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Gents

some advice please. I have a "worked" early 70's motor in my TR6. It has higher than normal compression, an external oil line and the usual valve cover vent to the air intake tube (via a flame arrester). At normal operating temps at idle I have (and the motor) suffered from a mild case of blow-by causing the odd splatter of oil to come up the dip stick tube. I've lived with this for many years now, but it's wearing thin. Wiping down the side of the motor at service internals is a job I could do without now. Would it do any harm to close off the dip stick tube with a solid "stopper", and rely on the valve cover vent to provide the pressure relief without doing any harm? New rings were installed about 1 1/2 years ago. Motor runs rich and I usually do short runs which probably doesn't help with the blow-by.

Regards.

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Gents

some advice please. I have a "worked" early 70's motor in my TR6. It has higher than normal compression, an external oil line and the usual valve cover vent to the air intake tube (via a flame arrester). At normal operating temps at idle I have (and the motor) suffered from a mild case of blow-by causing the odd splatter of oil to come up the dip stick tube. I've lived with this for many years now, but it's wearing thin. Wiping down the side of the motor at service internals is a job I could do without now. Would it do any harm to close off the dip stick tube with a solid "stopper", and rely on the valve cover vent to provide the pressure relief without doing any harm? New rings were installed about 1 1/2 years ago. Motor runs rich and I usually do short runs which probably doesn't help with the blow-by.

Regards.

 

Have you tried washing out the flame-trap with petrol? I have ditched it and use a catch-tank and the goo that gets to the tank could well clog up the flame-trap.

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The external oil feed line to the valve train is a contributing factor to the flame trap clogging up by it's putting more oil under the valve cover than necessary. With those short trips you're probabaly getting an emulsion partialy cloggong the trap.

I don't see the need for either the trap or the oil line.

Over here 71 was the last year they even used a flame trap in that location.

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First of all the flame trap does exactly what it says on the tin it should always be parrallel to the outlet of the rocker cover or up hill when the engine cools the emulsifying droplets will then drain inwards to the hoyt engine and then evaporate.If not fitted to a catch tank and you experience a sticking valve or backfire through the inlet goodbye catch tank! :blink: If you have excessive pressure from the dipstick you have way too much crankcase pressure re-ringing knackered pistons or oval bores will not stop it. "Simples" Ditch the oil feed pipe unless it has the correct restrictor fitted but even then not a good idea.

Regards Neil (ntc)

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First of all the flame trap does exactly what it says on the tin it should always be parrallel to the outlet of the rocker cover or up hill when the engine cools the emulsifying droplets will then drain inwards to the hoyt engine and then evaporate.If not fitted to a catch tank and you experience a sticking valve or backfire through the inlet goodbye catch tank! :blink: If you have excessive pressure from the dipstick you have way too much crankcase pressure re-ringing knackered pistons or oval bores will not stop it. "Simples" Ditch the oil feed pipe unless it has the correct restrictor fitted but even then not a good idea.

Regards Neil (ntc)

 

 

My plastic catch tank connects to the rocker cover outlet and has not suffered from any of the backfires - because it has no connection to inlet manifold, that's gone.

Peter

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Thanks all for replying. A clogged flame trap did cross my mind. I did blow thru it and flow seemed restricted, which I thought was normal. I will wash it out with petrol (and leave it to soak) on the weekend. The unit as it is plumbed now is down hill from the valve cover outlet pipe. Thick treacle gunge has been dripping into the intake tube.

I'll let you know how I get on. I have also been considering removing the external oil line as this was only fitted for track work.

Regards

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I think one of the problems is that the original breather system is too small. In their wisdom, Triumph have the same size outlet from the engine (~1/2") for the 2.5 as the 1300. So the gases coming out are under pressure and travelling fast which brings the oil along with it - made worse by no real baffling on the outlet.

 

This may be just adequate on a newish engine in top shape, but on anything else it'll be dumping oil into the plenum and probably generating positive pressure in the crankcase, encouraging leaks and general slobbering. This seems to be pretty common on 2.5s in all states of tune.

 

I've got just this problem on my PI. The engine is clearly not in top shape, but as I'm not in a position to deal with it properly just now I've made a breather/separator pot which attaches to the fuel pump hole on the side of the block. From the top of this I've got a hose connected to the vacuum side of the inlet via a 2.5mm orifice. The original breather hose has had a PCV valve added into it which allows air out of the engine but not in. The vent in the filler cap is blocked off.

 

The effect of this is that the crankcase pressure is now about 3 psi (0.2 Bar) negative at idle and light throttle. I've not driven it yet so don't know how it will be under load - want it remain just negative even at full chat, so might need to increase the orifice size a little. Might reduce oil consumption a little too - but I'm not holding my breath on that!

 

I'll be doing a more complete write up shortly and will post a link.

 

Nick

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You hit the nail on the head there Nick. My motor is performing well, burns little oil and I'm not in a position right now to do a full engine rebuild/recon. Just a work-around for the moment is all I need. I look forward to your results.

Craig

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The block vent I have used for years but not like that!!!!! I do not like the **** going back into the engine :D Use a catch tank open vent, NOT those silly bling things with a stupid little filter :angry: Oil consumption nil :P

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A cleaned out flame trap has greatly improved venting. No more oil finding it's way up the dip stick. I will however install a crank vent as per Nick's suggestion.

Thanks for everone's help/suggestions.

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Write-up here.

 

http://sideways-technologies.co.uk/forums/index.php/topic/5682-crankcase-breather-mod/

 

Still testing but performed well last night over 320 fast miles. Fuel economy would appear to be quite reasonable too as I have nearly 1/2 tank left.....

 

Nick

 

Excuse me, Nick - but did you really go 320 miles, and still have 1/2 a tank of fuel left? I only get about 180 miles to a full tank............

Austin

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Austin,

 

Yes, but this in a 2.5PI saloon, not a TR6 so direct comparison is not possible as the tank is bigger and the engine is in a slightly different state of tune (between CR and CP). Works out at 34 mpg (imperial) though which should be a bit more comparable.

 

Nick

 

 

Nick, Austin,

Main difference I reckon is that the saloon has the vacuum advance capsule connected up, allowing spark to be advanced

at cruise. Worth doing on your supercharged 6 Austin, - drill small bore take-off at throttle edge if your SU lacks one already.

Peter

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This saloon has 3D mapped distributorless ignition, so yes, considerable extra advance at cruise compared to mechanical only system. I'd consider load sensitive advance (vacuum on the mechanical distributors) to be essential for best torque and economy on a road car.

 

I hope to squeeze a bit more out of this saloon - still only partly mapped although the cruise areas are pretty good now.

 

Cheers

 

Nick

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  • 8 years later...

Reviving an old thread.

Older tr6 engine runs fine.

Picked up a moss scharger couple years ago fairly cheap.

It vents from the valve cover to the round air filter.

I'd like a little extra protection. SIMPLE as possible hopefully.

Maybe a tube off the fuel pump location that's blanked off with just a filter or catch can?

Or a tee off of the line running from the rocker cover to the air filter to a catch can? 

Educated opinions appreciated, mine are uneducated!

 

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I have a supercharged MB SLK and vent the crankcase (rocker cover) directly to  the ground alongside the transmission. No filter fitted and probably legal for off road use only. The original complex MB  venting system is notorious for contaminating the fuel metering sensors. 

I see no technical problem in venting a TR6 rocker cover directly to atmosphere , other than it may not be legal for road vehicles in your  jurisdiction. 

Can't get anything simpler than a direct vent to atmosphere.

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It is a litle antisocial to vent blowby directly!    When a catch tank can, er, catch the oilier emissions well.

fumblefingas, you want "protection".  From what?   Fire?  See above re, Flame trap.    Prosecution?   I think not, but a catch tank is easily fitted.

You mention using the blanked off fuel pump position (you have an electric pump?)   Good plan, as a hose from there can be run upwards to a catch tank in the bulkhead.     Then, most oil, splash or vapour, will settle or condense in the hose, and run back into the sump, without troubling the catch tank.    That can be vented to dispose of blowby gases, either via a small filter to remove remaining oil, or into your intake air filter housing, after the filter.

My system is in this manner and the catch tank never requires emptying!

JOhn

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