[David Ray]

SoCal, if you would, please continue with your tests and results, and put together a page (or, however needed) to add to my vacuum advance stop info packet. It is up to you, but it would be welcome, and credit would go to you, sir.

As far as GM performance crate engines go, the 69120 vacuum advance that comes with them works, except it needs the Crane stand alone stop plate, 99619-1, mounted as I outline. The ONLY changes I do to them is to speed up the mechanical advance, because it is way too slow because of ported vacuum used on those engines from disaster dyno setup and tuning, and the vacuum advance needs the stop to add 8 to 10 degrees of full manifold vacuum advance added to the idle initial timing.

Case in point: ZZ4, same 69120 vacuum advance, add stop and use 8 to 10 added degrees to the GMPP stock 11/12 INITIAL, for 20/22 IDLE timing degrees on full manifold vacuum, then, change ONE of the mechanical advance springs to attain the curve start at 850/900 rpms, limit to 2,900/3,000 rpms.

Crane series 99600-1 HEI adjustable vacuum advance option for the ZZ4, yes, it is an A series vacuum advance, add the stop as outlined in my packet, change the mechanical springs, time as noted, vacuum hose to full manifold vacuum souring, done.

A word about all the "Large HEi curve kits" available, they are NOT for street use, they are for DRAG RACING only, they change the amount of mechanical degrees available, because they also render the vacuum advane moot,and jack the initial advance to the moon, which is for very late intake valve closing camshafts, NOT fo street use. The aprings in the kits are about the ONLY useful items, the weights andcenter are useless for the most part. Unless you are running a Top Fueler/Funny Car on the street, the curve kit weights, and center are totally useless.

GMPP got the basics right, they just did the wrong thing in final tuning, they did it on a dyno, NOT by the best option, the "Sea of the Pants" dyno.

 

[SoCal805]

SoCal, if you would, please continue with your tests and results, and put together a page (or, however needed) to add to my vacuum advance stop info packet. It is up to you, but it would be welcome, and credit would go to you, sir.

I will document what I have done but my current set up is what I posted in #18 of this thread. I want to get multi use miles/driving conditions before making any changes which could be idle RPM, Idle fuel mixture, timing, carb metering rods and or jets, VA vacuum adjustments and finally the plate notch position if necessary

A benefit I discovered on the bench before installing was using my mighty vac on the Crane VA to not only watch how much vacuum it takes to initially start the VA rod to move but more importantly how much is applied to reach full travel at a particular detent position on the plate with different amount of turns out on the adjustable VA alan screw. I found that 1 1/4 turn out from full close got me 11.5" and 2 turns out got me 12.5". Given I just wanted 12 degrees of VA I set the initial detent on the 5th one. Its the VA vacuum # = x 2 degree marking on the damper so 11.5 x 2=23 degrees of actual timing so I wanted about 12 so used the 5th detent as my "base" setting. I didn't know if the actual results would = what math generated by testing various vacuum applied to VA can but they proved to be very close to actual results of timing read by my timing light

I can access the 8-32 hex head for the plate by just removing the cap with a socket drive from up top. You can use a Mighty Vac to apply vacuum to the VA can if you need to advance the plate if needed to access the 2 screws that hold VA can on

I left the stock springs in as I did not want to pile on those adjustments on top of the plate and VA adjustments. If I feel mechanical needs to come in any sooner than it currently does that is a simple access of pulling cap & rotor with dizzy installed in motor. I would just swap 1 stock spring to 1 of the stiffest springs that come in the crane kit and go from there if needed. Unfortunately the colors of the springs in the kit do not match the colors/firmness published in Crane 411 so its the "tug & feel" method to see which color is stiffer/softer. I also find "dizzy spring kits" are softer springs and are typically used for full WOT use conditions so caution should be taken when using these on street motors with VA, just my $.02

I have 2 modified motor cars. One carb the other a computer car. The later is all tuned via laptop and aftermarket software by a qualified tuner, Ed Wright, as that skill set and hardware is above my pay scale. Carbureted motors I can deal with and my Camaro crate motor, Blueprint 355, is calling for "not out of the box" adjustments. Part of the game but doable and satisfying when things run as they should

 

[David Ray]

I hadn't gone into using a device off engine, all my distributor machines have vacuum apparatii to test advances, but I never considered using a Mity-Vac, which is an excellent idea. This is why, when you get through with it all, finalize it, make it into a tech paper, and let me post it on the packet.

It should be another addition to help those get it done right, on, and off engine, and there ain't nothin' wrong with that, at all.

 

[NashvilleCat]

Hi Dave,
These specs are for a big block Chevelle. The LS will be on a computer.
I was planning on a limiter plate like you recommend. I want to be able to play with it and try settings from 10" to 14".
Cam in the Chevelle is 224/234 in a 489 with 10-1 comp.

 

[David Ray]

Yes, EFI computers with timing functions inside them do not use a mechanical/vacuum advance distributor, they are "locked out" for those uses. Those EFI timing parameters also have a vacuum advance section, along with other timing settings.

224/234 at .050, I am thinking, which is not the right settng for figuring timntg and DCR. What is the overall duration, and the intake valve closing degrees, please???

 

[David Ray]

I just came from a topic in the electrical section about wiring up a useless CS series alternator, OP and dhutton told me in no uncertain terms I was a dumb idiot, didn't know what I was doing, and a rave'r, so, I will now take action to stop posting here, so I don't "offend" all those Know It All's.

My sin, it seems, was outlining that all my Astro/Safari vans came with CS alternators, and ALL of them were internally connected, only ONE large positive battery cable out of the alternator, no other connections. I guess that was just not what they felt was useful. So, I'm done here, no more getting attacked for saying it like it is, let the Know It All's have it their way. I am tired of going to war just to defend the right answers given to those that want and need them.

One other thing was that I add my answers in Bold Text, it seems that is some sort of act of disrespect. All along, I have felt it was so I can see the text I am adding better than the not bold text, yet another act of my being some sort of Rave'r, it seems, I don't really know.

So Cal, if you still want to add your findings to the vacuum advance packet, they, and you, are welcome to do so, sir. .

 

[scblucam]

I just came from a topic in the electrical section about wiring up a useless CS series alternator, OP and dhutton told me in no uncertain terms I was a dumb idiot, didn't know what I was doing, and a rave'r, so, I will now take action to stop posting here, so I don't "offend" all those Know It All's.

My sin, it seems, was outlining that all my Astro/Safari vans came with CS alternators, and ALL of them were internally connected, only ONE large positive battery cable out of the alternator, no other connections. I guess that was just not what they felt was useful. So, I'm done here, no more getting attacked for saying it like it is, let the Know It All's have it their way. I am tired of going to war just to defend the right answers given to those that want and need them.

One other thing was that I add my answers in Bold Text, it seems that is some sort of act of disrespect. All along, I have felt it was so I can see the text I am adding better than the not bold text, yet another act of my being some sort of Rave'r, it seems, I don't really know.

So Cal, if you still want to add your findings to the vacuum advance packet, they, and you, are welcome to do so, sir. .

Don't go away Dave, you have too much knowledge. I actually like the bolder font so I can it.

 

[SoCal805]

Put a few hundred more miles on the motor. Opened up the adjustable VA another 1/2 turn to see if there was any difference and had to much idle timing so back it down 1/4 turn which kept the timing at 23 a idle and was also able to lower idle RPM some. I have 1 1/2 turn out on the VA for my set-up now.

Drivability is significantly better at idle and part throttle and I gained 4.24 mpg with the VA hooked up. MPG went from 10.2 to 14.5 mpg. Part throttle fuel combustion is better with more advance than it had without VA.

With the carb metering spring adjustment (went to lighter 3"hg vs stock 4"hg spring) and the Crane VA limiter plate pulling 10 degrees and timing/idle RPM and idle fuel mix adjustments the motor is just purring....YMMV