Alfa Romeo Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
47 Posts
Discussion Starter #1
Evening people,

I've just had my Sprint tuned on a rolling road and have been told that the reason for her chugging at low revs is because the vacuum advance unit on the distributor is broken.
Anybody know if they are replaceable / where I can get one ?
I've mailed Justsuds but not heard anything back yet.

Any help appreciated.

Thanks,

Stuart.

PS It's a Magnetti Marrelli distributor
 

·
Registered
Joined
·
175 Posts
iv done that job
i am running a marelli electronic ignition in an early sud

firstly to check operation just give it a rev while looking at the external bracket that goes from the diaphram to distributor. if it doesnt move then the diaphram is probably split (like mine was)
also (just in case) disconect the vaccum hose and feel for vaccum as you rev the motor .
if you confirm it is faulty you can either replace ,overide or repair it.

firstly, if you buy a new one, can i buy your old one?

secondly if you overide it you will still get most of your advance from the mechanical advance in the distributor. this is ok if its a sunday thrash car but not really if you do high milage and require good fuel economy and smoothness. the key is to ensure you have max advance at high revs 4000+ .the spring in the diaphram should hold things steady but make sure its not fluctuating . you can do this by looking for erratic movement of the bracket or with a strobe light while reving it steady.

thirdly you can repair it like i did. you cant buy the parts so you really have to do it yourself otherwise its too time consuming for a mechanic to improvise and he probably wouldnt be able to guarentee it. i peeled mine open and cut back a large diaphram from an lpg unit and crimped it back together again using a glue to seal it. not very good looking but effective
 

·
Registered
Joined
·
11,591 Posts
Vacuum advance only for fuel economy and not for performance.
I would block the tube from the distributor to the manifold immediately, if it has not been already done. The reason that the car is running rough at idle is that extra air is getting into the manifold leaning off the mixture.
 

·
Registered
Joined
·
47 Posts
Discussion Starter #4
Thanks for responding guys.

Justsuds have come up trumps. :)
New unit on its way.

Enri, once I've got it fitted and working Ok I'll let you know. I will certainly sell you the old one. I'll try and find out why it's not working.

Cheers,

Stuart
 

·
Registered
Joined
·
47 Posts
Discussion Starter #5
I've finally had the new unit fitted. God it makes a difference - the engine now pulls really smoothly.
And according to the rolling road she's making 104.5bhp at 5950 rpm.
Not bad for a 20 year old girl !

Enri, do you still want me to send you the old non-working unit ?
I'm afraid I don't know why it's not working but would guess that the diaphragm has split.
 

·
Registered
Joined
·
202 Posts
Thanks for responding guys.

Justsuds have come up trumps. :)
New unit on its way.

Enri, once I've got it fitted and working Ok I'll let you know. I will certainly sell you the old one. I'll try and find out why it's not working.

Cheers,

Stuart

how nuch did this cost you. thanks
 
1 - 7 of 7 Posts
Top