I had a data page with the directions on how the vacuum advance can is adjusted on the distributor, and it walked off on me (or my Chevy loving neighbor took it...)....

Can anyone confirm:

1/2 turn clockwise with 3/32" wrench = 2-3 degrees retard from current can setting

1/2 turn counter clockwise = 2-3 degrees advance




thanks, need to dial out a couple degrees at light throttle cruise...mechanical advance is fine (and veeeeryyyy fun when the vacuum advance is disconnected...but gas mileage isn't so hot...)

-D.Idiot

I think that (if you're referring to the vacum pod on the dist, I've learned the hard way that translations ain't that easy ) counterclockwise hardens the spring so that would retard that. At least on my distributer

take care!

_________________
Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

These instructions may help:
http://www.dutra.org/doug/draft-webpage ... ibutor.htm

My understanding of the vacuum advance pod is that the total amount of advance it provides is set by the length of the notches on the arm of the unit and the adjustment srcew will adjust the rate on which the advance "pulls-in" (In terms of Hg)

The amount of advance any vacuum pod gives is usually stamped on the arm of the pod. (the number shown is in cam degrees so double it for advance at the crank)
http://www.slantsix.org/articles/leanbu ... ce-pod.jpg
You can see the numbers on a couplwe of the pod arms shown, one is a "6.5X" (13 degrees) the other is an "11.0X" (22 degrees) You can not see the notch in this photo but it is on the wider section of the arm, right where it goes into the housing.

If you need less vacuum advance it is best to find a lower rated pod but I have been know to wrap a thin wire into the arm notch (or some epoxy)or bend-up one side of the pod housing ("tin can") wall where the notches bottom-out, in order to reduce the arm travel and the total amount of VA the pod will produce.
DD

I kind of thought so. I'll be pulling the dist this weekend and I have an 8.5 can to replace the 10 on the dizzy now...worst case scenario says I go to the 6.5 I have... I may have to order one that 'comes in' at a certain Hg range since light accelreation where the ping occurs happens about 14" Hg.... Full throttle is a no ping problem, but I must have some minor detonation since it lacks the power at WOT unlike running just the mechanical advance .....

-D.Idiot

p.s. currently getting 16mpg mixed driving (70% highway, 30% city and idling...), and long haul, all highway is 22 mpg (up from 19- 20.5)...not too bad for a Holley 600 cfm...

DI,

The vac advance does not function at WOT unless something is wrong. When you open the throttle, there is very little vac in the manifold, so the pod does not advance timing. It only works during part throttle cruise.

Do you know what your total (initial + mech) advance is? It should never be over 30 on a 225. You can lose mucho power with it advanced more than that.

If you adjust the pod to let off at a higher vacuum reading, that should take care of your ping, although 14" is pretty darn high... Replacing as you suggest may be better.

Lou

_________________
Home of Slant6-powered fun machines since 1988

Curve fell out and who was left....

Thanks Lou... things keep getting 'wierder' as I get deeper in the rabbit hole...

I'm now running another modified distributor after today:

I have found that my 'stock' OEM R9 will allow 22 degrees of advance at the crank...my last timing was set at 14 BTDC, and on the 'way' up the vacuum gauge to WOT the vac. adv. pod wouldn't cut out until 8" HG....

so 36 degrees = PING....


I fixed the part throttle problem by swapping in a new 8.5X vac. pod and adjusting it...only to have a brand new rotor fly apart in the dizzy @ 3000 rpm going up a hill (Doc's seen the Kuebler Street exit/ hill...it makes for a good ping test)....

I now am running the R9 (22 deg. adv, mech), 10 initial for 32 deg. all in by 2300. It runs great with no vacuum advance (I probably will drag race with the vac. pod disconnected at this rate...).

I then found the new pod I bought from Napa (Echlin brand) is very adjustable, but... the 'arm' is 1/8" to long, so when it's installed it 'tweaks' the advance plate enough to run my engine with some nice retarded figures (right off the bat, with no vacuum I lost all my initial and mechanical advance at idle and was stacked at 2ATDC @1000 rpm....)...

pulled that pod and took another 8.5X off a V-8 distributor and it gets the 17 deg. advance with no problems, but it doesn't let go soon enough (at 8"HG I'm still hauling down 14 degrees of vac. advance I don't need....)...

So I'm hoping to adjust that, or I may try a 6.5X I have laying on the bench)... I just need no more than 18 deg. vac. adv. that 'cuts out' around 12" Hg....

The other good news is that with hte 10BTDC, and finding the newer curve, I'm now idling happily with a Hpak at 900 rpm, pulling a steady 25" Hg.....

Just gotta get the 'economy' side of the curve dialed in....


thanks for the input,

-D.Idiot

DI, with all the hoops your jumping through to get this straight you may want to look into computer controlled ignition... on the megasquirt site I saw setups for stock distributor and DIS w/coilpacks even.

With one of the projects (megajolt light junior I believe) you could set spark advance in a table of RPM vs vac.

I already have that for the next motor... it will solve much with EFI, but is not effective with the broad range of weather changes we have here in Oregon, I already have even looked over Electromotive's line up and they are literally the 'Best' for DIS setups.

After a good talk today with a nice CNC contact, he commented on why 90% of the slant six crowd can't 'pony up' for good upgrades that are worth the money in performance...my only rebuttal was most of us are 'economical' otherwise we'd have swapped in a V-8 with a Rance EFI package by now...

Currently I'm only out 6 hours of trial and error on what the short overlap Hpak likes over say, a few weekends of trying to mate the crank trigger up to the harmonic balancer, checking for proper phasing, making sure the lines are sheilded from cross talk, then working with a minimal option computer that may need constant tuning anyway....

If my contact was true to his word, I should be able to get my pistons worked over and Reed's contribution ready for the long rod mill I have in mind... this will take a long bit of R&D also, but should prove the limits of the street trim long rod....

The object of the project is to make sure those who will make the next step have a better understanding of their project, and not make the same mistakes I made during my learning curve.... (that very well might be the very heart of the philosophy of 'education')....


tomorrow, I'll make a couple of minor changes, make sure I have a tank full of super, and 'get the knock out'....


10,32,49... hike..... 10, 32, 45.... punt...

-D.Idiot

You don't need a crank trigger you can use a locked out distributor with the EI magnetic pickups. You can even tweak the pulse count by altering the teeth on the ... err, sorry, proper terminology escapes my mind atm but I think its called reluctor? The steel wheel in distro with the 6 bumps on it.

And if your worried about the system being temp sensitive, well, so is the stock system your working on....


But I see where your coming from, you already have this much time vested into it so you may as well go full bore.

All I can say is good luck! The most I ever did with distributor recurving was use two light EI distro. springs and a 6.5x (I think) pod.

DI,

I've done a fair amount of this dist tweaking to get things right. It is worth the time for a street/strip car.

I would advise welding up the slots a little to get no more than 20 deg between initial and final mech advance. My '68 is at about 15 deg. This should allow a larger vac adv number, better idle, and best power.

Lou

_________________
Home of Slant6-powered fun machines since 1988

Pierre gets a cookie for using the magic word 'Reluctor'....

I'm almost there, it won't be long... Lou just tipped my next question to him, I was thinking about welding up a couple of governors for a very short throw, to jive with the longer vaccuum can, and more initial (would like to go back to 12-14 degrees....it reallllly liked that, and idle was much smoother....).

Time to whip up a 7R governor or close there abouts....

let you know in a couple of hours...thanks again!

-D.Idiot

The 3/32" allen key is my real buddy....

I have it set for 10BTDC, 22 mech... and it runs great at all ranges W/O the vac. can attached.

I adjusted the 8.5X can and it's now setup that I have vac advance from 22"Hg to 15"Hg (15" is about the top end of cruise, going up a hill, and getting ready to give it more than 1/2 the pedal...)....

Now I have to readjust the carb, since it loved the 14BTDC advance I had before, idle is a bit lumpy now, and it's slightly rich...time to put the allen key away and get a screwdriver....

While on my test drive I stopped by my buddy's place and dropped off a handful for governors for him to weld up, and told him to make this batch with smaller slots... so hopefully by next week I can run 14 BTDC again, 16 mech adv, and the 22 deg vac. can.....

thanks again,

-D.Idiot



10, 22, 17.....or... 14, 16, 22 ...