Poor compression - cause? Updated

[ericbushby]

I believe the wire wool in the vent pipe is a flame trap.
Hot gas can pass through it but flames cannot, it works just like a Davy lamp.
If there were flames in the air box they could not cause an explosion in the engine block.
Eric in Burnley
S3SE DHC

[SENC]

Here is a picture of what was on my Seven (pre-crossflow 1500cc, 116E essentially the same Kent block). I believe/understand this to be what was on the early Anglias. The wire wool was rolled up inside, and a tube would have exited the top to a road draft tube.

The following is essentially the same as your separator and I understand came from later Anglias and maybe early Cortinas. Similar to above, would have lead to a draft tube. Given the baffles and the fact that the tube would be vertical out of the separator the wool is probably not necessary as Andy suggests, but I wouldn't see any harm and maybe some slight benefit.

[2cams70]

The first is from the pre crossflow. It doesn't need to have particularly good oil separation capabilities because it just vents to atmosphere via the road draught tube. Acceptable in the 1960's to dump oil on the road and pump lots of hydrocarbons into the atmosphere.

The second is from the later crossflow engine. This is designed to be used with a closed loop positive crankcase ventilation system. It requires good oil separation properties because blowby gases are recirculated directly back into the intake manifold. Any oil content in the gas stream would result in a lots of blue smoke out of the exhaust.

The first system although less efficient at separating out the oil is probably is less restrictive than the second because in the second the flow of gas is designed to be assisted by active suction provided by intake manifold vacuum. The amount of suction is actually controlled and regulated by a PCV control valve.

[SENC]

The first is from the pre crossflow. It doesn't need to have particularly good oil separation capabilities because it just vents to atmosphere via the road draught tube. Acceptable in the 1960's to dump oil on the road and pump lots of hydrocarbons into the atmosphere.

The second is from the later crossflow engine. This is designed to be used with a closed loop positive crankcase ventilation system. It requires good oil separation properties because blowby gases are recirculated directly back into the intake manifold. Any oil content in the gas stream would result in a lots of blue smoke out of the exhaust.

The first system although less efficient at separating out the oil is probably is less restrictive than the second because in the second the flow of gas is designed to be assisted by active suction provided by intake manifold vacuum. The amount of suction is actually controlled and regulated by a PCV control valve.

Thanks!

[pharriso]

I'm making progress!

I cleaned up the old Kent breather by wire brushing & repainting, then bought some hi-tech Stainless Steel wire wool & lightly stuffed it in the breather, then used a new grommet & a PCV valve without inerds:

I then reconnected to my temporary clear catch can (aka water bottle) & then went for a couple of runs, totalling 26 miles in all. This is the amount of Oil blown over:

So at this point I am very happy

I think as several of you have suggested, with my Breather Box-less head having the Kent breather box allows the oil to drop out of the airflow & return to the sump. Adding the wire wire has helped seperate the airbourne oil. Just running the Burton elbow without an airbox was just carrying airborne oil straight to the Oil catch can. Given the amount of Oil being pushed out the engine I thought I had a compression issue, unfortunately reinforced by the results from the useless Harbor Freight compression tester.

Performing a compression test & leakdown test with good quality tools has confirmed that my engine is in good health,.
Will report back after a few more miles. As ever this forum is priceless

Many thanks for all your help!

[SENC]

And with that cleaning wool in there you're no longer being antisocial! Only clean air can get through now.

[2cams70]

I doubt you actually need the steel wool if you are using the crossflow breather. It's already adequately internally baffled. Sure putting the steel wool in there will further help reduce any oil mist but it will also increase restriction to blow by gases even further on a system that is designed to rely on intake manifold vacuum to positively draw off any fumes. It may stop the oil mist but it may also stop the blowby gases!

Time will tell however and I'd be interested in hearing about how it goes. The crossflow breather was never around when the LTC was originally developed of course and who knows - if it had been they may have adapted it somehow.

[pharriso]

I doubt you actually need the steel wool if you are using the crossflow breather. It's already adequately internally baffled. Sure putting the steel wool in there will further help reduce any oil mist but it will also increase restriction to blow by gases even further on a system that is designed to rely on intake manifold vacuum to positively draw off any fumes. It may stop the oil mist but it may also stop the blowby gases!

Time will tell however and I'd be interested in hearing about how it goes. The crossflow breather was never around when the LTC was originally developed of course and who knows - if it had been they may have adapted it somehow.

The Steel wool is open coil & loosley packed, here's a video file (.mov) showing there's still gasflow:
http://lionheartsolutions.com/sprint0260k/TwinkKentBreather.MOV
You may have to download the file & then play it.

I really appreciate your input on my crankcase ventillation issue

[sprintsoft]

Phil, That’s very good news!

How much higher is your catch tank than the breather, Is there any way to mount it higher so the oil has to work harder to pass?

Given the good state of your motor I think it’s not unreasonable to shoot for zero oil loss now

Iain

[Andy8421]

Phil, That’s very good news!

Given the good state of your motor I think it’s not unreasonable to shoot for zero oil loss now

Iain

Phil, I am glad all is well. Personally, I wouldn't worry about the amount of oil loss you are now seeing. Its not a modern design. To put it in context, a quote from Tony Rudd's excellent book about the time he was a Rolls Royce engineer before he went to Lotus:

"..a Merlin on full song, running 30 percent rich would use 180 gallons (of fuel) per hour and fling 15 to 18 gallons of oil from its breathers"

Things could be worse....

Rgds,

[nmauduit]

glad it turned out not to be an engine out problem... always good to have reliable diagnostic tools.

I also played with a oil mist condensation chamber concept (although diy) before an oil catch breather, originally coming from similar observations which turned out to be the initial symptoms of a head gasket leak, then kept on the setup (including the roundish alloy adapter above the fuel pump location). I ended up with a similar head as yours from that respect since I plugged the chamber port when I changed the head gasket. I did install a fuel pump blanking plate with a welded tab supposed to reduce the amount of splash up that block port.

In my case the oil catch is about head level, and the separator was then added below that, mid way between the "Kent" crank venting outlet (also acting as an oil return) and the catch. The separator has an input from the head (original Lotus venting port that normally goes to the air box), located at the bottom, then an output at the top goes to the catch breather. The return is of course also at the bottom and goes back to the block via the round adapter, also acting as a crank venting port if the conditions arise.

I eventually got to thinking that a sufficiently large sump return pipe is required to let incoming oily gases go up the condensation box (in my case filled with alloy sheetmetal as I did not want to risk stainless bits from a cleaning pad coming down to the sump over time), while cooled condensed oil is slowly sliding back down to the sump. This of course would depend on the viscosity of the oil, butI wondered if too small of a return tube could contribute to push out the condensed oil. I still need to do more extensive tests to assess what amount of oil still makes its way to the catch, and if it needs to be rerouted to the sump or not.

The main reason I kept such a contraption is that I did not want oil mist to be unevenly burned by the rear cylinders, then considered it an occasion to experiment for a later racer project (or possibly got trapped into a cognitive tinkering bias).