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Author Topic: 302 vacume readings  (Read 4427 times)

WaltZ

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302 vacume readings
« on: November 24, 2020, 05:46:10 PM »
what's a common idle vacume on a fresh stock dz 302
just curious what others may have
Thanks in advance
W
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mls68z28

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Re: 302 vacume readings
« Reply #1 on: November 25, 2020, 12:24:47 AM »
around 11
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Mitch,1968 Z28 03C Norwood,03/18/68,Seneca Falls NY,Z/28 Emblems.Purchase 05/04/78

firstgenaddict

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Re: 302 vacume readings
« Reply #2 on: November 27, 2020, 07:07:51 PM »

Around 11

x2
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James
Collectin' Camaro's since "Only Rednecks drove them"
Current caretaker of 1971 LT1's - 11130 and 21783 Check out the Black 69 RS/Z28 45k mile Survivor and the Lemans Blue 69 Z 10D frame off...
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PHAT69AMX

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Re: 302 vacume readings
« Reply #3 on: November 27, 2020, 07:23:23 PM »
Might anyone have tried changing to a B28 Vacuum Advance Canister and attaching it to manifold vacuum so it is deployed at idle, in an attempt to increase idle timing advance and an increase in idle vacuum levels?
The B28 starts advance at 4" vacuum and give full advance at only 8" vacuum and adds 16 degrees of advance.
Since it gives full advance at only 8  inches it is steady and does not hunt at idle on manifold vacuum above 8 inches.
And it is still possible to start the car when hot even though there is approx 22 degrees of advance at idle
since the vacuum advance is not deployed until after the engine starts.
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firstgenaddict

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Re: 302 vacume readings
« Reply #4 on: November 27, 2020, 08:47:26 PM »
As per the instructions of JOHNZ that is the exact can many of us use. 
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James
Collectin' Camaro's since "Only Rednecks drove them"
Current caretaker of 1971 LT1's - 11130 and 21783 Check out the Black 69 RS/Z28 45k mile Survivor and the Lemans Blue 69 Z 10D frame off...
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169INDY

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Re: 302 vacume readings
« Reply #5 on: November 27, 2020, 09:38:20 PM »
B28 = VC1810 ??
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Jim
68 SS/RS L35 Th-400 LOS
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firstgenaddict

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Re: 302 vacume readings
« Reply #6 on: November 28, 2020, 03:34:37 AM »
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James
Collectin' Camaro's since "Only Rednecks drove them"
Current caretaker of 1971 LT1's - 11130 and 21783 Check out the Black 69 RS/Z28 45k mile Survivor and the Lemans Blue 69 Z 10D frame off...
https://plus.google.com/photos/112392262205377424364/albums?banner=pwa

janobyte

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Re: 302 vacume readings
« Reply #7 on: November 28, 2020, 02:08:32 PM »
Quote from: firstgenaddict on November 27, 2020, 08:47:26 PM




As per the instructions of JOHNZ that is the exact can many of us use. 

X2
T off the manifold, 36*@3k, 72/76 jets. Just over 1.5 turns out gets me 11" at idle.

I think it was listed for 69's, picked up a nice manifold T to hook up vacuum to the distributor and brake booster.
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68 Z/28  born with: 302, drive line, etc..

PHAT69AMX

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Re: 302 vacume readings
« Reply #8 on: November 28, 2020, 09:36:19 PM »
janobyte - 36 deg total timing advance @ 3,000 engine rpms without any Vacuum Advance, correct ?
Then the B28 16 degrees of advance at 8 inches of Vacuum on manifold vacuum get's added to whatever it is at idle.

B28 Vacuum Advance Canisters can be hard to find.
Each Brand Name in their wisdom gave it a different part number which makes it difficult.
Manifold Vacuum can also be gotten to by using a Tee in the Choke Qualifier hose.

What might be the B28 equivalent Vacuum Canister for an HEI Distributor?
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janobyte

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Re: 302 vacume readings
« Reply #9 on: November 28, 2020, 11:34:33 PM »
Sorry didn't specify, correct. Hook your vacuum gauge up to the manifold in it's place.
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68 Z/28  born with: 302, drive line, etc..

PHAT69AMX

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Re: 302 vacume readings
« Reply #10 on: November 29, 2020, 03:53:34 AM »
the original factory 302 set up had a B9 vacuum Advance Canister
4 deg initial static at idle and 32 deg total mech all in by 4,400 engine rpms for 36 total dist # 1111480

Stock '69 Z28 302 Vacuum Advance is 'B1' on PORTED Vacuum, correct?
which has totally different specs than the 'B28' Can, no?  'B1' Can is:
16 deg = Full Vacuum Advance
 8" Vacuum = Starts Vac Advance
16" Vacuum = Full Vac Advance
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Stingr69

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Re: 302 vacume readings
« Reply #11 on: November 29, 2020, 03:00:23 PM »
The B28 hooked up to manifold vacuum is a modification that works well along with a more aggressive distributor advance curve.  Not trying to keep the factory smoggy original thing here.
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PHAT69AMX

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Re: 302 vacume readings
« Reply #12 on: November 29, 2020, 08:57:54 PM »
Stingr69 - ok, hear ya, yes, the change does make it idle better does it not?
Some folks like all stock, some folks will make slight mods for improvement.
A different Vacuum Advance Canister and re-curve are easily reversed back to stock.
Was a Mr Gasket Brass Travel Limiter Pin Bushing used and di it reduce Mechanical Advance from 32 to 28 ?
Were the lightest springs from the Mr Gasket Kit used ?  Might idle vacuum be more than 11 inches ?  Thanks
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