Itinerant Air-Cooled

Posted: **Sun Jan 05, 2014 2:44 pm**

Have a fairly stable performance base.
AFC FI, 8.6:1 compression:backdated exh:2 1/4 collector/magniflow.AAR plugged.
gauges Cht/Oil#+°/auto trans.15mpg+-
Keep on having a surging/miss/wonky advance along with good power. Good starting.
Going to check grounds, but question really is there another way to set advance? Like full advance in powerband? My idle is wonky, maniflod pressure low at low idle...so setting per bently seems to not be so great. (5°atdc everything connected).
Tried valves a little loose in search of more manifold vac.but now am back to zero lash cold per Raby, after reading of intake and exhaust timing ills with valve train movement loss of even 1.5mm

Posted: **Sun Jan 05, 2014 4:19 pm**

Classic Raby engine behavior that can be successfully mitigated.

Performance cams have so much overlap that your idle vacuum will be lower than the fuel injection likes.
Loping idle, lousy cold behavior, comes with the territory.
It is a deadly blow to disconnect the auxiliary air regulator. It needs not only to be hooked up, but jacked up for as much air flow as possible.

Do NOT ever time an SVDA to 5* ATDC. That specification is only for a certifiably functional vacuum retard unit that came with the original DVDA distributor. Set the timing at 3,400 rpm (no hoses on the distributor) to 28* BTDC, and see if your idle timing is now around 3-10*BTDC at an idle close to but not exceeding, 1,000 rpm.

Rehook up the vacuum advance hose. Blip the throttle repeatedly around 2,500-3,500 rpm and check that timing reaches at least 38* and preferably 40* BTDC. If you have a tee coming off the vacuum advance hose to the EEC valve on the air filter box, you must check that the EEC valve vacuum nipple holds a vacuum. If no, block the hose off so you can enjoy your vacuum advance.
Colin

Posted: **Mon Jan 06, 2014 6:11 pm**

thats huge, an assemblage of afew suspicions&ignorances!cam overlap/low manifold #s, OK!!thanks colin I will rest easier.

switched paradigms today and test drove with advance thrown in, so it ran and idled, no light..most surging /flatspot gone.
>>> My dist has fat AND thin vac lines, might have misreported SVDA... if it is DVDA as its stock,1975, one vac port on each side of can. Fatter, pulling, in max advance
direction. >>>does that change advance phasing for me?
Anywhoo it looks like its better already.
AAR valve can just be tweaked open?(no?)
or should it be opening in its thermal way? My FLAPS buddy suggested junkyard mitsubishi or other jap aars for some dependability? I looked at mine, but I forget its fault. No, I tried, and will help effort this Default air gate.
EEC valve, im just drawing a blank, will look up after I hit send..
thanks again for your help and knowledge!

Posted: **Mon Jan 06, 2014 10:10 pm**

Boxcar wrote: DVDA stock 1975,
AAR valve can just be tweaked open?
EEC valve, im just drawing a blank,

Stock DVDA small 4mm nipple pointing upwards is advance
larger 5mm nipple facing sideways near clip is retard (was)
Time with strobe light to 28*@ 3,400 rpm no fooling around. This is not a "by ear" engine.
AAR must be allowed to function or you will suffer a fast idle when warm.
Oops, you don't have an EEC valve, sorry.
Buy a '78 or later bus if you just have to have one . . .

Posted: **Tue Jan 07, 2014 5:46 am**

colin thanks for a quick reply!
no fooling around not a by ear engine, aye aye. had beetles and I thought I could I think. many moons ago.
WithBus l am by the Bently!
tho with the dvda& that THWARTING 5°atdc@950rpm spec I >>might have been. that is why I tried adhoc, while simultaneously rembering your specific mission, and itinerant air-cooled website two nights ago.
>>> recap 28°@3400rpm disconnected?then connect &confirm38/40°while blipping to 2500/3500rpm, correct sir?

My AAR shall function,do you go for full function?I read of your using the term jacking, yes?
"EEC"

well im saved from that for awhile.thanks//Eric

Posted: **Tue Jan 07, 2014 8:05 am**

Boxcar wrote:Bently!

B-e-n-t-l-e-y , for the record . . .

Boxcar wrote: 28°@3400rpm disconnected? then connect & confirm 38/40°while blipping to 2500/3500rpm, correct sir?

I do not restate, I invite you to re-read . . .

Boxcar wrote: My AAR shall function, do you go for full function? I read of your using the term jacking, yes?

Yes, we want a fully functional AAR that has been adjusted to maximum opening when cold.
ColinCold?YaWantCold?WeGOTCOLD

Posted: **Tue Jan 07, 2014 9:42 am**

Bentley. Bentley
Bentley. mille grazzi.
Yup cold, air at its combustable densist.
Didnt mean to coax needless repeat, but only to make sure DVDA timing drill was same as SVDA.
thanks! I will do.

Posted: **Sat Jan 11, 2014 11:13 am**

popped a Nissan AAR valve in.
Instant satisfaction.

Electrical conn.prongs on esteemed jap part
is same as german part.,BUT everything else about the connector and fastening are different.
So far ambient heat is closing the new AAR. Meanwhile I reluctantly bodge the new part to accept Bosch clipon female connector.
Something like progress.

Posted: **Sat Jan 11, 2014 12:06 pm**

Boxcar wrote:popped a Nissan AAR valve in.
Instant satisfaction.

Do tell. (and maybe show...)

I have been struggling with a performance cam for a few years. Idle is a bear. 'specially at elevations when cold. I always keep an ear open for things that can ease the pain. She loves the open road though.

I have found success w/:
Time at high rpm, no vac leaks, and (this may be controversial to some) set idle a bit above spec.

Posted: **Sat Jan 11, 2014 3:48 pm**

The Idle air (AAR ) gets a extra path to pull on the Air Flow sensing Vane.

In my case, I had a very low lopy idle.(review post?)typical so they say.
This helps, tho idle still low.

It is a big detail. Bosch AARs did not last. If you have one in place, as I did,chances are it is just taking up space, &or. creating vacuum leaks too. How is your idle manifold vac?
Devil of a location. To go in ? Without a fresh one?btdt. So My Nissan spare came from Ebay, out of Texas. 53$
Not perfect (connector nearly incompatable)but it opens when cold and closed on my stove w/o 12v.

I replumbed a "home run"to the S boot w FRESH 12mm braided vac hose, and those good bluecap non hose munching clamps.
After efforting the 12 v connection, I felt idle was not boosting as much as @first. Things did get warmer will drive some and withold conclusions till then.
Thats what I know.
Have to figure how to send low kb images, sorry for text only post

Posted: **Mon Jan 13, 2014 10:26 am**

Some drives in now. AAR from Nissan is deemed good.

Still have to do tach it up tuning. (my diagnostic meter (older common Sears)goes to 2K rpm only.

Cabin tach needs second body to do timing per spec.

Calling it a done deal now though. My problem was lack of info. Colin cleared it up.

Posted: **Wed Mar 01, 2017 4:09 pm**

So when I put the timing light on the engine I get erratic strobes...I mean like the distributor is throwing darts at target spark degrees.

This is with the DVDA,stock,OG distributor.
(Pertronix magnetic trigger installed.)

I never~ok maybe once,a few times,lubed the advance plate,or things in there.

Is that SVDA with Pertronix trigger from Bus Depot,PA. a possible replacement?

Sorry if this post regards the DVDA-SVDA switch exists otherwheres.
Eric

Posted: **Thu Mar 02, 2017 1:37 pm**

Amskeptic wrote: ↑
Sun Jan 05, 2014 4:19 pm
Classic Raby engine behavior that can be successfully mitigated.

Performance cams have so much overlap that your idle vacuum will be lower than the fuel injection likes.
Loping idle, lousy cold behavior, comes with the territory.
It is a deadly blow to disconnect the auxiliary air regulator. It needs not only to be hooked up, but jacked up for as much air flow as possible.

Do NOT ever time an SVDA to 5* ATDC. That specification is only for a certifiably functional vacuum retard unit that came with the original DVDA distributor. Set the timing at 3,400 rpm (no hoses on the distributor) to 28* BTDC, and see if your idle timing is now around 3-10*BTDC at an idle close to but not exceeding, 1,000 rpm.

Rehook up the vacuum advance hose. Blip the throttle repeatedly around 2,500-3,500 rpm and check that timing reaches at least 38* and preferably 40* BTDC. If you have a tee coming off the vacuum advance hose to the EEC valve on the air filter box, you must check that the EEC valve vacuum nipple holds a vacuum. If no, block the hose off so you can enjoy your vacuum advance.
Colin

It looks like the superseded timing regimin on the SVDA is tacit approval of the SVDA as a stand in for the OG DVDA.
Yes,the performance probs,or scatter of spark timing evidences when it's COLD out. But is it the 9550 cam overlap upsetting vacuum /advance curve applecart that DVDA distributor was designed for?
In far fewer words it is not a Worn distributor causing the spark scatter?
THANKS,just had a nice drive from NJ to Lower VT,even with this condition. As once oil,and heads are fully warm,bus runs well.
Even fueled with some Ethanol Free 93 up there...The 75 Westy ran like it had half an extra cylinder.

Posted: **Mon Mar 06, 2017 12:43 pm**

Boxcar wrote: ↑
Thu Mar 02, 2017 1:37 pm

It looks like the superseded timing regimen on the SVDA is tacit approval of the SVDA as a stand in for the OG DVDA.

is it not a worn distributor causing the spark scatter?

No tacit approval, just dealing with it. I mentioned DVDA idle timing tip for those who have it and need it as an intrinsic and necessary part of their engine's equipment. Do not time to 5*ATDC if you do not have a DVDA or if your DVDA retard unit is leaking. That is just a stand-alone fact.

NOW THEN, scatter is NOT necessarily caused by a worn distributor, in fact, it is unlikely.
It is caused by crankshaft float that spools the distributor drive gear back and forth as the brass gear pushes the teeth forward and backwards. Raby engines start their lives with .006" end play. That means you can WATCH the rotor in the distributor go back and forth as you push/pull the fan. Now imagine that motion at 3,400 rpm.
Colin

(got rid of that trashy emoji, this is not E! magazine trying to amuse preteen readers)

Posted: **Mon Mar 06, 2017 5:18 pm**

Endplay, was my job.

Was in spec. But! Worthy of looking at again.

Always happy to learn that new parts are not always the answer.RE:Bus Depot SVDA replacement for DVDA.

....That this evidences more when it's donkey freezing cold out,is just the effects of COLD on a similar condition?
perhaps then...
Its just not as noticible when amenable temps foster easier combusting,and don't signal the need to break the timing light out?

Will look.

Am eager to get back on the road!!

Thanks Colin,
//Eric

Itinerant Air-Cooled

Timing/advance 1.8 camper special, pertronix/orig DVDA

Timing/advance 1.8 camper special, pertronix/orig DVDA

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig svda

Re: Timing/advance 1.8 camper special, pertronix/orig DVDA