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coupe72001
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coupe72001 Mentor

coupe72001

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Hi all,

I don't have an air filter box because I have too many carbs on my L28. I have plumbed a catch can from the breather pipe on the rocker cover, and too the crankcase breather on the block. Said catch can vents exhaust gases through a small pod filter on top.

Anyhow, that's the theory. What actually happens is the catch can sprays liquid oil all over the engine bay like a garden sprinkler through the now oil soaked filter. An attempt to empty the catch can found that it was bone dry, every cup of oil lost has sprayed around the engine. I may as well have no catch can and let oil dump directly out of the breathers, I'm mopping it up at the end of the drive anyway.

Any ideas why my engine (flat tops, mild cam, balanced, extractors and carbs) is so keen to expel it's life blood under acceleration, and why my catch can is so inappropriately named?

Cheers,

Drew

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noddle Rising Star

noddle

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Posted (edited)

Hi all,

I don't have an air filter box because I have too many carbs on my L28. I have plumbed a catch can from the breather pipe on the rocker cover, and too the crankcase breather on the block. Said catch can vents exhaust gases through a small pod filter on top.

Anyhow, that's the theory. What actually happens is the catch can sprays liquid oil all over the engine bay like a garden sprinkler through the now oil soaked filter. An attempt to empty the catch can found that it was bone dry, every cup of oil lost has sprayed around the engine. I may as well have no catch can and let oil dump directly out of the breathers, I'm mopping it up at the end of the drive anyway.

Any ideas why my engine (flat tops, mild cam, balanced, extractors and carbs) is so keen to expel it's life blood under acceleration, and why my catch can is so inappropriately named?

Cheers,

Drew

fill the catch can with steel wool, or the stainless twisted cleaning pads, the oil vapor catches on this and should be caught

so the theory goes.

unless you have to much blow-by

Nigel

Edited by noddle
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V8skylineMAN Grand Master

V8skylineMAN

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If you have too much blow by, the steel wool will only slow it down. It will still blow through, just not straight away. Better to lose the filter, and plumb it back into the inlet. The engine will burn any excess.

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coupe72001 Mentor

coupe72001

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I thought blow by was a product of oil etc escaping past worn piston rings. Mine are less than 10,000kms, and the bores were tidied up at the same time... although I did fit the pistons myself (sinking feeling in stomach).

Jason, with your plumbing plan, would it go: rocker cover to catch can, catch can to crankcase breather, (pod filter delete). Basically a sealed system - or did I get the wrong end of the stick?

Cheers, D

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Ghostrider Grand Master

Ghostrider

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What about your head Drew?

Either your valve guides are stuffed, or the valve stem oil seals are stuffed, or both.

If it was me, I would be looking at the head before blaming the catch can.

When you fitted the pistons did you dowse the piston & rings combo in a bucket of thick gluey oil before install like the old BP Coarse Plus? This would make breaking a ring on installation near impossible if you had a good quality ring compressor.

But I think your problem is the head.

Cheers, D

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V8skylineMAN Grand Master

V8skylineMAN

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Jason, with your plumbing plan, would it go: rocker cover to catch can, catch can to crankcase breather, (pod filter delete). Basically a sealed system - or did I get the wrong end of the stick?

Cheers, D

rocker cover and crank breather to catch can, catch can to inlet somewhere after the air filter(thats how i do mine.)

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coupe72001 Mentor

coupe72001

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The head got cleaned up and all new valves at the same time as the block was reco'd and then re-cleaned up 2000km later when I jumped a tooth on the cam sprocket and bent half the valves. The head should still be in excellent condition, seeing I haven't had any big mishaps since then. From memory I struggled to find proper break-in oil, and doused the pistons and rings in regular oil prior to install with my quite good piston compressor. The car doesn't blow any smoke, so hopefully I didn't damage the rings much in the early days. I also took care running the engine in.

Jason, if you get a chance to provide a pic of the inlet that you have plumbed the can to that would be awesome. Same goes for anyone else who has a problem-free catch can set up.

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coupe72001 Mentor

coupe72001

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If it is breathing hard u can always make a return to the sump

Not a bad idea; I'd save a small fortune on otherwise wasted oil! Does it affect oil pressure having the blow by gases dump back to the block/sump instead of atmosphere?

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Ghostrider Grand Master

Ghostrider

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Catch cans to me are designed to take in the vapour coming from the rocker cover and or crank case and the theory of oil is heavier than air it should drop to the bottom of the can to accumulate, but it sounds like your vapour is under pressure, so I would be trying to find out why.

Have you thought about a compression test?

Test each cylinder, then re test after squirting some oil, or upper cylinder lubricant like redex into the bore. If it changes, you have ring issues, but if it doesn't, you might, or probably have valves not seating properly and therefore pressurising the rocker space.

Prevention is always better than a cure!

Cheers, D

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ydr030 Mentor

ydr030

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Run a catchcan with gauze but have a drain from it that goes to the sump. mine is t d into the turbo oil return and seems fine u could t into the dipstik tube if u want aswell just depends how much it breaths. Sr20s run a similar setup from factiry

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