engine breathing

[boxer]

I have done quite a lot of work to the engine on my tr6 and i feel that the breather from the rocker cover is not big enough.I have removed it from the carb intake and blanked carbs up (su,s).My idea now is to increase the diameter to approx three quaters of an inch.Have noticed crankshaft oil seal is blowing a bit of oil despite new oil seal being fitted and pulley being in a1 order so am wondering with all the extra work the engine is now doing it could do with some extra breathing .Thoughts please would be very helpfull

Bob

[Richard Crawley]

Bob

I can’t imagine any work you could do to the engine requiring a larger crankcase breather! If you have excessive crankcase pressure, something is causing it to build up; either the existing breather is blocked, the engine is full of crud or you have a problem with blow by on one or more cylinders. Have you done a compression test? You say you’ve done a lot of work on the motor, what exactly did the work consist of?

[Andy Moltu]

It's not that unusual on highly tunes/race TR6 engines to increase the size of the breather.

 

This can be done either by weling in a larger breather in the rocker box or using a modified blanking plate where the mechanical fuel pump would have been fitted to the carb cars. (I'm not sure if it's Racetorations or Moss that sell it)

[Guest ron]

I would agree with Richard, if you're getting excessive crankcase pressure there's something wrong somewhere no matter what the state of tune, it might be different with racing engines but not with road going ones, particularly with SUs restricting how much you can tune it.

Ron

[Mike G]

Bob

The first thing I would check is the flame arrester. They should be cleaned in paraffin, or white spirits.

 

Mike G

[Tom Fremont]

Bob,

 

I've used the carb PCV valve with my triple Webers for many years now. This keeps a slight vacuum on the rocker box and feeds whatever blow-by exists into the intake manifold downstream of the carbs. Oil consumption is holding steady at ~ 2000 miles/U.S. quart with ~ 70,000 miles on it. I couldn't be happier and will repeat it on the current project, using a NOS valve, which still appear on ebay from time to time. They seem to last forever, so if you find a used one it should be fine.

 

This method probably helps against small oil leaks due to the vacuum, and another big plus is it dispenses with the stench of the blow by gases that often just get vented into the engine bay - this was my main objective, as I found I was getting stunk up when twiddling with the carbs while running.

 

Obviously the foregoing comments about what might be causing your high volume of blow-by are to be heeded.

[boxer]

Thanks to all who have replied i will carry out further checks before i do anything else

Bob