Crankcase breathing problems (??)
Discussion
I have just supercharged my B series engine. Engine runs fine except for when exploring upper boost levels (say held in third gear upto max revs). I believe i am getting oil spraying from the tappet covers - on the exhaust side of engine - into my fabricated heatshield which is burning on the hot exhaust (made hotter by higher boosts of course). I say believe as i haven't been abloe to strip the s/c off yet, but by peering through a gap i can see that there is oil running down the heatshield and pooling at the bottom.
We are postulating that there is a crankcase breathing problem, in as much as the gases aren't being drawn out of the block well/quick enough at high boost. At the moment I am using standard B series breathing aparataus of the front tappet cover having a pipe coming off which re-circs into the carb.
I am interested in any more efficient ways of scavenging the gases off.
I have recently seen this
http://community-2.webtv.net/PAGEBUILDERPICS/CRANKCASEEVACUATION/
and was wondering what people made of such a contraption.
Thanks in advance!
>>> Edited by Buffalo on Wednesday 1st September 20:39
We are postulating that there is a crankcase breathing problem, in as much as the gases aren't being drawn out of the block well/quick enough at high boost. At the moment I am using standard B series breathing aparataus of the front tappet cover having a pipe coming off which re-circs into the carb.
I am interested in any more efficient ways of scavenging the gases off.
I have recently seen this
http://community-2.webtv.net/PAGEBUILDERPICS/CRANKCASEEVACUATION/
and was wondering what people made of such a contraption.
Thanks in advance!
>>> Edited by Buffalo on Wednesday 1st September 20:39
I can;'t definitely be sure that it is not, but i have only once noticed it coming out from the back of the car and there was "too much" smoke from what i saw in the drivers seat to be the rings, also it came in to the cabin through fresh air vents. It is a brand new engine that was run in before being 'charged, so although it may blow a little (stands to reason) i don't think this is the problem - at least not the main one.
Why would there be so much oil on the tappet side of the engine and why would oil be collecting in the heatshield on this side, if it was just coming past the rings? If it was going out through the rings i would have thought there would be nothing on the engine at all?
This is what is leading me to think its the tappet covers or similar as they would certainly be considered a weak spot being held on to block with one bolt per cover in the centre of each rectangular cover.
As ever, in accordance with sods law, to get to this side of the engine for a look-see, i have to remove supercharger, heatshield, exhaust, heat wrap etc etc etc
Why would there be so much oil on the tappet side of the engine and why would oil be collecting in the heatshield on this side, if it was just coming past the rings? If it was going out through the rings i would have thought there would be nothing on the engine at all?
This is what is leading me to think its the tappet covers or similar as they would certainly be considered a weak spot being held on to block with one bolt per cover in the centre of each rectangular cover. As ever, in accordance with sods law, to get to this side of the engine for a look-see, i have to remove supercharger, heatshield, exhaust, heat wrap etc etc etc
I assume you have a suck-through carb, so the breather is not connected to boost.
I wonder if the crank case is pressurising, or whether it is basically just leaking except when there is some vacuum to hold the covers on. Does it only leak under boost, or does it also leak at full throttle with no boost? It might be worth feeding the breather to a catch tank to make absolutely sure the crank case isn't pressurising.
I wonder if the crank case is pressurising, or whether it is basically just leaking except when there is some vacuum to hold the covers on. Does it only leak under boost, or does it also leak at full throttle with no boost? It might be worth feeding the breather to a catch tank to make absolutely sure the crank case isn't pressurising.
HOw do!
Carb is suck through HIF44.
I only smell oil at high boost - for example if i really boot the car or when travelling at high-ish speeds (over 75mph) and have to gun throttle to maintain speed up long incline - the long climb eastbound on M4 between M32 and Bath junction is a good example.
Driving using the boost but at more sensible levels does not seem to cause too much trouble, but i can still get oil pooling in heatshield that trickles out when i move off (if car has sat for couple of hours to allow oil to collect).
It is worse on hot days as i assume oil is hotter...
Pressure of crankcase is the thought i was coming to - i assume that the mods as per my posted link allows these gases to be drawn more rapidly from the breather pipe and negates a build up of pressure?
>> Edited by Buffalo on Wednesday 1st September 21:48
Carb is suck through HIF44.
I only smell oil at high boost - for example if i really boot the car or when travelling at high-ish speeds (over 75mph) and have to gun throttle to maintain speed up long incline - the long climb eastbound on M4 between M32 and Bath junction is a good example.
Driving using the boost but at more sensible levels does not seem to cause too much trouble, but i can still get oil pooling in heatshield that trickles out when i move off (if car has sat for couple of hours to allow oil to collect).
It is worse on hot days as i assume oil is hotter...
Pressure of crankcase is the thought i was coming to - i assume that the mods as per my posted link allows these gases to be drawn more rapidly from the breather pipe and negates a build up of pressure?
>> Edited by Buffalo on Wednesday 1st September 21:48
With standard ring gaps and a well maintained engine I wouldn't expect a piston ring problem. I'd look closely at pcv valves and crank case ventilation issues. You don't want pcv valves venting boost pressure back into the engine crank case. Maybe it's something simple like this. I once saw a well know 'blown' griff making only 3psi of boost. It was pressurising the cylinders and the crankcase, lol. A quick fix later and it was just pressurising the cylinders
GreenV8S said:
Wouldn't it make more sense to connect the breather between the throttle and the s/c i.e. in the unboosted section of the inlet manifold? Or <gulp> is there a problem with this layout?
He wanted the engine to suck dirty air from the rockers when under vacuum. Iirc he had the pcv fitted the wrong way round or it wasn't fitted at all. So he was providing boost pressure to the sump. My breathers went to the plenum as did my servo and worked fine with valves fitted.
Confirm - your breather hose (and brake servo) is attached upstream of the s/c isn't it?! I ask because I recall that on my A-series they were on the inlet manifold, i.e. with a s/c they would have been in the pressured section of the inlet path.
Other than that, it is also worth checking that the rocker cover gasket is properly installed - that is just as capable of leaking as the tappet covers IMO.
Other than that, it is also worth checking that the rocker cover gasket is properly installed - that is just as capable of leaking as the tappet covers IMO.
Right then...
I have blown through the re-circ pipe there is no resistance and i can hear my breath coming past the oil filler cap (i also sucked, but i don't recommend this at all - yuck!)
I ran the engine from cold at idle and let it warm up. After it got warm i pulled off re-circ pip. I didn't notice anything at first but then i did note the engine note changed slightly when off (i think it seemed to idle slightly quicker) and after a time noted that visible gases were coming from the pipe - more so when at idle than when under throttle; it seemed to clear on the throttle. I put the pipe against a piece of paper and revved the engine in between long periods of idle several times but no discolouration of the paper occured - i repeated this a few times but still no discolouration occured.
When i turned off the engine there was a puddle of oil about 4 inches across and deep enough to come up ones fingernail if you stuck your finger in it vertically. Thinking it may be the removal of the re-circ pipe that caused this (more oil than normal!) i ran engine again and removed pipe, but seemingly no oil leaked again. This oil may have deposited as i jacked the car up from the passenger side when wrigling around and may have run off the heatshield this way..?
Anyway, i can peer down the gap between the rear most two exhaust headers and the oil deposits below the rear tappet chest are glistening as if newly laid, but of course might just be "molten" due to block heat. I can peer from teh front past the belts at the front tappet chest but this does not seem dirty and if i cannot wiggle the vent pipe so assume this is on tight (i can't squeeze my hand down to the rear tappet chest as block temp is extremely high now).
What would be the effect of buggering the rear main seal? The oil seems to drip from the join between engine and gearbox - at least that is where it is running from, but the heatshield goes back this far too so might just be circumstantial. Also this is the lowest bit of the engine/gearbox.... Pushing the little circlip thingy doesn't release a torrent of oil at least anyway..? and it doesn't explain why rear tappet chest seems so oily.
One thing though the exhaust wrap straight opposite the tappet covers isn't dirty from what i can see so oil not coming out vertically moire likely dribbling out and down side of block.
Any thoughts..?
I need to get the car up on ramps at a garage so ican stand underneath or on jacks which aren't on a busy road as i just cannot safely wriggle under the car at the moment.
~PHIL
I have blown through the re-circ pipe there is no resistance and i can hear my breath coming past the oil filler cap (i also sucked, but i don't recommend this at all - yuck!)
I ran the engine from cold at idle and let it warm up. After it got warm i pulled off re-circ pip. I didn't notice anything at first but then i did note the engine note changed slightly when off (i think it seemed to idle slightly quicker) and after a time noted that visible gases were coming from the pipe - more so when at idle than when under throttle; it seemed to clear on the throttle. I put the pipe against a piece of paper and revved the engine in between long periods of idle several times but no discolouration of the paper occured - i repeated this a few times but still no discolouration occured.
When i turned off the engine there was a puddle of oil about 4 inches across and deep enough to come up ones fingernail if you stuck your finger in it vertically. Thinking it may be the removal of the re-circ pipe that caused this (more oil than normal!) i ran engine again and removed pipe, but seemingly no oil leaked again. This oil may have deposited as i jacked the car up from the passenger side when wrigling around and may have run off the heatshield this way..?
Anyway, i can peer down the gap between the rear most two exhaust headers and the oil deposits below the rear tappet chest are glistening as if newly laid, but of course might just be "molten" due to block heat. I can peer from teh front past the belts at the front tappet chest but this does not seem dirty and if i cannot wiggle the vent pipe so assume this is on tight (i can't squeeze my hand down to the rear tappet chest as block temp is extremely high now).
What would be the effect of buggering the rear main seal? The oil seems to drip from the join between engine and gearbox - at least that is where it is running from, but the heatshield goes back this far too so might just be circumstantial. Also this is the lowest bit of the engine/gearbox.... Pushing the little circlip thingy doesn't release a torrent of oil at least anyway..? and it doesn't explain why rear tappet chest seems so oily.
One thing though the exhaust wrap straight opposite the tappet covers isn't dirty from what i can see so oil not coming out vertically moire likely dribbling out and down side of block.
Any thoughts..?
I need to get the car up on ramps at a garage so ican stand underneath or on jacks which aren't on a busy road as i just cannot safely wriggle under the car at the moment.
~PHIL
Phil,
Could be the rear-cover seal leaking. Also, what about the rear of the cam-cover? I managed to get the cork seal kinked and this allowed a dribble to run down and appear to come from the back of the engine!
Does your bellhousing not have a drain-hole? (mine does, but that's because the early engines don't have a real rear-engine seal!). If there's a drain hole and no sign of oil coming out of it, I'd say your rear-seal is OK.
Anyway, I suspect that one or both of the cover seals is leaking. Unfortunately (as I found) this easiest to get at with the manifolds removed.
Sheepy
Could be the rear-cover seal leaking. Also, what about the rear of the cam-cover? I managed to get the cork seal kinked and this allowed a dribble to run down and appear to come from the back of the engine!
Does your bellhousing not have a drain-hole? (mine does, but that's because the early engines don't have a real rear-engine seal!). If there's a drain hole and no sign of oil coming out of it, I'd say your rear-seal is OK.
Anyway, I suspect that one or both of the cover seals is leaking. Unfortunately (as I found) this easiest to get at with the manifolds removed.
Sheepy
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