Vacuum advance unit fell off

[ClausB]

Hi guys,

my chim 450 was running on 7 cylinders - I stopped and saw, that one of the two screws, that hold the vacuum unit in place, is missing and the other wasn't tightened.

So... What to do now? Can I remove the inner plastic cap inside the dizzy to reconnect the arm of the vacuum unit? Do I have to adjust it afterwards?



Thanks in advance

Claus

[David Beer]

No connection, I have not had vac advance for maybe , 8 years . MY tuner TVR Power/ Austec/ mark Adams say no need . If you want a few MPG then reconnect, just don't accelerate as the the vac advance is cancelled anyway!

[David Beer]

Just checking you got the message.

[EGB]

Try connecting without removing dizzy cap. I made it with patience. As David says. No noticeable difference in performance vac on or off. Fit new screws tight.

[Barkychoc]

Whether you connect the pipe or not the vac unit needs to be fitted to stop the inner base of the distributor rotating internally and changing the timing.

IIRC if you just take out the three screws holding that plastic cover on (screws can be quite tight use the correct screwdriver) then you can see where it connects to.

Edited by Barkychoc on Thursday 6th June 15:31

[occasionaluse]

Mine ran for years without the vac advance - thought it strange when i couldn't see it - anyway must have fallen off as i have owned the car from new and i didn't remove it - there was one screw and that was it. I bought a new one - fitted it and did't have to take the cap off - could feel when it engaged - you will know. Results have been better fuel economy on long runs - nothing on performance.

[ClausB]

Hi,

thanks for your replies. I managed to drive back to my garage, which was 2 miles away, but it wasn't running well... Not even remotely. When idle, it was stalling, so I had to keep it alive by playing with the throttle under braking. Also it felt like it had 70ish bhp.

Barkychoc said:

Whether you connect the pipe or not the vac unit needs to be fitted to stop the inner base of the distributor rotating internally and changing the timing.

I think, that is exactly what happened. When the vac unit fell out, the inner electronics of the dizzy were turned, could that explain the symptoms I mentioned above?

Bought an ignition timing light today and will check the timing tomorrow.

As I don't have the bible around at the moment: what are the correct advance values for the Chimaera 450 serp (1999)?
28 deg advance above 3250 (vac pipe to plenum not attached, only mechanical advance)
4 deg advance in idle

Are those the correct values?

Thank you!

Claus

[ClausB]

Did adjust the timing yesterday - no wonder it was stalling when idle: The timing was 14° BTDC at 3500 r/min and approx. 4° ATDC when idle (counldn't figure out the exact value because my timing light only adjusts to BTDC values). Set it up to 28° BTDC at 3500, seems to run fine now, will be testing it on the road as soon as the weather gets better.

To all, who are looking for a photo of the dizzy w/o the inner dust cap:



The arm of the vacuum unit slides over the nipple from below.

Thank you again!

Claus

[Graham]

I lost the 2005 Class B TVR title due to those dam screws coming out from the lead with 3 laps to go in the last race, after leading all year !!!! apparently its well known for them to come out... nobody had told me though doh...

the symptoms your were getting were the same, timing moves all over the place.. missfiring and everything..