154 on all cylinders.... Burning oil like no tomorrow

[MantisX620]

Hi Ratsun family,

 

Ive been burning a shit ton of oil lately. I can drive my truck from my house to my parents house(about a 25-30 min drive one way) and by the time I get home, park and let the oil settle, im about halfway on the dipstick when I started at full. I ran a compression check and im getting a smooth 150+ on all 4 cylinders. No oil leaks at all.

 

Also, I notice on first startup, is when I can see visible smoke. After it warms up, I dont see any smoke visibly.

 

Heres the thing, theres someone locally selling a supposed fresh L20 for 300 bucks. Id like to keep mine if I can figure out whats wrong, but I also dont want to wait too long on getting a known good engine.

 

What else could it be thats making it chug oil?

 

Thanks all

MantisX

[ariascarlos1990]

When was the last time the valve stem seals have been done?

[72240z]

I second that, stem seals seem likely. Can be other causes but thats got to be the most common.

[datzenmike]

1/2 quart in 1/2 hour you'd see the smoke. Check the underside of the motor and transmission for oil spray.

[MantisX620]

Just laid under it with my shop light and its dry as my feet. Im not sure when the valve seals were done, ive only owned it for a year. Im willing to try valve seals though as im sure thats cheaper than 300 on an engine.

[metalmonkey47]

Is it leaking from the rear main and puddling in the bellhousing?

[ggzilla]

im getting a smooth 150+ on all 4 cylinders

That is half the data. What is the compression for the wet compression test?

 

I notice on first startup, is when I can see visible smoke.

That is the valve stem seals (or more precisely, worn valve guides).

 

After it warms up, I dont see any smoke visibly.

Normally you won't see it, but the smoke tests will tell you. Click Engine Smoke Testing.

[MantisX620]

So I took off my valve cover just to take a look and its black as night all inside. Im starting to think this motor hasnt been taken care of the best. Ill try to get pics up once I replace my shop light bulb.

 

Ive decided to bite the bullet and change the seals. I just have paranoia about screwing up the timing or dropping a valve. Anyone find a cheap valve compressor that can do it without taking out the cam?

 

Thanks

MantisX

[Z-train]

150 pounds is out of "serviceable specs".

[ggzilla]

Why change the seals -- it's not going to fix the problem. That much oil loss can only be caused by bad rings or external leaks. Do the smoke tests and save yourself time and money.

[ggzilla]

Yes, 150 is out of spec with a calibrated gauge. But 150 pounds on all four with many gauges means the rings are good. I've seen many gauges that are not well calibrated, which is why many repair manuals tell you not to look for a specific number. Do the wet test to verify these results. If the dry test is 150, and so is the wet test, compression rings are good.

[MantisX620]

Ok I'll run another dry and do a wet tomorrow and see what I get. Thanks guys, gave me alot to check and think about.

 

MantisX

[banzai510(hainz)]

YOu PCV sytem ok???

Your not routing a hose wrong or soemthing?

tale a photo of the valve vover and the crankcase pipe going out to the intake.

 

half oil is too much and you should be seeing it!!!!!!!!!

 

what the spark plugs look like???????

 

offer 200 for the motor as I bet there isnt that many L20 for sale on the east coast

[Z-train]

Yes, 150 is out of spec with a calibrated gauge. But 150 pounds on all four with many gauges means the rings are good. I've seen many gauges that are not well calibrated, which is why many repair manuals tell you not to look for a specific number. Do the wet test to verify these results. If the dry test is 150, and so is the wet test, compression rings are good.

FSM says below 164 is out of spec.Kinda point-less chasing a consumption issue when the rings in general are toast.

[MantisX620]

Point taken guys, I think ill go ahead and call them up and see if I can get it. They claim the rings and bearings were redone, block and head decked, only 500 or so miles and they pulled it to do a SR20.

 

My first Datsun transplant, this should be fun!

 

Thanks again

MantisX

[Z-train]

FIVE HUNDRED MILES and the compression is only 154?It should be over 180.I just did my compression check and they were between 172 & 180 and this is with 100K on the motor.

 

BTW-when you did the compression check,you did pin the throttle wide open didn't you?

 

 

You're pissing on a forest fire.Pull it and take it apart.

[MantisX620]

No no, misunderstanding. The engine in my truck now has 154 compression. The engine im looking to go buy has just over 500 miles.

 

Yes, did have the throttle wide open, when testing.

[Z-train]

O.K......but 154 is rebuild territory.

[ggzilla]

154 is NOT always rebuild territory. Sometimes it means GOOD. Unless you have a tested, calibrated gauge a specific number is just spouting hot air. As I said, 154 is out of specifcation, but is rather meaningless.

 

Do the wet compression test to confirm good or bad.

[Xnke]

Even 154 can be just absolutely peachy too, depending very much on the valve lash, cam timing, lobe profile, ect. Compression testing is best judged by comparing cylinder-to-cylinder specs, as long as the cylinders are within 10% of each other, the rings are probably fine.

 

OP, your valve stem seals are toast. Replace them. Your valve guides might be worn, but even at 100K miles++, I've only seen one or two bad valve guides in stock engines...those old cast iron guides last a LONG time.

 

You can loose a LOT of oil really quickly throught the PCV system if it's not plumbed right or if the valve has failed on a block with so-so rings. Check it.

 

If you're loosing a pint of oil in 30 minutes of run time, that's a SERIOUS amount of oil...if you were burning all of it then you'd be doing a public service by killing ALL the mosquitos in the neighborhood as you drove through. That'd be a FUCKLOAD of oil smoke.

[MantisX620]

So I checked today and the PCV hose was not connected to anything, so PCV was venting to atmosphere. So I guess the rings/seals truly are shot.

 

Also, I went and bought another L20. Im hoping this one will will do better. I will be cleaning the pcv element and hooking the PCV system back up with this engine.

[I'm BLUE]

if you still plan to keep/run that engine for another purpose ....A leakdown test will answer many suspicions if you need 100% confirmation/direction rather than going blind.

Cool.

Usually a good running used engine is best way to go ( for me )

[king bee66]

if the pcv valve is not connected to anything that means your motor is spitting oil out

[72240z]

if the pcv valve is not connected to anything that means your motor is spitting oil out

 

I hope your just trollin him and dont really believe this lol

[I'm BLUE]

 

 

I hope your just trollin him and dont really believe this lol

 

Lol

 

Oh yeah I forgot ...

Concerning your newly acquired l20b

 

You can perform a compression test ... With a good charged battery ... And engine tied down on the cherry pick ... Or whatever .... Before dropping her in and installing. Saves a lot of heartache if in case it turns south on you.... Perform dry and wet compression tests. :) .

 

Good ideas

* Inspect rear main seal and replace

* Inspect clutch components. Disc is usually a good idea.

* Inspect timing chain slop ... Easier to replace on ouside of rig if needed or advanced to compensate for stretch.

 

Use Anti-seize on your spark plugs.. as the threads will last longer :)