there is the "Way things should be" and then "There's the way they are".

2005 Silverado 3/4T Crew Cab
1981 Luv 2WD
1979 Luv 4x4 Currently going through Open Heart and Cosmetic surgery
1995 Roughneck JetBoat
1981 Luv parts trk

Sounds like a carb/fuel thing to me. Coolant smoke is white, and should be present all the time so I wouldn't be too worried about that right off.

If it is somehow getting a burst of excess fuel at high RPM, like from a dribbling clogged secondary jet or somesuch, that would explain the smoke at high RPM/speeds. Leaking carb internals could be pooling some fuel up somewhere too that gets consumed all at once when the airflow gets high enough to pull it into the engine.

Also, don't forget to check out the points, as well as the cap/rotor and timing. Black/grey smoke is basically poorly burnt fuel, if there spark is weak/off it could cause much of the same. A mid/high RPM stumble was the usual sign on my 76 that it was time to replace the points.

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95 Isuzu Trooper Daily Driver
86 Isuzu Trooper reliable backup
77 LUV 2wd stock beltway blaster (resting)
79 4x4 LUV project: 2.6L, 5spd, 31s (eventually)

MEPR: Man, my 4x4 makes all other LUVs look good

Yeah i pulled the thermostat due to overheating a month ago. It was stuck shut and it looked pretty bad so i figured it would be better to run it without one. It has run great up until this issue. Will do a compression check and get a muffler and check everything else out. I am able to get up to 65 mph now. but sometimes it smokes still.

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1977 Stock Luv.