14 replies to this topic

[johnR]

I went to top up my oil yesterday and found mayo in the filler neck. There was no sign of it on the rockers or the dipstick but the coolant level was down a bit.
I decided I'd change the head gasket to be on the safe side and have done that today although there was no real signs of a failure on the old one.
Any thoughts on this? Also I have imperial feeler gauges and the Haynes manual sys 0.33mm for the valve clearance. measuring the gauges with a micrometer I found 10 thou to be spot on but then when I remembered I had an older Haynes with imperial measurements I found it says 12 thou. Which is best?
JohnR

[carbon]

The mayo build-up can happen where car is used for shorter trips, and engine never really gets properly hot.

 

Also if crankcase ventilation is not working well this can promote mayo build-up.

[sledgehammer]

as carbon say's , cold weather , short journeys will probably leave a bit of mayo in a few areas

 

give it a long run as a treat , will warm it up properly , the water vapour will have time to reduce in the crank / rocker areas as the temp increases

 

but the mayo may be still around , until the spring comes & temps rise

[cal844]

Give the car a good long drive, to get up to temperature and burn off moisture

[johnR]

looks like I was a bit quick to change the gasket then - what valve clearance gaps do people use? 10 or 12 thou?

[ChopperHarris]

12 here

[carbon]

As Chopper says, 12 thou valve clearance with standard cam and rockers

[minidaves]

12 thou, and mayo is normally down to water or condensation, short journeys are terrible, it needs a good run and check the breas are clear and the cap is good and air tight

[johnR]

Many thanks I'll know another time and will re-adjust my gaps
JohnR

[Alpenflitzer]

We are used to adjust the outlet valves a little higher than the inlet valves. E.g. Inlet valve 0,29 mm  Outlet valve  0,32 mm

Dont you?

[carbon]

I use 12 thou inlet and exhaust, that's as recommended in workshop manual.

 

For high lift rockers you need to open up clearances, also some performance cams may differ slightly.

[sledgehammer]

We are used to adjust the outlet valves a little higher than the inlet valves. E.g. Inlet valve 0,29 mm  Outlet valve  0,32 mm

Dont you?

 

I used to run 12 thou on inlet & 15 thou on exhaust with modified heads / hotter cams

 

but now it seems everyone else runs 12 thou for both (unless different rocker ratio)

 

easier to do the valve lash that way 12 thou for all 

[spiguy]

I use 12 inlet, 15 exhaust personally (on a 1275)

[FlyingScot]

I use 12 inlet, 15 exhaust personally (on a 1275)

Same!



FS

[tiger99]

As correctly stated above, mayo is due to condensation. Some people have cured it on various engines by thermally insulating the rocker cover, making a jacket from some suitable material.

 

But I noticed very many years ago that my old man's Vauxhall Viva, notorious for this problem, did generate a great deal of mayo when using Duckhams oil and very little when using Castrol XL.

 

Nowadays you would probably use Castrol GTX or some special "classic" oil, e.g. Millers, and that may do the trick. For various reasons, it is never worth using cheap oil, except in an engine and gearbox that are due for scrapping.