17 replies to this topic

[myredmini]

Hi, basically, i have just pulled my tired 998 out and dropped in a 1275. The compressions are 190-200 across the board. Decent oil pressure. It runs very smooth but i have a smoke problem.

If i drive it 3k and above, lift off for a few seconds and then re accelerate it smokes. It doesnt smoke under acceleration or on over run just on re applying throttle. Its a plume of blue smoke, i know this is oil. I thought it was stem seals. I pulled the head, fit new stem seals and re fit and the problem is still there. Does this sound like oil control rings are worn/damaged?

Cheers

[nicklouse]

i would go deeper to the valve guides being worn.

[minimans]

What seals did you fit? if the wrong type they may have lifted off the guides or been crushed by the valve keeper?

[myredmini]

I fit the mpi type seas from mini spares. Is it more than likely top end issue?

[Midas Mk1]

I fit the mpi type seas from mini spares. Is it more than likely top end issue?

 

I found these loose on my new guides last year, ended up using some NOS ones my dad had from 25+ years back, which grabbed then guides alot better. 

[myredmini]

I fit the mpi type seas from mini spares. Is it more than likely top end issue?

 
I found these loose on my new guides last year, ended up using some NOS ones my dad had from 25+ years back, which grabbed then guides alot better. 

These were a firm fit on the guide. Heads coming off tonight, got another head im going to try off an engine that didnt smoke.

The crap on the back of the inlet valves would explain valve guides..

[carbon]

Have you fitted valve stem seals on both inlet and exhaust valves?

 

I am guessing you have them only on the inlet valves...

[minimans]

you only need them on the Inlets unless your guides are shagged! Inlets suck oil in exhaust blows it out..................

[myredmini]

Stem seals on both

[carbon]

That pretty much rules out the exhaust guides then.

 

It's incredible how much difference these can make, on a 1330 with no exhaust guides fitted I have seen oil consumption of 100 miles per pint on long motorway trips with hot engine.

 

More recently the 1293 was getting a bit smoky on start-up and also after overrun, just fitting exhaust valve guide seals cured this.

[carbon]

Dan,

 

Just to check, what grade oil are you using and roughly how many miles per pint oil consumption?

[myredmini]

Its running 20w50. Ive just removed the head, fit a different head with better valve guides, new stem seals and it still has smoke. I think a tad less but that could be me hoping. Must be more terminal. I cant imagine it clearing up. As for comsumption i have not used the car enough with this engine in to tell yet.

Thanks for the replies

[cal844]

Its running 20w50. Ive just removed the head, fit a different head with better valve guides, new stem seals and it still has smoke. I think a tad less but that could be me hoping. Must be more terminal. I cant imagine it clearing up. As for comsumption i have not used the car enough with this engine in to tell yet.
Thanks for the replies

Leakdown test will help diagnose?

[myredmini]

Its running 20w50. Ive just removed the head, fit a different head with better valve guides, new stem seals and it still has smoke. I think a tad less but that could be me hoping. Must be more terminal. I cant imagine it clearing up. As for comsumption i have not used the car enough with this engine in to tell yet.
Thanks for the replies

Leakdown test will help diagnose?

For compression issues yes, but the compressions are perfect. Im starting to think oil control rings

[nicklouse]

 

 

Its running 20w50. Ive just removed the head, fit a different head with better valve guides, new stem seals and it still has smoke. I think a tad less but that could be me hoping. Must be more terminal. I cant imagine it clearing up. As for comsumption i have not used the car enough with this engine in to tell yet.
Thanks for the replies

Leakdown test will help diagnose?

For compression issues yes, but the compressions are perfect. Im starting to think oil control rings

 

rings would have the problem for most of the time, I would still say guides.

 

if you have slight oil burning all the time and then more on acceleration then then more likely to be the rings.