22 replies to this topic

[neilbut1988]

I have a 1275 a series engine with some starting and low rpm issues. At tickover the engine is only running n cylinders 2 and 3. Compression on all cylinders are good and valve clearances are set to 12tho. When the revs are increased the engine seems to run on all 4 but at tickover plug caps 1 and 4 can be removed with no change!?!?

[neilbut1988]

Plugs 1 and 4 are wet and the carb is a weber 40 dcoe.

[Carlos W]

Has this problem just started, or have you done anything which coincides with this?

 

Are the leads in the correct order?

[Tamworthbay]

Have you whipped a plug out and checked if it's sparking?

[neilbut1988]

I have a good spark on all 4 cylinders and the engine has just been full rebuilt. Its a 1275 with a stage 3 mini sport head, calver 13ot cam and 40 dcoe.

[neilbut1988]

And yes the leads are correct

[KernowCooper]

Have you checked your inlet manifold is not drawing air ? wd40 around the flanges and check for any signs ?

[Tamworthbay]

Compression test would be worth doing.

[Spider]

Sounds like the idle mixture has been set too rich.

[jaydee]

Seen it happening with long duration cams and weber carbs, its either a too low advance at idle or too rich mixture at idle

[The Matt]

Are you running a standard distributor or are you running Megajolt or similar?

[The Matt]

It does just sound like my old 1380 was when I first fitted the 45, though.  

 

Idle mixture might just need a tweak.  Mine seemed to flood more on the outer two cylinders, possibly related to the siamese inlet ports and the way the fuel/air is drawn through the carb.  Probably exaggerated if you're running a 'swan neck' manifold too?

[dklawson]

And yes the leads are correct

 

You said this is a freshly rebuilt engine.  The following is not meant to be derogatory so do not take it that way.  Are you SURE the plug wire order is correct?  It is very easy to put the distributor drive gear in a non-standard orientation during an engine rebuild.  It is also very easy to forget and put the plug wires on the cap in a clockwise vs counterclockwise order.  

 

Though you are sure you have this right, take off the valve cover and make sure that when the timing pointer is at TDC, the rocker arms above cylinder #1 (water pump end) are "loose" and can be wiggled which indicates the valves are fully closed (#1 at TDC on its firing stroke).  If the dizzy drive gear is in the correct orientation, the distributor rotor will be pointing somewhere between 1:00 and 2:00 o'clock.  The spark plug lead for #1 goes there and the remaining wires go 1-3-4-2 counterclockwise around the cap when you are looking down on the top of the installed cap.

[neilbut1988]

Glad you have said that about the plug leads because I throught I had got it wrong so I have checked and I have it correct. With the engine running at 800 rpm it is running on cylinders 2 and 3. Pick the revs up to 1500 and you can hear 1 and 4 start to fire properly. I have tried adjusting the mixture screws (I wound them in until the it wouldnt run at all and backed them out until I got a good engine note) am I doing this correctly?? Would a new coil help?

[neilbut1988]

The car is running a 23D a series distributor.