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I have a 1975 manual trans. bus that has a 1700 with duel webber 34ict's. The engine is from a 914. It has a vacuum advance distributor but only one hose is attached to the vacuum unit on the distributor. The side that I believe is the retard has nothing hooked to it. Should there be a hose hooked to it that isn't there anymore? Should I just put a mechanical in? Any suggestions would be great, the engine and tranny are currently out as I am putting a new throw out bearing in. So it is easy to get to right now. Thanks guys, all your advice has helped me get my first bus on the road. -Tim

The vacuum advance on that engine...depending on which can it used, had a pretty good curve. Some on the 1.7 had the adjustable vacuume advancde. Arm #W 917. It can be used with the retard disconnected. You can also put on a single advance can. The retard was only useful on D-jet...and was actually kind of redundent of you had the deceleration valveattached to the engine. Ray

You have an older style distributor with the vacuum advance and vacuum retard (probably a 205). This was intended to work with stock dual carbs like Solex PDSITs. The vacuum retard pulled the timing back to something like 10 degrees after top dead center (ATDC)at idle. Now that you have Webers, you only need the vacuum advance hose hooked up and the retard port on the distributor can be plugged (besides, I don't think there is anyplace to tap into the weber carb for the vacuum retard). Without the retard hooked up and with the weber carbs, you need to time the distributor differently than stock, like 7 or 8 degrees before top dead center (BTDC) at idle, to get the right amount of advance in your timing as the engine speeds up. Those of you that have weber carbs pipe up if I am wrong.

I have a stock 1700cc system with the dual solex carbs and the dual vacuum distributor, but the retard side isn't working. It ran like crap at anything over 1500rpm until I realized the timing should be much more advaced because the retard was gone. Now its happy timed at 8 degrees BTDC at idle and gives somewhere up to 30 degrees of advance at 3000rpm.

If for some reason you decide to get rid of your distributor, let me know; I want it.

Hey thanks guys for the quick replies. So, I should just plug the retard and time the engine to 7 or 8 BTDC? Is this right?

Since you are in uncharted waters, you should probably do your first timing job dynamically at 3,000 rpm to 28* vacuum advance temporarily disconnected. Then see what your idle timing is. Reconnect vacuum when you're done.
Colin

It's common to disregard the retard hose on a dual vacuum distributor. In that sense, it makes it perform like a single vacuum distributor.

Do not plug the hole on the vacuum canister, or you will not get proper advance from the other port. Leave it open so the diaphram can still move like it needs to. If you live in a dusty climate, you could put a piece of foam/sponge over the port to keep the diaphram clean, and still allow it to breath like it should.

I most definitly would not set the timing like you would a 009 (total advance 28-30 degrees). Static time it to 7.5 BTDC. If the centrifugal part of the distributor doesn't have enough advancement to it, you could end up at 15-20 degrees at idle which would cause hard start problems when the motor is hot. If it has something like like 30 degrees of advancement, you will end up at "0" degrees at idle, and it will run like a pig on the bottom end.

I know that the water buffaloes can tolerate higher initial timimg. ( i.e. the 10-20 range ) But how do our aircooleds handle increased initial. Sure makes them snappy, but if it's doing more harm than good......

not speaking from personal experience, but as I'm sure you know jake seems to love 10+ degrees initial, 28 or so total, not counting any vacuum advance, which he doesn't believe in.

Eaallred wrote: Static time it to 7.5 BTDC. If the centrifugal part of the distributor doesn't have enough advancement to it, you could end up at 15-20 degrees at idle which would cause hard start problems when the motor is hot. If it has something like like 30 degrees of advancement, you will end up at "0" degrees at idle, and it will run like a pig on the bottom end.

Either extreme as pointed out here, is a problem. Perhaps getting the centrifugal curve mapped out would remove these unacceptable variations. Your more dangerous unknown, by avoiding starting and idle issues with idle-based timing, is what is the actual timing at speed on the highway? That is where engines self-destruct. Poor starting or a pig bottom end will tell you at least that the advance needs to be checked. Otherwise, you have this great starting and initial take off, but do not have any idea why your CHTs are high, or why # 3 piston decided to seize a ring at 98* outside of Barstow.

Actgually, if this engine is type 4 based with a 205...it almost always runs much better with about 10-12* initial. Just make sure that the top end does not go too high. All of this is adjustable internally by the way...with a few simple tweeks. Do not just let the idle advance fall where it may simply because you got what you wanted in the top end. Adjust it!. This can be done down under the breaker plate in the spring and weight area. Just open it up...look at it....and think about it. Its real easy to make an advance stop down on the spring plate. Its also very seay to install an advance adjustment screw on the vacuum can. Like I noted, the 914/411/412 (some of them) unit used a can with the adjustment built in. Also...not all of the vacuum retard units brought the idle advance down below "0". Only a few did. There were at least two dozen different cans (including watercooled). Also, adjusting the retard stop takes less than 10 seconds on any of them. I still use retard on the FI...because when the fuel leans out on high speed over-run, there is a danger to having rpm related advance at 28*....its stupid to have it that high when your fuel supply is reduced because the throttle is closed. So...my retard unit brings me back to idle timing...which is 12* BTDC. Ray

Paradox - I think its safe to assume you can run your dual webers without the vacuum retard hooked up. As to where you should set the timing, we have almost as many opinions as posters on that question. Are you thoroughly confused?

Let's see if we can get an answer to your timing issue and to a related one: Where should the timing be set (idle and total advance) for a dual vacuum dist, retard disconnected and dual weber ICTs (Paradox' question)? Also, what should the timing be for a stock dual vacuum dist., with the retard side NOT WORKING, running stock dual solex PDSITs (my question)? This is for the 1700cc type 4 engine. Anybody willing to stick out their neck out on this?

Here are the specs on the stock dist as listed at oldvolkshome.com. Your dist may be something other than stock, I suppose. You should check.

Bus & Pickup 1973 * 1700 Manual Trans

Distributor: VW 021-905-205J, Bosch 0231 173 009 or 010 > 021-905-205N, 0231 181 005
Can Use: VW 021-905-205N, Bosch 0231 181 005
Points: 01 011
Condensor: 02 054
Rotor: 04 033
Note: Originally equipped with Speed Limiting Rotor 04 016 (5400rpm)
Dust Cover: 039-905-241, Bosch 1230 500 139 > 1230 500 147
Cap: 03 010
Distributor Cap Clip: 03-905-265, Bosch 1231 251 033
Parts Kit (Shims, Washers & Hardware): 059-998-211, Bosch 1237 010 007
Coil: 00 015 (Blue Coil: 00 012)
Vacuum Can: 07 113
Ignition Wires: 09 171
Spark Plug: W8CC
Timing Set At:: 10deg ATDC @ 800-950rpm w/strobe, vacuum hose(s) connected
Advance/Retard Range: Vacuum: 7-12deg Adv, 16-18deg Ret; Centrifugal: 9-14deg @ 2000rpm, 21-25deg @ 3400 rpm

Ok guys my distributor is a 022-905-205AC thanks for all the replies. I will try and play with it. I am not sure yet what I will time it to. I am not even sure all the hoses are pluged in right. I am still sorting that out. I will try and take a pick of all the different hoses and maybe someone can help me straiten them out. Thanks again everyone. -Tim

Satchmo?. . . . . I think we lost him.
The Bentley suggests that the start of the centrifugal advance is between 1,000 and 1,200 rpm. That's when the light starts dancing away from the 10* ATDC at idle. At 1,600 rpm, the centrifugal advance should be found somewhere between 9* and 14* on the 021-905-205 J and it should be done at 3,400 rpm somewhere between 21 and 25*.
His distributor, on the other hand is listed in the Bentley as starting at the same place as above, but it needs to be between 11* and 17* at 2,000, and ends 21-25* at 3,600 rpm, which is really winging it with your timing light inches from the whipping v-belt. Thank goodness it is not an early Porsche 911. I used to go deaf timing that thing at 6,000 rpm, with the workshop manual note: do not maintain this speed for more than 5-10 seconds. You bet.
Colin

It's all good, IMHO, if you're dealing with a NEW dizzy and dealing with a stock engine and dealing with smog. But after ~30 years of rebuilt units out there, it's hard to get the factory spec. I recently spun four on the Sun machine and they were not even close to factory spec. Yet all of them had shiny new rebuilt stickers on them. I don't buy junk from the junkyard. So ya got to ask yourself what is the intended use. We all know that our engines run good with some advance. It is also considered safe to have the mech. max out at ~30*. Add some vacuum on that for a total of ~40 and as I said earlier, you're all good. My limited info on the motor company was that the various BTDC and ATDC settings were mostly for smog and the latter cooling. I personally like to run as much advance as possible with out pinging, per application. Generally speaking, low compression can use faster and higher advance. And high compression likes lower advance. This is why you'll see hipo engine builders stop the advance at ~28*. I have my stock 78 FI westy set up at 27-28 mech. max , ( helps maintain cool running when loaded going up-hill, etc. ) but the vacuum adds 16* for those nice flat highway runs. But that's just me. I'm getting 20+ mpg on the highway. I guess that there is/can be no real answer for the original question. What was it again? But if you'd start with stock numbers and do nothing else but to add a few *'s to the initial , it'll clean up the bottom end. At least it's a start untill you learn the deal.

For all of my fancy-pants numbers spewing out, I should mention that I am running my original distributor at 439,000 miles, the timing mark dances like a moth around a light bulb, and my seat-of-the-pants timing method is that it starts well, does not run hot, it does not ping, and I get 20-23 mpg, good nuff.
Colin