vacuum advance

[jeff10049]

Last weekend I fainally hooked up the vacuum advance on my 1960. I figured out that the ferrul and nut that come with a copper oil line kit fit the dist. Even though I thught I had the curve pretty good without it hooked up I have to say it runs a little better mid range with it retimed and hooked up.

My question is what was that copper bulbus thing in the original line for? Was it purely a resivor to delay the advace did it contian an orfice at one end or the other? Im certian I dont need it but in keeping the original look I may make one out of two copper pipe stub out ends and if Im making one may as well make it correct.

[MPlayle]

This thread on a MG forum may have the answer:

https://www.mgexp.com/forum/mgb-and-gt-forum.1/contamination-oil-or-gas-or-in-vacuum.3480396/

I found it doing a search of "vacuum advance fuel trap" (my hunch) and it seems a mix of a fuel trap and vacuum stabilizer.

[jeff10049]

ineresting had not thought of a fuel trap. But the way they are mounted that makes since and it would stablize the vacuum some. If I could find an original line even a damaged one with the bulb intact I could take it apart and see if theres more to it than just a chamber.  Later cars seem to just have a line.

[MPlayle]

From a brief reading of that forum thread, it depends on where the vacuum port at the carb is: carb or manifold.

[jeff10049]

I hooked mine to the original ported port on the carb. so it only receives vacuum when the throttle is opened.

Turns out you can buy a new line last I looked I did not see the copper line but now an ebay seller has new ones. I think that can is just a fuel trap after reading through the links posted.

The seller gets $60 for the line not bad I guess but since I'm this far I think I will just finish what I started and make a little can for my line.

[MiniDave]

I thought you wanted advance in high vacuum situations like low or part throttle, and that when you opened it up it retarded a bit again?

Until we hit the vacuum retard era in the 80's for emissions, that's how they are supposed to work right? So it should pull from after the throttle plate - ie: manifold vacuum.

[94touring]

I have mine max out at 44 degrees at full vacuum, and I see 40-44 cruising around.  Stomp on the gas and it goes back to 30 degrees at WOT.  And yes needs to be after the throttle plate.

[jeff10049]

I'll have to check that port on the carb I maybe it is manifold vacuum it is the factory location so it might be.
I think I just got use to chevy with there ported vacuum setups we aways switched those over to manifold vacuum so they worked better.

[John Gervais]

I salvaged a copper 'bulb' that had a small-diameter copper pipe at each end for a fishing project from an old refrigerator once.  I never thought it could have also potentially been used on the dizzy.

[jeff10049]

 

I salvaged a copper 'bulb' that had a small-diameter copper pipe at each end for a fishing project from an old refrigerator once.  I never thought it could have also potentially been used on the dizzy.

77.gif I have some RV air conditioners in the scrap metal bin at the shop and I think they have some bulbus things in them thanks for the idea.  4.gif