26-06-2011, 10:01 PM #1
SB Chev Fouling Spark Plugs and Burning Oil
I bought a HG Premier with stock 350 chev about 2 months ago and the engine appears to be a little sick. Symptoms that I have noticed are:
Oil usage Approx. 1L every 1500km (Doesn't blow whit smoke at all)
Burnt Oil Smoke coming from Oil Filler Cap (Sometimes visible while stationary at lights, sometimes not visible at all with bonnet up)
Excessive Fuel usage (Currently getting 20L/100km and I basically just putt around rarely getting over 2500rpm
Badly Fouled Spark Plugs in Cylinders 5 and 8 (These were new 2mths ago approx 3500km) - I have attached pics of Cylinder 1 versus Cylinder 5 plugs
Possible oil spotting on Ignition Leads/Cylinder Head Sides on RH side when standing facing engine.
Obvisouly I'm going to have to get this looked at by a mechanic however is there any analysis/diagnosis that I can do myself? Car runs really well, starts first time etc in the morning but can tell that something is just not quite right....
I am on the Gold Coast and work in Burleigh Heads, so any reccomendations on mechanics would be appreciated.
26-06-2011, 10:48 PM #2
Not what I would of expected as far as oil fouling goes! Have you done a compression test?
Do a wet and dry test, Maybe just valve stem seals gone, if its not running rough.
Obviosly you know what cylinders are playing up? What sort of valvetrain has it got?
27-06-2011, 04:49 PM #3
No compression tests have been done as yet. Definitely not running too rough at all.
Cylinder 5 and 8 plugs were REALLY bad when i replaced them 2 months ago (or at least the mechanic did) and cylinder 5 is shown in the images compared to cylinder 1. I couldn't get no.8 ouu due to the steering box being in my road.
I actually have no idea about the valvetrain at all. Only info I have is thats its pretty stock and has been modified to take regular unleaded.
27-06-2011, 05:28 PM #4
- Join Date
- Feb 2009
- Upper Hunter NSW
Smoke coming from pre PCV breather is an indication of ring blowby occuring and a symptom of a tired engine, though not necesarily meaning its stuffed but poor fuel economy is another indicator of an engine that is putting quite a bit of it's power past the rings.
1 litre oil every 1500 km's is fair a bit,though I've seen much worse in still running engines.
20 litres fuel per 100 KM does seem a bit if its a standard engine and you are light on the pedal.
It's probably got carboned up oil rings as well where the carbon build up accumulates to a point where the oil rings aren't able to control the amount of oil usage as they should, and this then produces more carbon accumulation through oil burning in a slow snowball like effect.
The wet and dry test as already mentioned should give you a better idea as to whether it's a top or bottom end compression problem ( if any problem is there ).
Grey/white smoke emitted upon rev up via exhaust after a longish engine idle period or initial start up after sitting overnight etc can indicate worn valve guides and/or buggered valve stem seals and this can be a source of oil consumption as well though not necessarily and indication alone of a low compression/excess fuel usage problem.
Another worn valve guide/stem seal test is to throttle hard after driving down a long hill and watch for excessive smoke from the exhaust that occurs for a few seconds.
Oil spotting is most likely oil being blown from the oil filler cap under crankcase positive pressure from ring blowby.
You could clean all the accumulated oil in the filler cap with kero and blow dry with an air blower to temporarily stop the oil spotting.
The dark plug is most likely from an oil fouling cylinder.It's obviuosly still firing OK as it's not wet from oil according to the photo.
It all seems to indicate a tired engine needing a freshen up, doesn't mean it isn't running reasonably well but does seem that it could be running better.
27-06-2011, 10:07 PM #5
Thanks for your detailed post, greatly appreciated.
I should have mentioned that 'supposively' this engine is fresh as in < 4000km, however has been sitting around doing nothing for about a year, and did the 4000km over the prior 2 years.
I'll do the smoke tests that you have mentioned and advise of the outcomes.
Compression Test - While i'd like to do this myself I don't have a guage OR a socket/ratchet combination that get get to all of my cylinders. Might just take it somewhere to do it for me.
Oil Spotting - yup, makes sense, is on the side of the filler cap. It's not spitting THAT much so I'm happy to leave it as is for now
Dark Plug - Photo was taken directly after taking it from the engine.
Will be interesting to see if the engine is actually tired, ring issues from rebuild (assuming fresh) or something else...
If it does need a rebuild.... I don't like my chances of not doing mods.....
28-06-2011, 07:55 AM #6
When I had a couple of shot valve stem seals on the fuelies, would completely cover the plug in oil and start misfiring! after a couple of hours cruising,
Like you say it may have been a problem with gthe build, when you pull the filler plug off the rocker covers, and you can see the valve gear and top of head, does it look like clean steel or is it all gunked up with old oil?? Maybe a clue to a tired engine, or overheated one!!!
Hope the prognosis comes back good.
30-06-2011, 01:12 PM #7
01-07-2011, 09:24 AM #8
Best to do it along a quiet road and have an observer look at the amount of smoke ( if any ) is coming from the exhaust.Unless it is really bad it can be sometimes hard to see it through the rear view morror whilst driving.
This valve guide/stem seal test would be only one of the tests you need to do to establish where your oil fouled plug problem is coming from.
If the engine was supposedly "freshened up" recently it may depend on the way the engine was "freshened up".
New rings and gaskets is not really a freshen up if the engine is worn to the point that it needs a rebore etc.
Don't discount broken rings either, as they can be easily broken in the hands of someone who may be inexperienced and can also break in a well worn engine bore with worn piston ring grooves causing "ring flutter" and eventual ring breakage.They also lose their sealing ability in a worn bore.
There may be a combination of factors causing your problem, you have to conduct a number of tests to get a better idea.
Whoops............ just realised my son Brady was still logged in so this reply is under his log-in, not mine ( FB MAD ) .
Same person, different generation !!
Last edited by HQGTSbrad; 01-07-2011 at 09:26 AM.Holden, the great way to move.
19-09-2011, 09:16 PM #9
SOrry for taking so long... I had a lot of issues getting the car registered in QLD, so some fouling plugs, breathing a bit of oil smoke and poor fuel economy were the least of my problems...
So I have decided to take it to a mechanic to have a look at. Thanks for all of the advice and will make sure I let you know how I go. I already had the compression checked and it was OK, and it def blows smoke intially under WOT when doing the test described.
Last edited by MidLifeChev; 19-09-2011 at 09:26 PM.
23-09-2011, 11:18 PM #10
perhaps you are simply driving it to slowly?
or mabe you have this ring flutter?
mabe!rev the chev kev!
24-09-2011, 12:28 AM #11
Took my car to Leon at Sth Tweed Performance, and it has come back a new car.... It starts easier, is MUCH smooter, more responsive and more torque. He reduced the jets and power valve, gave it a tune and what do you know, it doesn't breath oil smoke anymore....
Will update economy after I have run a tank through it.
24-09-2011, 09:20 AM #12
26-09-2011, 03:33 PM #13
I still have 1/2 a tanks so can't be all bad!
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