Smoking diagnosis

acadian · Apr 28, 2021

Had the head and barrels off recently, cleaned up the exhaust valve seats and renewed the valves, guides were in good order, also installed new rings and lightly honed the jugs, piston clearance still within spec, rings gapped at .0045 top and .0055 second (first time trying the larger 2nd ring gap approach).

After a few shakedown miles she's smoking oil, particularly noticeable on engine braking.

So far I've performed the following diagnostics: leakdown shows less than 10% on both jugs, cold compression 110/120, warm compression 160/160.

Now, I'll admit that struggled with the fiddly oil control rings supplied (three piece with thin rails).

I intend to disconnect the oil feed to the head to see if it's the inlet seals or gasket. But based on how the problem presents on engine braking, I'm thing the oil rings are to blame.

Thoughts? Anything I missed?

baz · Apr 28, 2021

Disconnecting the oil feed to the head is good
It'll show any valve guide/seals problems
If it's mainly smoking on engine braking my money is on a displaced guide seal
Is it smoking one side only?

maylar · Apr 28, 2021

Engine braking (decel) is a high intake vacuum condition, intake seals would be my guess. Rings usually smoke under power.

acadian · Apr 28, 2021

baz said:
Disconnecting the oil feed to the head is good
It'll show any valve guide/seals problems
If it's mainly smoking on engine braking my money is on a displaced guide seal
Is it smoking one side only?

smoking on both, but much more pronounced on one side, there is some smoke on acceleration but only up to 1/4 throttle, it clears up above that

MexicoMike · Apr 28, 2021

Valve guides or seals. Did you remove the rocker shafts? If re-installed incorrectly they will also cause excessive oil that the seals cannot control.

Carl H · Apr 28, 2021

acadian said:
Had the head and barrels off recently, cleaned up the exhaust valve seats and renewed the valves, guides were in good order, also installed new rings and lightly honed the jugs, piston clearance still within spec, rings gapped at .0045 top and .0055 second (first time trying the larger 2nd ring gap approach).

After a few shakedown miles she's smoking oil, particularly noticeable on engine braking.

So far I've performed the following diagnostics: leakdown shows less than 10% on both jugs, cold compression 110/120, warm compression 160/160.

Now, I'll admit that struggled with the fiddly oil control rings supplied (three piece with thin rails).

I intend to disconnect the oil feed to the head to see if it's the inlet seals or gasket. But based on how the problem presents on engine braking, I'm thing the oil rings are to blame.

Thoughts? Anything I missed?

The ring gap spec is approx .010- .012 = 10 - 12 thousands , The piston clearance spec is .004 = 4 thousands .

acadian · Apr 28, 2021

MexicoMike said:
Valve guides or seals. Did you remove the rocker shafts? If re-installed incorrectly they will also cause excessive oil that the seals cannot control.

Rockers not removed

Carl H said:
The ring gap spec is approx .010- .012 = 10 - 12 thousands , The piston clearance spec is .004 = 4 thousands .

I should have clarified, rings were gapped at .0045/.0055 per inch of bore

concours · Apr 28, 2021

"Fiddly" oil ring. Ends on the expander are painted for easier viewing. There is no forgiveness there.

acadian · Apr 28, 2021

concours said:
"Fiddly" oil ring. Ends on the expander are painted for easier viewing. There is no forgiveness there.

Wasn't that style, these were Deves branded rings

Schwany · Apr 28, 2021

Did similar many moons ago. Took about 7000 miles for the rings to seal. In my case the light hone wasn't enough, I did not replace the guides, and I don't have guides that use seals, so it puffs a bit on deceleration. I blame all my puffing now on the guides and seals. Only puffs when the oil thins out and the motor is fully warmed up. I wish I'd done the guides when I had the head work done. Another coulda shoulda life moment.

I should get a quart of cherry fuel fragrance for the hard decelerations.

marinatlas · Apr 28, 2021

After a freshly rebuilt engine (200 miles),yesterday Ihad notriced little smoke but worse, crappy misfire above 3000 rpm, everything new (guides and so on By Pete Lovell) so this morning take the head off and could see two new black inlet oil guide seals popped out , so they are pumping oil ..........just put new red viton seals from Carl H( had ordered 20 weeks ago in case off...!!) right now , and have a cuppa , before fitting the head back , may be I will order the new seals from JS in case the red one do the same comedy................

Fast Eddie · Apr 28, 2021

You sure it’s not just oil from the honing?

You‘re not using some kind of unhelpfully thin break in oil etc are you?

Head gasket leak from pushrod tunnel to combustion chamber is a possibility, have you re torqued properly?

What rings did you use? Poor quality rings can cause smoking.

Before I tore it down I’d try re torque ing and giving it some good high rpm runs to bed things in.

acadian · Apr 28, 2021

Fast Eddie said:
You sure it’s not just oil from the honing?

You‘re not using some kind of unhelpfully thin break in oil etc are you?

Head gasket leak from pushrod tunnel to combustion chamber is a possibility, have you re torqued properly?

What rings did you use? Poor quality rings can cause smoking.

Before I tore it down I’d try re torque ing and giving it some good high rpm runs to bed things in.

Rings are Deves branded, have no prior experience with them. I'm hesitant to think guide seals as it wasn't smoking prior and I didn't disturb anything on the inlet side. Will give it some more road time to see if things bed in, I've got a new set of hastings rings on order just in case (the ones with the colour coded expander ring), and I have some KPMI viton stem seals if that does prove to be an issue.

Fast Eddie · Apr 28, 2021

Yup, try a bit more right hand to see if things bed in.

The other thing that has often happened to me is that post rebuild I’m just more sensitive / paranoid!

Saber · Apr 28, 2021

marinatlas said:
After a freshly rebuilt engine (200 miles),yesterday Ihad notriced little smoke but worse, crappy misfire above 3000 rpm, everything new (guides and so on By Pete Lovell) so this morning take the head off and could see two new black inlet oil guide seals popped out , so they are pumping oil ..........just put new red viton seals from Carl H( had ordered 20 weeks ago in case off...!!) right now , and have a cuppa , before fitting the head back , may be I will order the new seals from JS in case the red one do the same comedy................

I had the same experience. Smoking after new (black) seals and rings. I took it apart over the winter and both seals were popped off. Going with better seals, new valves, guides, and rings this time around.

Tornado · Apr 28, 2021

Might want to check the oil drain passage under edge of right side intake valve spring seat. Check how quickly oil is draining from the inlet rocker box. I had a slow drasin, able to clear it by running a wire down that opening to timing chest. And blasted it with a long straw and WD40

MexicoMike · Apr 28, 2021

Yes, poor rocker box draining has the same effect as an incorrectly installed rocker spindle - oil submerging the guides/seals. No valve seal can deal with that.

It's possible that with new rings you have better cylinder sealing and, therefore more vacuum on coast-down. But I assumed you installed new valve seals when you "renewed" the valves so that should not be a factor.

Carl H · Apr 28, 2021

marinatlas said:
After a freshly rebuilt engine (200 miles),yesterday Ihad notriced little smoke but worse, crappy misfire above 3000 rpm, everything new (guides and so on By Pete Lovell) so this morning take the head off and could see two new black inlet oil guide seals popped out , so they are pumping oil ..........just put new red viton seals from Carl H( had ordered 20 weeks ago in case off...!!) right now , and have a cuppa , before fitting the head back , may be I will order the new seals from JS in case the red one do the same comedy................

Never had a seal come off, I use the Black Diamond guides and fit valve to guide clearance they recommend . Some times people put seals on that don't fit the guide properly. they have to fit properly. The groove in the guide keeps them on , and viton is a high heat and chemical resistant rubber and is highly wear resistant. BD recommends 1 thou on the intake and 1.5 thou on the exhaust clearance valve to guide with a hone finish.

Torontonian · Apr 28, 2021

You left out mentioning the intake valve seals on the original post.
Kibblewhite sell vastly superior teflon seals as opposed to black plastic O.E.M. ones that harden , crack , or pop off causing hydraulicking effect as they ride free up and down the intake stem(s).

marinatlas · Apr 28, 2021

Torontonian said:
You left out mentioning the intake valve seals on the original post.
Kibblewhite sell vastly superior teflon seals as opposed to black plastic O.E.M. ones that harden , crack , or pop off causing hydraulicking effect as they ride free up and down the intake stem(s).

Yes mine were those black plastic OEM, and they pop off..........now will see with the red one, the head is fitted , carb too then too lazy to finish this evening!

Smoking diagnosis

Similar threads