Ignition timing issues

[Phil Wright]

Evening all,

After 3-4 years of hard work the second restoration of my spitfire is now complete, and i'm looking forward to getting involved in club events again.

Unfortunately however i'm having an issue which has left me stumped so thought i'd see if anyone else has any ideas. The car is just about ready for MOT now, however I can't get it to run right. The engine has been rebuilt totally, with a Kent Fast Road 83 cam (TH5), 123 ignition, rebuilt carbs, gas flowed head, new loom etc. When I start her up she's tricky to fire and when she does run the engine is clearly not running correctly (lumpy and not responsive), as as though the timing is way off. When I connect my timing light I can see the flash is very retarded. However, if I advance the ignition to where it should be (8 BTDC) the engine just stops and won't restart. Backtracking slightly, the install procedure for the 123 dizzy has been followed, and the static timing set point is where the strobe thinks the timing should be, but the engine won't run on this setting. The only way I can get the engine to start is by turning the distributor clockwise to retard the timing.

I've done this many times before on my car, however this camshaft is new to me and I installed a new timing sprocket an chain which had no timing marks. I've checked the cam timing, and with No. 1 on the firing stroke @TDC, valves 7 & 8 are 'on the rock'. Also, I set and re-checked the install figure of the cam, which is inlet valve of No. 1 (valve No. 2) at full lift at 103 degrees, the install figure for the cam. The distributor drive is set in the position shown in the haynes manual.

Everything seems right but i'm not getting anywhere. I'm all out of tea now too! If anyone on here has any suggestions i'd love to hear them. I feel i'm doing something daft, but cant think what it is...

Thanks

Phil

[Pete Lewis]

I saw your post on the Ct forum,

 

so youve checked the cam timing etc have you checked when no1 is firing the rotor is pointing at no1 ht terminal and youre not trying to time with the wrong cyl.

 

and dont forget firing order is 1342 anticlockwise

 

we had some fun with a spitty not firing and when it did very sick, after checking the basics anpull of the air piston revealed the whole fueling needle had fallen out of the piston , so its wouldnidle rough but

any attempt to throttle stalled imeadiately

that was a bit of an odd fault.

 

pete

[Phil Wright]

Thanks Pete,

 

Yes, thought i'd post on here too incase there is a different audience.

 

Thinking about it, i'll try rotating the distributor drive one tooth counterclockwise tomorrow to see if that does the trick. As I mentioned above when it's at its happiest, the timing light fires a fair way to the advanced side of the crankshaft pulley. I'll also go through the whole system to make sure i've not missed anything daft.

 

Both carburettor needles were well secured into the pistons, and were at the correct height above the bridge. She will run, just not smoothly and the tickover is erratic.

 

Helpfully, the (brand new) starter solenoid shorted today and the starter motor fired (whilst the engine was running) and wouldn't switch off the ignition, despite the key being removed. I'll dig out the old original one tomorrow and fit that instead.

 

I'll look again tomorrow with a fresh pair of eyes.

 

Phil

[Pete Lewis]

on some 6 cly the timing ring on the front pullet bonding lets go and the rim moves round ,, you cant have that on a 4 cyl.  but there has to be some reason the static timing is 

not where you expect.  ,  if using a strobe for dynamic try reversing the HT pick up on the lead  , some give  very odd readings if they dont like the pick polarity

 

moving the gear wont do much other than reposition the dizzy case to suit the new gear position , its only importance is  position  to clear the vac unit from fouling the head

 

dont know about 123  is s programable one,  most electronics will still trigger a small bulb in the dizzy line to check static timing just the same as with  points

 

 

Im sure the problem will be printable when you find it   let us all know 

 

have you checked the tdc mark  is actually tdc ??

 

Pete