4.5 Distributor modifications!

[Tomguy]

Here's the requested thread where I explain how I adjusted my distributor's advance, with pictures!

The first thing you must do is remove the distributor from the engine. This means not only unbolting it, but unplugging the EFI harness, and the points wire as well. Once that's done, you can take it out and work on it. BEFORE TAKING IT OUT, MARK WHERE THE ROTOR IS! Make sure the rotor is not advanced (turned as far CCW as it will go) and either mark where the rotor tip is, or memorize it. I have a good memory with this type of stuff, but if you're unsure, simply mark it!

Picture 1: In the order marked, remove:
1) The clip for the vacuum retard arm, then the arm itself from the sliding plate;
2) The screws holding the vacuum retard unit on (2x);
3) The screws for the cap clips (Don't lose the nuts! 2x);
4) The screws holding the plate itself on (2x);
5) The screws for the EFI trigger points, then the trigger points themselves (2x, not pictured).

Picture 2: In order to remove the plate on which the points and vacuum retard attatch, you must rotate it until the flat part of the plate (circled) is at the nub inside the distributor (arrow). You cannot just pull the plate out, the nub keeps it in there.

Picture 3: With the plate removed, you can see the stop plate for the mechanical advance. This is what we want to adjust now.

Picture 4: Carefully bend the stop plate to about 1mm from the inside edge of the distributor. It's about 2-3mm total from its original position. It will add a few degrees on to the maximum advance.

Picture 5: Now, you will want to adjust the advance curve so that it doesn't hit this new advance point too early. Mark the current position of the adjustment plate against the shaft and bottom plate with a sharpie. (You can see some previous marks (scratches) I had made when I didn't have a sharpie handy).

[Tomguy]

Picture 6: This is the easiest way to make the adjustment. Squeeze the plates (adjustment and bottom, stationary) together to tighten up the advance. You don't need much of a change, a little bit goes a long way in terms of adjustment differences.

Picture 7: You can see I didn't move the plate much - maybe 0.5mm - from its previous position. It takes tweaking and testing to get it exactly right. It's a trial and error process with this (Unless you have a way to spin the distributor and know its RPMs and at what point it maxes out in advance!)

Picture 8: Reassembly is simple, just one key thing: Make sure that, when reassembling the clips for the distributor cap, you put the one with the "Tab" on it on the bottom of the distributor. Otherwise, your cap will not fit back on properly!

Once you have the distributor reinstalled, you will need to re-gap your points, then re-time your engine. Check and see at what RPMs your maximum advance is, and at what degree reading. Higher advance at lower speeds will give better performance, but too much advance will cause pinging!

[tosbt]

I am always intrested in anything that will give the 4.5 better performance. I thank you for your detailed post reguarding timing advance. Just one comment though, is it worth it? What is the net effect of this advanced timing adjustment? Lower engine revs with better performance? Better combustion? Better miliage with the same performance?

[Tomguy]

Could just be in my head but I think it has better throttle response in the mid-range most noticably.

[gerryvz]

This is really good stuff. Thanks for sharing for those people who are interested in getting the benefits from this mod.

Cheers,
Gerry

[tosbt]

Got to hand it to Tomguy, he's got a future!

[fasted]

The instructions c/w photos by Tomguy are great stuff for us who like to tinker. This episode should be included in the DIY database.

Ed

[ctaylor738]

Send an email with the link to the webmaster and ask him to put it in the DIY.