Datsun 260z problems.

[Whatnotacos]

Hi there

I was wondering if anyone could help me with some technical problems?

I own a 76" Datsun 260z 2+2, Recently the car started to misfire and was way down on power. So i changed the spark plugs which where very black with carbon deposits and it ran really well. I then took it out for a about a hours drive running errands.

It has started to misfire and be down on power again, I checked a plug and it has done the same thing to the New plugs (Black). Any reason why the carbon deposits would clog the spark plugs again so quickly, or is it just a characteristic of a car with carburetors? Bear in mind this happened maybe about after an hours drive.

If anyone has any advice it would be welcome

Thanks
Conor

 

[Dale]

Well it sounds like it is running too rich. Have you replaced or cleaner the air filters recently? If not, maybe the air flow is down?

 

[moggy240]

how fresh is the petrol

 

[Whatnotacos]

Thanks, The filters have been replaced recently and just checked, they are cleanish. I think you are right about it running to rich, The car is emitting a large amount of fumes and a bit smokey, would this be a indication of it running rich? How would I alter the ratio? where in the carb is it situated?

The car has been filled with the highest octane fuel i could, i believe BP high octane is a very fresh.

Thanks for the help

 

[jonbills]

If it used to work, and now doesn't, it could well be your floats levels are off - perhaps the floats sprung a leak or the valves are gummed up. or maybe the pistons are stuck in the carbs. (hmm, are they called pistons?!)
if the car is new to you, and it's never worked, could be something worse, but start with checking the carbs are clean and working properly.

 

[Zed-the-red]

what carb are on the car? if they are the flat top things then they are rubbish and a pain to get right. If they are the round top SU copies.. then these are pretty basic.
If the black deposits are sooty then the carbs are running rich one carb does 3 cylinders.. so if they are off it will be obvious which carb is the problem. If they are oily black and glossy with oil then this is a bit more serious as it could be piston rings, worn valve guides etc. A compression check will tell you.. which are bad.
Hopefully its not the rings and its just the carbs.. check the dash pot oil.on top of the domes with a black screw...that will make the carbs act like idiots if theres no oil in them. make sure there is some in there! lift each of the pistons in turn and see if they drop easily and are not binding. they should fall with a dull thud and smoothly. You could also have a sticking valve in the float bowls so a look there will help.
Its best to consult a manual regarding the set up as its a a bit to involved to do here.. there are loads of videos on line about setting up SU's.. good luck.

 

[Farmer42]

what carb are on the car? if they are the flat top things then they are rubbish and a pain to get right. If they are the round top SU copies.. then these are pretty basic.
If the black deposits are sooty then the carbs are running rich one carb does 3 cylinders.. so if they are off it will be obvious which carb is the problem. If they are oily black and glossy with oil then this is a bit more serious as it could be piston rings, worn valve guides etc. A compression check will tell you.. which are bad.
Hopefully its not the rings and its just the carbs.. check the dash pot oil.on top of the domes with a black screw...that will make the carbs act like idiots if theres no oil in them. make sure there is some in there! lift each of the pistons in turn and see if they drop easily and are not binding. they should fall with a dull thud and smoothly. You could also have a sticking valve in the float bowls so a look there will help.
Its best to consult a manual regarding the set up as its a a bit to involved to do here.. there are loads of videos on line about setting up SU's.. good luck.

Hi

I have the same car as you and it recently did the same, eventually conking out. It turned out to be a dead condenser on the distributor that burnt out the points. This in turn stopped it firing properly leading to the black deposits on the plugs. I changed them and reset the carbs and bingo! it sorted it.

Try changing the points and condenser. Most car parts shops have them or can get them easily, you don't have to go to a specialist Z parts dealer. I paid about £10 for both.

Good luck

 

[Whatnotacos]

Hi all
The Car has the original carbs, not SU's. In fact I have just ordered SU's as I was advised by someone, who said much the same about the orignal carbs being "useless" and that's why most people change them. I didnt consider the points, thanks for that suggestion.

Thanks all for the help
will update.
Conor

 

[SKiddell]

Make sure the choke mechanism is fully functioning and not "stuck" on, check air filter "winter/summer" setting on filter housing (if one fitted), points, condenser etc all the usial supsects that have been mentioned.

Then feed back info so we can eliminate.....Occams Razor is particularly pertinant to cars