Ferrari 308 Gtb - Blowing Smoke!!!

[trev]

Hello all, I took the old girl out for a spin today, being the first opportunity since a full cambelt and valve service in April.

I warmed her up and bled the air from the radiator and she was running perfectly.

I drove approx. one mile to get petrol, which was mixed with lead replacement/ octane boost as usual. When I drove out of the petrol station she was fine, but about 300 yards down the road she suddenly started running very roughly and blowing blue-ish smoke out of the left hand exhaust pipes as you look at the back of the car.

I could not stop on the road as it was dangerous, so I limped her home (about 1 mile in 4th gear doing approx. 1500 revs, as this seemed to keep the smoke down, anything higher started blowing the smoke again.

All cambelts, leads and fittings seem to be in good shape, but there was a steady dripping of fuel from the rear right hand carburretor as viewed from the back of the car, with a strong smell of fuel when I opened the rear deck.

Does anyone have a suggestion of what has gone wrong or where to start trying to find the problem. I can say the engine sounded more like a two stroke and was probably not firing on all cylinders when this happend but there are no obvious nasty noises like broken metal bits coming from the engine.

It happend almost like someone had switched half the engine off!

[steve]

After the engine was shut down was there gas still leaking inside that carb. If gas is dripping inside the carb then you might be fouling out the plugs for this carb. I would thing that the carb. float is hung up and not seating causing fuel to spill directly into the carb. This could be caused by the car sitting for a long time and the float valve staying open. Also the float could have a leak and is not working. So if you have raw fuel in the carb and it is wet you will need to pull the aircleaner and take the top of the carb off to check the float. Not having any more info I would point to this area. Good luck

[trev]

Many thanks Steve, I will have a look, but I think it is probably the case that I will have to resort to paying a specialist to go over the engine, as I am worried I could cause more damage through lack of knowledge.

The fuel was leaking out quite fast from the carb and I know they are probably due for a rebuild - is this something that is easy to undertake myself? I am not a mechanic, but I have rebuilt SU carbs on an MGB successfully and still drive the car 10 years later.

Obviously I am interested in any other offers of advice.

[Racer86]

Trev, if you rebuilt SU carbs in the past, get a book an rebuild your carbs. You can do this. Floats, needles, and seats are all very similiar in function in all carbs. Cheaper, more fun and you learn about your car.

[trev]

Hello all,

The car has been at the Ferrari specialist that i bought her from for a week now, after they recovered her on their trailer.

The cost is growing by the hour, but not much I can do!!!

They found the jet casting / needle valve had cracked and split off into the carb allowing fuel to flood the carb. Arefurbished carb has been sourced and fitted.

The engine was run, but continued to blow excessive smoke, so they shut it down.
On checking the oil, it was heavily contaminated with fuel, so an oil and filter change was done. She still blew smoke, but slightly reduced.

The theory is that we still have contaminated oil in the system that was held in the oil cooler / pipework, so a second oil change is being done in the hope this is the cure.

My fear is that the fuel that has got into the oil has taken away the protection of the oil and caused damage to the pistons / bores, which I guess is serious!!!

Anyone have any ideas of anything els to check out or try?

Your help / advise is most welcome.

[sjbdeebo2]

Its a scary thought but I'm sure it'll be fine. Fuel does tend to eat through a lot of things, but I'd keep a positive attitude. Be happy you drive a Ferrari

[Racer86]

A leakdown test will show if your cylinder bores were scuffed by gas washing the oil off the bore surface. Cam lope surface and followers should have a visual inspection for any scuffing, Bearings should be fine if the engine was not run hard with the gas/oil problem.

[trev]

Hello all,

The news is not good so far. New carb fitted and two oil changes done, but she is still smoking heavily!

My budget does not allow for the sort of money I'm being quoted for an engine rebuild, so I am trying to find any advice as to how to get round the problem without a full rebuild.

A couple of people I have spoken to, have suggested it could be a burnt valve that is causing the problem and others say the bores will have been damaged and possibly pistons too.

One point of contact has asked if the cylinder liners are wet or dry, but I can't find the answer - Does anyone have the answer for me?

I understand that whilst the engine is apart, you would be wise to refurbish all components, but if the engine was running well right up to the carb breaking, perhaps just addressing the cylinders / valves, may be enough to get her up and running again?

As always, any advice is very welcome.

[steve]

Have they done a compression test or a leakdown test? I would think that this should be done before you just tear down the engine. What are the results of the test.

[trev]

Hi Steve,
I have been speaking over the telephone to these guys as well as another engine builder and have advised the Ferrari specialist that I would not be willing to spend the kind of money they are quoting.
I told them last night that I would be over today to see the car and discuss the alternatives. Early this morning, I received a call from them to advise me they had another look at the car after they closed the shop last night, and that they had tried something.

They ran some oil into the bores via the spark plug holes and ran the engine, as they suspected the Oil seal on a piston had 'nipped up' whilst the fuel was washing the bores and had therefore alowed oil to pass into the combustion area, whilst letting oil past the piston to dilute the oil.

The result was that huge amounts of smoke were produced, but then got less and less until the smoking stopped!
It is therefore their opinion that the suspicion of the oil seal/scraper ring being trapped on the piston seemed to be correct and that it had now freed itself.

They advised me that the car was therefore back to full health and that I was free to collect it.

I could not collect the car today, but did visit the workshop. The car was not there as they are storing her at their other facility, but they showed me another piston and explained the theory more fully and advised there would be no grey area as the piston was either letting oil past or not and it would seem we have been very lucky and the seal ring had been released to perform it's function without any obvious consequences.

They have advised they will perform a compression test just to be sure the readings are consistent, but that they are 99% sure everything is OK. I must admit I am surprised they have not done a test before now, but they assure me they are confident it was not required as the engine is actually running very smoothley and not lacking any power.

I checked with the other engine builder, who seems to concur that if the smoke has stopped, it is entirely likely the oil ring theory is correct and he has seen it happen before, but he also recomends a compression test as being needed.

I will wait for the results of the compression test and if it is OK, I think I will collect the car and just take it easy with her until I become more confident that the problem has actually been solved.

If anyone has any other points of view, I would like to hear them in order to try and avoid making the wrong decision in collecting the car.

As always, many thanks for any advice.