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post #31 of 80 (permalink) Old May 26th, 11, 03:00 PM
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Re: Timing & Vacuum Advance 101

Quote:
I'd run the vacuum advance. Even at the drags, your engine spends a lot of time running at less than wide open throttle (returning, staging, tuning, etc).
On the other hand this is done in lower gears with very high rear diff ratios, So manovering locked out dedicated track cars is done at rpms higher than the ave street strip car....generally they have moved to magnitos anyway....
But your point is still raliveint and not incorrect.

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post #32 of 80 (permalink) Old May 27th, 11, 11:27 AM
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Re: Timing & Vacuum Advance 101

I suggested that VA was ok at the drags, because at idle (sittin' around idling happened way too much at the tracks I raced), the extra 10-12 degrees of timing would help keep the engine a bit cooler.

No big deal either way at the track.

But on the street,..
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post #33 of 80 (permalink) Old Jun 1st, 11, 04:09 AM
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Re: Timing & Vacuum Advance 101

Chassis dyno mech locked mine out for runs and I used almost twice as much gas on the way home compared to having vac.adv. working prior to ! I guess I'll have to chg it back for normal driving !
I had a total of 54 deg with it connected so I guess I need to chg the shim to bring total down ?

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post #34 of 80 (permalink) Old Jun 4th, 11, 09:14 AM
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Re: Timing & Vacuum Advance 101

I got a b-28 can and it seems to be for a billet dis, does anyone know the part number for an HEI dist.
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post #35 of 80 (permalink) Old Jun 4th, 11, 02:00 PM
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Re: Timing & Vacuum Advance 101

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I had a total of 54 deg with it connected so I guess I need to chg the shim to bring total down ?
54 all in ..yep many stock dizzies have such total, and on the surface seems one hell of a lot....then one get down to thinking it thru in the real world.
Generally these cent curves are all in around 4000 /4500 rpms
The VA is working between around 10 and 16"

As the cars speed increases, there is a larger load on the engine to movethe mass at that speed, and over come aerodynamics....which means the 18 or 20" of cruise engine vac at around 40/50 mph starts to drop....rather quickly down to 14" /15"
Which mow meand the VA is dropping out.
Which means the engine doesnt ever get up to or even near the 54 degs.

Which comes back to what I keep on repeating, one need to know exactly what the wengine vaccuun charactorists are with a in car vac gauge.
AND the high adance dizzies tend to be post pionts dizzies, which I keep on saying, are very different to pre HeI mid 70s dizzies....

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post #36 of 80 (permalink) Old Jun 4th, 11, 02:54 PM
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Re: Timing & Vacuum Advance 101

I seen that very same write up on another site?????


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post #37 of 80 (permalink) Old Jun 4th, 11, 04:57 PM
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Re: Timing & Vacuum Advance 101

Quote:
Originally Posted by mhaseleu03 View Post
I got a b-28 can and it seems to be for a billet dis, does anyone know the part number for an HEI dist.
http://www.corvette-restoration.com/...c_Adv_Spec.pdf

scroll to the end for HEI, looks like the AR31 would be the B-28 equivalent

67 new build alum. 406 | 69 RS/SS 496 631 HP / 618 TQ | 73 Z28 Survivor 36k miles | 89 IROC Z 2500 miles | 02 SS 35th Anniv. LE 645 miles |11 SS Berger 550HP (1 of 25) | 14 ZL1 6M Recaros
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post #38 of 80 (permalink) Old Jun 7th, 11, 04:34 PM Thread Starter
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Re: Timing & Vacuum Advance 101

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Originally Posted by dawg View Post
I seen that very same write up on another site?????
Yup - I wrote it originally as a paper in early 2003, shared it on several different forums, and later dressed it up, expanded it, and published it as a feature article in the November, 2003 issue of "Corvette Enthusiast" magazine, when I was the Technical Editor. Here's a link to the published CE article, offered on our CRG site under "Technical Articles".

http://www.camaros.org/pdf/timing101.pdf


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post #39 of 80 (permalink) Old Jun 7th, 11, 05:50 PM
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Re: Timing & Vacuum Advance 101

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I seen that very same write up on another site?????
I have been messing with dizzies timing, curves for some 40 yrs now....
Sry its not plagerism...Like john and a hand full of others we have known about this stuff way before his articule was published...
A quick skim thru the ACDelco servive manual specs tells on these things
Playing with pionts, and HEI dizzies be they , Chev, jowett, what ever, tells one these things...
With all due respect, just cause a guy with a biit of good old common sence knowledge, right an articule that happens to be pretty well on the mark, doesnt make that person the only one in the world who knowsd about this stuff.
Like I said I have been tuning moding since way before the internet ever existed.

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post #40 of 80 (permalink) Old Jun 7th, 11, 06:15 PM
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Re: Timing & Vacuum Advance 101

But he WROTE AN ARTICLE and you didn't.

Can't really defer to someone who hasn't taken the time to write it up, now can we? You sound kind of jealous Steps.

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post #41 of 80 (permalink) Old Jun 7th, 11, 10:47 PM
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Re: Timing & Vacuum Advance 101

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You sound kind of jealous Steps.
Get real m8..
its a good articule, basic,, enought to get someone started ...
Im not interested in publishing articules re camaro....
Articules on LPG, impco, and kakariki, yeah I have and do...that where most of my time goes, breeding endangered parrots, conservation...

But I certainly dont appreciate being called out or infered to be called out for plagerism m8

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post #42 of 80 (permalink) Old Jun 21st, 11, 06:58 PM
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Re: Timing & Vacuum Advance 101

I found this info in my archives. I don't know who to give credit to, but it's good info:

Vacuum Advance


GM hasn't made vacuum advance units for decades, but they still sell them, made in the aftermarket by Standard Products (and Echlin before that) and boxed by AC-Delco.

All of them provide 16* of advance, and the four calibrations that cover most usages in terms of when they start pulling and at what vacuum level they're fully-deployed are as follows:

VC-1802 (stamped B22) - starts at 8", done at 15"

VC-680 (stamped B1) - starts at 8", done at 16"

VC-1765 (stamped B20 or B26) - starts at 6", done at 12"

VC-1810 (stamped B28) - starts at 4", done at 8" (same as the original Delco "236-16", sold under GM #88924985 and AC-Delco #D1312C). I buy them in bulk for about six bucks each from GMPartsDirect.com. This is the most aggressive unit available, and is the only one that works properly with a "30-30" cam.
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post #43 of 80 (permalink) Old Jun 21st, 11, 10:24 PM
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Re: Timing & Vacuum Advance 101

Do not confuse dizzy degrees with crank degrees.
And the canistors where for stock un bored engines, running on leaded fuels with intial cent around 2 to 10 degs....very different kettle of fish to our old engines today, with very different vac charactoristics.

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post #44 of 80 (permalink) Old Jun 24th, 11, 04:47 AM
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Re: Timing & Vacuum Advance 101

Yer right Steps... have to keep that in mind.

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post #45 of 80 (permalink) Old Jun 24th, 11, 04:20 PM
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Re: Timing & Vacuum Advance 101

Quote:
But he WROTE AN ARTICLE and you didn't.
Can't really defer to someone who hasn't taken the time to write it up, now can we? You sound kind of jealous Steps.
Quote:
Yer right Steps... have to keep that in mind.
Now u are a mod right?
lets just put this out in the open..it appears u are baiting m8...not something a mod should be doing...rather stopping others doing so...
I believe its about good info here?
or even discussing the validity of info given..???

My Spelling is not incorrect...it is creative

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