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I recently acquired a 1275 S which hasn't had much mileage following a complete restoration more than 10 years ago. For the last year its only been driven one other time. On a long trip recently I noticed a plume of smoke behind when lifting off suddenly at high revs in 4th gear. I immediately thought it must be worn valve guides and valve stem seals.

Funny thing is that below 5000 rpm there is not a hint of smoke. accelerating past 5000 rpm she immediately starts smoking again, this seems more like rings? She stops smoking almost immediately below 5000 rpm. Possibly there's oil entering the inlet manifold through the breathers?

The car was serviced with carbs, timing etc all set correctly before the trip. Oil drained and 5l of oil added, so not over-filled.

Please could you let me know if you think its due for a complete overhaul of the motor (rings at the very least), and the MED head (guides and seals). How can I eliminate each potential cause? Thanks for your help!

100 views, no response Any advice welcomed

Disconnect the breathers and stick the pipe down the back of the subframe and block up the carb stub. Now see if it's still doing it, my initial thoughts are it's running to rich and weakening out above 5000rpms.

Smoke while deceleration is normally indicative of rings. Smoking only above 5000rpm indicates the rings are not working well at that speed. Perhaps some replacement high performance rings. I am of course assuming oil smoke and not fuel smoke which is black.

Smiffy wrote:Disconnect the breathers and stick the pipe down the back of the subframe and block up the carb stub. Now see if it's still doing it, my initial thoughts are it's running to rich and weakening out above 5000rpms.

gpmini,
Your information is quite scant. What year is your car and does it have original breather equipment? Has it been checked? As Smiffy points out, it would be worth diconnecting it and giving it a try.

Regards
Al

Frogeye61 wrote:Smoke while deceleration is normally indicative of rings.

I must disagree. Smoke when decelerating comes from the valve guides.

Valve guides and/or bad v.g. seals.

i am for valve guides

Thanks guys! Think I'll have the guides done, will post the outcome

Try changing the oil, might help.

Failing that, I'm inclined to suggest blow-by (rings).

I'm using Castrol 20W50 mineral oil. What oil would you suggest using?

Comma Sonic 20/50