Engine rebuild smoking

[emccallum]

Complete engine overhaul. Stock build L24/e88.  First start this weekend.  10w30 dino oil, engine fired up, held revs 1500-2k for about 30 min shut down and let cool. Noted a small amount of blue smoke. Restarted fine tuned timing, carbs etc. and blue smoke continued and got worse.

Called engine guy. He thought the rings weren't seated. Said to run hotter 180-200 for an hour then shutdown, let cool. Lots of smoke. Engine seems to run well and no noises. Just smokes. Coolant is fine, engine runs with gauge right in the middle. 

Builder came by today checked plugs, compression and valve train. He isnt an SU guy, but really thinks the issue is too much fuel. Wet black plugs. Compression #'s were all 175-180. All immediately jumped to 90 at first rotation. Warm engine, throttle wide open, all plugs removed.

Carbs are fresh from ztherapy. SM needles. I just dont see how they could dump that much fuel to cause the amount of smoke I am seeing. I am thinking valve guides. Is there any way the ATF fluid in the carbs could be getting sucked into the intake? I told the engine builder I would check out the carbs. The engine builder did the block and a machine shop did the head. Thinking the head is going to come off. Just wanted to get some input from the forum. Fun, fun.

I often wonder what people who dont work on cars do with all their free time and money 🙂

[DatsunZGuy]

The only time I experienced ATF being burned off by the carbs is when I overfilled it.  Eventually the excess gets burned off. 

I would try running the carbs a bit leaner or maybe popping off the tops and re-seating the needles and see if anything changes.  

[Patcon]

The compression numbers look good. I have heard of people running ATF in their SU's.  I don't think the ATF is the issue. It will draw it out if the pistons are overfilled. It will stop once it's pulled down some. I wouldn't mess with the needles yet as they're fresh back from Ztherapy.

I might also make it a little leaner with the knobs.

I would expect the floats to be right after the refresh too. You could check them but I wouldn't go adjusting them right away.

If you restart it, does it smoke a lot and then get better. Typically valve seals and guides will drip onto the backs of the valve stems and smoke heavily when first started.

Also wet looking plugs are typically oil unless you have a lot of extra fuel! The smoke would be obviously black at those levels too.

 

[emccallum]

Smoke is blue/white. Smells like an oil burner.  After sitting not much smoke at first, then it gets worse as it runs. As you rev the smoke increases. Like its injecting oil into the cylinder, or sucking it in. 

When I lean out the carbs with the knob, it starts to fall off. Best running at 2 3/4 turns. 

Motor really runs very well. Valves might be a bit loose. Just smokes. Oil level is stable and oil looks good.

It reminds me of an air cooled Porsche that has oil dripping into the heat exchangers. I wonder if my garage find exhaust might have been filled with oil or burning off old deposits? I would think that would all burn off pretty fast. 

[Patcon]

You would think oil in the exhaust would taper off as it burns out, not increase with run time.

Does the head have new valve seals?

[emccallum]

7 minutes ago, Patcon said:

You would think oil in the exhaust would taper off as it burns out, not increase with run time.

Does the head have new valve seals?

That is my thought as well. Kind of grasping at straws with that one. 

As for new seals, I would certainly hope so, but i dont know for sure.  That is something that could be done without removing the head. 

I am thinking of doing a leak down, I know that wont cover the seals, but it may give me some more info. 

[Zed Head]

13 hours ago, emccallum said:

engine builder did the block and a machine shop did the head

Details might show something.  "Did" is not enough.

Valve seals can get damaged during installation.  You might even see something just by removing the valve cover and taking a look.

Is there blowby?  Smoke from the oil filler cap?  Wrong/poor rings and ring sealing should show up there also.

[emccallum]

Yep, and it is getting harder and harder to find people with integrity.  I have restored several cars over the years, and the last couple of years has been the hardest ever to get work and parts. I am thinking this is my last restoration.........until this pain is forgotten and another project drops into my lap!! 🤣🤣

I looked at the valve train and didnt see anything but it may be worthy to look again more closely. Felpro valve cover gaskets suck. 

I am running it with nothing on the valve cover breather port and no smoke is coming from there. I did remove the oil cap while it was running to make sure I could seeing oil spalshing around and didnt note any smoke.

Could it possibly be water from the manifold heater getting into the intake? I bought new carb insulators to make sure everything had fresh gaskets. I assume the new OEM insulators have gaskets on them?? They appeared to have a gasket, and it isnt leaking water. The carbs are the style that have water jackets in them.

 

[Zed Head]

Oil smoke has a distinctive smell, and so does gasoline vapor.  Might be worthwhile to run through the cloud and see what it smells like, if your nose works.

And water vapor dissipates pretty quickly.  You could put a smooth cold surface at the exhaust pipe, a mirror or a piece of chromed metal, and see what condenses.  If it's as bad as you describe you should get something.

Edited April 17, 2023 by Zed Head

[emccallum]

smells of oil to me. I just need to find out where its coming from....bottom or top. Hoping the top. 

[emccallum]

I have run out of easy stuff to check. PCV and carbs seem ok.

I ordered some valve seals and I am going to check and replace them as a first step. If that doesnt do it, then I guess my only option is to pull the head and bring it to a different machine shop for evaluation. I will keep you guys posted. Thanks.

[Zed Head]

I wonder if a bore scope would show anything?  Down the plug hole and maybe down the intake runners.  Leaking valve seals should cause oily intake valves.  Of course, if it's that you'll end up removing the head anyway.

Still interested in what the block and head guys did or said that they were going to do.  No details.

Have you checked the spark plugs?  Maybe it's just one or two cylinders.