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Triumph Repair/smoking engine


QUESTION: Dear Howard,
I have a triumph spitfire 1500. It is fitted with a fast road cam and a unleaded stage 3 head. It has had the piston rings changed recently. It is also fitted with an uprated oil pressure relief valve as it is fitted with an oil cooler.

I have noticed that there is oil on the spark plug in piston three (2nd to back of engine). Some in number 4, but appears a lot less. The engine smokes particularly when idling. I am at a loss as to the route of the problem. It failed it's MOT because the hydrocarbons where to high.

Reading some of your comments else where I may just try and replace the oil pressure spring with a standard one. Do you thing that really could be a cause?

Okay, lets assume that is not the cause. How can I diagnose whether it is the valve guilds or the piston rings that are leaking oil? I don't think it is likely to be the head gasket.

Anyway, like I said the smoke is obvious when in idle, but seems to go when I run the engine. Also I have removed the oil feed to the head and I think there was some improvement there. Suggests guides? The smoke does not particularly appear to be blue, but i can't say for certain!

Any ideas would be very gratefully received. Thank you very much for your time.

Bets wishes,

ANSWER: Hi Chris,

You didn't say anything about blue smoke during acceleration only at idle. So that would point towards valve guides not rings. However if it were brought to me in a dealership I would run tests for both.

First warm up the engine and oil (which takes longer then coolant temp) Check to see that the oil level is not above normal and have someone stand behind the car while you accelerate down the road through the gears. They need to note if there is any blue smoke noted out of the tail pipe when shifting or accelerating.

Next run a dry and wet compression test. The "Dry" test is just a standard compression test. (Throttle open and at least 5 or 6 revolutions). Write down the readings. Now run the "Wet" test which is done by squirting 3 or 4 squirts of engine oil (about a table spoon of oil)in the spark plug hole and quickly run a second compression test (throttle open).

The "Wet" test will be higher then the "Dry" test but it should not be more then 10% to 15% higher. The "Dry" test should have been from about 125 PSI to 170 PSI with little difference between cylinders and each "Wet" test should only be a little higher on each cylinder.

This is a good preliminary test of the rings along with the acceleration test run.

Next remove the valve cover and start the engine and watch the amount of oil coming out of the rocker arms especially toward the rear. There should not be any noticeable excess of oil between the front two cylinders then the rear two cylinders. Triumph does not use valve stem seals so if you get excess oil in the area of any valve spring it can cause excess oiling of the guide and since there is a vacuum at each intake valve, it draws excess oil into the intake of that cylinder.

This condition is usually noted by an excess of blue smoke on first start up and oil smoke (blue) at idle (when vacuum is at it's highest) There may be some on a shift in the acceleration tests but little to none while accelerating.

The oil pressure relief valve in the block has little to nothing to do with oil burning. It only restricts the oil pressure from going too high at higher RPM and that is only on the bearings. Your oil pressure on the gauge should read about 25 to 35 PSI at idle with warm oil and 45 to 70 PSI at 2000 RPM. If your pressures are higher then that it is possible to flood the cylinder walls with oil from the rod bearings and also flood the head with oil from the rockers especially if a rocker is has a problem. Too loose and it will splash excess oil on the valve spring or even too tight and force excess oil out onto the valve collar which leaks in between the split keepers and runs down the valve stems. (this is why MG put a "O" ring just below the valve keepers to stop excess oil from running down the valve stems.) (they don't use a valve stem seal either)

You can have a combination of these conditions so you need to run all the tests to decide what is the best course of action to correct the problem.

Keep in mind that oiling of a plug can also be caused by a misfire of that cylinder but you didn't say anything about a miss.

Let me know,


---------- FOLLOW-UP ----------

QUESTION: Hi Howard,
Thank you very much for your comments and advice. It is much appreciated.

Picked up the car from the MOT station today as it was left there because it had a brake fault. Anyway, car is running very badly missing and smoking badly . Not sure why such a sudden change in the amount of smoke.

Anyway, I checked the plugs when I got home and they were all full of DRY soot. Was surprised that even cylinder 3 had no oil on the plug. Removing the oil feed to the head might have improved things there.

The smoke is now coming out of the exhaust not only upon idle but under all driving conditions. I'm pretty sure it is not blue but is was hard to tell. Can small petrol so I need to now fix that problem before proceeding.

Anyway, I did the compression check as you suggested and these are the values I got. From cylinder 1 to 4 in PSI: dry 180, 180, 180, 182 and wet: 205, 200, 200 and 205. Thus, although the dry test is a little higher than we expected (175 top), the wet test was around 15% higher or so. I think everything is as expected? Do you agree?

I could not restart the car after the compression test. Perhaps the battery had died or the pressure in the cylinders was to high so preventing the engine turning so I'll let the oil drain out over time and retry (at least thats how I saw it!!!). Consequently, I could not do the value guide test as you suggested but I will get round to doing it soon.

So, the question now is why is the car misfiring? Obviously, I need to check the carbs, but don't see why they should be at fault (assuming the MOT station did not fiddle with them). However, I was wondering if the coil might be faulty. The condenser is new so I'm sure it can't be that. I'm going to replace the coil to see what happens as it is fairly cheap to do before I touch the carbs.

The only other thing that puzzles me and might be of relevance is that when I first start the car it needs hardly any choke to start. It's a bit lumpy (but has a fast road cam) and any attempt to pull the choke out further causes the engine to stall. Not sure if this is relevant?

Anyway, if you have any other opinion on this I would be most grateful. Once again thank you for your time.

Best wishes,

ANSWER: You need to forget trying to guess what part might be at fault and concentrate on which system is at fault. The 3 systems that make any gasoline engine run are Compression, Fire and Fuel.
If your gauge is correct then compression is not the problem. If this engine had a cam then most likely the Compression has been raised also which would explain the high readings. That means you MUST run a high octane fuel.

Fire (Ignition) is always second to check. Confirm that the timing and the firing order is correct. Then test the ohms of each wire and the coil wire (about 5 K ohms per foot of wire)
Clean and gap the plugs.

You first said that a plug was oil fouled and then you said some plugs had "Dry Soot". Oil fouled is usually "glossy black" but "Dry Soot" (flat black powder) is not oil but excess gasoline.

Blue smoke is oil, white smoke is either coolant or brake fluid and black smoke is excess gasoline. With the "Dry Soot" you had to have black smoke out of the exhaust.

Even though these things point toward "Fuel" as the problem you MUST first do the ignition system. Timing, firing order, plug wires and coil wire and then plugs cleaned or replaced.

Then you can look at fuel. What kind of carburetors do you have on this car? Two SU's, two Strombergs or one Stromberg. Or has someone put an aftermarket carburetor on it? Also what kind of choke does it have?

Then I can tell you how to proceed.


---------- FOLLOW-UP ----------

QUESTION: Hi Howard,
Thanks once again for your quick response and invaluable advice.

Okay, my first oversight is that I'm trying to run the car on standard petrol. For some reason I had not appreciated that the compression was significantly higher. Just filled the car with standard unleaded petrol as it happens. typical! Anyway, it is a relief that the compression seems to be okay.

I will check the leads, but these were just replaced so I suspect that they are okay. The only item on the ignition that was not replaced was the coil.

When I noticed the oiled plug (cylinders 3 and 4, but especially 3) it was when the oil feed pipe to the head was in place. As oil is fed to the rear of the head I suspected, rightly or wrongly, that extra oil may be accumulating around the valve guilds of cylinders 3 and 4 (which seemed to be the worst, especially number 3). I removed the oil feed a few weeks back and ran the car for some time. The smoking was significantly less when the oil feed pipe was removed. After the MOT I rechecked the plugs and found to my surprise that the plugs were, in all four cylinders, fouled with matt black  dry soot. But, at this stage the car was not running the same as when I took it into the MOT station. It was misfiring and smoking significantly more not just on idle. So there is a question of whether the carbs were adjusted by the MOT station.

So back from the MOT station I got a friend to drive behind me. They said that the smoke is not like a diesel smoke, meaning it was not obviously black. They said it looked more white and perhaps had a slight blue tinge. Okay not that helpful I guess! I will check this agin, but it may take me some time. For reasons I can't go into here the car is stuck up in London while I'm in Brighton!!! One thing that was evident was the smell of petrol in the emissions. So clearly some petrol id not igniting which is in line with the misfiring (coil?, but I will check the leads anyway as you suggested).  I will also check the firing order in case the garage has tampered with that too. But certainly it was correct when I took the car in.

I have two SU cards, but I realise that the needles I have on them may not be up to the job. I think they are AAQ (suitable for stage 1 head), but looking up some detail on this it might be that I need ADQ (stage three head needles-do you agree on this?). It has the standard SU carb choke on it. Sounds like I probably need to do some further work here? There is a sports exhaust fitted and a pair of K&N air filters. The car is also fitted with a servo brake system. I mentioned this as you stated that perhaps brake fluid might be the cause of the white smoke!  I guess I could remove the connection to the servo and check if the smoking gets better/stops, but only after doing the electrical checks of course?

Anyway, sorry about being so vague on parts of this, but it is difficult to be certain when the car is so far away. However, if you can let me have your opinion on what else I could usefully do on my next trip up I will endeavour to get as much done as possible. In particular should I replace the needles and coil as I do need to travel so far anyway. Probably costs more to do the round trip then the cost of these parts so I may save my self some effort here at least. I wait for you list of things to do in anticipation!:-)))

Thanks again.
My best wishes,

Chris, You can't run the engine without oil to the head or you will destroy the rockers and shaft and probably destroy the valves and guides.

You can not run regular gas with that high of a compression. You will destroy the pistons.

Flat black powder on the plugs is 100% sure excess gasoline and since you have SU carbs they do have adjustable jets and you must check the float levels and see that when the choke is off that the jets have returned all the way up.

It is no use wasting your time with anything else until you correct these items.


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Howard M. Fitzcharles III


Triumph TR-4 up & Spitfire, and Engine theory


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Associate member SAE EAA member

Import Car magazine

ASE Master Auto with L-1 certification up to 2000

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