Seight Rocker cover breather.

[Badger56]

Hi all,

 

My Seight is running a TVR 4.0l V8 on a Edelbrock 1404 4 barrel carb with a Offenhauser inlet manifold and K & N pancake air filter. The Rocker covers are both vented to atmosphere with no pipe to the carb vacuum.

 

Having had the car set up on a rolling road I noted quite a lot of oil smoke from one of the vents at full revs (has an after market filter on it) due to "blow by" and I'm thinking of connecting one of the rocker covers to the carb either via the air filter or to the PCV vacuum pipe at the front of the carb.

 

I'd use a standard TVR flame trap and a pipe into the bottom of the pancake filter as first choice as this seems to be the least likely to mess up the carb settings.

 

However I'm toying with the idea of connecting to the PCV as I understand you get a better vacuum and therefore less oil leakage.

 

Questions are:- Does anyone have any experience of this? pictures would be great and even part numbers, sources etc.

 

And do I need to fit a PCV valve in the second option as I'm not clear if one of these would have been fitted as standard, is it therefore needed? 

 

Any thoughts or recommendations gratefully received.

Cheers

Dave

[Labrat]

I am running the weber 500 on the performer manifold. I have replaced the rocker covers and put Edelbrock push in breather connectors with braided hoses venting both heads to an oil catch tank which in turn has a breather to the atmosphere. This replaced the standard breather connecting to the bottom of the air filter (which tended to pop off at inopportune moments) and a flame trap on the other bank. It seems to work a lot better. I took all the vacuum stuff off as well as the choke etc… Works pretty well :-)

 

Luke.

[Badger56]

I am running the weber 500 on the performer manifold. I have replaced the rocker covers and put Edelbrock push in breather connectors with braided hoses venting both heads to an oil catch tank which in turn has a breather to the atmosphere. This replaced the standard breather connecting to the bottom of the air filter (which tended to pop off at inopportune moments) and a flame trap on the other bank. It seems to work a lot better. I took all the vacuum stuff off as well as the choke etc… Works pretty well :-)

 

Luke.

Thanks Luke, I've read that the rocker covers should operate at a slight vacuum to prevent oil leaks etc, also read that catch tanks are a popular way to go i.e. no vacuum so a bit confused as to whats best. Do you suffer from leaks or fumes? (that's the Westy not you of course :-) )

[Labrat]

I've not had any issues since I made the change over to the catch tank (touch wood).

[Badger56]

I've not had any issues since I made the change over to the catch tank (touch wood).

Thanks Luke.

[Yanto]

Mine is set up the same as Luke's, rocker covers to oil catch tank and vented to atmosphere there, it runs Jenvey TBs though although I suspect in reality for rocker breathing it doesn't make much difference.

 

Not sure I understand how pulling a low vacuum on the rockers will stop oil leaks though, where would the oil be leaking from that a vacuum will stop, my gut feeling is that pulling a vacuum will increase any leakage?

 

Cheers

 

Ian

 

ETA: mine breathes a bit, but is mostly water vapour so can be seen more on a cool day, no oil/combustion smoke.

Edited July 29, 2016 by Yanto

[Badger56]

Mine is set up the same as Luke's, rocker covers to oil catch tank and vented to atmosphere there, it runs Jenvey TBs though although I suspect in reality for rocker breathing it doesn't make much difference.

 

Not sure I understand how pulling a low vacuum on the rockers will stop oil leaks though, where would the oil be leaking from that a vacuum will stop, my gut feeling is that pulling a vacuum will increase any leakage?

 

Cheers

 

Ian

 

ETA: mine breathes a bit, but is mostly water vapour so can be seen more on a cool day, no oil/combustion smoke.

 

Hi all,

 

I think the theory with the oil leak is that the crank generates pressure in the crank case which forces oil out of any available route, also that there is a degree of "blow by" i.e. pressure from the cylinders passing the pistons and forcing fumes and potentially un burnt fuel into the oil causing contamination. After a bit of research I decided to give a PCV set up a go as it should produce a cleaner engine and prevents the above as well as steam turning the oil to mayonnaise.  When I had a recent rolling road set up I was amazed just how much smoke came from the rocker cover vents which demonstrated the amount of pressure in there.  My engine is healthy with good compression by the way.  My set up cost me about £30 using a standard TVR flame trap (£20) which has had a PCV valve (£3) fitted in the top of it, this is then connected to the center PCV pipe on the carb (petrol pipe £3).  I'm having the rolling road work finalised this week and I'll let you know how it goes and how the car runs on this set up. My theory was if it doesn't work I can remove it.  

Cheers

Dave 

[Badger56]

Hi all,

 

I think the theory with the oil leak is that the crank generates pressure in the crank case which forces oil out of any available route, also that there is a degree of "blow by" i.e. pressure from the cylinders passing the pistons and forcing fumes and potentially un burnt fuel into the oil causing contamination. After a bit of research I decided to give a PCV set up a go as it should produce a cleaner engine and prevents the above as well as steam turning the oil to mayonnaise.  When I had a recent rolling road set up I was amazed just how much smoke came from the rocker cover vents which demonstrated the amount of pressure in there.  My engine is healthy with good compression by the way.  My set up cost me about £30 using a standard TVR flame trap (£20) which has had a PCV valve (£3) fitted in the top of it, this is then connected to the center PCV pipe on the carb (petrol pipe £3).  I'm having the rolling road work finalised this week and I'll let you know how it goes and how the car runs on this set up. My theory was if it doesn't work I can remove it.  

Cheers

Dave 

So had the rolling road work done today and the car runs beautifully ( I can recommend Hi - Tech Motorsport in Kidderminster ) the set up above does seam to reduce smoke and keep the engine cleaner, I also think it leaks less but that's only my perception and could be wrong. Only thing I have to sort now is a squealing water pump / alternator or belt tensioner, which started after the car had been at max revs for a while. Oh well the joys of Westfield ownership.