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Timing marks line up with timing scale weirdly on '79 bus
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Happyfolk
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PostPosted: Sun Dec 07, 2014 10:21 pm    Post subject: Reply with quote

I'm fine with 28* for my '79 since that is within Bentley's specs but if I had a '75 I'd have more trouble going with 28* if Bentley says 16-20*.
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Wildthings
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PostPosted: Sun Dec 07, 2014 10:27 pm    Post subject: Reply with quote

Happyfolk wrote:
I'm fine with 28* for my '79 since that is within Bentley's specs but if I had a '75 I'd have more trouble going with 28* if Bentley says 16-20*.


The Bentley doesn't say 16-20 anywhere. Learn how the DVDA distributor works and you will find that except during decel and at base idle the DVDA will have pretty much exactly the same timing as a SVDA.
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Happyfolk
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PostPosted: Sun Dec 07, 2014 10:33 pm    Post subject: Reply with quote

Bentley/oldvolkshome says earlier type 4 engines are 5* ATDC at idle and 21-25* centrifugal advance, so 16-20* max BTDC at higher rpms with hoses off?
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Wildthings
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PostPosted: Sun Dec 07, 2014 10:36 pm    Post subject: Reply with quote

Happyfolk wrote:
Bentley/oldvolkshome says earlier type 4 engines are 5* ATDC at idle and 21-25* centrifugal advance, so 16-20* max BTDC at higher rpms with hoses off?


Feel free to use any timing specs you like, its your engine after all.
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PostPosted: Sun Dec 07, 2014 10:42 pm    Post subject: Reply with quote

You probably have more experience with these engines than I do. I'm just pointing out apparent discrepancies between the Bentley "bible" figures and yours. I'm just trying to discuss the discrepancies.
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PostPosted: Sun Dec 07, 2014 11:23 pm    Post subject: Reply with quote

Happyfolk wrote:
You probably have more experience with these engines than I do. I'm just pointing out apparent discrepancies between the Bentley "bible" figures and yours. I'm just trying to discuss the discrepancies.


There is no discrepancy between myself, the Bentley, and Oldvolkshome, you just need an understanding of how the DVDA distributor works.
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PostPosted: Sun Dec 07, 2014 11:50 pm    Post subject: Timing marks line up with timing scale weirdly on '79 bus Reply with quote

The earlier 5 ATDC&10 ATDC were for emissions purposes with dual carb
engines and air injection & vacuum retard can @ idle on the distributor.
The late type 4 has none of the above,so do avoid 5 ATDC & 10 ATDC
when timing a bus with fuel injection.
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Randy in Maine
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PostPosted: Mon Dec 08, 2014 8:29 am    Post subject: Reply with quote

Happyfolk wrote:
Bentley/oldvolkshome says earlier type 4 engines are 5* ATDC at idle and 21-25* centrifugal advance, so 16-20* max BTDC at higher rpms with hoses off?


Incorrect. Pull those vacuum hoses off the distributor and time them to 30 +/- 2 (and I like 28 BTDC in a bus) when all of the centrifical advance the distribitor has to offer is all in. that wil be about 3500 RPMs or so. Here are the graphs from Ratwell....

Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


so if you set your timing to about 30 BTDC using just the centrifical advance of about 24 once the engine is loafing at idle the initial timing will drop down to about 7.5 BTDC. Once you hook up the vacuum you will also get a little more advance at "high speed low work" conditons and also with the retard hooked up (if you have it) you will have intial timing at the 5-10 ATDC like you are supposed to.
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PostPosted: Mon Dec 08, 2014 8:37 am    Post subject: Reply with quote

Happyfolk, RandyInMaine is right.


The advance figures are added to baseline no hoses no vacuum timing. The 5* ATDC is not a baseline, it is brought there by the retard unit. Once you pull off the retard hose on an engine that is set to 5* ATDC, you'll find baseline timing around 7.5* BTDC.

The important thing here is not to get stuck on numbers! These distributors open up their advance range as they get sloppy. *Adjust* to 28* BTDC at 3,200-3,400 rpm, and watch your baseline idle timing get pushed back towards 0* as the distributor ages. And we say "so what", who cares what the idle timing is as long as we can get a decent idle speed, we're good. On the highway, however, where the engine has to work, we want the timing to be right on.
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Happyfolk
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PostPosted: Mon Dec 08, 2014 9:54 am    Post subject: Reply with quote

OK, makes sense. Thanks for all of your replies! I want to get my timing optimized to make sure it is running as good as possible.

I had an identical bus 25 years ago. Same year, same color. Always wished I never had sold it. We could only afford one car at the time, and living in Wisconsin if I had kept that bus it would be a pile of rust by now. Now I can keep this one in the garage for the winter and enjoy it spring, summer, & fall.

I want to keep this one running good and know how to fix it if needed. Shortly before putting it away I experienced the old loose double-relay ground issue. It died at a couple of stops and then wouldn't start. I happened to wiggle the double relay and then it started right up. When I got home I found that the bolt was loose holding the double-relay and had to put a slightly larger bolt in to get it to tighten properly. Was running great before putting it in the garage.

I start it up every once in a while when it is above freezing and let it run a few minutes. Always puts me in a great mood Laughing
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PostPosted: Mon Dec 08, 2014 1:45 pm    Post subject: Timing SVDA & DVDA Reply with quote

Happyfolk wrote:
Bentley/oldvolkshome says earlier type 4 engines are 5* ATDC at idle and 21-25* centrifugal advance, so 16-20* max BTDC at higher rpms with hoses off?

I see how you are looking at this.
Initial setting 5*ATDC + 21-25*centrifugal = 16-20* max BTDC
Image may have been reduced in size. Click image to view fullscreen.


The Retard and Advance vacuums are having a (tug of war).
At idle the Retard is winning.
Off idle the Advance is winning.

If you open the throttle enough or, disconnect and plug the Retard hose.
The Retard quiets pulling all together.
So the Retard has no effect on Advance with the throttle open.

As suggested if you set the initial timing at 5*atdc.
Pull and plug the Retard hose. The timing would move to about 7.5*btdc.

The total advance with the hoses pulled and plugged would be about the same.

Timing to 28* hoses off at 3400 rpm, is not in the Bentley.
Porsche did have a procedure for setting the timing at full advance.

Make sense?
Tcash
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Randy in Maine
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PostPosted: Mon Dec 08, 2014 2:10 pm    Post subject: Reply with quote

Happyfolk wrote:

I start it up every once in a while when it is above freezing and let it run a few minutes. Always puts me in a great mood Laughing


It would be better to take it out and drive up to the Dells on 94 to get a bratwurst and a Blue Ribbon and then go back home. Sometimes you have to let them ponies run in the winter and a little drive like that will get the engine and oil up to operating temperature and will evaporate any moisture in the oil.

It will be summer any day now. Laughing
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PostPosted: Mon Dec 08, 2014 2:23 pm    Post subject: Reply with quote

Quote:
Bentley ... says


Everyone has given good advice and we all agree on it. I don't know if these 2 cents worth will help any. You seem to have a good grasp and attitude on it. And you are also a prior bus owner so you are aware of the weak spots on these buses.

the moment the spark is applied to the mixture has to increase with RPM for several reasons. They are a combination of the time it takes the gasoline and air to burn, and the time it takes for the coil to discharge its spark.

The auto industry used two mechanisms at the time our buses were built. They were an automatic mechanical advance, and a vacuum driven advance.

In trying to control smog emission it was discovered that at idle a late ATDC spark lowered some emissions. So, some cars had (1) an automatic mechanical timing advance (2) an automatic vacuum timing advance (3) an automatic vacuum timing retard.

Generally the timing retard only works at idle - it is overcome with the vacuum advance and mechanical advance. The mechanical advance comes in based on RPM starting around 1000 - 1100 RPM and usually peaks around 3500 RPM+/-. The vacuum advance starts when the throttle is opened and follows the vacuum signal from a port built in just a little distance towards the air cleaner side of the throttle plate.

The equipment needed to calibrate the mechanical or vacuum advance and retard are hard to find these days. The only one here who has a Sun tester is Glenn, and he doesn't work on aluminum body distributors as they are fragile and parts are not available. Bosch built them as throw away.

After all the years and all the discussions, add in the wear on the distributors, changes in gasoline formulations etc, the general consensus is to set the distributor with the hoses off, preferably plugged, at 3500 +/- RPM when the timing stops moving. The range 28 degrees to 30 degrees BTDC seems to run the coolest. While you can get more power at say 32 degrees BTDC, you also get more heat and right now heat seems to be the main enemy of these motors. We can no longer walk into a Foreign Car Parts, or Volkswagen Dealer and ask for a new set of factory heads. Repops only are available and expensive. Even piston sets and bearings are getting scarce. If you take the car to be smogged in California (1976 & later) you will want everything working and the timing set to factory specs. If you want your bus engine to run as cool as possible set the timing to 28 to 30 BTDC. FYI - this discussion occurs about 20 times a week around here and any old timer will usually offer the suggestion once and then leave the new owner to "well if he/she wants to do it another way it is their privilege." Getting both power and longevity from a VW engine does require skill. While we usually follow Bentley in all manners, jetting and timing we have our own set of standards learned along the way. Bentley will get you perfectly tuned by factory standards for the fuels that were available when these buses were new, and the parts unworn.
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Pointers on rebuilding an engine:
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Setting Engine Timing: http://kentcomputer.com/77VW/Timing.pdf
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PostPosted: Mon Dec 08, 2014 2:32 pm    Post subject: Reply with quote

Randy in Maine wrote:
Happyfolk wrote:

I start it up every once in a while when it is above freezing and let it run a few minutes. Always puts me in a great mood Laughing


It would be better to take it out and drive up to the Dells on 94 to get a bratwurst and a Blue Ribbon and then go back home. Sometimes you have to let them ponies run in the winter and a little drive like that will get the engine and oil up to operating temperature and will evaporate any moisture in the oil.

It will be summer any day now. Laughing


The Dells is a ghost town this time of year. The bus is from Arizona and doesn't know what to think of the snow. It's made it this long without any rot I just can't expose it to the salt. Hopefully we get a good mid-winter downpour to rinse off the roads so I can take it out on a brat run! It's supposed to be near 50 here later this week. Very Happy
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PostPosted: Mon Dec 08, 2014 3:07 pm    Post subject: Reply with quote

Happyfolk wrote:
Randy in Maine wrote:
Happyfolk wrote:

I start it up every once in a while when it is above freezing and let it run a few minutes. Always puts me in a great mood Laughing


It would be better to take it out and drive up to the Dells on 94 to get a bratwurst and a Blue Ribbon and then go back home. Sometimes you have to let them ponies run in the winter and a little drive like that will get the engine and oil up to operating temperature and will evaporate any moisture in the oil.

It will be summer any day now. Laughing


The Dells is a ghost town this time of year. The bus is from Arizona and doesn't know what to think of the snow. It's made it this long without any rot I just can't expose it to the salt. Hopefully we get a good mid-winter downpour to rinse off the roads so I can take it out on a brat run! It's supposed to be near 50 here later this week. Very Happy

Then in the meantime stop running it while it's stored, you are doing it more harm than good.
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PostPosted: Mon Dec 08, 2014 4:38 pm    Post subject: Reply with quote

I agree.

Just fill it up with "stabilized gas" and park it out of the way until spring.

Another option would be to find a reason to be in Key West for the rest of the winter.
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PostPosted: Mon Dec 08, 2014 9:20 pm    Post subject: Reply with quote

Duly noted. I'll refrain from starting 'er up until I can go on a full-fledged brat run and get it up to operating temperature.

I had this bus 3 months before the first snow and two of those months it was in the body shop. I've waited this long and can wait some more. I'm getting older so the months are passing faster all the time. Spring will be here soon enough.

I swear though, just the sound of a VW air cooled engine puts me in a good mood no matter the circumstances. I got behind an old bug on the way to work a while back and rolled the windows down even though it was only about ten degrees outside so I could hear that engine. He had a white Great Dane in the back seat! Great start to the work day!
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PostPosted: Mon Dec 08, 2014 9:56 pm    Post subject: Reply with quote

Happyfolk wrote:
I swear though, just the sound of a VW air cooled engine puts me in a good mood no matter the circumstances.

The sound of that first awakening in the spring is even sweeter, go sit in the bus and fiddle with other things like that sketchy rear dome light, intermittant side marker or squeaky clutch pedal and save the big action for springtime, the wait makes it even better Very Happy
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PostPosted: Mon Dec 08, 2014 10:12 pm    Post subject: Reply with quote

busdaddy wrote:
Happyfolk wrote:
I swear though, just the sound of a VW air cooled engine puts me in a good mood no matter the circumstances.

The sound of that first awakening in the spring is even sweeter, go sit in the bus and fiddle with other things like that sketchy rear dome light, intermittant side marker or squeaky clutch pedal and save the big action for springtime, the wait makes it even better Very Happy

I've got a new turn signal switch to install and a backup light switch. The gas pedal is rubbing/sticking slightly on something inside the front skid shield. True, there's always something to fix. Spring will come quick.
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PostPosted: Tue Dec 09, 2014 7:59 am    Post subject: Reply with quote

The gas pedal is rubbing/sticking slightly
http://www.buttysbits.com/throttle-kits.html
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