v8 running real bad

hi,hope someone out there can help.
got a v8 3.5 disco on s.u carbs which has started running really badly.
it starts first turn, ticks over and revs really well.
the problems start when i hold the throttle open or try to drive the thing; it just loses power straight away.
i've set the timing (6deg btdc) and set the carbs according to haynes, but i have noticed that while i rev it and watch the marks with the timing light they don't seem to drift like i thought they should.(does that make sense?) could it be a fault with the vacuum advance, the dizzy or just the mixture?
it also seems if you watch the timing marks real close to miss a beat every now and then!!
any help or advice gratefully recieved
thanks in advance
rick

Silly question time.... its got SU carbs, is there any oil in the dashpots? ( it'll misbehave summat rotten without the damping effect of the oil)

thanks l.c
yeah, checked that.
just annoys me that it was running so well then this started.
thanks again

Next thing to check would be the module on the side of the distributor, I worked in a garage years ago & they had a Snap-On thingy that connected to the pins on the module & basically 'revved it up', if you heard it stutter or misfire ( Im talking about a buzzing sound made by the Snap-On gear rather than it revving the engine) the module was fubar... might be worth asking around a few garages to see if you can get it checked for the price of a pint before adopting the modern approach of 'fit a new one to see if it cures it'

You need to check the advance mechanisms in the distributor. First check the mechanical advance by removing the distributor cap and see if you can turn the rotor arm a few degrees, it should spring back.

Then check the vacuum advance, disconnect the vacuum pipe off the manifold and suck it, there should be some resistance, watch the base plate it should rotate slightly.

Good luck.

thanks guys. i ll check those later and let you know. just a thought tho ,does this module thingy come off to be replaced?

hi
just tried the above with the vacuum advance.
the rotor arm does tun a few degs but does not spring back, and no matter how hard i suck i cant see any movement in the base plate. thre is a one way valve on the pipe, which seems to work the wrong way,i.e the red side marked dist. nearest the dist. and i c\ant suck through it at all.
any advice? is the dissie u.s. if it is i've got a spare 3.9 i; can i use the dissie from that although it's the one with the amp mod under the coil. thanks in advance
rick

rickdulas said:

thanks guys. i ll check those later and let you know. just a thought tho ,does this module thingy come off to be replaced?

Click to expand...

If its held on by a couple of small bolts ( 6 or 7mm head) then yes you just need to remove the bolts & it will pull away from the dizzy body

Oh dear... another one. Please if you are going to be removing the rotor arm, press down on the eight sided star or break it off rather than lifting it. That's how all my current problems started Hope you get it sorted quickly! Matt.