H30/31 and 034 SVDA....amazing performance

[tom_hd02]

I know, I know.... the title sounds like a science fiction movie, but, how could this be possible?
Yesterday I installed a H30/31 carb (125 main, 65 angle jet, 50 right side jet) with a Chinese 034 SVDA distributor on my bone stock 1600cc dual port engine. The engine performance was incredible. I timed the distributor at 7.5° BTDC at idle and 30° at 3500rpm with vacuum line disconnected (max advance is 40° with vacuum line connected). I know this carb and distributor don't match, but how can this be possible? The engine runs better than ever, pulls strong, great acceleration, way much better than a 34pic3 with the same distributor. I got the feeling that this is to good to be true. Could I be hurting the engine by running this combo? Is too much advance bad for the engine?

All opinions are welcome.

[Glenn]

The H30/31PICT should not be providing enough vacuum to cause the canister to add advance under load.

What you could be feeling is just the mechanical part of the distributor.

What distributor did you have before?
_________________
Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

#BlueSquare

[tom_hd02]

I was running the h30/31 with 205T vacuum only distributor. It ran ok, but not that well. After that, I installed a 34pic3 with a 034 distributor, great mid to high rpms, but I couldn't get rid of the flat spot and hesitation at low rpms. That's when I switched to the the h30/31 with the 034 just to see how it ran.

[Juanito84]

You shouldn't be getting too much advance. More than likely you're not getting enough. Can you plug the venturi port for the vacuum advance? But then again, if you like it you should probably leave it alone.
_________________
If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[Frank Bassman]

This is truly mind-boggling. To tell you the truth, I've seen bastardized engines running an svda with a h30/31.... usually accompanied by a very high idle. (I'm talking 1100 rpm range) Do you have an uncharacteristically high idle? (Above 800-900 rpm?) If so, what you may be feeling is the centrifugal advance only doing its dance while not even using the vacuum can, since that's centrifugal advance rpm territory.

Or maybe, the Chinese finally came up with a vacuum-centrifugal distributor that actually does work with the H30/31...

But I highly doubt that.

[XXX/Rx/RnR]

I have a 034 with that carb. Mine came from aircooled .net and was setup for the t-4 in my baywindow with fi and it runs great. Timed at 28 degrees with hose off and plugged full throttle. Hose on advances to bout 40. Used the scale off the bus to mark the pully. Advanced the same in the bus. I can't tell any difference between the 205an that was in there and the 034 that's in there now.
_________________
78' westy, 2.4 195hp ecotec, audi turbo a/t, a\c, 2 1/2" lift spindles, index rear, 930 cv's & axles, 225x65x17 BFGs ## 77' hardtop 2.0 T-4 duel 44 weber's, 225x50x17s ## 74' baha bug

[ashman40]

OP, where are you connecting the vacuum advance hose on the carb?

Normally, vacuum advance connects to the left side vacuum port on the Pict carbs ("A" in the above pic). For many Pict-3 carbs this is "ported vacuum" from just above the throttle plate. For the Pict-1 and H30/31 carbs this left side port is "venturi vacuum" from the narrowest part of the carb throat (very small changes in vacuum which increase with air speed flowing through the throat).

If you are connecting your vacuum advance hose to one of the rear facing ports of the carb (probably B in the above pic) it will see intake vacuum. This vacuum responds nearly the same as the SVDA distributor expects... at speeds above idle. But at idle, the SVDA vacuum can will see more vacuum than expected. The result will be increased idle rpms and the timing readings with vacuum hose connected will be much higher than typical at idle.
_________________
AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[wcfvw69]

The H30/31 carb usually matches well with the 205T or 205K vacuum only distributors. If your motor is dual port and running a dog house fan shroud, you shouldn't be running either of these vacuum only distributors as they retard 3* on number 3 cylinder. This was for the single port motors that were not running doghouse fan shrouds and had the oil cooler in the way of cylinder 3 cooling air.

Back to your distributor. In most cases, the 205T has never been cleaned and serviced during it's life time and will have a frozen or a very sticky advance plate in it. As a result, the vacuum can struggles to advance the timing and you have a poor running engine.

I'm currently running a H30/31 carb with a German made 009 distributor. It runs perfect. No off idle hesitation or any other issue.
_________________
Contact me at [email protected]
Follow me on instagram @sparxwerksllc

Decades of VW and VW parts restoration experience.
The Samba member since 2004.

**Now rebuilding throttle bodies for VW's and Porsche's**
**Restored German Bosch distributors for sale or I can restore yours**
**Restored German Pierburg fuel pumps for sale or I can restore yours**
**Restored Porsche fuel pumps or I can restore yours**
**Restored Porsche distributors or I can restore yours**

[tom_hd02]

Frank: The idle ranges between 900 and 1100 rpm (which is unusual). With the 205T the idle was very stable at 850-900rpms. I’m still trying to fine tune the idle. At what RPM does the centrifugal advance kick in?

Ashman40: the vacuum hose is plugged in to the “A” port. I have a vacuum gauge; I will hook it up and measure both “A” and “B” ports at idle and report the results.

wcfvw69: I disassembled, cleaned, and lubricated the 205T. The advance plate moves freely. I installed a petronix points replacement, which (supposedly) eliminates the 3° retard on #3 cylinder. The engine runs fine with the 205T, but not as strong as with the 034.

[ashman40]

[Juanito84]