Vac Advance and Ign Amps - 3.5 'flapper' 4CU

[mk1fan]

Right, I know these have been done but I can't find the threads and Google is not responding favourably to my inputs.

So, question 1.

Should the pipe on the reverse of the vac advance be blocked off? Some pics I see have it bunged. Some don't. Mine is not.

Q2.
Where to buy 'good' versions of both? Powerspark on ebay have both items 'cheap' but their dizzy's get poor reviews when coupled to TVR configured engines.

Thank you.

[mk1fan]

Just to clarify.

I am referring to parts fitted to the dizzy.

The vacuum advance that is fixed to the dizzy and has a vacuum pipe connected to the plenum. This has a second nipple on the revers of the vacuum chamber. It is this nipple I am refering to. Some pics have it bunged. Some not. Mine is not bunged.

The ignition amplifier fitted to the side of the dizzy. Lucas DAB135 I think is the orignal part number. It is a 2-pin connection version.

Other than blanking the second nipple, replacement is a secondary concern as I have the CTS to swap out first.

[mrzigazaga]

Hi mate


My outlet on the back of the dizzy vac is open to the air...The last time I looked for an ignition amp I could only find the 3-pin...Its not much to make up a lead..I did have one but gave it away...

I normally buy parts from known classic range rover sites and always make sure they are suitable for EFI.

[KKson]

On both my Wedges the second nipple on the vacuum advance is open - as far as I can see these are the vent hole, i.e the vacuum sucks on one port and the air comes in through the second. Therefore just leave it open.

Re the ignition amp, I recently got two old but original stock Lucas units off eBay - the packaging was a little tatty but the modules are great. They are about if you go searching. The three pin modules usually come with a converter cable so no big deal whether it's a two pin or three pin.

Cheers.

Edited by KKson on Sunday 17th September 13:52

[Engineer1949]

the original dizzy that came with the car is sealed with a little rubber hat

john

[mk1fan]

Thanks guys. I have also been told by a third party it should be bunged. Bit of heatshrink I think.

[KKson]

Engineer1949 said:

the original dizzy that came with the car is sealed with a little rubber hat

john

John, I stand corrected. Will the omission of the bung therefore impact on the vacuum advance? If the air into the back of the diaphragm is restricted then will this give a smoother advance? If there is a bung in the back connection (so to speak) then how does the air get in without the diaphragm trying to create a small vacuum on the back side of the diaphragm? Thanks.

[wild rover]

My 390 has a bung fitted with a piece of tubing and set screw, sealing the opening.

[Engineer1949]

i think the idea is when the bung is fitted it has ambient air pressure and it does indeed pull a very small vacuum when sucked from the other side it slows the operation down a bit well thats my theory also some have a valve in the tube from the plenum which also slows the action down.


john