11 replies to this topic

[Badoff]

i've had my 1340 mayfair back on the road for a couple of months now and ive had problems ever since. The engine has been idling erratically and theres a flat spot at about half throttle, so i checked the mixture with a colourtune and all appeared ok. I adjusted the tick over and got it about right afterwards when driving it was still idling erratically so i checked the timing. It appears that my marks on the distributor from the rebuild were well out by about 20 degrees according to the haynes manual. So today ive adjusted to roughly 6 degrees advance correct acording to the manual, i've just about managed to sort out the idle speed but the flatspot seems to have got worse. Am i gonna have to save up another £90 to go back to the rolling road? any ideas would be appreciated.

[Jordie]

is the needle correct?

Does the flat spot get better if you add a little choke?

[Badoff]

the needle was made up at my last rolling road session so it should be spot on.

Now you mention it it does seem to be better with the choke out.

[Jordie]

running too lean, could be caused with the denser cold air. Turn mixture a touch richer.

[Badoff]

Thanks will give that a try tomorrow

[Badoff]

Forgot to mention the engine was running on after switching off thought i had fixed this with the timing adjustment but happened again today, seems to be less though.

[Dan]

If your car came off a rolling road in this condition, take it back and tell them you are not satisfied with the work done. Running on is VERY bad for an engine's long term health, as is running lean (particularly a flat spot on part load where the engine spends a good deal of it's time). And they should have got it timed in properly whaerever your own marks were.
However if it was rolling roaded before the rebuild then yes, it will need to be tuned again. It won't be the same after being rebuilt.

[Badoff]

My car was running fine when it came off the rolling road after the engine rebuild. I then had to remove the engine to have the front end replaced, sorry shouldnt have said rebuild i didnt touch the engine apart from taking a few of the ancillaries off to add a fresh coat of paint hence the marks on the dizzy. Surely my marks that put it at about 20 degress advance cant of been right? couldnt beleive it when i saw it I take it its not normal to run that much advance?Starting to think there maybe some bigger problems as i said the mixture and timing seem to be correct. Maybe a carb rebuild or a new dizzy?

[Dan]

Aaah, ok I understand now. Did you take off the carb? Sounds like there may be an induction air leak somewhere. The running on may well be linked to the running lean as lean running develops much higher temperatures in the combustion chamber and piston crown than proper fuelling.
Something must be amiss with the timing, I can't believe you got the marks out by 20 degrees! But what that might be I can't guess at just now, anything else that's a little odd?

[Badoff]

yeh i took the carb off along with the manifolds but put all new gaskets on at refit worth a check though.

The only other weird thing recently, the car was not gotting up to temperature it was sitting just at the top off the blue section of the temp gauge rather than at the line in the middle. I instantly thought cold weather summer thermostat, change the thermostat, only to discover the new one i bought was exactly the same. I swapped them anyway and sure enough up to temp obviously a dodgy thermostat. Could this have caused any damage as i was running the car for a few weeks before i changed it?

[Jordie]

Doubt it would have caused any major damage, but you probally will have noticed an increase in fuel consumption.

I'm with dan on this one, i rekon a leak. I have had a couple of carbs crack across the butterly. Remove and check surfaces, replace gasket and use abit of blue gasket paste.

[Badoff]

Thanks for the advice think this one will have to wait till the weekend to check out. Will let you know how it goes.