TheSamba.com :: View topic - 009 or SVAD, when no ported vacuum...only manifold vacuum...?

Mon May 12, 2025 5:03 am

Hi,

My camper (T2b) is fitted with a 1641 (but otherwise stock) type 1 engine, with an SVDA dizzy and a pair of 36IDFs.

The carbs have no provision for a ported vac advance vacuum...not even a blanked off spigot that could be drilled & tapped.

Up to now I've run a vacuum hose from a barbed fitting in one of the manifolds to the vac advance can on the dizzy.

However...I'm wondering (I've been reading the Internet!!) if this is the best setup. Specifically, i've been read that the SVDA needs a ported vacuum signal, rather than a MAP signal.

Since a ported vacuum signal is impossible (short of buying new carb$), what's my best way forward...?

keep the SVDA and the MAP signal
replace the SVDA with an 009

I don't have the (notorious) 009 flat spot, but also, the engine feels a little down on power at the top end.

Mon May 12, 2025 6:30 am

20 some reads and no replies...
here's a couple things for you, 1. drill your own ports, not that hard ive done it several times. 2. leave it on manifold vacuum, it only makes a difference at idle, not on top end.
read up on hooking your dizzy to ported vs. non ported vacuum.

Mon May 12, 2025 7:09 am

If it were me, and I don't like them, is to replace the distributor with a 009 or 010. as for hooking to port vacuum don't. IMHO

Mon May 12, 2025 8:26 am

Sure, it's a bit more complex, but you could also get a 123 bluetooth and program it to a timing curve that works well with your carbs & engine because it load senses on MAP and is not dependent on the carbs themselves.

By leaving the 123 bluetooth connected to manifold vacuum, reliance on the ported vacuum's interplay with the vacuum can on the specific SVDA that you are currently running is a thing of the past.

Unless you are able to recurve that SVDA to what your engine likes, your timing curve overall is probably a compromise anyway.

There's a good bit of information on here about programming the 123 BT that could get you really close.

Mon May 12, 2025 8:35 am

You can also lock your 009 and add a CB Black Box for programming the curve.

https://www.cbperformance.com/product-p/2013.htm

Mon May 12, 2025 9:32 am

Mon May 12, 2025 10:45 pm

Another option is a 123Tune distributor.

The 123Tune can be programmed to use manifold vacuum by telling it to ignore the vacuum below a programmable RPM, say 1200 RPM . Its not perfect, the ported vs manifold signals behave differently as they originate in different ways. But you still can get that extra 9 degrees of advance at light load.

Same for any mappable ignition system with a proper lookup table. The 123tune has a pair of curves like the original distributor curves, and an extra RPM limit for vacuum.

Mon May 12, 2025 11:34 pm

Quote: The carbs have no provision for a ported vac advance vacuum...not even a blanked off spigot that could be drilled & tapped.
OP, do your carbs have a flat, undrilled spot on the housing as per Alstrup's photo even if yours don't have a plugged port there?

Wed May 14, 2025 8:20 pm

Since you have a bus just get yourself a 123. They are the best way to go. You can program everything you need into them.