TheSamba.com :: View topic

Fri Oct 12, 2018 8:39 pm

I own a 1974 Super Beetle with a stock 1600 dual-port engine. It has a Bosch SVDA 034 distributor, coupled with a German Solex 34 pict 3 carburetor. The car came from the factory with this combination, and my engine runs great in all respects.

But I have a question that has to do with a discussion I had today with another VW enthusiast, who I’ve been trying to convince to get a Bosch 034 to match with his 34 pict 3.

He’s reluctant to go this route for two reasons. The first is the opinion of a well-known (but I won’t name) near-by VW vendor who tells him that an 034 has the propensity to over advance, which would of course, burn up his engine. The second reason is that he has a prominent San Francisco Bay Area VW mechanic who recently told him the same thing: 034’s have a tendency to over advance and kill motors.

Conversely, I’ve told my friend that I’ve always run a Bosch 034 (the current one is a new Mexican Bosch SVDA 034) with my 34 pict 3, and I’ve never had any symptoms with over advancing. If anything, my spark plugs and tail pipes tell me that I run a bit on the rich side.

Regardless, I need no convincing concerning my carburetor/distributor combination. But I have to wonder if this over-advancing concept is nothing more than a myth (like so many myths about our VW’s), or if anyone here has actually heard of similar tales.

I’d especially like to hear from our distributor-rebuilding pros, as to whether they know of any properly-working Bosch 034’s causing over advancing.

Thanks for any knowledgeable replies.

Tim

Fri Oct 12, 2018 9:11 pm

Who are these well known Bay Area experts?

Vacuum advance on those dists are load dependent. Once you floor it the vacuum advance is no longer in play. It allows more advance when you are under light throttle from the vac advance.

If it did not work it would not have been used (SVDA and DVDA dists) for years by VW and vac advance dists used for years on many factory carb based engines.

Tell him to read up on SVDAs here and how they function. Let him drive your car. Then he can make a decision for himself.

Fri Oct 12, 2018 9:52 pm

I've noticed much better drivability with the 034. Obviously I can't see the advance while driving under load, but I don't get any pinging that I notice.

With the Bosch 009 I would get some pinging in the mid range while accelerating hard during hot weather.

Also after long freeway runs, the engine doesn't seem as hot after installing the 034 than with the 009. No temp readings to back that up other than my hand and my nose.

I think the engine is happier with the 034 than the 009.

Now this is all very un-scientific, just my observations.

Sat Oct 13, 2018 1:51 am

You were very specific about describing the "good" distributors as Bosch 034s. Actual Bosch-made distributors from Germany or Mexico have a good reputation.

If the mechanics are referring to the current batch of "SVDA clone" distributors which are patterned after the Bosch 034 distributor... these have a less stellar reputation. It would not surprise me if the amount of advance they produced was greater or less than spec.
If this is the case then it is NOT a statement about "Bosch 034" vacuum advance (SVDA) distributors but on the current availability of actual "Bosch" distributors compared to low quality clones currently being produced.

Sat Oct 13, 2018 6:08 am

ashman40 wrote: If the mechanics are referring to the current batch of "SVDA clone" distributors which are patterned after the Bosch 034 distributor... these have a less stellar reputation. It would not surprise me if the amount of advance they produced was greater or less than spec.
If this is the case then it is NOT a statement about "Bosch 034" vacuum advance (SVDA) distributors but on the current availability of actual "Bosch" distributors compared to low quality clones currently being produced.
^^^^^^^^^
THIS

Sat Oct 13, 2018 9:47 am

I don't buy it, just another myth to drive up prices of German parts.

Think of how many millions of Chinese distributors are out there in use in various cars around the world.

Not saying I don't prefer German, but I don't believe those distributors are destroying cars.

Sat Oct 13, 2018 10:54 am

Good points here, concerning the 034 clones. However, I remember when I first got my bug in 2012, I had mentioned my 034 at the local vendor, and he actually got miffed when I defended the distributor by mentioning that VW wouldn’t have installed them if there had been problems with over advancing.

To them, the 09 is the only way to go. I didn’t go for that, of course, but seemingly, this shop continues to have this opinion.

There was no mention of clones. No one asked if i was referring to a genuine Bosch. I can only assume that they were talking about all 034’s.

I still need no convincing that a good 034 is the way to go if you have a 34 pict 3. I just wanted to know if others actually had any personal experience that might have backed up the claims of these two different shops. That was, did anyone have an over advancing issue with a Bosch 034.

So far, no one seems to have any first-hand experience with an engine failure being caused by the “myth”.

It makes you wonder where these myths get started.

Tim

Sat Oct 13, 2018 11:27 am

Fiddlestyx wrote: I don't buy it, just another myth to drive up prices of German parts.

Think of how many millions of Chinese distributors are out there in use in various cars around the world.

Not saying I don't prefer German, but I don't believe those distributors are destroying cars.
I've tested a dozen different 009 and 034 clones and found inconsistent curves from brand to brand and sometimes in the same brand.

For 009 clones i've seen everything from 14* to 44*.

Their quality is minimal. Some have vacuum canisters fail too quickly. some have poor quality bushings and cause timing scatter.

They usually give less than optimal performance. The only way they destroy an engine is to over advance and slowly "cook" the engine.

Sat Oct 13, 2018 11:56 am

Someone school me on what an 034 is, and explain why a SVDA with a 34 PICT3 carb would be used on a 74SB, and a DVDA with a 34 PICT3 would also be used on a 74SB. What determines whether you use a SVDA or a DVDA?

Sat Oct 13, 2018 12:04 pm

The dual vacuum and vacuum retard which was to reduce emissions. If you don't care about emissions, you can disconnect the retard hose.

Sat Oct 13, 2018 12:09 pm

Tim Donahoe wrote: He’s reluctant to go this route for two reasons. The first is the opinion of a well-known (but I won’t name) near-by VW vendor who tells him that an 034 has the propensity to over advance, which would of course, burn up his engine. The second reason is that he has a prominent San Francisco Bay Area VW mechanic who recently told him the same thing: 034’s have a tendency to over advance and kill motors.
The title is BOSCH 034.

I truly doubt the "well-know" vendor is selling BOSCH 034, i bet he's selling Pertronix SVDA which is made in CHINA. Only the Pertronix module is made in the USA.

And the "prominent" mechanic is most likely doing the same.

First SVDA and 034 have become a generic term for vacuum mechanical distributor. And 009 has become a generic for mechanical only. No all are exact copies of the genuine Bosch units.

So lets be clear is we are talking about Bosch or aftermarket chines clones.

Sat Oct 13, 2018 12:10 pm

Glenn wrote: The dual vacuum and vacuum retard which was to reduce emissions. If you don't care about emissions, you can disconnect the retard hose.

1-By disconnecting the retard, how does that affect performance & timing?

2-Are the Advance sides of the vacuum cans the same whether it's a SVDA or a DVDA?

Sat Oct 13, 2018 12:20 pm

Dwayne1m wrote: Someone school me on what an 034 is, and explain why a SVDA with a 34 PICT3 carb would be used on a 74SB, and a DVDA with a 34 PICT3 would also be used on a 74SB. What determines whether you use a SVDA or a DVDA?

One difference could be: 1974 California model versus federal, or non-California model.

The Mexican Bosch SVDA was a copy of the 1974 federal model distributor.

Sat Oct 13, 2018 12:20 pm

Here's some marketing bull sh!t.

Quote: Enjoy Pertronix quality with this 034 style mechanical/vacuum advance SVDA distributor. It comes with all the best stuff from an 009, an 010, and an 050 and put it all into one!
Notice they call it "034 style" meaning its a vacuum/mechanical like the original. Doesn't mean it has the same curve.

"best stuff from an 009, an 010, and an 050" All 3 of those are mechanical only. Notice they picked popular models from the Type 1 and Type 4 because they market this as a one size fits all.

Quote: Type I - Beetle, Bug 1946-1979
Karmann Ghia, 1956-1974
Thing, Type 181, 1973-1975
Type II: 1950-1979 Bus, Transporter, Station Wagon, Kombi, Westfalia Camper (not '79 California model)
Type III - 1962-1973
Type IV (412) 1974
Vanagon 1980-83, 2.0 liter (except California model)
Most four-cylinder, air-cooled Porsche with points distributors (not for early 1970s D-Jetronic fuel injection, which is triggered by special contacts in the bottom of the early D-Jetronic fuel-injection distributor). The SVDA 034 distributor works great with later L-Jetronic fuel injection systems (1975-on VW bus fuel injection).

OK.. how do you connect the vacuum port to a 1946 Beetle or a 356 Porsche??

Sat Oct 13, 2018 12:40 pm

Since the 034's are hard to find in working condition, which other svda would work with the 34pict3?

Sat Oct 13, 2018 2:17 pm

My 1974 Super was first purchased in Oregon. It would have had the Federally Mandated distributor. I’m assuming this was the Bosch 034.

Glenn, the vendor in question does not sell any type of 034. He only sells 09’s. He’s very down on 034’s for the reasons I stated previously.

Cal, as far as finding a good Bosch 034 SVDA, I see them from time to time in the Classifieds. Off the top of my head, Bill (wcfvw69) sells them completely restored. In fact, he restored my original Bosch, although I haven’t used it yet because I’m saving it for when and if my new Mexican Bosch screws up on me. It’s also nice to have one set up in case I take a long trip and my points screw up. I did install it in my friend’s Karmann Ghia to show him how much better a good German 034 does with his 34 pict 3. But ... although his engine ran better during the test, he’s still worried because of the anti-034 comments he’s been getting.

Tim

Sat Oct 13, 2018 2:41 pm

Tim Donahoe wrote: Glenn, the vendor in question does not sell any type of 034. He only sells 09’s.

Tim
Are the Bosch German or Brazilian 009s? The Chinese aftermarket are just as bad as the Chinese aftermarket 034s.

I tested on with 44*, so if you static time your engine with one, you'll have 51* total advance. If you set it @ 3500rpm at 32* BTDC, you'll have 12* ATDC at idle.

Quote: Empi now offers two different versions of their popular centrifugal advance distributor. The performance engine model (C13-9430-B) has an advance curve that will allow idle at nearly 0 degrees and advance to 40 degrees. Perfect for engines with performance camshafts and using larger performance carburetors. The second is the Street model (C13-9431-B) which has the same advance as the old Bosch 009 distributor.

40* full advance will cook a engine, even a high performance engine.

I have a 2180 with 9.5:1 compression. I run a Bosch 010and found 30* is where it runs best. At 32* it runs hotter and performance is no better. I bet at 40* it wil lrun worse and run much hotter.

Sat Oct 13, 2018 2:47 pm

I find this to be an interesting discussion. Although not an 034, I have a 205t that is timed at 0tdc. This can be done by the factory manual statically or timed at idle. This distributor should not be timed at full advance, is the 035 different?
I used to have a Chinese 009 and before that a sticky 205t. I feel like the engine may run warmer with the 205t vs the 009 and my 205t is on the money. This is proverbial of course.

Sat Oct 13, 2018 3:08 pm

Frodge wrote: I find this to be an interesting discussion. Although not an 034, I have a 205t that is timed at 0tdc. This can be done by the factory manual statically or timed at idle. This distributor should not be timed at full advance, is the 035 different?
I used to have a Chinese 009 and before that a sticky 205t. I feel like the engine may run warmer with the 205t vs the 009 and my 205t is on the money. This is proverbial of course.

The 205T you are probably talking about is a SVA distributor, not a SVDA like the 034. The 205T does not have any kind of mechanical advance. The 034 uses both vacuum and mechanical advance. Very different distributors and are timed differently.

Sat Oct 13, 2018 3:19 pm

Tim, how old are these mechanic bros that told you the 034 had such issues? How many 034 OEM distributors did they actually find issues that you stated? :-k