vacuum advance - how much movement to expect?

[kevtherev]

lets just see if the timing does what it's supposed to do

before we explore other avenues

[sarran1955]

Hello,

This might help..

http://www.youtube.com/watch?v=fOiSOObjk2E

Cordialement,

[ghost123uk]

I don't know about how much movement you would expect to see and sadly, I ain't going out in this weather to find out, but if you take the cap off and then the plastic cover thing, then suck, you should be able to guesstimate whether the base plate is moving 6 to 8 degrees (in view of what Harry says above re dizzy degrees to flywheel degrees - I never thought about this until now)

Re Coil, in my experience coils either work or they don't though sometimes they can get iffy when good and hot, unlikely in this weather. Although there are specs given for measuring the coil windings I find they are not an accurate way of testing a coil (though they will give a "maybe good or dead" result). The best way I find is by substitution with a known good one (same type of course). Anyone near you with a T25 WBX

[kevtherev]

I don't think we need to travel back to the 70's

there are many reasons for lack of power.
timing is the biggest
then comes
fuel pump
fuel filter
uneven or low cylinder compression
vacuum leaks on the inlet side
clutch slip
brake bind

like I say lets make sure the timing is correct

[8ball]

like I say lets make sure the timing is correct

Okay then, I'll order a timing light tonight - any recommendations, or are they all much of a muchness? I don't mind spending a little bit more to get something that's going to do the job right, but don't necessarily want something OTT that I'm rarely (hopefully!) going to have to use.

[kevtherev]

I use mine regularly
gunsen are good timing lights

[BOXY]

how much movement of the control arm should you expect to see when sucking really hard on the inlet on a fully working vac advance unit

When you suck the vac tube the arm only moves a few mm's. Only two things can really go wrong with the vac advance. 1) The diaphram cracks and you have nothing to suck against so the arm doesn't move. 2) The end of the arm comes off the pin in the dizzie and doesn't pull mechanism, so again no visible movement.

As for timing guns, for a once a year check up a cheap Gunson type gun is good enough. If you've got any neighbours with an old car like an MG why not see if you can borrow one?

[8ball]

Okay then, well there's definite movement in the arm, so I guess it's fair to say the vac unit is working as it should. Quick check on Amazon brought these two up:

http://www.amazon.co.uk/Draper-52616-Xe ... 976&sr=8-1

http://www.amazon.co.uk/Gunson-G4113-Ti ... 976&sr=8-3

they look identical, but the Draper's a tenner cheaper...

http://www.amazon.co.uk/Gunson-77008-Ti ... 976&sr=8-2

is it worth shelling out the extra for the advance feature?

[HarryMann]

You don't need to check your timing once its set... it cannot move or wear out.

The only objective would be to check cent and vac adv.
Poss a good local garage could plot it for you, though many will not do simple things the way you ask...

[Trundler]

Tried to post this as a new topic but the software aint playing so sorry for the thread hijack... I have a strange pinking noise on light throttle openings at mid- revs. It does this on both petrol and LPG so I'm suspecting ignition and specifically the distributor advance retard. Strange thing is that it does it more on (higher octane) LPG than on petrol It seems to disappear at higher revs or as more throttle is applied.

As I understand it, the vac advance advances the ignition at lower revs or lighter throttle when there is less vacuum so if it didn't work the timing would be relatively retarded (perhaps like me!) at those revs so you wouldn't expect pinking.

It is most audible in 2nd gear at the sort of revs where you might change up to third under gentle acceleration, which makes me worry about motorway cruising as revs/throttle must be similar, though you can't then hear the pinking for wind and transmission noise.

Any ideas?

[ghost123uk]

You really should have started a new thread

If it does it on LPG it is unlikely to be pinking, also if it does it the same or more on high octane petrol, and disappears at higher loads also points to it not being pinking.

Your symptoms sound a bit like small end wear, but as far as I know, these engines are not generally prone to that.

[jamesandtheopenroad]

Hi 8ball

So cleaned up the dizzy and replaced the vac advance (as well as cleaning up the earth connections on the engine and resetting the timing) and it's running much better.

I got my vac advance from http://www.simonbbc.com/ignition-spares ... vance-unit.

[HarryMann]

Qu. Has someone been altering the timing in the past as far as you know?

History is important to get to the bottom of things sometimes, esp. history of meddling.
If it is pinking, and not just rattling tappets, then carbon build up or the wrong plugs, even a chipped valve could be cause though that's a long shot.

[kevtherev]

I am lost now
Could a mod move the hijacker out of this?

[Trundler]

Sorry, I'm happy to but out.

I would have started a new thread but the site wouldn't seem to respond. I thought it was a (loosely) related subject though.

Over and out.