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78 Datsun 620 Smog help


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#21 rharm78

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Posted 18 October 2017 - 09:26 PM

I went with the hot type plug because i figured if i had a hotter plug it would burn more or cleaner? I replaced them awhile ago but the truck has not had too many miles since then either, like maybe 1,000 but i doubt that. Probably more like 600 ish. I thought regardless if it made a difference it was still a plug that is recommended in the factory service manual i have so it should be ok. But it was just something i thought i would try, i did not expect it to solve my engine issues. I know the engine is worn out, but it still has some life in it. If i can get it smogged and drive it once a week(if not more) that would be awesome. Yes the engine does consume oil, but i did not think it was to the point to where it was fatal. and if it is then its rebuild time



#22 rharm78

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Posted 18 October 2017 - 09:27 PM

I also run 91 because its what the manual says with all the emissions crap. 

 

And thank you so much for all the replies so far!



#23 flatcat19

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Posted 18 October 2017 - 09:29 PM

NGKs are backwards from most in how the heat range is numbered, though it's similar to Denso (might be a Japanese thing...).  Lower number=hotter plug, higher number = colder plug.  You rarely, ever, want a hotter plug.  Oil fouling is one of those instances, but it's a band aid, not a permanent fix.  And it won't solve the emissions problem.


I knew there was some correlation to my thoughts.

I don't work on cars that require plugs that are not NGK or Denso.

You can't hang if your nuts haven't dropped...it's physics


#24 datsunaholic

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Posted 18 October 2017 - 11:06 PM

I also run 91 because its what the manual says with all the emissions crap. 

 

And thank you so much for all the replies so far!

 

91 octane RON.  US pump octanes are typically displayed as R+M/2 (RON + MON /2).  The MON of most "Regular" unleaded is around 82, which is a pump R+M/2 of around 87. 

 

Running higher octane than necessary can cause lower economy (more fuel use).  My '76 runs best on 89- on 87 it pings badly, but running premium kills the mileage by about 10%.  I also have a higher compression head, though. 


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Well, at least he gets 24 hours notice. That's more than most of us get. All most of us get is, "Mind that bus!" "What bus?" _splat_!

#25 datsunaholic

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Posted 18 October 2017 - 11:17 PM

I went with the hot type plug because i figured if i had a hotter plug it would burn more or cleaner?

 

No, just keeps the plugs cleaner but risks preignition since the plug retains more heat.  You really want the coldest plug that doesn't foul.  Unfortunately since you're burning oil that does mean a hotter plug, but if you're burning enough oil to throw the emissions off, I don't think anything short of a rebuild will make it pass.  And no, it doesn't have to smoke to be burning enough oil to throw off the emissions.  One of mine was burning a quart every 500 miles before it started showing smoke, and that was WITHOUT a catalytic converter, which will mask it to some extent.


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Well, at least he gets 24 hours notice. That's more than most of us get. All most of us get is, "Mind that bus!" "What bus?" _splat_!

#26 datzenmike

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Posted 19 October 2017 - 04:54 AM

Check that the oil is not over filled.

 

Try a thicker oil like 15W40.


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#27 rharm78

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Posted 19 October 2017 - 06:42 AM

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?

#28 datzenmike

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Posted 19 October 2017 - 08:55 AM

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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#29 Stoffregen Motorsports

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Posted 19 October 2017 - 08:59 AM

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.



#30 datzenmike

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Posted 19 October 2017 - 09:03 AM

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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#31 racerx

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Posted 19 October 2017 - 10:27 AM

Would sea foam work in this case?

#32 Stoffregen Motorsports

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Posted 19 October 2017 - 10:30 AM

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



#33 flatcat19

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Posted 19 October 2017 - 10:30 AM

Seafoam is a top end cleaner.

You can't hang if your nuts haven't dropped...it's physics


#34 MikeRL411

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Posted 19 October 2017 - 01:20 PM

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. 



#35 racerx

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Posted 19 October 2017 - 04:41 PM

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

#36 rharm78

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Posted 19 October 2017 - 10:08 PM

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

#37 racerx

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Posted 19 October 2017 - 10:24 PM

Timing chain should b good

#38 racerx

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Posted 19 October 2017 - 10:35 PM

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

#39 rharm78

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Posted 19 October 2017 - 10:37 PM

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

#40 datzenmike

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Posted 20 October 2017 - 04:52 AM

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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