Smoky engine after a long lay up

[Peter Roberts]

My restoration is now almost complete so have got around to running the engine. When i laid the car up about 3 years ago it was running well and not smoking with good oil pressure so did not rebuild.
On starting it started to smoke a little but as i have run it more and got it hotter the smoke is increasing. Its not blue smoke as you would expect with worn rings or valve seals and does not blow out of the exhaust as with worn engines but sort of drifts up from the exhaust ends as if there is a fire in the silencer . The smoke is nearer white than blue but it is not steam.
I had a similar experience with a 3.2 Carrera that i bought that had been laid up for a few years. That turned out to be oil that had seeped past the rings over time in the flat engine. That was a dry sump unit so the oil had drained from the tank back into the suimp and raised the level. It subsequently got blown into the silencer which was then burning off inside the silencer and creating smoke. After a week or so it stopped as all the oil in the silencer had then been cooked.
Has anyone else had a similar experience with a 356 engine ( not dry sumped) or is it wishful thinking on my part to save me taking the engine out again.?

[Ashley James]

If it was okay when you stopped using it, it should be okay now and will settle down once you start using it. Starting and running engines without going anywhere often causes problems

[Peter Roberts]

These cars can be head scratching at times.
Went out this morning and started the car. No smoke . Ran for 15 mins to get it warm and still no smoke so my idea of oil in the system might be correct as by now it has burn off.
Did have another problem which i am trying to think through. Rev the engine and it refuses to come back to tickover but remains at about 2500 rpm. Checked throttles and both had returned to thier stops as i have additional springs fitted to ensure this. Leaving it run for a few mins and it gradually returns to a normal tickover of 800rpm. The idle jets are set at 3 1/2 turns out as a starting point. Fiddled with idle jets and it does not alter the tickover at all. I have rebuilt the Dellorto's during the refurb but did not change the jets. Throttle pump is set to 0.5mm clearance as listed in the manual.
As there are no other adjustments to be made why is it taking so long to come down to tickover. The only other issue may be float height as i did not check this but if this was the problem i guess it would stay at 2500 rpm and not drop down to that lovely lazy 800rpm tickover that it has always had.
Anyone have any ideas?

[Ashley James]

Sticky bob weights in distributor or sticking throttle linkage. Might be flooding as well.

[roy mawbey]

Peter,

Ashley has a point regarding bob weights. Take off the distributor cap and rotate by hand the rotor from stop to stop a few times. It should return positively to the stop when released. If you have not applied a drop of oil to the end of the rotor shaft where there should be a wad of cotton wool material in the bore then do so. Don't flood it a few drops that will find its way down to the advance springs. I had the same problem once and even applied a light spray of WD40 inside the holes you can see where the contact breaker points are mounted to. Only a quick light spray!! I expect you have already checked that Peter.

Regarding your carbs, I only have 356 experience on the Zeniths. With mine the idle jets and main jets are of a defined diameter you do have though two separate mixture screws that need to adjusted and usually balanced with a syncrometer type tool. The throttle linkage arms with the ball ends must be free to rotate when the arms are in contact with the throttle stops. That tip for Zeniths is most important. Your carbs do they not have specific bore sizes? You say you can adjust the idle jet?

The other aspect to check is the inlet carb to manifold gaskets are there any air leaks? The engine not being used for some time might have have an influence there. Checked the nuts are tight? There are on Zeniths other jets to look at also.

Roy

[Peter Roberts]

Thanks for the pointers guys.
I have checked the bob weights and they have a full instant positive return but i have given them a spray of WD40 anyway. I also set the timing with a timing light and the timing was coming back to 5 Deg when the revs dropped to tickover.
The link arms i have ensured do not hold the throttle open as when i am having this over rev i have tried forcing them back against the stops but it make no difference. I also have additional return springs fitted. Disconnecting the arms also makes no difference.
I did a full rebuild on both carbs with an OEM kit so gaskets, fuel pump diaphrgm and parts are correct. I did not change any jets as the car has always been right in terms of tickover and throttle response.
One thing i did not check was float height when i replaced the float needle valves. Having read up in the last few days it appears the fuel level can make a big difference to the engine running.
I do get the impression it is running rich. It starts from cold without pumping the throttle and from a starting point of 3 1/2 turns out on the idle jets adjusting each way seems to make no difference.
The throttle pump arm is set at 0-.5mm clearance so there is a full stroke with the throttle pump.
Tomorrow i will be checking the float levels as that seems to be the only variable setting i have not checked and will report back.
The annoying thing is that when it settles back to 800 rpm tickover it just runs like a watch as if nothing is wrong.

[POR68]

Each one of these can be different Peter. I remember the adage that most problems are electrical/ignition based. Of course, not all. On good advice on the best sequence, I start with the valve clearances to make sure they are correct and with no sticking. Next check the points' condition and gap and test the condenser on my multimeter (these are fallible components). Then the distributor timing (point about the lubrication of the weights is good) at 3k RPM and then idle and last - set the carbs balance with drop links off. I use 2 Synchronometers - one on each carb. Then carefully setting the drop link threads to ensure no drag and equal weighting. Turning the mixture screws should make a difference. If all this does nothing then you can suspect the operation of the carbs. If you didn't check the float levels earlier then check them and ensure the jets are clean and the right aperture (do you have any pin gauges?), squirt volumes are within spec and so on.

My car had not done a lot of kilometres when I bought it and a long run of over 1500kms did it wonders.

[roy mawbey]

Yes Peter, Merv is correct the mixture screws should influence the running.You said in the first mail you had Dellorto carbs? I presume this was a mistake? and they are Zenith 32 DINX.

Three off half turns out for the mixture screws is a start point. If you used a syncrometer you would see the differences when you turn mixture screws. For the car to start from cold without depressing the accelerator to the floor a few times is unusual. When you take off aircleaner and you look down the venturi and you depress the throttle lever do you see the the accelerator pumps squirting fuel out of the nozzles?

I wonder if over time not in operation the fuel has dried out to gum up areas. I might well take off the square jet cover on the side and check again the idle jets. The jet hole is very small make sure they
are clear.

Roy

[POR68]

Peter, while not the most expensive these are good value (for Zeniths at least and most others) and both can clean and check the sizes of your jets. I keep them in the car. The apertures, if not correct for your engine build, will affect idling and running through the rev range. Jets can also 'evolve' over time.

https://www.ebay.com/itm/Carburettor-Ca ... 1a6caccd14

[Peter Roberts]

I have been in contact with Dellortto who suggest that usual reason for overeving when throttle is closed is a leak on the carburetor or inlet flanges. This makes a lot of sense because if the butterflys are closed where else is it getting the air from to over rev? Today the crabs and manifold are coming off to see if i can find any problems. Not a job i relish as some of the bolts are a bugger to get at.
With regards to the jets i will check they are clear with the carbs off but this car has run perfectly all the years i have had it so do not suspect its a jetting problem unless they are blocked

[Kneeslider]

If you haven't already pulled the carbs off, then get it running, and warmed up, then while the engine is idling, spray some carb cleaner at the joint between the carbs and the manifolds, and around the throttle spindles, any leak in this area will allow the carb cleaner in, and the idle speed will change, sometimes it can be enough to stop the engine completely. If there is no leak, then for the price of a can of carb cleaner, you have saved yourself a lot of work. Always spend time checking and testing before wading in, or you will never find the problem.

[Peter Roberts]

Sometimes you miss the obvious and then feel a right fool. Consensus on the fast running was sticking weights in the distributor and after a good oiling seemed to cure itself but this still left me with setting the idle.
I removed the carb again and stripped it down to make sure it was clear and i found one of the springs was missing from the idle jet. I have taken those jets out a dozen time but the springs always stayed in situ, or so i thought. one must have slipped out without me noticing. Got a new spring and it is now reacting to adjustment. Not yet got it spot on as it ticks over at 1000 rpm and tries to stall at 800 rpm. As its not been used for so long i am happy to leave it at 1000 until i have had it back on the road for a while and given it a good few runs.
My thanks to all you good people for your advice during my 2 weeks of frustration.
All the smoking has also gone so it must have been oil passing the rings during storage.
I am now typing with my dunce's cap on to show myself how stupid i have been.
Good news is it should be back on the road next week.
Thanks again