Constant Blue Smoke

[Paul Smith]

Ok a bit miffed now, she is back together modified the air box slightly fitted it all nice tight started her runs, revs and idles like a dream.

Now the nightmare - She is blowing dirty dark smoke which i kind of expected as she is running rich, but she is also blowing the dreaded blue smoke. I thought it'd burn off as we put a dribble with the pistons as you do to stop any scoring on the initial start up but its not clearing. I have tried a few times now including tonight where I stood out there for about 30 mins gently easing her up to arround 3.5k rpm but it showed no sign of letting up. Any suggestions as I'm at the stage where I really do not want to take the engine apart again GRRRRRRRRRRRRRRRRRRR.

I damaged a piston years ago and as a result it blew smoke but some how doesn't seem the same as now. As for valve stem sills i had a very expensive proffessional company put the head together for me so this sort of thing wouldn't happen (normally I'd do it)
:down:

 

[frank]

cylinder honing too deep maybe paul ?

 

[Paul Smith]

cylinder honing to deep? I haven't rebuilt the bottom end? fwn

 

[frank]

cylinder honing to deep? I haven't rebuilt the bottom end? fwn

cant be that then eh :grinning: head gasket maybe ? (are all 4 plugs oily ?)

 

[Paul Smith]

the pistons didn't leak before, so not sure what would have made them go this time.

Is it possible the piston ring is sticking?

 

[lucifer]

Is that another cylinder head or the same one that came off and just rebuilt?

 

[sr20bud]

could be a dodgy valve stem seal?

 

[Paul Smith]

Its the one that came off rebuilt, hopeing its not a stem seal (if you iknow what i mean)

I'll check the plugs when i get home but they are brand new. Could over fueling cause this? Maybe fuel washing the oil off the bore and burning explaining the dirty and blue smoke.???

 

[frank]

I'll check the plugs when i get home but they are brand new. Could over fueling cause this? Maybe fuel washing the oil off the bore and burning explaining the dirty and blue smoke.???

wishful thinking paul :wasntme: did you scrape any carbon off the tops of the pistons ?

 

[Paul Smith]

Yeah I did clean over the tops nothing major just get some flakey bits off

 

[frank]

Yeah I did clean over the tops nothing major just get some flakey bits off

hmmm, can be fatal to let the scrapings clog the rings paul

 

[Paul Smith]

Its possible I was careful even used a tac cloth but its not perfect so it is possible maybe need to find something to dissolve it ???

 

[frank]

Its possible I was careful even used a tac cloth but its not perfect so it is possible maybe need to find something to dissolve it ???

the pistons are tapered eh paul (.6mm smaller at the crown) so they will collect a lot of debris
if the valvestems/inlet tracts are,nt wet with oil, my money would,nt be on the valveseals personally.
cant you borrow a bore-scope to view the pistontops for oil puddles ?

 

[Paul Smith]

How could I check the valve stems to see if they are wet? Do u have any good tricks to clear these?

 

[frank]

How could I check the valve stems to see if they are wet? Do u have any good tricks to clear these?

you would have to remove the mani i guess paul, and shine a torch (preferably soon after a 5 minute run of low throttle/high inlet vacuum)

 

[Paul Smith]

Cool ill check that might put some cleaner through with an oil change

 

[frank]

is this a skimmed head paul ? because a big hike in c/r can make previously worn (but servicable) rings far worse at sealing

 

[Paul Smith]

Yep she is a skimmed head thats a worry, although the piston looked in good shape but its hard to tell

 

[frank]

Yep she is a skimmed head thats a worry, although the piston looked in good shape but its hard to tell

most of the cg,s i,ve stripped had very congealed oil control rings paul , this current one was 2 coilpack ones made into 1 and were really bad (totally stuck fast into the groove ) but once cleaned and restretched they,ve proved to be a very tight seal (even at 12:1 c/r)

 

[lucifer]

Sorry been away But I actually agree with all Franks suggestions, I don't feel its going to be great news though, oh Dear mate, Hope it turns out to be something simple, You are due some good luck surely, keep us posted on this mate.

 

[Paul Smith]

Ok i've been thinking and got some tests for this morning,

 

[Low Rider]

Hope all goes well Paul, wouldn't be nice to have to strip down but a problem found is a problem solved. Makes me thankful of making the choice to opt for a bottom end rebuild with new rings and ultrasonically cleaned pistons....we still have to see what condition all the bearings are in though

 

[Paul Smith]

I have done a compression test and tried a few different setups.

Cyl 1 - 17 psi
Cyl 2 - 17 psi
Cyl 3 - 17 psi
Cyl 4 - 17.5 psi

I swapped the plugs out for some others i had around which were bosch super 4's and as a result the smoke has all but a very tiny occassional amount cleared. I believe the last plugs which were NGK BCP7ES plugs are breaking down and are running to hot. What I need to do is decide what plugs i am going to need and purchase those.:grinning:

 

[Paul Smith]

Anyone any good at working a compression ratio on this figure.

Frank/low rider what plugs do you run?

 

[Guy]

Shouldn't those figures be around 160-180 psi on the 6th crank?

 

[sr20bud]

Shouldn't those figures be around 160-180 psi on the 6th crank?

thats what i would of thought

 

[Low Rider]

It depends on the compression ratio and choice of cam but 17psi sure isn't right. I'm assuming you have read in bars and have increased the compression a fair bit with the skim, (Frank would know by how much), but if you're around the 12:1 mark then the figures seem reasonable...

 

[Guy]

If it's BAR, that's 246 PSI which is very good isn't it?

 

[Paul Smith]

I agree it does seem a little high but she is as smooth as anything so id say 1 bar is good

 

[frank]

(Frank would know by how much),...

i,ve never tested mine i,m afraid, and like you say, very dependent on the inlet lag/cam eh