10 replies to this topic

[TheOldOne]

Hi all
1098cc Clubman Pre A Plus 295 Head and HS4 Carb.
My engine is smokey on overrun and sometimes under load.
If i rev it to say 3000rpm it will smoke a bit then stop but when i let throttle off it smokes again.
Smoke is grey blue in colour and quite heavy.
Is this likely to be valves/guides or pistons?
I did a compression test and all cylinders were similar 170-175 psi hot with throttle fully open.
Oil pressure when hot 50 idle and 70-75 running.
Also on idle if i remove the oil filler cap(ventilated type) the revs die down and if i put my hand over filler revs will go up again.
No smoke from filler or breather.
the breather from the tappet cover is connected to the carb, not the manifold, is this correct?
What are my best options please?
Any more checks i can do.
Any help would be much appreciated.

Thanks

Tony

[sledgehammer]

Does it smoke on start up for a sec , then clear ?

I would do the valve stem seals & head gasket

look at the bores , when you have the head off

check the vent pipes clean , & oil traps are not blocked

vent pipe usually goes on the carb - on a brass tube

[TheOldOne]

Anybody else help please!

[Boycie]

As above really. From your tests it doesn't sound like crankcase pressurisation is a problem and the smoke patterns (signals?!) agree with excessive valve guide clearances. The oil pressure is largely irrelevant and the compression readings, while perfectly ok, don't gaurantee that the oil control rings are doing their job correctly.

As said, I would remove the head, measure the valve guides/ stems and rebuild with fresh gaskets and seals.

[minidaves]

sounds like 1100 typical problems rings.

[yousmeg]

sounds the same as mine - mines a standard 1100

heres a vid to show what mine was like



we suspect piston rings and are 90% sure these were the problem. since then the engine has had a full rebuild and is now sat on the bench waiting to be dropped in again (hopefully no smoke this time!)

[TheOldOne]

Thanks for the replies.Looks like a engine out and strip.
The joys of old cars!!!!

Tony

[oltonlad]

i have the same problem with my 1098 +20" but the smoke isnt that bad at all really but i'm building another 1098 at the moment with a 266 cam and head porting/re-shaped chambers etc, the guy that i bought the engine from did say that it smoked on start up and then cleared, when i stripped the engine i found that the bores had been de-glazed so i presume that its had new rings, when i inspected the head i found out why it was smoking on start up......some muppet had put the valve stem seals on the exhaust stems and not on the inlet stems, i'm not surprised it smoked on start up lol!!.....

[TheOldOne]

Took the head off today,oil clinging to Nos 3 & 4 inlet valve faces and stems and oil sitting on piston crowns.
Bores are very clean with no scoring and no visible signs of wear.

[oltonlad]

it definetely sounds like valve stem seals, its a common problem, when you remove the valve springs check to see if there is much play in the valve guides, a little play is ok but not too much.

[TheOldOne]

Quite a bit of play and no stem seals at all.I have a 12g295 head which i am going to get new valves and guides for and re ring the pistons.
I have started a new thread (Piston ID) and will update as i go along.Engine out this weekend and a good inspection of all major parts.

Thanks

Tony