24 replies to this topic

[valve bounce]

a serise 998 +20 bored, mg metro cam, 12g295 head 2000 miles since rebore new pistons rings etc. new valve guides and stem seals 100miles since.

right ive been having problems with my mini probucing abit of blue smoke the bottom end was all refured 2000 miles since and then with the standard cylinder head on the car didnt produce any noticably blue smoke. anyhow now i put my 295 head on, recently skimmed new rimflow inlet valves new steel valve guides and proper cap type stem seals on all the valves. but the problem is it still throws out blue smoke, it seems that if you go for a while a speed there is no smoke but then if your ticking over say at traffic lights it starts to smoke.

now im really stuck, normaly im fairly good at figuring stuff like this out but im really stuck, so please i need your help

ps if the oil level is at minum its seems to smoke less than at max?

[Retro_10s]

It can only be two things really, worn piston rings or valve stem seals.

Did you run the engine in correctly?

How much oil are you putting in the dashpot on the carb?

[me madjoe 90]

Could be drinking oil through the breather but i doubt it.......

[Dave 1293]

have u been on a rolling road with ew head? is it an oily smell the smoke?

[valve bounce]

i was told the piston ring needed 500 miles of carefull driving to run in and thats what i did. i did a compression test at work and they were all 185 and 200 and didnt alter when i squirted oil in the bores, so im hoping its not the rings

[mini-man-dan]

What oil are you using? Are you still on running in oil? This is (I believe...) thinner so will be easier to pass past piston rings etc...

Dan

[valve bounce]

oil is 20-50w halfords classic oil

[Cater_Racer]

MY belief is that if it smokes when you wellie it its the pistons, but if it smokes on tickover its the valve stems...... IMHO

[bmcecosse]

Is there pressure in the block - pushing the oil past the rings when idling ? And - NEVER run a Mini at the Min mark on the dipstick - it's death to the bearings - because it WILL surge away from the pick-up on the slightest bend............

[me madjoe 90]

Is there pressure in the block - pushing the oil past the rings when idling ? And - NEVER run a Mini at the Min mark on the dipstick - it's death to the bearings - because it WILL surge away from the pick-up on the slightest bend............

A lad from my collage run his for a few months of day to day driveing just below minimum, it was a worn out old 998 but dident do any harm.
Ran quite nice for a 90tho engine that got thrashed and never looked after. Maby this was just a one off

but Id never run it a max eather because this is bad for gear box

[bmcecosse]

Why on earth should it be bad for the gearbox!?

[Burnard]

While your talking about oils, is it ok to use 15w40 mineral oil, or 10w40 part synthetic instead of the 20w50?
Or is 20w50 just the best thing to run it on?

Edited by Burnard, 20 June 2010 - 11:02 PM.

[me madjoe 90]

Why on earth should it be bad for the gearbox!?

As for a gear box to be lubricated effectivly it needs the oil level to onlycover one of the lower shafts or half way up the lower shaft as this lower shaft will pick up oil on its gears and then coat the other shafts gears efficiantly. This decreasis wear between the gears ect..... l

But with the mini gear box with it being the sump as well. The oil level is alot higher Any way wich is generaly bad for the gears as rather than them getting coated evenly they are submerged in oil and when rotating they throw the oil away from them rather like a propeller increasing wear as theres less oil between the meshing of the gears.

so i supose its just a gear box disign flaw. But there is method in my madness trust me

[me madjoe 90]

While your talking about oils, is it ok to use 15w40 mineral oil, or 10w40 part synthetic instead of the 20w50?
Or is 20w50 just the best thing to run it on?

use what oil you like as long as its mineral. Most people perfer 20w50 as its thicker and generaly better for an old engine.
the thiner the oil they tend to get abit more tappety and so on, and leak more
but if you have a fresh re-built very high performance engine some people like to use synithetic

[lawnmowercrap]

Why on earth should it be bad for the gearbox!?

As for a gear box to be lubricated effectivly it needs the oil level to onlycover one of the lower shafts or half way up the lower shaft as this lower shaft will pick up oil on its gears and then coat the other shafts gears efficiantly. This decreasis wear between the gears ect..... l

But with the mini gear box with it being the sump as well. The oil level is alot higher Any way wich is generaly bad for the gears as rather than them getting coated evenly they are submerged in oil and when rotating they throw the oil away from them rather like a propeller increasing wear as theres less oil between the meshing of the gears.

so i supose its just a gear box disign flaw. But there is method in my madness trust me

Actually most modern gears / gearboxes are nearly always fully submerged apart from final drive as this needs to be the quietest gear.

In a Mini gearbox they are constantly submerged in oil which means the lubrication is VERY VERY good. Instead of relying on the oil being thrown around it actually 'sucks' the oil into the gears meaning they are constantly lubricated.

My 998 did 1000 miles about a 1/4" below minimum and it caused no damage. It then ran for about 3000 miles and still counting at 1/4" above max with no problems. Though if you do overfill it it may lead to overpressurisation of the crankcase and cause the seaks to push out.

I would only use 20/50 oil, halfords stuff.


Does it smoke on throttle i.e down motorway, or does it smoke on overrun, when you are off the throttle and the engine is coming back down the revs?

Lee