Bis Engine Refresh

[punkydog]

I am getting a lot of blowby in my Bis engine, if I remove the dipstick when running it spays oil everywhere and if I put my finger over the tube it feels as if I have it over a sparkplug hole. New oil smells of petrol and exhaust fumes. I have pulled out the engine, bit confused on how to remove the coolant impeller, does the bolt have a cover on it? Years of running without antifreeze has turned it into a rusted glob. Apparently pistons, rings, liners are not availble but everthing else is. My intention was  to simply rebore and get the head sorted- no point doing one without the other, plus a good clean up and timing chain. Can anyone offer advice on the piston front?
Secondly, the bellhousing had more gearbox oil in it than I would like to see, is the front seal, assuming it has one, accessible from the front, like regular set ups?From the manual it looks like the bellhousing has to be removed and it replaced from the back.

[Chris Lakin]

hi Brain, well, funny enough ive just had a major amount of petrol in the oil!!! i change dthe carb hopping it was that, but recently i have change dthe fuel pump, when i took old pump off it was dripping with petrol. But i changed oil for the first time since ive changed the pump, and i can still smell as slight wiff of fuel, maybe i need to flush it through a few times? to get rid of the trace. Do you have the old orginal fuel pump on? is your exhaust really old and rusty?? (mine is)

if i remove the disptick on my BIS oil sprays everywhere, thats normal. isnt it? thats just the oil pressure?

if you remove the oil sump the pump and thermostat housing come away with it.

regards

Chris

[126cab]

Hi yes it is quite normal for oil to spray out of dip stick hole when removed, i was quite alarmed when i forgot one to put it back in, there was oil every were, their is is a lot of pressure in there.

[fiatfsm]

on the airooled, the gearbox oil seal on the input shaft is accesible from inside the bell housing, remove box from engine job. would think the Bis was the same but not sure.

[punkydog]

So pulsating pressure and spraying oil from the oil sump is normal on these? Perhaps someone with a good engine could tell me. The sealing disc from that oil filler plinger thingy had been removed , I thought to relieve this pressure, I noticed that stronger springs are available - what does that achieve? The centrifugal oil whatsit was solid and the water pump full of radweld or something. Are piston rings N/A? The bores look OK, no discernible ridge but I will have them measured, I assume because of the size of everything tolerances are smaller.

[Chris Lakin]

blimey m8, you make it sound as though my engine is falling apart!!!

Dave's BIS here is in perfect condition body wise and engine wise, he said the same happens. i can honestly say to, if you take the dipstick out oil spurts out when engine is running.

[126cab]

hi,Yes its true they are only a small sump not much room designd to work like that, you will find the air cooled is the same m8.


Ps my engine has only done 17000 miles from new

[punkydog]

Having given it some thought, whilst cleaning fiat crud from my fingernails, pressure in the sump is going to throb, I am just used to 4 or 6 more cylinders. The pistons both travel back at the same time one on an induction cycle the other on a cpmpression. However I don't think I should be getting fumes from the sump just after starting up.

[Lewey]

The engine works just like any regular in-line 4 or 6 cylinder engine.  It is unusual for a 2 cylinder engine in this respect, but for the purposes of analysis of your problem it will behave the same as other engines you are used to.

1 piston is on a compression stroke whilst the other is exhausting.  On a 4 cylinder engine, 2 are compressing, 2 are exhausting.