Oil in combustion chamber

Post by **winger300** » Thu Mar 25, 2004 8:57 pm

After taking the head off my engine (to change it for a 12G940) i found that chamber 3 on the head was really oily, around the intake valve.

Before i took it off, the engine was burning loads of oil, and smoking out of the rocker cover. However the exhaust was not smoking at all. Is this just the valve oil seal?

I was thinking the worst, like worn piston rings, but changing the head has fixed it.

Post by **Cam** » Thu Mar 25, 2004 11:06 pm

Was it worse when starting from cold? If so then that points to stem oil seals, but if it was REALLY bad all the time then you could have had a very worn/damaged valve guide. You can check by removing the valve spring and checking for lateral play in the valve against the valve guide, purely an academic excercise though as you have cured it now by removing the head!

Post by **winger300** » Thu Mar 25, 2004 11:16 pm

yeah, a 150 mile drive almost burnt all the oil from max to below min on the dipstick. The smoking started immediately from cold, and was worst at idle speed.

I'll probably junk the head altogether, as the surface is really uneven. The old gasket was completely glued to it, and i had to grind it off using the wire brush on the angle grinder. Due to me doing this, my initial thought was a blown head gasket, but when taking it off this looked ok.

Post by **winger300** » Sun Mar 28, 2004 9:25 pm

It seems i'm still burning a fair bit of oil. About a pint every 200 miles. Before changing the head it was smoking a lot out of the rocker cover, now theres no smoke out of the rocker cover, however when i rev the engine hard when stationary there is a puff of blue smoke from the exhaust (none from the rocker cover though), but theres no smoke at constant high revs.

Also i tried the suggestion of rolling down a hill with the foot off the throttle, and then accelerating away at the bottom, and it doesn't smoke. Can't see any smoke in the rear view mirror whilst driving either.

Now, i've changed the manifold, head and carb, but i'm using the AAM needle. I think i should be using something more like a BDE, which means it's running slightly rich, could this be the problem? as the smoke is only when flooring the throttle, does this indicate something with the vacuum advance?

I think the engine may have overheated when i ruined the other head, and i've read something about the cylinder bores glazing, can anyone shed some light on this matter?

Post by **rayofleamington** » Sun Mar 28, 2004 10:40 pm

rolling down a hill with the foot off the throttle, and then accelerating away at the bottom, and it doesn't smoke.

probably not the valve guides then. Worn rings / dodgy bores etc..

?

running to rich? The simple guide is:
blue smoke is oil, black smoke is fuel, white smoke is water..
however in real life it's not always easy to tell.

Post by **Cam** » Sun Mar 28, 2004 11:10 pm

With your head, a decent inlet and exhaust system and a HS4 carb, the AAM needle should be pretty good. Something like a AAC will be too lean with your setup. You mention a BDE needle?? I think they are for the larger jet size (1 3/4" carbs). Which carb are you using?

Post by **57traveller** » Mon Mar 29, 2004 9:14 am

Cylinder glazing is a gradual process and doesn't just happen overnight. Overheating shouldn't have caused any problems - only if you kept driving in that condition, then horrible things could happen. The worst case a seized engine and/or cracking of engine castings.

Post by **brixtonmorris** » Mon Mar 29, 2004 11:33 am

if youve got worn crank main bearings, the rear one, you are going to lose more oil then burning it. the greater the revs the greater the oil loss

Post by **winger300** » Mon Mar 29, 2004 11:36 am

im using an HS4. The WinSU program suggests the BDE needle for my setup.

Post by **Kevin** » Mon Mar 29, 2004 12:42 pm

The WinSU program

Excuse my ignorance but whats that.

Post by **MrA.Series** » Mon Mar 29, 2004 1:25 pm

Kevin wrote:
The WinSU program
Excuse my ignorance but whats that.

It's a Windows application/program that was found on the net (can't remeber who - sorry whoever it was!)
The demo download was free and then you pay to continue using it if you like it. What you do is select the type of car you've got (A-series engine'd), the type of carb your running, it's manifold in use, exhaust system, runnig style, and other such info,.....

...and it spews out what needle you should be using for the best output and performance of you car.

Post by **winger300** » Mon Mar 29, 2004 1:29 pm

http://www.morrisminoroc.co.uk/index.ph ... pic&t=3157

It also lets you compare needles, and it shows that the BDE is consistantly leaner than the AAM needle im using. So i assume i can just set my mixture to slightly lean at idle, and it will be pretty close to the BDE profile across the rev range.

Im getting oily spark plugs in chamber 3. So i guess there is the problem. It only smokes when i rev it really hard, which i suppose is the point where there is most compression. Can the piston rings be placed? or will the block need re-honing also?

It will probably be easier to buy a recon short engine i think

Post by **Kevin** » Mon Mar 29, 2004 1:57 pm

If you want to check the rings do a compression test then squirt a drop of oil into the bore and then re-test if the measurement goes up you know the ring/rings are worn.
The rings can be replaced but you need them to be of the Cords type of ring with a stepped top ring to miss the bore ridge, and you can do this with the engine in place.

Post by **Kevin** » Mon Mar 29, 2004 2:15 pm

In case anyone wonders what CORDS piston rings are
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... gory=27376

Post by **Cam** » Mon Mar 29, 2004 2:50 pm

The BDE needle is for the 0.100" jet (1 3/4" carbs). The AAM needle is for the 0.090" jet (1 1/2" and some smaller carbs).

The profiles are:

AAM = 890 850 824 785 752 715 673 630 590 567 543 519 496 472 448 448

BDE = 990 950 923 900 879 853 820 790 755 725 698 668 638 608 578 548

So you can see that the BDE won't actually fit in the jet until station 5! So it won't fit in a HS4!

The BDE is consistantly leaner in comparison to the AAM but I would imagine that the BDE is being compared to a 100 thou jet and the AAM compared to a 90 thou jet? In which case they are very similar.

Post by **Kevin** » Mon Mar 29, 2004 3:01 pm

...and it spews out what needle you should be using for the best output and performance of you car.

So that programme quoted earlier may be a bit iffy then ?

Post by **Cam** » Mon Mar 29, 2004 3:10 pm

Who knows??

These 'programmes' are fine in theory but who knows which carb it was on about? It was stated that a HS4 was used, but maybe the programme altered things and gave the best needle info out for you to fit a carb around??

Who knows!

Sorry to go all old fashioned and mechanical (he says when sat in front of a computer all day!) but you can't fit a pint in a half pint pot!

Post by **Kevin** » Mon Mar 29, 2004 3:25 pm

Sorry to go all old fashioned and mechanical (he says when sat in front of a computer all day!) but you can't fit a pint in a half pint pot!

Quite correct Cam going all old fashioned and mechanical, but if you were a beer drinker you would know that if you drink the 1st half then 2nd half will fit in the glass this comes from the beer drinkers bible `How Not to Spill a Drop` I know Ray must have a copy

Post by **rayofleamington** » Mon Mar 29, 2004 3:47 pm

I'm allegedly teatotal...

Honest Doc - they made me drink em... I didn't want to.

Post by **Cam** » Mon Mar 29, 2004 4:19 pm

but if you were a beer drinker you would know that if you drink the 1st half then 2nd half will fit in the glass this comes from the beer drinkers bible `How Not to Spill a Drop`

Ah yes! but what do you do with the 2nd half while the 1st half is in the pot? Does it stay in the pub tap/spout or whatever you beer drinkers call it. Sorry to be so ignorant of such matters but I have not had an alcoholic drink for about 13 years! (probably explains a lot!)