Engine still smoking after rebore, suspect valve guides?
Turbo Mini Forums

Hi all!

This will be a long post as I will try to give you as much information as possible.

I had problems with my engine smoking and bad leakdown results, so I had it rebored:
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=123583

But its still smoking (on idle) and I cant understand why (but I suspect the valve guides)!
I have ran the new pistons for about 280miles now and the smoke gets worse.

The compression is ok (190PSI, 195, 200, 195).
The leakdown is ok (9%, 10%, 11%, 12%).
I have changed seals and bearing in the turbo. I have also run the engine with the oil pipe to the turbo disconnected, just feeding it with a oil can (to make sure the oil pressure wasnt to high for the turbo).
I have run the engine with no oil in the dashpot.

After reading a bit on this forum I jacked the front off the car up 8-9 inches and it stopped smoking almost completely.
Lowering it with the engine still running and it was smoking again.
After letting it cool down a bit I removed the plugs and could see oil on top of the pistons!
I replaced the valve seals (they were not very tight on the stem) with Viton valve seals.
Started the engine, and when the oil on the pistons had burned off it ran with no big amounts of smoke for a while. Took it for a spin but when I got back it was smoking again.
There is no smoke when I drive, the smoke is worst when the engine been idling for while and I rev it (cloud of smoke).

I took the valve springs of again on one inlet valve and lowered the valve down the bore and measured the id of the guide. I measured it to 7,17mm(0.2822"), also measured the valve stem 7,06mm(0.2775") and a new guide 7,13mm(0.2807) for reference.

This makes the clearance 0,11mm (0.0043"), the "wiggle" of the valve when its closed (measured at the top of the stem) is 0,19mm (0.0074"). Is this to much??
Also the guide might be worn a bit oval (hard to measure but it looks like it).

The valve guides are less than 8000miles old and the valves are less than 3000miles (yes I changed the valves without changing the guides, might have been stupid?).
Is it possible that the valve guides(cast iron) are worn out after
8000miles? (I have 1.5 rockers)

At the moment Im using cheap 10-40 mineral oil (for running in the bores), can it be to thin oil causing the smoke?

What should I do? Change guides? Change oil? Put realy big wheels on front? Only drive uphill?

/Jonas

Definately the guides in my eyes, what cam are you running?..... is the rocker geometry correct due to the 1.5's..?

This is most likely the cause, the rockers side loading the valve stem and thus wearing the guides prematurely.

And I would use 20-50 oil really, I found anything thinner really turns to water after a good thrashing.

Hope you sort it.

Were there some mods to the head, to allow oil to drain away from around the guides easier ?

Or better valve stem oil seals ? Not sure if exhausts usually use them, but it can be worth fitting them to exhausts too if they arent there.

I know when I first fitted a turbo engine to my mini, I was plagued with this smoke. Too long ago to remember what actually sorted it though.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

sounds identical to my problems mate, i took my head off tonight and am off for new guides in the morning. i'll let you know if it sorts it.

You need to measure the 'wiggle' (lol) of the valve at around 1/4" lift for any kind of meaning.

This is almost definately guides. Ignoring how old they are, tell us the material, and if you are running standard or hi-lift rockers, and if these are roller tip or not...

I have cast iron guides, std valves, std Metro turbo cam, Viton valve seals (since two days ago, before that std ones), Minispares 1.5 non roller rockers.

Is there anything in this combination that would cause the guides to wear out fast.

I dont want to put seals on the exhaust guides, have done that before and dropped a valve.

Stevie, I havent heard of a oil drain mod before, please tell me more.

Why do Minispares sell these rockers if they wear the guides at this rate!?
I realy like the characteristics of the engine as it is but I might have to go back to std rockers then.

Would manganese bronze last longer?
Im a bit short of time as I need to get it sorted before the IMM. I allready have new cast iron guides at home. Also manganese bronze guides needs to be reamed and I have no reamer (dont think I will be able to find one in sweden as its inch size).
Would it be unwise to use cast iron guides again?

1.5 rockers will imply more side loadings onto the valves. This is made worse with bigger cams.

This will be lessened with roller tipped rockers.

You makes your own decision as to useage, and pays what you can afford. If you want the best of everything, you have to pay for it.

Jonas. There are small drain galleries from the valve seat, to the rear of the head, to allow oil that gathers to drain away. I think it involved making these deeper.

I dont ever recall doing it myself, but I did read of it somewhere back in the nearly 90's when I had my problems.

But as I say, I think fitting valve stem oil seals to the exhaust guides was what sorted mine.
I mostly used Duckhams Q oil in mine, so I cant say that any fancy synthetic oils did it, although from time to time I did use 10/60 Castrol RS.

Not long after that, I fitted a modified head. I only, ran a standard cylinder head for a few months. But I do remember when I first got the car running, it smoked like a train, and it was valve guide/oil/stem seal related..

I know that I never got valve guides re-fitted, simply to cure this problem, but valve guides are without doubt a major part of the problem.

Its relatively easy to throw on a set of valve stem oil seals on the exhausts though, so worth a try first.

I dont think std cast iron guides would be wise in a turbo engine, especially if you are upping the boost.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I´ll fit guide seals to the exhausts tonight and see if it makes any difference (Ill use the worn ones that was on the intakes).

If it does help I dont know if I want to leave then there as I have done this before and dropped a valve!
By the way, the exhaust valves and guides has done less than 6000miles.

I always ran seals on mine. Never had a problem and covered some 30K a year when it was my daily driver, back in 94/95

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I have now put valve seals (took the worn ones from the intakes and fitted them without the springs) on the exhausts.
Its smoking a little less but I still get a puff of smoke when I rev it when its been idling for while.
I can also still see oil on top of the pistons.
I think Ill need to take the head off and change all guides, hope I will get the parts fast so I make it to the IMM!

While Im at Im thinking of getting the manganese bronze, but I will still have trouble reaming them.

What size should the reamer be, for both intake and exhaust (std metro turbo)??
Where can I buy the reamers??
Anybody here that have some for sale?
I need to order the parts immediately to make it in time!

You need to take the head and valves to a machine shop with a Serdi, and trust it into their hands.

Iron guides are my preference!


Also - did you try running it without the inlet pipe / plenum attached (to isolate if oil is leaking past the compressor wheel)?

I think I found the right one (should it be 9/32"?) for the intakes, will this do:
Ebay item: 300123781041

Will a 8mm reamer do for the exhaust?
(Should be reamed to 8.036-8.049)

Will a 8mm reamer do for the exhaust?
(Should be reamed to 8.036-8.049

YES NEVER HAD A PROBLEM

Are these the ones to have?:
HSS Hand Reamer Spiral Flute 8mm
Ebay item:300123780989
HSS Hand Reamer Spiral Flute 9/32 Inch
Ebay item:300123781041

I need to order the reamers today to be able to make it to the IMM in Denmark!

Thanks in advance!

there the ones jonas order those buddy

Thanks everybody!

I have ordered reamers and guides, hope they will get here fast.

I will report when I have fitted them.

i have the same problem ive re-bored the engine = no good still the same, i change the valve guides = no good still the same, i changed the turbo for a new one = still the same and finaly i tried put valve stem oil seals on inlet and exhaust = no good so im all out of ideas but the head mod could be my next plan of attach

Be careful, Ive no idea how thick the casting is in that area.

As I say, Ive never seen it done, but I did read about it somewhere.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Hi,
Miniwid ... Does jacking it up make any difference to yours?
If not the head mod won't help...
Cheers,
Gavin :)

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if you have used iron guides with lagish cam and high lift rockers then they will be cream crakered pretty quick.

try bronze guides as thedo make a difference if using the above.

always looking for them bigger bunches of bannanas

About fitting the new guides, at what height should I put them?
According to the manual they should be put 13.72mm above head, but according to this thread:
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=127827
14.2mm is standard.
Will 13.7mm be ok with std cam and 1.5 rockers?

yes

i press them in 13mm EDIT:- from the valve spring seat to the top of the guide

Edited by BENROSS on 16th Jul, 2007.