Struggling with PDSIT synchronization

[rustbus]

HI Guys,

I had a thread going in the samba but thought i would post here for ideas too....not too many over there that seem to post about dual PDSIT's

i hope its ok i post it here too - and thanks Colin for the response on samba,

here's what i initially posted:

guys,

My bus has been freed from the shackles of the shop and out into the sun - did a dual carb tune up on it per Amskeptic, and drove it all around yesterday.

before i took it out i checked the oil level, and its seemed high...i was super frustrated as i'm paranoid about the gas getting through these old carbs and into the crankshaft...

i started it anyhow, then shutdown and waited for awhile. checked the oil again, and it was much lower (had been sitting for weeks prior) so i said "screw it" and took it out, tuned it, (valves are set, plugs gapped, timing @ about 26/27 @ 3200-3400rpm and dwell always on with magnetic points) i have no idea what gas in oil smells like, i know this oil smells different than unused oil, but this oil has about 10 km on it.

after the tune it ran well. booted around town, very little hesitation, etc. but I'm not confident it is running its best... and when i grabbed the intake manifolds under the carbs, the left side was cool and right side hot. so after about 10minutes of cool down i cam back to it with my lazer thermometer, and found the hot side at about 80-90C and the left side at about 50-60C...this shouldn't be?! what causes this?

after all the effort i've put into the bus over this winter, i must figure out these carbs or im gonna freak!

any advice? why is this happening? anything i can check? i'm gonna go out and tinker now... Crying or Very sad

then colin replied to me (thanks!)

Chill pill.

With engine off, loosen each spark plug wire at the distributor cap.
Start engine. Pull each wire off one at a time, and see which cylinders make the rpm drop *less*.
Check plug color for differentials.
If the weak cylinders are biased to one side of the engine, adjust that side of the engine at the mixture screw for a little more fuel if the plugs were not already sooty. If the hot side of the engine has whitish plugs, you have a vacuum leak nearby like a brake booster elbow causing lean heat.

Check for an intermittant cut-off solenoid (ignition on see if solenoid chatters when you wiggle its wire) or a choke heater failure (carefully touch each choke cover after five minutes of running, they should have equal and noticeable heat).
Colin

then i went out and did as he said:

thanks Colin,

I pulled plugs earlier - not in an organized fashion as you've mentioned, but noticed obviously that the left/colder side made almost no difference in RPM. specifically #4, thats left rear i believe. left front made a touch of difference, but a near stall when pulling the right side plugs.

so i'll go out and test it like you've said. I'll double check for vacuum leaks, but my booster elbow on the left sure seemed fine. Also, I have no chokes, they are completely disabled (and I don't feel i suffer much for lack of them)

then

ok, heres some info i found today



the cold side is all sooted up ...checked compression while i was there.

when i pulled the plugs at the distributor cap, 3/4 made almost no change, maybe 50rpm. pulling 1/2 brought it down by 200rpm

i checked the solenoids, they click well, and noticed no loose connections on any wires. they are screwed in in tight.

double checked both booster elbows, they look and feel good. found a extra little vacuum nipple on the right side carb, capped that, no real change. i did not double check the manifold bolts but i'm certain they are tight (but will check) UNLESS - i have the booster elbow that has the small nipple to the air horn - could that be faulty and leaking O2 in?

not sure what to do? cant make the left side any more rich right? i just rebuilt these carbs and paid extra special close attention to detail. could a loose part be causing this? like a main jet loose or anything?

stumped? any help appreciated... maybe i need to run the tuneup procedure again? i set my throttle plates back when i rebuilt them, so i didnt second guess them this time... i figured i set them best in my hands when they were all clean...

also noticed that the right carb mixture screws spins kinds easy....maybe too easy? or not related...

anyhow! tomorrows another day.



SO - today i will run through Colin's factory adjustment procedure again....I'm thinkning i must have slipped up...I'm also tempted to pull the carbs and make sure i dont have a loose jet or something, but im not sure that is a possible explanation.

when i rebuilt these carbs i took what i thought was some serious care and attention. i dont think there are any plugged passages. lots of carb cleaner, lots of compressed air, lots of disassembly and cleaning...

anyhow, i will report back with EXACTLY how my tuning efforts go today.

thanks Gents!

[rustbus]

well the last couple hours were frustrating - hopefully I'm narrowing things down


went through the procedure again. noticed that the left side of the engine sounded like one of the cylinders was firing intermittently. so i put the timing light on #3 and notice a very erratic spark signal in the flashing light. so i put in a standby NOS distributor that i have, which has points, and this really smoothed things out. so i reset the timing. both distributors @ 28*, hoses off, 3200+rpm.

with the old dizzy i was getting like 0 degrees at 700rpm with no hoses on dizzy. with hoses on and idle up, i was getting around 12 ATDC. high.

so new dizzy goes in. now i get about 2* ATDC @ 800rpm and no hoses, (good) with hoses @ 1000rpm i get about 12 again.... too high.

so i proceed to go through the rest of the tuneup procedure.

during "2. Synchronize High Speed Air Flow"

i had to crank on the 1972 10mm adjustment nut about a full turn or so to get the carbs near even. adjusting this here made a BIG up change in idle....? but i think i got them near sync'd, im using both an original UNI-syn and the new snail type. i can get sync almost exact with either unit. this part seems to go pretty easy.

during "3. Synchronize Idle Air Flow "

I notice a BIG difference in unisyn readings. right side way higher. like 1 bar left vs 3 bars right on the unisyn. to i go in after the throttle stop screws as instructed. 1/8 turn on each screw and i get a bit closer, but still far apart. so i go and turn them both another 1/8 turn (oppsite directions as instructed) even closer, but not same. i leave it there, as i'm getting into those screws quite a bit at this point. retard is still OK. (checked by pulling off dzzy, idle up)

during "4. Synchronize carburetor mixtures: "

I'm pulling the 1972 reference hose and finger-on-off. finger off idle up, rich, so i 1/4 turn each mixture screw in. closer. one more 1/4 turn in and i notice near no change in idle speed - as desired right? (at this point the screws are about 2 turns out each). next.

now heres where things go off track for me. when fine tuning with the central idling loop off and pulling the idle cutoffs, i'm getting almost no noticeable change in RPM at all. either side. perhaps the more slightest 25rpm varying drop when i pull either. i say to myself "must be in the sweet spot?" and i have no choice but to move on, even though colin says to expect some 50 - 150 rpm drop...strange, but i move on... idle kicks back up nice with hoses and idle circ. back on.

for step "5. Set Central Idling Speed/Mixture: "

this step gets me excited, as i cant really find the point where the mixture screw makes a difference. hear i can run he mix screw in until it almost chokes, but when drawing it out slowly, i can hardly pick out the fine spot where idle stops changing. the idle seems a little too "rough" for this level of fine tune. (like varies up/down 25rpm-ish) but i give it a go (a half-assed go) anyways and the idle sits in around 1000rpm no problem. I need to do this step better...?

-it actually idles really nice throughout this procedure and at the rpms that colin says to expect when popping off hoses or idle circuits

so i think, "great, smoother idle, less jumpy plug #3 spark, sounds good, so i step on the gas and *hesitiation*. sigh. so i go back and pull the left side plugs at the distributor cap, and almost no change. (#3 makes a maybe 25-50rpm change, #4 - basically nothing) pull the right side plugs, shes ready to stall.,,, arrrrrg, right?

I go for a drive anyhow and the power is better now at higher rpms. feels smoother at speed. got up to about 75mph decently quick, and it seems peppier at speed, but big on hesitation after lights.

before this i pulled the carbs and checked the main jets. tight. i checke the manifolds and carb to manifold connections. Tight. i checked the elbows again. sound, (they are new) everything on this bus is basically set up exactly stock for a 1972 engine with oil bath. all hoses on correct.

any ideas? after the drive with the hesitation i threw in the towel for the day, hot, grubby hands, and a little frustrated. actually, very confused too.

i'm not totally confident with
-where my throttle plates are now.
-why my idle cutoffs seem to play no part
- why the left side isn't contributing, at least at idle (pulling plugs)
- why i have hesitation - bad idle circuit mixture?
- why my left side plugs are black and right side white

any help appreciated

[Amskeptic]

so new dizzy goes in. now i get about 2* ATDC @ 800rpm and no hoses, (good) with hoses @ 1000rpm i get about 12 again.... too high.

You need to be very careful and comprehensive in your posts if we are going to have a snowball's chance in hell of getting anywhere. For example, "2*ATDC @ 800rpm no hoses" must be prefaced with you stating what you actually adjusted the distributor to at 3,200 rpm no hoses. I have to know that number (should be 28*BTDC) before I can tell you which way to play. When you then paranthetically write "(good)" to the right of the comma, I do not know which specification you are declaring good. "with hoses I get about 12 again" 12 again what? too high what? 12*ATDC is too retarded.
You should expect idle timing to be 5*ATDC at 850-950 rpm at idle. When you take off the retard hose, the idle speed goes up and then, around 1,100 rpm or so, the centrifugal timing is certainly going to kick in and yank it up to 12-16*BTDC, that is normal. When you put the retard hose back on, the idle should plummet back down below 1,000 rpm and the timing should be 5*ATDC

i had to crank on the 1972 10mm adjustment nut about a full turn or so to get the carbs near even. adjusting this here made a BIG up change in idle....?

We have to be careful here, because if you go cranking too much, the adjustment can actually start to open a throttle plate at idle. You can see it at the stop screw. This is not allowed. Disconnect a throttle link and make sure that it can go back on the lever without actually opening the throttle plate. If it does crack open a throttle plate, re-configure the synchronization to allow the link to snap on the throttle lever without disturbing the throttle plate (i.e. the stop screw)

"3. Synchronize Idle Air Flow "

I notice a BIG difference in unisyn readings. right side way higher. i leave it there, as i'm getting into those screws quite a bit at this point. retard is still OK. (checked by pulling off dzzy, idle up)

At this point, you are wise to stop. Make a note to self, left is lazy.

"4. Synchronize carburetor mixtures: "

when fine tuning with the central idling loop off and pulling the idle cutoffs, i'm getting almost no noticeable change in RPM at all. either side. perhaps the more slightest 25rpm varying drop when i pull either.

You seem to be getting fuel without consent. Are both idle cutoffs seated in the carbs? 1/4 turn out can dump fuel into the idle passages even if the wires are removed.

"5. Set Central Idling Speed/Mixture: "

this step gets me excited, as i cant really find the point where the mixture screw makes a difference. hear i can run he mix screw in until it almost chokes, but when drawing it out slowly, i can hardly pick out the fine spot where idle stops changing.

Use the reference hose to find the mixture spot. AFTER you have the timing squared away, you should set the idle speed for 950-1000 rpm, then crank the mixture screw cw until it leans out (rpms drop) then back out until finger-off gives you a noticeable but not exorbitant rpm increase with reference hose finger off.

big on hesitation after lights.

Based on plugs, you might have a rich drown-out, not lean hesitation. Check accelerator pump rods for equal adjustment (early bus you just pick the hole in the lever, later buses have adjustable nuts that are more difficult to determine without taking the carbs off).

before this i pulled the carbs and checked the main jets. tight.

What size or your main jets? Have you checked the sizes of the idle cut-offs? I think they need to be 55.

i'm not totally confident with
-where my throttle plates are now. both 1/3 turn in from contact
-why my idle cutoffs seem to play no part see if they are seated firm but not nuts
- why the left side isn't contributing, at least at idle you sure about float levels? base gaskets are aligned correctly between carb and throttle body and phenolic spacer-to-manifold?
- why i have hesitation - bad idle circuit mixture? I think rich bog
- why my left side plugs are black and right side white (I do wonder about basic carb function all orifices and air bleeds)

any help appreciated

Keep me updated. I can respond here and a reminder in PM is acceptable if I don't get back here quick enough.
Colin

[rustbus]

hey thanks for the thoughtful response Colin. i'd do anything to have you up to visit, but i think i'm way off the Itinerant Map! i appreciate you working to bear with me.

Tomorrow I will do two things - remove the carbs again and absolutely verify that the gaskets aren't causing any trouble at the carb to throttle plate to manifold. I know i took super care when attaching the throttle plate to the carb in particular to make sure i wasn't blocking any orifices. but i will check it out carefully.

then i will repeat the timing steps, and take careful notes

- but yes both carbs were set to 28* @3200rpm...now i'll fess up - my tach/dwell only hits 2400, but i rev it well off the gauge and i can get it to the point where i can't rev it beyond 28* BTDC. I'm sure i'm well over 3200rpm at that point. - so with the new distrib, i was @ 28*@3200rpm (estimated, but max advance) then with both hoses off and idle circuit unplugged, she fell down to about 700-800rpm, i see 2*ATDC. - by good i meant that i was within your recommend 0*-7.5* range in this instance. I then pop both hoses back on the distributor and re-engage the idle circuit, (now my memory is fuzzy, i believe it was at about 1000rpm), and I saw 12* ATDC. (this I will confirm and note all RPM's and timings)

while the carbs are off I will reset the throttle plate screws to 1/3 turn after touchdown. I believe i must have been moving the throttle plate which picked up the rpms while sync'ing high speed..

I will verify the seating of the idle cutoffs. I crank on them with my fingers as best i can, i'm an ex-rock climber so i do have a good grip for this sort of thing, they sure seem to come to a firm stop... but this has burned me before (on my last set of carbs) perhaps that little black rubber is keeping them out.... i also don't know the history of these cutoffs. they are 55's though.

My main jets are 137.5's. I was actually hunting for some 140's, but this is all i had. well, i have smaller ones too.

also this pic didnt seem to come up on my last post..I think my photobucket is glitched!?



thanks again, I'll report back in the next day or two when I can tackle this again!

[rustbus]

i likely shouldn't post, I came back more confused than yesterday!

as i walked up to the bus today after work, even with the good breeze today, i smelled gas.

the right carb was dripping fuel steady from that nozzle in the center (not the accel one, but the pot metal one sticking dead center) this fuel was migrating out of the throttle plates and dripping off the manifold studs, and there was a damp spot on the ground. oil level did not appear to have changed much.

another confession - in my paranoia about gas in crankcase, i've used a fuel line clamp on the bus when not in use. yesterday i didn't put it on, thus found this bad needle valve.

so i pulled the carb off and replaced the old solex needle valve with a aftermarket one. seems to work properly now. checked the float bowl level in both carbs, came up with 15-16mm down from top edge. i think i need 14mm here? i believe i have a couple thinner washers....(I have some new solex needles on the way and i will get to 14mm once i have those in hand.)

after that, i reset the throttle stop screws, they were way out to lunch, likely as a result of my recent tune attempts. linkage back on, and the linkage was not affecting the throttle plate position - looked very even side to side to.

reassembled everything and fired it up, in the interest of warming it for timing check.. idled smooth-ish. i tightened the livin bananas out of the idle cutoff jets, but they still have little or no effect when i pull the wire.

found a weird effect when i was checking the accelerator pumps. when i give the right side a little push/pump, the engine nearly stalls. when i give the left side a little push, nearly no effect. i'm going to pull these apart tomorrow hopefully and make sure nothing is wrong in there. makes no sense to me though why that might occur. regardless, i screwed the little brass adjustment nuts all the way in, and that seemed to clear up some of the hesitation when punching the gas.

any chance the accel pump system is messing with me?

now with the float levels under control somewhat, i noticed a more significant change when i pull the plugs on the left side. 4 still only makes it stumble, 3 a little more, 1 is quite noticeable, and pulling #2 still has the strongest effect....but its somewhat comparable now.

i didn't get into double checking the timing,,,,this "NOS" distributor is making a whining noise, which i can change by applying pressure to one side....doesn't sound right to me.

that coupled with the strange behavior had me throw in the towel for the day, a little upset, time for dinner, etc. plus i said i would only be out there a minute and that turned into 2 hours!

tomorrow i will attempt to be more organized in my trouble shooting, but that bad needle valve kinda set the tone for today...

leaky carb pics....

[Amskeptic]

i likely shouldn't post,

Naw, it's OK.

All right, so we got a leaky needle valve out of the picture. However, do not go "bananas" on your adjustments. If you adjust the accelerator pump delivery, you do not want to necessarily go all the way to the end of the adjustment range, you could inadvertently go from rich stumble immediately to lean stumble, and you would not know the difference! We need to try to land within the factory parameters. I think we have a clue here if the cut-offs do not kill the idle . . . you are getting fuel through some other means. Are you carb-cognizant? Familiar with accelerator pump check balls and their reasons? Do you have the accelerator pump injection nozzles both accounted for as you look down the carburetor throats? Float level should be 13mm with tops off.
Where are you located by the way?
Colin

[rustbus]

thanks for the positive-ness Colin, i certainly need it!

I'll watch it on the accel pumps adjustment, i think i can see what you are referring to, as with the brass nut threaded all in the squirt seems to come a little later.....

I do know that the ball checks exist, and my guess at their function is to prevent fuel coming back from the nozzle side to the diaphragm side. the diaphragm pump gives a push, thus pushing the ball up and out of the way, fuel gets around it, and the ball falls back preventing any "leakback" into the diaphragm space...thats my guess. during the clean and rebuild, i was aware of them, i could hear them moving end to end when inverting the carb, and i do believe when spraying in through the top i got no carb cleaner passage (just back into face/eyes), but i did get passage when spraying in from the pump side. best i could determine they worked OK.

Now, thing rolling around in my mind is the little "spacer" thing that went in there (in the accel diaphragm pump zone). i installed them on both carbs, even through in my various carb sets they are present some times and not others. i will post a pic of this little thing when i get home. it appeared its function was to limit the accel. pump volume....? (looks like an aluminum 'plug' that fits into the center of the diaphragm area, friction fit, with notches to get a screwdriver in there to turn it out presumably)

both injector nozzles are present, and I took care to set them in solid. I will pop tops off once the new solex needles show up and reset the level to 13mm down from edge w/tops off (may 3rd?) (i found a nice guy down in the states there that found some old stock and a original rebuild kit complete in original Solex Tin! (will post pics on arrival)

unfortunately, I'm way up in Edmonton Alberta, Canada, that's like what, near 600km/6 hours north of the Montana border! there's a local aircooled club, but they are kinda into CIP as a supplier and default to "just install a single progressive" type solutions....no dual carb experts....I was kinda hoping i could turn myself into the resident PDSIT guy!

again, thanks, I'll post more findings as soon as i can.

[rustbus]

here's some photos of my situation.

here's the little "plug/Spacer" i was talking about - what is its function? the question - do i remove it?



heres the 2 cutoffs,

note that while both SAY 55, the holes on the right hand one look/are much larger. the unit on the right hand in this photo is from the left side (troublemaker) carb. the unit from the right, looks bent at the threads, because it is. i noted that there is a nick on the jet on the end, and this nick grabbed a little pot metal from the carb - i saw the shavings upon removal...could cause leakage past it, but, i wouldnt think it the cause of my trouble.


this last pic is to show its not all bad, since rather than NO engine hatch on my 1972, I have a HUGE engine hatch, so access is good for all this screwin around! now thats a PO hack!

[rustbus]

Ok, i reassembled the accel pump as it was, and warmed it up for a timing verification.

I think i must have pulled the distributor around removing the retard hose, as the idle timing was way out. no biggy, have timing gun

so, at max advance, a steady 28*

remove both hoses, turn off central idle circuit, gave 600rpm, and about 3.5 to 4* ATDC

now idle circuit back on and hoses back on, idle at about 750rpm.....16* ATDC!! vacuum signal from carb is strong, i can feel it with my finger and has a profound affect on idle.

16*..... is this supposed NOS distributor out to lunch? what are the chances?.... i can't see how i can get anywhere close to the spec'd 5* for the 1972 bus....should any allowance be made for this 411 engine? different cam, etc? probably not, i think the Type IV's wanted 5 or 7 BTDC, according to Muirs book...

I stopped here today as i obviously need to sort this timing out. funny thing is, the old distributor read high ATDC as well....closer to like 10* or 12* though....

sorry if this reads like i'm chasing ghosts....its incredible the variables!

[Amskeptic]

Ok, i reassembled the accel pump as it was, and warmed it up for a timing verification.

I think i must have pulled the distributor around removing the retard hose, as the idle timing was way out. no biggy, have timing gun

so, at max advance, a steady 28*

remove both hoses, turn off central idle circuit, gave 600rpm, and about 3.5 to 4* ATDC

now idle circuit back on and hoses back on, idle at about 750rpm.....16* ATDC!! vacuum signal from carb is strong, i can feel it with my finger and has a profound affect on idle.

16*..... is this supposed NOS distributor out to lunch? what are the chances?.... i can't see how i can get anywhere close to the spec'd 5* for the 1972 bus....should any allowance be made for this 411 engine? different cam, etc? probably not, i think the Type IV's wanted 5 or 7 BTDC, according to Muirs book...

I stopped here today as i obviously need to sort this timing out. funny thing is, the old distributor read high ATDC as well....closer to like 10* or 12* though....

sorry if this reads like i'm chasing ghosts....its incredible the variables!

The retard is supposed to yank the timing down from around 7.5*BTDC to either 5*ATDC for the '72 bus, or 10*ATDC for the '73-'74 buses.
To test the distributor, set to 28*BTDC at 3,200 rpm, and keep the hoses off while you let the engine go down to idle without the central idling circuit. Any rpms below 1,000 rpm should see timing between 7.5*BTDC and maybe 2*BTDC. If you have timing below "0" (in the ATDC range), then the distributor centrifugal weights are sloppy.
IF centrifugal advance is OK, but the retard hose goes nuts and yanks the timing down to 16*AFTERTDC, then it may have a bent stop for the vacuum lever. Take vacuum can off and you can see a post and you can see a cutout along the lever. These units have different lengths of cutout to provide different degrees of movement. You might have a damaged post, bent post, or wrong unit.
Colin

[satchmo]

I'll throw in my two cents so this doesn't seem like a private conversation between rustbus and amskeptic.

You never really know if the distributor you have is stock for your bus/engine/carbs unless you were the original owner. This may cause countless headaches as you fiddle with the carb adjustments, the central idle circuit, and proper timing. This page (http://www.oldvolkshome.com/ignition.htm) may help you identify the carb body and the amount of centrifugal advance you should have, but there really isn't any reference that I know of that helps identify how much advance or retard there is on an unknown vacuum can. Even the numbers stamped on the arm of the vacuum can don't seem to be cross-referenced anywhere. I have no idea how VW kept these straight and sorted.

Like amskeptic said, you can extend the amount of advance or retard on the vacuum can by filing the notches/cutouts in the actuation arm. However, that doen't help you much if you don't know where you started.

I would suggest a trial run with the idle around 5-8 degrees BTDC with the hoses off the can and plugged. See how much centrifugal advance you get when the engine is at 3,200 rpm. Write that down. Then attach the hoses. See what the retarded idle reading is and write that down. Then run at 3,200 again and make a note of where the timing is. These numbers should give you a good idea of your distributor's degrees of centrifugal advance, degrees of vacuum advance and degrees of vacuum retard. With that info you can see if you have the distributor your engine is supposed to have by checking the oldvolkshome website.

Tim

[rustbus]

heheh, thanks satchmo for breaking it up in here, before long i'd be driving amskeptic nuts! Thanks Colin!!!

I've viewed my distributor at oldvolks, part number says it is this one: http://www.oldvolkshome.com/ignition.htm#B1972 (both, the NOS one and the one i've been using to date.)

i was out confirming timing already before i read your post satchmo, but i will try that approach as well, perhaps tonight or tomorrow...

but i went out and performed the distributor test just as colin wrote:

over 3200rpm, hoses off, circuit off, set to 28* exact.
let it come down to idle, we're at 2* AFTERTDC, thus "the distributor centrifugal weights are sloppy."
hoses back on, circuit back on, right back up to near 16*ATDC.

SO! - fed up with this "NOS" distributor, i reinstalled the first one.

again, over 3200rpm, hoses off, circuit off, set to 28* exact.
let it come down to idle, we're at 2/3* BeforeTDC. - (not great, but, within the low end of the required 7.5 to 2 range, ya?)
hoses on, circuit back on, idle 700-800, we're pushing 10-11* ATDC - (top end of your required range, right? 12*max?)

given this amount of "pushing the limits" can we still take the next step into the tuneup procedure? or does this need sorting now...? i have one last dizzy, but its from an FI engine and feels a little sloppy-ish, and its single vacuum. oh and theres a 009 kicking around, lightly used

ps - any comment on that weird plug in the accel pump zone? what IS that thing?!

thanks -


Kris

[satchmo]

I think that silver plug in the accel. pump is supposed to be there, so put one in if you have it. I have never seen one of those come in a carb tune up kit, however.

Your original distributor sounds better than the NOS one, as far as being close to spec is concerned, so use it. I think you can set your max advance between 28 and 32 degrees BTDC and it won't cause problems (although you do need to pay attention to the possibility of pre-ignition/pinging when over/near 32 degrees, depending on altitude, etc).

In fact, assuming mid-range values for vacuum advance, vacuum retard, and centrifugal advance as listed on the oldvolkshome chart for the distributor for the 1972 1700cc engine, and a starting point of 5 degrees ATDC at idle (hoses connected), then you get the following:

1) Vacuum retard goes away with initial rpm increase, advancing timing by 13 degrees and putting you at 8 degrees BTDC
2) Add in another 14 degrees as engine speeds up and the centrifugal advance kicks in - now you are at 22 degrees BTDC
3) Finally add in another 10 degrees for vacuum advance at 3000 rpm giving 32 degrees BTDC
4) At 3600 rpm, the oldvolkshome chart says your distributor has from 23-26 degrees of advance, giving a final potential of up to 34 degrees BTDC (assuming you started at 5 degrees ATDC and have a functional vacuum retard).

It doesn't work quite that way in reality, and you really don't want to run at 34 degrees BTDC, but this gives you an idea of what your distributor is designed to do, and approximately where the timing should land with hoses on, hoses off, and during revving. There is some wiggle room around the 28 degree setting for max advance.

Don't use your FI carb here since it doesn't have a retard function and won't work with the central idle system you worked hard to restore. And certainly never use a 009 distributor on any stock VW carb set-up.

Tim

PS: I think I would also replace that bent idle cut-off solenoid too.

[Amskeptic]

I think that silver plug in the accel. pump is supposed to be there, so put one in if you have it. I have never seen one of those come in a carb tune up kit, however.

That is the accelerator pump small end spring seat/guide. It needs to be there.

At 3600 rpm, the oldvolkshome chart says your distributor has from 23-26 degrees of advance, giving a final potential of up to 34 degrees BTDC
you really don't want to run at 34 degrees BTDC, but this gives you an idea of what your distributor is designed to do, and approximately where the timing should land with hoses on, hoses off, and during revving.

That is the beauty of vacuum advance. It "knows" to drop out under load when vacuum drops due to open throttle plate. With a full load floored accelerator pedal at 50 mph in 4th gear, for example, the timing will not exceed the maximum centrifugal (22-28*). When you troll down the street at light throttle or go downhill, closed throttle, the vacuum advance will bring the timing to 32-38* BTDC under light-to-no load as designed.
Colin

[rustbus]

well alright then gentlemen, I'm going to set this thing @ 5*ATDC per oldvolkshome, and let it advance as it sees fit. I'll post the figures here for interests sake. (i suppose these will be max advance with no load figures.)

After that i will undertake the synchronization/tuneup procedure again, and post results.


and find another 55 idle jet that aint bent - i'm pretty sure i have a spare.

cool!