• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Vacum Advance on '78 B

Share this page

S

sbndave

Freshman Member
Country flag
Offline
Hi Folks,

I can't seem to find the answer in my book (Haynes) as to what this device is with I THINK is part of the vacum advance system. The line coming from the distributor SEEMS to go to a small electric device (realy valve?) then to the manifold supply. I say "seems" because it wasn't hooked up when I got the car, but the length is about right. The electic device is on teh driver's (left) side of the car attached to the brake servo.

What I this thing and how do I make sure it's working?
 
Hello Sbndave,
unusual, could this be a modification on a PO's part. The vacuum advance is a self regulating system and I can't imagine what would be the point of controlling it electrically. If the car runs fine without it connected, I would remove it.

Alec
 
sbndave,

That part you are looking at is a legitimate factory part on later Rubber Bumper MGBs. It is called the vacuum advance valve and gets an electronic signal when you shift up into fourth gear advancing the distributor about 3 to 4 degrees. There should be another vacuum line going from that valve to the manifold.

It may have been disconnected by the previous owner for some reason. A simple test to see if it is still working is to make sure everything is attached as I described and start the engine. With the car idling push in the clutch and shift up into fourth gear and the idle speed should increase.

Should you find it doesn’t work or for some reason you don’t want it – let me know and I will take it off your hands for a fair price? Mine is shot and I haven’t been able to find a replacement.

/ubbthreads/images/graemlins/cheers.gif
 
Bret- I've got 2, one I know works and the other I think works. Contact me off board with your address if you are still in need. It's called TCSA switch(trans. controlled spark advance) and is an on-off vacuum switch that lets the vacuum advance function only in fourth gear. Since installing a Eurospecs dizzy I just go straight to the manifold for vacuum, runs great. If you eliminate this switch you will have to retard from factory specs and how much is subjective. Even the pros say when you're timing it after starting modifications, the most reliable way is road testing for driveability. Basically keep advancing until it pings in fourth going up a grade, then turn it back a little. Lots of luck.
Tim Matheis
 
Hi Tim,

Check you’re email?

Anyway regarding the vacuum advance settings – because I live in California I have to have my MGB smog tested every other year. And now thanks to Governor Arnold who just signed a new bill into law the other day, I will have to have my car smogged for as long as I own it or reside in this state /ubbthreads/images/graemlins/mad.gif. That means I will need to keep my car’s emissions system basically stock as well as all settings, in order to pass the strict emissions standards. /ubbthreads/images/graemlins/smile.gif

The only other choice is that I will have to wait for the new EFI system that Moss motors has just developed for the Zenith-Stromberg single carb MG’s. According to Moss the EFI kit when it goes on sale is a direct replacement for the ZS and has already been certified by the California Air Resources Board (CARB).
/ubbthreads/images/graemlins/thumbsup.gif
 
[ QUOTE ]
I will have to have my car smogged for as long as I own it or reside in this state /ubbthreads/images/graemlins/mad.gif. That means I will need to keep my car’s emissions system basically stock as well as all settings, in order to pass the strict emissions standards. /ubbthreads/images/graemlins/smile.gif


[/ QUOTE ]

Well, you could always do a bi-annual engine swap..
Seriously considering this one as I despise my air pump and ZS carb.. Wish they only did tailpipe testing..

/ubbthreads/images/graemlins/frown.gif
 
Disclaimer: I’m not suggesting anything deceitful. /ubbthreads/images/graemlins/angel.gif

But I know a couple of folks that have found creative ways of circumventing California’s strict emissions laws.

The first guy re-titled his vehicle as an earlier pre-74 MGB. I’ll leave that to you’re imagination as to how that was done – any guess would probably be correct. Anyway this guy has a 78B (like mine) with a side draft Weber/header setup that is totally illegal in our state.

The second guy still has all of the required emissions equipment. But it all sits in well organized & labeled boxes in his garage. All are well maintained and he actually re-installs it every two years just for the emissions test. According to this guy – it’s not as big a deal as an entire engine swap and he claims he can make the swap over a weekend.
/ubbthreads/images/graemlins/yesnod.gif
 
Back
Top