Elans puffing blue smoke

[holywood3645]

This is Keith Franck post from 2001, I had to cut and paste to get it active. I notice my car doing the same thing when the motor get Hot (above 190deg) its fine when its colder.
Any ideas? and only when I sit at lights for a while and when its hot.the motor has about 3000 miles since rebuild.new ringd were installed as pistons were fine.
James


"All I can say is there must be a lot of Elans out there puffing blue
smoke. Particularly after waiting at a signal for a minute or two and Its a
then pulling away from a rather large smoke screen. I've got first-hand
experience in this area too. It's annoying and extremely embarrassing.

Luckily my chrome rings finally seated after 20K miles within a two week
period. Was I happy! I had used my own advice initially and still the
rings wouldn't seat. I was to the point of desperation of nearly
building and installing a water injection system which would spray into
the webers to wash off the cylinder walls to force the rings to seat or
scuff the piston skirts, one or the other or both.

While there is still tooth to the finish of the cylinder walls you need
enough forces to cause the compression rings to lap themselves. This is
best done quickly and that means sustaining the highest pressures in the
combustion chambers until the blue smoke diminishes.

These engines are pretty much bullet-proof. Why do you think they
dominated in the racing world for so long?
--
Keith Franck

[pharriso]

Worn valve guides?

[holywood3645]

Guides were new 3000 miles ago!

[rgh0]

A smoking engine is caused by 2 issues potentially.

1. Worn or poorly seated oil rings
2. worn or poor tolerances when fitting new valve guides

In twin cams it is almost always worn or badly reamed valve guides.

A few questions more can help diagnose what is the potential problem.

1. Has the issue been their since the rebuild 3ooo miles ago?
2. What running in procedure did you use with the rebuilt engine. However the running in procedure is mainly for the compression rings not the oil rings as they don't see the combustion pressure.
3. Does it smoke under high revs and heavy load or just after its been idling for a while and you take off
4. When the guides were replaced did you also fit new valves and what were the clearances on the valve stems set at was the rebuilder an experienced twin cam guy as most engine guys are used to rebuilding engines with valve stem seals and don't understand how critical it is to get the right stem clearances on a twink.
5. What sort of oil rings were fitted - modern 3 rail type or the oil single piece cast type
6. How was the bore honed for the new rings - was it done with a proper honing machine to get the required finish?
7. what oil are you using
8. If I had the engine in front of me I would check the blowby out the breather to judge if it was normal or excessive to get some idea of how well the rings were seated also

cheers
Rohan

[holywood3645]

1. Has the issue been their since the rebuild 3ooo miles ago?
A1) Only recently started to notice But weather has been pretty cold , and had trouble getting engine much hotter then 165deg. Recently hotter weather,

2. What running in procedure did you use with the rebuilt engine. However the running in procedure is mainly for A2) the compression rings not the oil rings as they don't see the combustion pressure.
Light load Short shift, Increasing RPM and shifting after RPM intervals 2000, then increased after about a week to 3000, then another couple of weeks at 4000, At least 800 to 600 miles before 4000 rpm. Then up and down to 5000. Haven't really pushed it much higher than 5000 Used 10/40 during run in.

3. Does it smoke under high revs and heavy load or just after its been idling for a while and you take off.
A3) Only after idling after a while at lights and hot.

4. When the guides were replaced did you also fit new valves and what were the clearances on the valve stems set at was the rebuilder an experienced twin cam guy as most engine guys are used to rebuilding engines with valve stem seals and don't understand how critical it is to get the right stem clearances on a twink.
A4) Professional Head rebuild by well know lotus specialist. All new parts (guides valves springs etc)

5. What sort of oil rings were fitted - modern 3 rail type or the oil single piece cast type
A5) New from Omega pistons for forged pistons

6. How was the bore honed for the new rings - was it done with a proper honing machine to get the required finish?
A 6) Yes, Machine shop rebore to 83.5 with hone,

7. what oil are you using
A7) 20/50 Castrol Added ZDDP adative a couple of days ago

8. If I had the engine in front of me I would check the blowby out the breather to judge if it was normal or excessive to get some idea of how well the rings were seated also,
A8) the blowby pipe is to a vent
It only really when car is hot. > 180 deg F, A little smoke when it has been parked for a week or 2 and more than

I can't see anything in my mirror under heavy acceleration.

James

[rgh0]

First thing I would try would be a 20/50 or 20/60 full synthetic oil as these as less affected by temperature than mineral oils. Redline oil in particular is better at high temps than other full synthetics as it uses a different base stock but it costs !

Generally if you don't see it under full power but only after idling then its valve guides. They should be right if done by an experienced twin cam builder but anyone can make a mistake.

Does your head have the cross drilling behind the NO4 exhaust port? This aids oil drainage at the rear of the head and leaves less oil there to go down the guides.

If blowby is normal and compression pressures normal then the rings are bedded in and the oils rings should be working OK. always possible an oil rings was not fitted right or broken on installation but again you should see blue smoke when running under power at high speed if this is the case.

In the end I would pull the head and check the guide stem clearances and make sure they are at the bottom end of the tolerance range.

cheers
Rohan