if you take 3mm off the piston, or space the cover 3mm or whatever, you still need to keep the origonal preload on the spring and to do that you could put a 3mm spacer in there but it will stop the piston from moving wont it?? isnt it the actual spring that stops it from going all the way that it can? or is it the smaller piston in the middle that does the timing. cuz if its the big piston, you could just get a spring with the same preload but fewer coils so it can trvael farther. wouldn't that be easyer and cheaper than making custom cnc covers?

Before you get him to cut it, measure the depth of the stop on your 1.6 pumps cover. My AAZ and LR were 3mm, if yours is the same then cutting 3mm is too much. So should only remove 1.5mm.
 As for the spring going into coil bind it's not even close. Remember that the piston only moves 9.78mm stock. The AAZ main spring is 36mm free length, 18mm OD, 2mm wire thickness, 6 coils and 15.8mm solid length.
 As for the smaller piston the only thing I can think of is that it controls the fuel pressure on the spring side of the piston. Why? I don't know maybe to make a non-linear advance curve.

The depth from the covers sealing side face to where the piston makes contact with the cover.

I just wanted to write: this is the best thread ever!

Good work Jake and Spike etc.  I cannot see why this would not work, as it would be equivalent to lopping off the side of the timing piston.  But, FAR FAR easier, cheaper, adjustable (potentially), and would not require new seals etc.

I am going to have a look right now at a spare pump I have around.  Who knows, maybe by tomorrow I can test out a modded cover!

Jake, I can't wait to hear more about your test results  :wink:

Ok, I had a chance to investigate the timing mechanism on my spare NA pump.  This is such an easy fix!  I have the solenoid pump advance integral to the cover on this pump, but otherwise it should be the same as a standard cover.

Opening the solenoid/cover revealed two ~1.5mm disk type washers placed at either end of a very stiff red spring.  Hmm timing curve adjustments!  I was able to move the timing piston a bit, but chose to open the cover on the other side of the pump for maximum fun.  This action allowed me to move the piston in the advanced state easily.  All in all, the piston was able to protrude somewhere between 4-5mm measured with me trying to hold a dial indicator steady  :? .  Not a fantastic way to measure, but I can say with certainty that the stroke past the cover is way over 3mm.

Now, for the most interesting discovery:  the rear plate causes a restriction, stopping the piston in the retarded direction!  From the pump body, the piston was able to protrude ~1mm.  So, you should be able to widen the overall timing advance curve angle by ~5mm overall!  Granted, the rear plate is more difficult to remove with the pump attached to the car.

As a check, to see if the timing piston spring would return the piston *past* the rear plate, I reinstalled the front cover with the spring and the shims.  Then, the rear plate was removed, and the piston moved slightly.  Next, the timing lever was moved to full cold start advanced and released, and sure enough the piston protruded ~1mm past the pump body.  This was exactly as before when I moved the piston by hand to full retard.  I did this several times, with the same result.  The piston simply prefers a final resting state past the cover.  In addition, you can actually find evidence of the piston hitting the plate by observation.

Timing is everything  :twisted:

There is still plenty of material for sealing the pump.  One method yes requires pump disassembly, the other does not.  

I was able to mod the front cover for zero dollars, and only about 30 min of my time.  The pump can now advance fully, over 4mm beyond stock.  I will report back later today with the results after I install the cover.  For now, the rear cover will stay as is.

I don't have allot of time right now to reply but don't get too crazy with total timing. The total amount the the piston will move is limted by the pump case. I measured the AAZ pump the piston could only protude 6.5mm before the timing pin contacted the case. If the pin breaks your going to have some big problems. Because the cage that holds the camplate rollers is only notched so much to clear the governor asm. If it rotates too much then there going to make contact, which WILL kill the pump very quickly.

Send them my way and I'll FTP them.
Advanced timing increases cylinder pressure. A bit too much and bye bye headgasket.