puff of blue smoke at higher rpm decel

[Belgian1979]

Next is the wiggle test. But as at that time I will already have taken off the springs, I can just as well replace the seals. However it seems that valve guide wear is difficult to pinpoint.

[naukkis79]

If oil come from guides/valve seals engine will normally smoke at startup when oil has had time to drain downward. If only smoking is from high rpm decel I bet on piston rings.

[Belgian1979]

Compression test was ok.

[Ted Gerstenslager]

Do the rocker studs go into the intake port?

Yes, but they have silicone on them

Not good.
Firstly silicone is the slipperiest stuff and it will cause you to overtorque any fastener.
Only some silicone will live in a hot submerged oily environment.
Permatex white thread dope with teflon, permatex good old black with the brush.

Only a few simple places oil can get sucked in, guides, but that will show up as a puddle of oil most times on top of the valve.
Rocker studs
valve cover studs where ported into the intake ports
intake gaskets/ poorly fitting intake manifold
Trans that still has vac modulator

[Caprimaniac]

Bet on intake gaskets or rocker studs.

Wasn't this engine assembled a year or two ago? And heads delivered from a good source? Cannot see the valve guides have been worn to such an extent after such a short time, unless you have some serious valvetrain issues or really bad parts.

[Belgian1979]

Bet on intake gaskets or rocker studs.

Wasn't this engine assembled a year or two ago? And heads delivered from a good source? Cannot see the valve guides have been worn to such an extent after such a short time, unless you have some serious valvetrain issues or really bad parts.

More like 3-4 years
Should look up who supplied them to me at the time, but they were assembled Darts.

[Belgian1979]

Do the rocker studs go into the intake port?

Yes, but they have silicone on them

Not good.
Firstly silicone is the slipperiest stuff and it will cause you to overtorque any fastener.
Only some silicone will live in a hot submerged oily environment.
Permatex white thread dope with teflon, permatex good old black with the brush.

Only a few simple places oil can get sucked in, guides, but that will show up as a puddle of oil most times on top of the valve.
Rocker studs
valve cover studs where ported into the intake ports
intake gaskets/ poorly fitting intake manifold
Trans that still has vac modulator

Thanks. I assume with Telfon you mean Teflon rope around them ?

[naukkis79]

Compression test was ok.

Compression test won't find stuck oil rings. Excessive oil in piston actually rises compression pressure.

Is engine cruise AFR have been richer than stoich? Have seen plenty of stuck oil rings with overly rich cruise afr's.

[Belgian1979]

Compression test was ok.

Compression test won't find stuck oil rings. Excessive oil in piston actually rises compression pressure.

Is engine cruise AFR have been richer than stoich? Have seen plenty of stuck oil rings with overly rich cruise afr's.

Impossible to say, I have an AFR table that runs slightly rich of stoich all the time above idle. EGO correction would bring it back to what it needs to be according to the AFR table.

[Belgian1979]

Changed the seals on 2 cylinders. Wiggle test revealed I had some movement on some valves (exhaust).
Assume that the guides are not good anymore.
If I change this, it will happen when I do exchange my lifters as well, as in my case I need to take off my heads for that as well.

[naukkis79]

Impossible to say, I have an AFR table that runs slightly rich of stoich all the time above idle. EGO correction would bring it back to what it needs to be according to the AFR table.

Newer run richer than stoich at light load, it will ruin your engine. Unburnt gas will made excessive carbon built and rich afr will keep piston temperature lower than optimal which open up piston to wall and ring end clearances. When tuned ok you want to be much leaner than stoich at cruise and have plenty of accelerator shot to keep acceleration crisp, much much harder to tune right than rich-everywhere but if engine sees any mileage at road it's the only way to get any life of it without sticking oil rings into pistons.

[naukkis79]

And with closed-loop correction it's even more crucial to aim at stoich or leaner. With light part-throttle load rich afr will lower EGT to point where lambda voltage drops -> false lean condition and ecu will richen afr even more.

[Belgian1979]

It hunts severely when running stoich or leaner and even constantly starts missing. Some cams just don't let you do that

[naukkis79]

It hunts severely when running stoich or leaner and even constantly starts missing. Some cams just don't let you do that

Get rid of closed-loop autotune, if you have problems with stoich AFR closed-loop is not usable either. Even with very mild stock cams std engines have almost zero ignition advance at light load to keep EGT high enough to keep lambdas alive. With high-overlap cam EGT recirculation with rich afr will certainly lower egt to point where false lean happens, and ecu corrects to very rich afr, which ruins engine incredibly fast.

[modok]

Looks to me that, when intake was designed, part load operation was not one of the criteria.