Engine rebuild smoking

[Zed Head]

Not sure a leakdown test would show the source of the oil.  It shows whether the rings or the valve seats are sealing well, holding pressure in the combustion area.

The valve seals were apparently just eyeballed.  A borescope might still show something.  Oil soaked intake valves, versus clean ones.  The oil from the crankcase must come through the intake system or past the rings.

Or just pulling the intake manifold.  Or the head.  Pulling the engine is pretty easy though.

 

On the rings - he implied that he got the rings from a suspect vendor.  So it's an issue of ring quality or type or labeling.  All of them.  Seems like the builder would have noticed but who knows.  But for some reason emccallum had the boxes.  Not sure how the rings got on the pistons.

[Tirnipgreen]

Too Rich...? Remove air filter cover, take a thin, flathead screwdriver and raise the carb piston about 1/16" to 1/8"...if it starts to die, it's too lean. If the RPMs increase, it's too rich. From a lifelong Triumph owner...!

[Yarb]

If you read further back in the thread he has lost a quart of oil. IMO carbs are not part of the equation. These carb’s from what I understand just got back from Z Therapy. 

[Tirnipgreen]

I would think it's a bad ring...but threw the carb stuff at anyone who cares...!

Edited April 26, 2023 by Tirnipgreen

[billgtp]

I would do a cylinder leak down test before I take anything apart. At least this would give you idea of condition of lower end.

[HusseinHolland]

7 hours ago, Zed Head said:

Not sure a leakdown test would show the source of the oil.  It shows whether the rings or the valve seats are sealing well, holding pressure in the combustion area.

The valve seals were apparently just eyeballed.  A borescope might still show something.  Oil soaked intake valves, versus clean ones.  The oil from the crankcase must come through the intake system or past the rings.

 

It would definitely indicate if the rings are the issue, I've specifically diagnosed an issue with oil consumption on my K24 that way. One bad oil control ring. It was consuming a quart every 200 miles. True that if the valves are fully seating, it's not going to indicate if the valve seals are the issue. As you said, either removing the intake or carbs & looking into the ports for oil on the valve stems would likely be the way to go for that aspect. 

[emccallum]

FWIW, when I replaced the valve seals (which were fine) I used compressed air to hold the valves in place. On several cylinders I could hear air escaping somewhere at a pretty good rate. It wasnt coming up through the valves. I couldn't feel it through the dipstick but I didnt close off the PCV hose, so it may have been coming through there. At that point I knew swapping seals was a waste and the motor needed to come out. Pretty sure the issue is going to be rings, but I will know for sure pretty soon.  Thanks for all the comments and support. @Patcon has offered to drive down and help me pull the motor. Great group here.  

 

[Yarb]

@PatconCheers to you friend for helping Sir!

[bartsscooterservice]

On 4/25/2023 at 2:09 AM, emccallum said:

Good points. PCV is clear, and oil was 5qts and to the full mark. 

Like a dumb*ss I threw away the old rings and boxes, so I dont know what they were.  I bought rings, rod/crank bearings. No pistons or head stuff.

Spoke the the engine guy at length today. He did some homework on the SU's and asked me to check the fuel pressure. 2psi. He said pull the motor. 

I checked the dipstick for any fuel and noticed its about a qt low. I think the missing quart is all over my shop and concrete! I will post up what I find. May pull it on Friday if I can find a spotter. 

Bad video attached.Enjoy my pain 🙂

 

 

Let some good shop do the engine !, and rebuild the head also properly, horrendous valve clatter ! A proper shop will replace these and polisch the cam, or replace the cam, this will stop the rattle with proper valve adjustement.:

 

Datsun 240Z 260Z 280Z ZX 1970-83 L24 L26 L28 Valve Cam Rocker Arm | eBay

My L24 is silent, no rattle can,  it's a common myth L series rattle, but that's BS 

 

 

[dutchzcarguy]

WOW.. what a noise that thing makes, what was the rpm in the video?  2000, last seconds going to 3000 rpm? Does not sound very nice! Sounds more like you had a box of cutlery on top of a very shaky engine!  sigh 🙊

[dutchzcarguy]

I also would have liked to hear the sound in the enginecompartment.....  So far it's far from the right sound.

[Patcon]

So I don't want to get ahead of Ernest but I'll post up some info from today.

I went and helped him get the engine out. We tore it down to the long block

The intake valve stems were really clean looking. The exhaust ports looked really wet!

It's a little hard to see in this picture. That is actually a puddle of oil in the exhaust port!

This is actually liquid like oil that was seeping down under the gasket.

Pretty much all of the ports had the same situation. The PCV hose was nice and clean. I would say all of this is coming from the bottom end and it's not isolated to one cylinder.

To me that rules out a broken ring or bad ring indexing or something isolated like that. This is an issue across all the cylinders.

I also don't believe the engine builder is going to be the issue. He's apparently been building races engines for probably 40+ years. If I had to guess, I would suspect the oil rings destroyed themselves. Possibly poor quality rings...

Will be interesting to see what he finds when he tears it down