What an awesomely super-fun day of revelations my '85 XJ-S had for me today, and it's only 9 am!

Pretty much been through the car top to bottom and the only thing left that I hadn't done was check the timing. I hadn't done this before because my timing light was broken and it took me a while to get around to buying a new one. Had to prioritize the broken stuff over the fact that car really was running very well.

So, I pulled the vac line off the tee on the RH rear manifold to disconnect the vac advance, shimmed the throttle open to hold 3000 rpm, and crawled under with the light. No mark. What the hell. After several stops, cleanings, and trying to shove my head in such a position that I could actually see the marker, I found the VI - WAY off the scale towards the advanced side. Like, an inch or two off the marker completely. Don't get it, because the car has never pinged or anything.

Anywhoo, maybe someone can chime in here - I assume I only get a limited amount of movement out of the timing adjustment screw before it bottoms out? Or will it keep on moving the distributor as far as I need to go? I started turning the adjustment screw clockwise and the VI started to come back - but I ran out of adjustment right when the I hit the edge of the marker on the advance side. Still nowhere even near 18 BTDC.

So, maybe someone can answer this - am I jamming on something, or is that as far as the timing adjustment will go? I already pulled this distributor and rebuilt it from the ground up - I am NOT looking forward to tearing my entire vee out all over AGAIN. For what it's worth, the dizzy went back in exactly the same spot it came out - so if it's one tooth off, I've been driving it one tooth off for a year now, and God knows how long it's been that way before that.

What a great day. Please tell me I'm jamming on something and I don't have another multiple-week vee teardown ahead of me.

D

 

You can undo the distributor fixing screws (three allen headed bolts accessible though the dizzy with the cap and flash shield off). These are in slots so it might be possible to just move the dizzy enough in situ, having loosened these bolts. If not, remove the dizzy from its spiral drive and move it one tooth in the direction required. If the dizzy has been removed before, it is odds-on someone put it back in what they thought was the correct position, but did not take into account the spiral nature of the drive cog, which turns the rotor as it is pushed home.

So, put the motor at TDC for cylinder A1, then set the adjuster to the middle, then undo the dizzy and refit making sure the rotor is pointing straight at the A1 position (marked on the cap by a small "1" cast into the plastic). Then set the timing as before, and with luck there will be enough adjustment to get it spot on.

Greg

 

Another thought is that your timing isn't actually that far off but, instead, the rubber bonding on crank pulley/damper is breaking...allowing the outer part to slip and thus putting the timing marks out of position.

Not unheard of on the V12s.

Cheers
DD