TR6 Timing adjustment

It’s winter so of course i’m fiddling with my 1975 TR6. I decided to check the timing and the initial setting looked pretty good. However when I went to loosen the nut to allow me to turn the distributor, I discovered that the adjustment was maxed out. My question is whether you can advance the timing by some other means? This car has electronic ignition but I would think that doesn’t matter.

Our GT6 is under cover out in the rain so I can't go look at the moment. The following is from memory.

Are you using a Delco, Lucas, or aftermarket distributor? I don't remember the Delco dizzys having any external timing adjustment so you have to turn the distributor body to set the timing. The Lucas distributors typically have a knurled thumb nut to make minor timing changes. I cannot say what aftermarket dizzys have. In all cases you can loosen the pinch plate and turn the dizzy body a few degrees to alter the timing.

Please elaborate a bit about what you have and what is limiting your distributor travel.

The distributor looks standard, it just doesn’t have any points. I’ll try to take a couple of pictures later. Basically there is the standard slotted pinch plate attached to the distributor that allows you to turn the distributor body when the nut is loosened. In this case the bolt is already at the end of the slot so I can only turn the distributor one direction. Inside the distributor it does look like you can loosen a small screw and make another adjustment but I’ve never had to do that in the past. I’m pretty busy with family stuff this morning but will try to get a couple pics later today.

The GT6 used the Delco distributor. I believe at least early TR6 used the Delco as well. I'm sure some have been converted to use use the Lucas. I'm posting two picture links below to help you identify which you have. Electronic ignitions can be fitted to either.

Delco:
https://cdn8.bigcommerce.com/s-5e3d...s/15292/3282/D46H_w__42286.1532440056.jpg?c=2

Lucas:
https://www.74tr6.com/pics/newengine 177 (Small).jpg

On both you will notice a pinch plate at the distributor base. If you loosen the "horizontal" pinch bolt the distributor can be rotated clockwise or counterclockwise just about as far as you can imagine until you run out of room to swing the vacuum advance OR the tach cable limits the possible motion.

To add to what Doug has stated. Before you loosen the pinch plate and try to move the distributor by hand make a mark on the distributor and a matching mark on the pinch plate so that you can tell where your present setting is. Sometimes a distributor is hard to move and you move it a lot more than you intended.

It does sound like you have loosened the bolt that holds the clamp onto the pedestal instead of the clamp's horizontal pinch bolt and fastener around the waist of the distributor....Only the tach cable would prevent over advancing if the distributor was installed properly oriented as Doug pointed out.

Sometimes people tighten the pinch plate too much and gouge the distributor body, I would check and make sure that isn't the problem preventing easy, full movement.

Thanks Doug, It looks like I have the Lucas distributor. Attached is a picture showing the nut that allows for adjustment of the distributor. You can see the slot. The bolt is tight against the end of the slot so no more adjust is available at that point. The second pic is the interior of the distributor. I was looking at the small screw with the slot and wondering if an adjustment can be made there.

Thanks Gleman. Always a good reminder.

Pool boy, I think you are right. I’ll take another stab at it by loosing the horizontal clamp. I don’t need much adjustment so this should be the solu5ion.

Firsttimer said:

The second pic is the interior of the distributor. I was looking at the small screw with the slot and wondering if an adjustment can be made there.View attachment 56722View attachment 56723

Click to expand...

An adjustment can be made there...but you'll want instructions. You've got a Crane XR700 ignition. Here's a link to its installation and adjustment: https://www.triumphspitfire.com/images/cranemanual.pdf

If the engine appears to be running well, I would not make any adjustments to the placement of the electronic ignition components inside the distributor. I would focus only on that external pinch clamp.

Per our earlier discussion, there are vertical and horizontal bolts for the dizzy clamp. The vertical bolts are shown in your first picture. The long horizontal bolt is not clearly shown but it will be obvious which it is. Loosen the horizontal pinch bolt and turn the distributor body to adjust the timing where you want it.

I also feel it is worth pointing out that you may be missing a distributor component. Your pictures show what appears to be a 25D6 series Lucas distributor. Look at the bottom, right of the distributor body in your second picture. You will see a "C" shaped opening. There is normally a thumb nut in that location. The thumb nut should be mounted on a threaded rod that is connected to the breaker plate. By turning that (missing) thumb nut you are able to advance or retard the timing by a few degrees as needed. The nut really needs to be there so the timing doesn't randomly change on you while driving. Of course... a previous owner may have locked the breaker plate to prevent that wandering timing... but that would also disable the vacuum advance.

I am not very familiar with the 25D6 distributor... only 4 cylinder 25D4. Can someone confirm whether the 25D6 should have the advance/retard thumb nut?

While the thumb wheel can be added to the TR6's Lucas 22D6 distributor with a vacuum Retard module, they didn't come that way.
If added, the retard module would have to have been 'unpinned' so that it can move as the thumb wheel is rotated. The module in "Firstimers" module is pinned, therefore the points plate will only move in reaction to vacuum in the retard module.

Thanks for that. As I mentioned, I am more familiar with 25D4 dizzys than 22D6.