XK120: Does My Distributor Drive Timing Look Correct?

(Christopher Potempa) #1

I’m slowly rebuilding the engine on my XK120 and have hit a snag with setting up the timing. The book says to align the slotted shaft in the block parallel with the crankshaft when #6 piston is at TDC. Per the pictures, you can see that piston couldn’t be more TDC. And yet the slotted shaft is still slightly off. This is the best I can get of all the gear positions. Is this still correct? All parts have virtually no wear. I’ll add that I don’t have my flywheel on yet (the engine stand won’t accommodate it – I’ll lower it into a rolling cradle when the time comes). I’ve also attached a picture of my partially disassembled distributor temporarily dropped in place showing the slot on the cam pointing towards the rear. Does that look typical for this setup? Sorry, I’ve misplaced the rotor at present. All comments welcome. Thanks.

(Rob Reilly) #2

Yes, that’s fine. I forget the number of teeth in the driven gear, but moving it one tooth would put you 360/(no. of teeth) degrees off.
There is a spec in the manual about which side the driving dog slot should be when firing on either #1 or #6.
Bear in mind that the upper distributor shaft, the one with the rotor slot, can be put in two ways with respect to the lower shaft with the driving dog.
I once put in a different distributor, wouldn’t start, and it took me awhile to figure out that the rotor shaft was assembled 180 degrees off from the old one.

(Lee140FHC) #3

Reorienting the dizzy drive gear by only one tooth would move(rotate) the shaft much further away from the desired position…however…I would make double sure that the gear is all the way home (rearward) as I don’t remember mine being that far from parallel to the block centerline. IF the gear were to be moved rearward, the shaft slot would move to more parrallel.

(Christopher Potempa) #4

Okay, here is what it looks like having rotated the gear one tooth CCW towards the rear as viewed from above. It seems like the book ideal is right between the two. Unless someones states otherwise, I’m inclined so far to leave it set like Rob mentioned with the first picture.

(David Jauch) #5

If the distributor doesn’t have any special features the orientation won’t make much of a difference, but it might help you to install a distributor and check where the rotor points, then adjust if needed, and because the unit can be rotated you do not have to make any precise adjustment yet. The crude orientation seems ideal (what can you do!) and when you set static timing in a few… days, the fine details can be taken care of as long as the rotor roughly points to #6 on TDC (compression).
I think it looks decent.

(Christopher Potempa) #6

Okay, thanks for that. I’m a little eager to move past this for now as I’m wanting to bolt on the oil pump, pipe, baffles and timing items which leaves me loathe to have to revisit this if I initially get it wrong.

Happy Easter all.