Timing - what gives?!

The Original Tom · Post by **The Original Tom** » Fri Jun 22, 2007 7:40 pm

Grr! I modified an old LR series 3 vac module to fit my V8.
I measured up all the distances, like the mount to the eye where it joins the base-plate to actuate the advance, and both were IDENTICAL.
I opened out the mounting plate so it would suit the bigger diameter of the V8 dizzy and re-measured and it was exactly the same again.
Now I've fitted the vac unit the car runs like absolute s***. It's fine if you only partially open the throttle, and it'll rev to the red-line happily, but if you floor it, the whole engine shakes on the mounts, the revs drop and it sounds like it's dropped a bank of cylinders!
Even if I unplug the vac hose it does the same thing, I've tried every conceivable timing position with and without the vac pipe connected, re-positioned the dizzy, moved it to a tooth either side of the correct position, rotated it 180 degrees, all to no avail.

I'm so close to driving it into a river it's unreal. Tomorrow I'm going to try removing the vac unit and putting the old one back on. Maybe I did only get 11mpg but at least the f****** thing ran without problems.
I still, however, refuse to pay £40 for a new unit as it's daylight robbery and apparently it makes the thing run even worse!

AAAAAAAAAAAAAAAAAAAAAHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!

Help me!

ian.stewart · Post by **ian.stewart** » Fri Jun 22, 2007 7:45 pm

sounds like a good reason to fit mapped ignition!!!!!!!!!!!!!!!!!!!!!!

The Original Tom · Post by **The Original Tom** » Fri Jun 22, 2007 7:57 pm

Which type do you suggest? I've looked at EDIS 8, but megasquirts are a rediculous price, and that'll take more setting up than a dizzy surely?!

bill shurvinton · Post by **bill shurvinton** » Fri Jun 22, 2007 8:20 pm

Megajolt...

It is more work as you have to fit a crank sensor but the gains are well worth it.

The Original Tom · Post by **The Original Tom** » Sat Jun 23, 2007 5:21 pm

Well I romoved the working unit today in my lunch-break, and put the broken one back on - it now runs well again!
I wonder:
When I stripped the dizzy, it was in very neat and shiny condition compared to the rest of the engine when I got it, so I wonder if someone locked up the vac unit on purpose, and fitted weaker centrifugal advance springs for better performance. Therefore the vac unit cause over-advance and makes it run crap? But I thought vac units only worked on a partly-open throttle and not when you floor it? Which is why I don't understand the difference between a working unit at full throttle, and a broken one at full throttle.