My combo is in signature. I currently have an MSD vacuum advance distributor that says it adds 10* at 15 lbs of vacuum. I have had some funky idle/vacuum issues (wandering idle 200+rpms and problems with low vacuum readings). Currently my cam gets 13-14* at 800 rpms. I'm thinking that because its so close to where the can opens(and I had an MSD tech say their numbers are just "approximate"), I'm thinking the vacuum advance was flutering in and out on occasion.

I ordered the Crane adjustable vacuum advance can, but in their directions there are no mention of actual numbers. Alls they say is "turn clockwise initially and back off until no knock is heard." There is no mention of degrees or anything. Well how does this thing work? Where should I set it and how on my combo? I'm uncertain on when the vacuum can adds timing...is it under or over the set vacuum? If anyone could help me setting this thing up it would be appreciated. Thanks!

Nick

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81 Z-28 355 Home Ported World S/R Heads(1.94/1.5) XS268 solid cam (230/236@.050, .477/.488 Net Lift), 650@ DP, Tremec TKO 5-speed, 3.42s, Nitto Drag Radials. 13.4@102.9 w/ 1.95 60ft time.

Hi Nick,Firstlyy,please forgive me for asking but have you got your vac take of for the vac advance in the right place,it should come out the side of the primary metering block of the holley carb.The vacum advance should not be operative until you are up of idle speed.The best way to check how much vac advance your putting into your engine is to have a timing light set up ready.wind your idle screw in until your engine at about 1500rpms.Disconnect your vac line from the vac advance(do this at the holley metering block where it should be fed from),then take note of your timing,then put the vac tube from the vac advance in your mouth and suck for all your worth if you make a note of the timing you will see how much it has advanced.I found my engine could tolerate no more than about 8 deg.So you can then adjust the canister to give you your required amount of advance by keep sucking and adjusting the allen key in the canister.Hope this was of help to you Mark.

Not to start a manifold v. ported debate, but I have mine on manifold and thats where i like it.

From what i gather about the crane unit, turning the screw with the allen key does not adjust how much vacuum advance, just the rate at which it comes in, correct? So if I turn it all the way clockwise, it will put all the vacuum advance in at a very low vacuum reading, right? But how do you know at what vaccum reading it will put all the vacuum in?

And does anyone know how much total vacuum advance this canister gives when it is fully actavated? It doesn't say that either anywhere in the directions.

You're running the vacuum advance off a full manifold vacuum port now and it's a few inches of vacuum shy of pulling it "all in?" Yeah, that'll play havoc with the idle, especially in gear. You'll get a "rolling" idle up and down.

You can do like Toecutter says and hook it up to an off-idle port if you can live with the lower idle quality you'll get from the lack of advance and, frankly, that might be your best bet.

BUT..... since you already have the Crane unit you might as well give it a shot. There are 2 adjustments:

1. The vacuum advance RATE: how much vacuum it takes to bring all the vacuum advance in. You should try somewhere around 0-4 turns out (remember you turn it all the way CLOCKWISE until it stops and then CCW the number of turns you want). 0 turns is about 8-9" to bring it all in, 4 turns is about 11-12".

2. Vacuum advance AMOUNT. That's done with the little lockout cam supplied with the canister (little black metal flat thing with a hole in it and little "teeth" along one side). You mount it using the screw on the end of the vacuum advance arm that holds the end of the canister arm to the distributor body. Just take out the screw, drop the plate on top (in the proper orientation- teeth pointing towards the mag pickup) and put the screw back in. It roatates around the screw to provide adjustment. The "teeth" are little notches that catch the metal rod of the vacuum advance arm and prevent it from returning fully home- the rod settles into whatever notch you select by turning the lockout cam. If you use the notch that is FURTHEST from the attachment hole you will lock out the maximum amount of vacuum advance the unit is capable of. This will leave you approximately 12* of maximum vacuum advance (the unit supplies about 22-24* if you don't use the plate at all- way too much).

Now that you've locked out as much as possible you MUST reset your base timing with a timing light. The lockout cam basically advances the timing which you must rest back to whatever your normal intial setting is. Seems odd, I know but it ends up leaving you with less advance LEFT TO GIVE. So you reset the base timing to whatever you want after you do this and you're good to go.

I'm not describing this very well, but read the directions and then read what I posted here again and it'll begin to make sense. Trust me, it works. Used the Crane kit many many times.

http://www.kendrick-auto.com/Image162.jpg

The best way to use a Crane adjustable can is to adjust it to the minimum vacuum required for full actuation then use a Kendrick stop (pictured above) on the lower end. As Damon points out, the Crane stop subtracts from the lower end of the adjustable range, which is where you need to be working with a low vacuum motor. The Kendrick stop limits the upper end, so you get the actuation at lower vacuum. You can see some pics of the Kendrick products at:
http://www.kendrick-auto.com/ignition.htm

They also offer adjustable vacuum advance cans for HEI and regular distributors.

I've also used the new Pertronix adjustable vacuum advance cans and they are very nice. The adjustment is a physical stop in the can and does not change the base timing or the vacuum requirement. They start actuating as low as 5" of vacuum.

Thanks guys. At first none of this made sense but i went at looked at the parts and instructions. So the difference between the kendrick stop and the crane stop is basically where it is mouted in relation to the "pin" of the vacuum advance(whereas the crane is mouted above the pin and the kendrick stop is below).

So if I lock out 8 degrees of the vacuum advance can(for lets say only 12 degrees of vacuum), my idle timing will advance 8 degrees because of how the stop is positioned? and I would have to decrease my non-vacuum idle 8 degrees to put it back where it was?

But like onovakind says, when you use the crane stop the vacuum canister basically won't start advancing until a higher vacuum because of how the pin is being repositioned?

Whats stopping me from getting a short 6/32 screw, drilling, and mounting the crane stop in front of the pin? How would the distance from the pin equate in terms of degrees? Like if I mount the plate .060 from the pin how much degrees would that be? I could also just mount a solid piece of thin metal in front to adjust but i would need to know how the distance equates into degrees.

Long winded post, I apologize.

I think you have the basic idea. The Crane limiting cam subtracts off the BOTTOM end of the vacuum advance range (the low-vacuum part of the vacuum advance curve) and, in the process, advances your base timing.

The limiting plate that onovakind posted takes off the TOP end of the advance range (the high-vacuum part of the vacuum advance curve) and will NOT advance your base timing.

Your idea about drilling a screw through the vacuum advance arm and mounting the Crane limiting cam on the opposite side of the vacuum advance pushrod would accomplish the same function as the limiting plate that onovakind posted.

Hold on, I just checked out that vacuum advance limiter you posted, onovakind. From the pictures and descriptions it looks like it's doing the same thing as the Crane limiting cam, basically. Are you sure these things are taking away from the top end of the advance curve? Check out this picture from their website. If you look at the lines the top end of the advance curve is still in the same location but the lower end (advance arm extended) is prevented from returning fully home. This would be the same function as the Crane limiter cam:

http://www.kendrick-auto.com/igniti5.gif


Aw, screw it. I'm just going to buy one and play with it.

AllGo- for now, you already have the Crane stuff so why don't you just use it? Set it up like I describe. The Crane unit can go as low as about 9" of vacuum which should be plenty low for what you're doing anyway. I've used that unit many MANY times and never had a problem with it.


[This message has been edited by Damon (edited July 06, 2005).]

[This message has been edited by Damon (edited July 06, 2005).]

[This message has been edited by Damon (edited July 06, 2005).]

I just talked with the guy at Kendrick and he says the limiter plates can actually be used either way.... limitng the top end OR the bottom end, depending on how you adjust it.

I had much the same issues and could not get it any better with the crane unit. After, onovakind posted about the pertronix I went and bought one. MUCH better. My idle has stabalized somewhat and now idle rpm only drops 150-200 rpm when i drop it in gear.
Hope this helps

Jerry

Funny you should mention that..... I went to buy that same Pertronix unit 3 weeks ago after reading that post as well. Back-ordered from the manufacturer, nobody has them in stock. Mid July at the soonest is what I was told.

I've got a Crane unit ready to try, but it sounds like the Pertronix is better. Is that part# D9006?

Assuming my engine gets 13-14 inches of mercury at idle, how soon can i safely start brining in the vacuum advance? Assuming I have iron heads, short quench, 9.5 CR, and have not really ever had a problem with detonation on 93.

I used a T and my vacuum engine and sucked and found the vacuum canister I toke off my MSD distr. (that comes stock) starts advancing the vacuum advance at 7" and isn't all in until 15." Using the crane all the way clockwise there isn't enough spring tension to put the vaccum advance back to where it is not advancing the timing...however, with 3 turns, I can get the vacuum advance starting to come in at 4-5" and all in at 10"....is 4-5 too low?

I also made a homemade kendrick stop but its not adjustable but wasn't able to start the car to see what it limits my vacuum advance too(I just cut the originally distance in half so it should give 10-12*).

Thanks for all the help Damon. I owe you one!

Nick

You got it right- why don't you use that 3 turn setting. 4" to start kicking in the vacuum advance is just fine. And 9-10" to bring it all the way in is fine, too. The key to your application is that you want it ALL in at a vacuum level that is less than what you draw at idle (by maybe about 2" or so). If you're pulling 13" at idle like you say then you would want the vacuum advance "all in" no higher than about 11".

Couple things to remember....

1. When you use the Crane lockout cam you're going to be chopping off the bottom (low vacuum) end of the vacuum advance curve. If it's starting to retract the rod at 4" without using the lockout cam then it'll take more vacuum when you DO use the lockout cam. Typical example..... using the lockout cam it'll lock out the part of the vacuum advance from 4" to, say, about 7". So it won't be kicking in any vacuum advance until you get to 7" manifold vacuum when all's said and done. This is as it should be.

2. Remember that vacuum advance will RAISE your idle vacuum. Always check your manifold vacuum level WHILE THE VACUUM ADVANCE IS CONNECTED, like how it would be running normally. You may only pull, say, 10" of vacuum without it but 13" with it connected. The 13" number would be the highest vacuum level you would want the advance "all in" at, so you can feel free to set it a little below that (~11") and rest assured it will be fully kicked in at idle.

I made a homemade kendrick stop that isn't adjustable and it limits the vacuum to 13-14 degrees so i'm gonna wait till i drive it around and see if thats okay. Idle is much better now and does not wander around anymore! Thanks everyone for your help.