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rharm78

78 Datsun 620 Smog help

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Check that the oil is not over filled.

 

Try a thicker oil like 15W40.

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I'm running 20w50 right now. I know it's not overfilled I checked it yesterday before I started it.

 

Again I knew that the hotter plug was not going to fix my oil consumption issues. I thought it would buy me more time because I did not realize it was this close to needing a rebuild.

 

So I guess the reason why it is not passing is the engine is so worn out its burning to much oil? That sucks lol

 

I was thinking about doing a tranny swap anyways so I guess this is my chance.

 

I know this may be ignoring the obvious answer which is oil consumption, but could it be an egr or anything like that?

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ERG is to reduce NOx

 

 

 

Take top off air filter while running. Is gas dripping into the carb barrel? 

 

Look at round sight glass on front of carb. Is the fuel level at the dot in the middle?

 

Inspect air filter element. Is it covered in oil from the vent pipe?

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There is one way to loosen the rings of a dirty engine, but it requires that you be able to drive it for 500 to 1000 miles before any results may be known. Add a quart of ATF to the engine oil. Its detergent properties can help loosen stuck rings. I have used this trick in the past and had success, but it only adds a marginal amount life to an engine. It may smoke during the process and you have to change out the oil after the 500 to 1000 miles before you will know if it worked or not.

 

If you have the time, it may be worth a shot.

 

Other mystery fixes have been sold over the counter, but this is the one trick I know.

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Sometimes the carbon around the rings is controlling the oil being burned. I 'inherited' my dad's old car he drove 3 miles to work and then back for 4 years. When I drove it 30 miles plus a day within 2 months it started smoking.

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Would sea foam work in this case?

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I have never used sea foam, but I thought it was just for cleaning out cruddy intakes. Mainly on EFI engines. Don't know.

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I'm running 20w50 right now. I know it's not overfilled I checked it yesterday before I started it.

 

Again I knew that the hotter plug was not going to fix my oil consumption issues. I thought it would buy me more time because I did not realize it was this close to needing a rebuild.

 

So I guess the reason why it is not passing is the engine is so worn out its burning to much oil? That sucks lol

 

I was thinking about doing a tranny swap anyways so I guess this is my chance.

 

I know this may be ignoring the obvious answer which is oil consumption, but could it be an egr or anything like that?

 

A dirty trick used car vendors used to pull.  Remove the spark plugs and add about 1 teaspoon of castor oil into each chamber.  Reinstall plugs and fire up the engine.  The castor oil forms a rubbery seal around the top of the pistons and give a temporary boost in compression due to reduced leakage past the pistons.  This is why WW1 fighter planes used castor oil based lubricants and also why pilots liked to guzzle champaigne after flights, to get that yucky taste out of their mouths. This will reduce temporarily the amount of oil leaking into the exhaust. Should help reduce the exhaust hydrocarbons during test. 

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Just read sea foam and claims to clean, upper and lower engine, intake and carb

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So should I try these on an engine that's already worn out or should I go for a rebuild?

 

About two years ago I did a headgasket, the bore looked good. No deep marks. Probably could get away with ball honing it? That's probably what I would end up doing. Install new rings and a valve job. New oil pump. Put it back together and reinstall. I would do an in-frame but the rear main leaks pretty bad, along with other external oil leaks so mind as well pull it. The timing chain isn't even 10,000 miles old, would I have to replace that? I assume not.

 

But as I said before if it is worth it to just keep driving then I will do that

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Did u read the part about how u did ur compression check?

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Yes after I warm the engine up with throttle wide open, right?

 

I should be able to check that on Saturday. I have a long commute everyday so I don't get home until it's too late to work on the truck

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Rebuild only if it needs rebuilding.

 

Is your carb over full?

 

 

Let me ask.... how much oil do you use? I would guess if you can get 2-3K on a liter this is pretty good.

Worn valve seals will eat oil and are easy/cheap to replace.

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I'll have to check the carb later. Probably tomorrow when I do compression check.

 

I use a quart at least every 500 miles.

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Well stop right there.....

 

Put some cardboard under the truck over night to make sure it isn't just leaking.

 

1 Qt /500 miles it must be smoking pretty bad. There's your fuel for over rich

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Well I know the truck externally leaks oil pretty bad. Also hence why a rebuild probably isn't a bad idea.

 

It doesn't smoke. At least not that I ever noticed. Actually I take that back. The one time I remember it smoking was once when getting on the freeway, the auto tranny kicked down and I looked in my rear view mirror and there was definitively something. It was at night, but I could see a large cloud coming out of the exhaust pipe through the headlights of the car behind me. It worried me for a while but it never smoked any other time. And it was a rare instance where it kicked down to a high rpm

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So should I try these on an engine that's already worn out or should I go for a rebuild?

 

 

Why not try? What have you got to lose?

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True. I'll add some atf and do a compression check before and after. The engines already going south I don't think much can hurt it lol

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I'm w mike, don't rebuild unless u have to. Do a compression as mentioned first, maybe even do wet also.

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@500/Qt I think it's cooked.

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Wet compression check? As in adding oil to cylinders to see if the compression goes up? Isn't that a tell tale sign of the rings being bad?

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Yes, as well as valves, headgasket

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