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#2451287 - 02/13/18 03:08 PM Where do you have your vacuum advance hooked up?
wesgtx440 Offline
enthusiast

Registered: 10/12/11
Posts: 285
Loc: Dayton, WA
Ported or manifold vacuum.

And if you feel like sharing. Why did you choose one vs the other?
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#2451333 - 02/13/18 04:18 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
BigBlockMopar Offline
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Registered: 01/22/03
Posts: 3387
Loc: The Netherlands
I always prefer manifold.
Makes for a cooler running (idling) engine.
(And my MegaSquirt ECU wants it there smile )

On another car with a large(r) cam it's connected to ported, to prevent too much ignition advance fluctuations at idle.

IMO, ported is mostly more an emission thing because it helps for a more complete burn and hotter exhaust temps (at idle), although the factory used ported advance for as long as I know. Perhaps they installed it like that for a more steady/stable idle-quality.
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#2451343 - 02/13/18 04:26 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
BlueRacer69 Offline
mopar

Registered: 10/25/15
Posts: 476
Loc: Michigan
Ported. Or the port that is more to the passenger side of the carb.

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#2451359 - 02/13/18 04:48 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
scratchnfotraction Offline
I Live Here

Registered: 05/29/03
Posts: 15186
Loc: Florida
I followed the tips in the Book from Don at FBO I use one of the mech advance plates.

I set my base timing at 14* with the mech advance 18* - 32* total. 88-440 truck-whiplash cam 230/245 @.050 .518/.518 with the edelbrock RPM duel plane intake....running the holley 440 STREET dominator single plane intake I run the dist locked out on 0* timing set at 34* IIRC

I installed a new reman 318 1st of January. got a new stock replacement points dist. -ditched PCV for a evac system. -stock tbi roller cam/headers/q-jet.

set the timing at 10* adjusted carb A/F ratio with vac gauge for highest reading re-adjusting curb idle to 750 rpm.

hooked can up to full vac port on carb and that raised curb idle but cleaned up the idle and very smooth. re-adjusted to the 750 rpm.

nice smooth daily driver 16.5 mpg no ping anywhere in the rpm range and have dropped back to 87 pump gas..still no ping under load.

after reading the book I understand it a little better. at first with the big lumpy cam I had no power and heated up driving.

once I got the initial timing advance to where the engine wanted it and limited the mech advance it tuned right up and became street friendly.

got to get the spark ahead of the slow burning pump gas so it all burns in the cyl not the exhaust tubes. it had killer exhaust fumes that had me thinking it was way rich but it was really going lean. which in the book it said this is cause by it burning all the oxygen and leaving the unburned fuel trying to burn as it goes out the exhaust tubes thus making the engine temp rise and header tubes glow red with lots of smelly fumes.

so after 20 yrs of ported vac with mostly stock cams/dist/daily driver junk I have them on full vac and very happy with the results set up this way.

this is the first time I have had a 318 on 87 pump gas not PING! over 1/2 throttle from a stop light in traffic running a 195* thermostat.

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#2451365 - 02/13/18 05:21 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
BigBlockMopar Offline
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Registered: 01/22/03
Posts: 3387
Loc: The Netherlands
FYI, my 'smogger' (mid '80s) 318 with its now digitally controlled ignition through a MegaSquirt ECU idles in 'Drive' with 24° ignition advance at 550-600rpm (Propane fueled).

At that number it makes the highest engine vacuum / lowest engine load, so generating the least amount heat.
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#2451392 - 02/13/18 06:33 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
BDW Offline
master

Registered: 05/12/05
Posts: 3509
Loc: Florida
I've always used ported, but had to switch to manifold when I converted to FiTech.
Their poor design didn't open the port until 2500rpm or higher.
Couldn't understand why my gas mileage went down after the conversion, then checked timing and found this is a known issue with them.

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#2451394 - 02/13/18 06:36 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
5thAve Offline
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Registered: 01/19/03
Posts: 2746
Loc: Posts: 4034 - Register...
Ported here. Once you're off idle and on the throttle it's all the same it just keeps the timing down at idle.

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#2451404 - 02/13/18 06:50 PM Re: Where do you have your vacuum advance hooked up? [Re: 5thAve]
YO7_A66 Offline
master

Registered: 01/20/03
Posts: 5190
Loc: Indiana
I run the FBO distributor that is made for manifold vacuum. 30 degrees timing at idle as long as my idle vacuum is above 12". up
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#2451421 - 02/13/18 07:41 PM Re: Where do you have your vacuum advance hooked up? [Re: YO7_A66]
ahy Offline
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Registered: 01/22/07
Posts: 7627
Loc: IN
A key is to make sure the distributor curb, carb and tuning specs are set up correctly for one or the other.

With a carb, I prefer ported vacuum. Keeping timing steady at idle helps stabilize idle. With manifold vacuum, vacuum and timing will jump around and harder to keep idle steady.

With FI and computer controlled timing, manifold vacuum. Set the timing curve as it needs to be. It can be vacuum in-sensitive at idle if desired. Or it can advance if idle speed drops to hold it steady (opposite what manifold vacuum does with a carb!).

Beyond that, manifold vacuum with a carb is a Chevy thing...

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#2451440 - 02/13/18 08:11 PM Re: Where do you have your vacuum advance hooked up? [Re: ahy]
hooziewhatsit Online   content
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Registered: 10/05/07
Posts: 2828
Loc: State of Jefferson
As long as your vacuum at idle in gear is higher than the vacuum needed to actuate the vac advance can, you'll have a steady idle. If your vacuum is too low and the can moves, then nothing will ever settle, and you'd be better off using ported vacuum.

I have mine hooked to manifold since I didn't want to take the distributor out to put in the limiting plate, and I wanted more timing at idle.
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#2451558 - 02/14/18 01:03 AM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
StevenMcGovern Offline
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Registered: 02/14/18
Posts: 4
Loc: California
I will go with manifold vacuum as it has more advantage compared to the ported. Vacuums helps in stabilizing and steady timing. so I will prefer this.

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#2451568 - 02/14/18 02:58 AM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
RamblerMan Offline
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Registered: 02/02/03
Posts: 4061
Loc: Castlegar, BC, Canada
All my junk is mostly stock, so they all run full manifold. Nice smooth idles, no overheating. Good gas mileage and smooth steady cruising.

I can see the guys with modified engines running ported and that's Ok too!
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#2451661 - 02/14/18 11:15 AM Re: Where do you have your vacuum advance hooked up? [Re: RamblerMan]
wesgtx440 Offline
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Registered: 10/12/11
Posts: 285
Loc: Dayton, WA
All good stuff, thanks for all the input. So is there a difference in vacuum cans for ported vs manifold vacuum?? Say like a stock points dist. in '70 was hooked to ported vacuum correct? Are the newer distributors ie: mopar performance electronic ones, firecore, FBO, set up with a different advance unit that is designed to use manifold vacuum? or does it basically just boil down to how much vacuum your engine makes at idle and what it prefers timing wise?
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#2451662 - 02/14/18 11:24 AM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
hooziewhatsit Online   content
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Registered: 10/05/07
Posts: 2828
Loc: State of Jefferson
Originally Posted By wesgtx440
All good stuff, thanks for all the input. So is there a difference in vacuum cans for ported vs manifold vacuum?? Say like a stock points dist. in '70 was hooked to ported vacuum correct? Are the newer distributors ie: mopar performance electronic ones, firecore, FBO, set up with a different advance unit that is designed to use manifold vacuum? or does it basically just boil down to how much vacuum your engine makes at idle and what it prefers timing wise?


A vacuum can is a vacuum can. The only real differences are how much additional timing they provide, and what vacuum level they start to move at.

Most can have the vacuum level changed by using an allen wrench through the nipple to adjust the spring load on the diaphram. (A mity-vac comes in very useful for adjusting this)

To adjust the amount of advance a physical stop needs to be added to the arm.

Otherwise, it's based on your specific engine's idle vacuum, how much mechanical advance your distributor has, and how much total timing you want.
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#2451694 - 02/14/18 12:56 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
Cab_Burge Online   content
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Registered: 08/23/03
Posts: 31224
Loc: Bend,OR USA
Early GM, Chevys, used manifold vacuum until the early to mid 1960s, Mopar and Ford have always used ported vacuum advance that I'm aware of shruggy
The major difference in using manifold vacuum advance it is advanced most at idle and then drops off as the vacuum declines to the throttle, ported vacuum doesn't start to work until there is airflow past that port work scope


Edited by Cab_Burge (02/14/18 12:57 PM)
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#2451740 - 02/14/18 02:50 PM Re: Where do you have your vacuum advance hooked up? [Re: Cab_Burge]
wesgtx440 Offline
enthusiast

Registered: 10/12/11
Posts: 285
Loc: Dayton, WA
I guess the way I see it is if you have an engine that starts fine with the static advance setting and it idles good, then ported vacuum is the way to go. If you have an engine that idles good with more advance than allows for starting with out kickback, then manifold vacuum is the better one since you can retard the timing to allow it to start and then have it advance a set # of degrees with the vacuum to where it idles good. So at WOT, both manifold and ported vacuum signal will drop significantly and mechanical advance takes over at that point correct? Sorry for all the questions, just trying to educate myself on this subject beer
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#2451743 - 02/14/18 03:03 PM Re: Where do you have your vacuum advance hooked up? [Re: scratchnfotraction]
Triggerfish Offline
top fuel

Registered: 07/25/05
Posts: 1897
Loc: Blairsden, CA
Originally Posted By scratchnfotraction
I followed the tips in the Book from Don at FBO I use one of the mech advance plates.

I set my base timing at 14* with the mech advance 18* - 32* total. 88-440 truck-whiplash cam 230/245 @.050 .518/.518 with the edelbrock RPM duel plane intake....running the holley 440 STREET dominator single plane intake I run the dist locked out on 0* timing set at 34* IIRC

I installed a new reman 318 1st of January. got a new stock replacement points dist. -ditched PCV for a evac system. -stock tbi roller cam/headers/q-jet.

set the timing at 10* adjusted carb A/F ratio with vac gauge for highest reading re-adjusting curb idle to 750 rpm.

hooked can up to full vac port on carb and that raised curb idle but cleaned up the idle and very smooth. re-adjusted to the 750 rpm.

nice smooth daily driver 16.5 mpg no ping anywhere in the rpm range and have dropped back to 87 pump gas..still no ping under load.

after reading the book I understand it a little better. at first with the big lumpy cam I had no power and heated up driving.

once I got the initial timing advance to where the engine wanted it and limited the mech advance it tuned right up and became street friendly.

got to get the spark ahead of the slow burning pump gas so it all burns in the cyl not the exhaust tubes. it had killer exhaust fumes that had me thinking it was way rich but it was really going lean. which in the book it said this is cause by it burning all the oxygen and leaving the unburned fuel trying to burn as it goes out the exhaust tubes thus making the engine temp rise and header tubes glow red with lots of smelly fumes.

so after 20 yrs of ported vac with mostly stock cams/dist/daily driver junk I have them on full vac and very happy with the results set up this way.

this is the first time I have had a 318 on 87 pump gas not PING! over 1/2 throttle from a stop light in traffic running a 195* thermostat.

I have the same FBO complete system (with coil) on my 64 Belvedere's orig stock 383. PIA to get it to stop pinging at WOT. Don says my carb is too lean & I must use manifold vacuum. I don't know if the orig afb has manifold vacuum so he says to find a port on the intake. I tried adjusting the can & still no help. Might ditch the system & go back to the dual point with pertronix dizzy.




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#2451745 - 02/14/18 03:09 PM Re: Where do you have your vacuum advance hooked up? [Re: Triggerfish]
wesgtx440 Offline
enthusiast

Registered: 10/12/11
Posts: 285
Loc: Dayton, WA
Did you previously run the dual point with no issues?
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#2451751 - 02/14/18 03:18 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
hooziewhatsit Online   content
master

Registered: 10/05/07
Posts: 2828
Loc: State of Jefferson
Originally Posted By wesgtx440
I guess the way I see it is if you have an engine that starts fine with the static advance setting and it idles good, then ported vacuum is the way to go. If you have an engine that idles good with more advance than allows for starting with out kickback, then manifold vacuum is the better one since you can retard the timing to allow it to start and then have it advance a set # of degrees with the vacuum to where it idles good. So at WOT, both manifold and ported vacuum signal will drop significantly and mechanical advance takes over at that point correct? Sorry for all the questions, just trying to educate myself on this subject beer


Pretty much up

Some cams like more timing at idle. This raises the idle speed, giving you enough room to close the throttle blades so it will idle on the idle circuit. Some don't.

To do this, you can:
use ported vacuum
crank up the initial timing, and limit the total timing.
But, like you mentioned, you might run into kickback issues.

Or,
use manifold vacuum
a more reasonable initial timing (maybe still limiting the total),
And have the base timing jump to initial + vac advance once it starts.

Once the throttle is open past idle, both manifold and ported are the same. At wot, both are near zero so there is no advance added. The only difference is at idle with the throttle closed.
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#2451754 - 02/14/18 03:22 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
hooziewhatsit Online   content
master

Registered: 10/05/07
Posts: 2828
Loc: State of Jefferson
Quote:
PIA to get it to stop pinging at WOT.


At WOT, there's no vacuum advance, so I would look at the total timing, fuel, or both.
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#2451938 - 02/14/18 09:34 PM Re: Where do you have your vacuum advance hooked up? [Re: hooziewhatsit]
Cab_Burge Online   content
I Win

Registered: 08/23/03
Posts: 31224
Loc: Bend,OR USA
Originally Posted By hooziewhatsit
Quote:
PIA to get it to stop pinging at WOT.


At WOT, there's no vacuum advance, so I would look at the total timing, fuel, or both.
That be true with manifold vacuum but think about how much air is flowing past the ported port at WOT making negative pressure at that point, I'll bet it is not zero work
Note to self for future test, hook up vacuum gauge to ported vacuum port and test that for vacuum wrench work
I remember on my old airplane with a manifold pressure gauge it had near zero at WOT above 3000 Ft elevation but I think it had .5 to 2.0 lbs. at WOT below 3000 Ft, maybe not confused
What say some of you other pilots on here about your experiences or knowledge on this?


Edited by Cab_Burge (02/14/18 09:35 PM)
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#2451957 - 02/14/18 10:08 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
moper Offline
I Live Here

Registered: 02/03/03
Posts: 12670
Loc: Columbia, CT
There's not enough vacuum at WOT to get any advance into it that way. I always run ported. Never had issues with kickback or "running hot". Pinging is much more a function of the carb and distributor working together than either one separately creating or stopping it. With the fuels available these days, tuning is a big deal and it's a dying art.
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#2452070 - 02/15/18 08:38 AM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
scratchnfotraction Offline
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Registered: 05/29/03
Posts: 15186
Loc: Florida
IIRC there is a # stamped on the arm of vac can IIRc you get about half that # in mech advance. so you can search out a can that will give the advance needed.

my understanding is with a stock dist on ported vac it adds to much mech advance. up to 50* or more.

the can is adding mech advance and the weights are adding more mech advance when rpm increases.

I tried last night to swap it onto ported and the results were poor.

I removed can from full vac, rpm drops, adjust back up to 750 curb idle, hook line to ported vac, adds no mech advance, test drive and 1/2 throttle from stop it pings and spark knock.

change back to full vac on can and adjust curb idle back down to 750, test drive, no ping or spark knock.

dist & carb working together may be what I stumbled upon on mine.

on my junk, following the steps in Don's book and not the way I have always done it fixed a lot of things I have put up with for yrs.

I will be hooking up the vac gauge on ported vac to see what it is doing at 1/2 throttle from a stop. and get a WOT reading.

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#2452235 - 02/15/18 02:43 PM Re: Where do you have your vacuum advance hooked up? [Re: scratchnfotraction]
wesgtx440 Offline
enthusiast

Registered: 10/12/11
Posts: 285
Loc: Dayton, WA
Thank you everyone for feedback it has been very informative. I have definitely learned a lot.
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#2452385 - 02/15/18 09:27 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
Cab_Burge Online   content
I Win

Registered: 08/23/03
Posts: 31224
Loc: Bend,OR USA
I haven't used vacuum advance on any of my hot street cars in years, I did hooked up the vacuum advance on my 1969Dart GTS 383 4 speed to the stock location for ported vacuum, I didn't see any gains or losses with that car shruggy
I do set all my distributors up to have between 14 to 18 degrees at idle and no more than 34 degrees total up So maybe that has a lot to do with my results shruggy
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#2452396 - 02/15/18 09:50 PM Re: Where do you have your vacuum advance hooked up? [Re: Cab_Burge]
BDW Offline
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Registered: 05/12/05
Posts: 3509
Loc: Florida
Ebooger has written many articles explaining why you want (and need) as much as 45-50 advance during cruise for max performance and mileage.

34 total at WOT is fine, need the extra 15 from vacuum advance when cruising / light load.

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#2452401 - 02/15/18 10:08 PM Re: Where do you have your vacuum advance hooked up? [Re: BDW]
hooziewhatsit Online   content
master

Registered: 10/05/07
Posts: 2828
Loc: State of Jefferson
Originally Posted By cnxt
Ebooger has written many articles explaining why you want (and need) as much as 45-50 advance during cruise for max performance and mileage.

34 total at WOT is fine, need the extra 15 from vacuum advance when cruising / light load.


I concur.

Vac advance is only used at light/part throttle cruise (or idle, if on manifold).

If you have a race car that is either idle or WOT, you won't see much benefit drive
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#2452511 - 02/16/18 09:57 AM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
dragon slayer Offline


Registered: 06/27/14
Posts: 153
Loc: VA
I would highly recommend you read the Chrysler Master Training Document #240 Combustion in Engines and #241 The CAP story. Can be found here:

http://www.imperialclub.com/Repair/Lit/Master/index.htm

Lot of conflicting information out there. The above are good simple explanations of the combustion process.

For those that have hot cars and use Manifold vacuum to supplement idle timing, don't you really risk detonation when you race it at the track? Mechanical timing will come in quicker then the vacuum timing will fall off and you will windup with too much total for a period.

Each motor is different, but carb, fuel, cleanliness of motor, blue printing all come into play on how a motor performs.

Ignition is not an explosion, it is a timed burn. If you can't start your car with 16 initial when hot nor get it to idle correct with less initial, can't the issue be something else?

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#2452828 - 02/16/18 08:04 PM Re: Where do you have your vacuum advance hooked up? [Re: dragon slayer]
fourgearsavoy Offline


Registered: 12/07/04
Posts: 9282
Loc: Rittman Ohio
I haven't seen many replies about compression ratio shruggy I run close to 11-1 compression on pump gas so I wouldn't want anything over 34 degrees timing EVER on my engine. I wouldn't recommend any type of advance until we get all the engine specs.
40-45 degrees of advance would cause some major detonation on a high compression street/strip engine. That's where the caps start walking and the cracks start opening up twocents

Gus beer
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#2452951 - 02/17/18 03:22 AM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
383man Offline
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Registered: 01/19/03
Posts: 26841
Loc: Balt. Md
Ported vacuum is manifold vacuum but its just a port above the throttle plate so it don't come on until you step on the gas. It will still drop to about 0 vacuum at WOT. I agree with most that so much depends on the combo. Working as a tech from 1974 up to 2011 most of the older dist cars I worked with seemed to use ported vacuum for the dist but I did see them both ways from the factory as some used full vacuum at idle. Myself I don't use ported or manifold vacuum on my 63 and that's because I got a great deal on a Mallory race dist and I use it and it has no vacuum advance on it. I have it set up with about 24 degrees at idle and the rest of the timing set up to come in fast. I have my full total mech advance in by 1800 to 2000 rpm. The car runs great like that for me. If I had a vacuum advance on my dist I would have tried it to see how the car likes it since mine is mostly a street car. But I will say it runs good with the quick mechanical advance I run. Ron


Edited by 383man (02/17/18 03:24 AM)
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#2453427 - 02/18/18 09:53 AM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
NachoRT74 Offline
master

Registered: 08/14/07
Posts: 5054
Loc: Caracas, Venezuela, SouthAmeri...
there is something mentioned around... rough iddle cams with probably variable iddle vacuums IF using some vacuum advance would require ported since the vacuums becomes more regular incresing rpms. manifold vacuum could be variable

Or simply no vacuum used at all.

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#2461602 - 03/05/18 03:23 PM Re: Where do you have your vacuum advance hooked up? [Re: NachoRT74]
wesgtx440 Offline
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Registered: 10/12/11
Posts: 285
Loc: Dayton, WA
So I finally got around to messing with the install of the new firecore dizzy and timing this past weekend. I ended up using ported vacuum, on the fast ez efi. My initial was 18 degrees and then it pulls another 5 degrees when you hook the vacuum line up. Still playing with it though to see what it is going to like best. Making small changes and then test driving for now. Thanks again for all the replies.
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#2462032 - 03/06/18 12:31 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
Triggerfish Offline
top fuel

Registered: 07/25/05
Posts: 1897
Loc: Blairsden, CA
Originally Posted By wesgtx440
Did you previously run the dual point with no issues?

Just read your reply & I hand no issues with the orig dual point dizzy, coil & regulator.

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#2462510 - 03/07/18 09:27 AM Re: Where do you have your vacuum advance hooked up? [Re: scratchnfotraction]
383man Offline
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Registered: 01/19/03
Posts: 26841
Loc: Balt. Md
Originally Posted By scratchnfotraction
IIRC there is a # stamped on the arm of vac can IIRc you get about half that # in mech advance. so you can search out a can that will give the advance needed.

my understanding is with a stock dist on ported vac it adds to much mech advance. up to 50* or more.

the can is adding mech advance and the weights are adding more mech advance when rpm increases.

I tried last night to swap it onto ported and the results were poor.

I removed can from full vac, rpm drops, adjust back up to 750 curb idle, hook line to ported vac, adds no mech advance, test drive and 1/2 throttle from stop it pings and spark knock.

change back to full vac on can and adjust curb idle back down to 750, test drive, no ping or spark knock.

dist & carb working together may be what I stumbled upon on mine.

on my junk, following the steps in Don's book and not the way I have always done it fixed a lot of things I have put up with for yrs.

I will be hooking up the vac gauge on ported vac to see what it is doing at 1/2 throttle from a stop. and get a WOT reading.










That's very interesting that it pings at part throttle with ported vacuum and does not ping on manifold vacuum. In theory ported is manifold vacuum but its port is above the throttle blade. I would like to know how much vacuum yours pulls at part throttle on ported and manifold vacuum. Actually at 1/4 to 1/2 throttle both ported and manifold vacuum are still pulling a good vacuum. When we used to test for plugged exhaust systems we would watch the manifold vacuum at idle and then raise the rpm to about 2000 rpm in park with the eng under no load and normally the vacuum will actually increase a little bit and hold that. If it did not increase any and started dropping then we would look for a restriction in the exh system.

I wonder if as CAB pointed out that because of where the ported vacuum port is in the carb it gets a slightly stronger signal at part throttle as both ported and manifold vacuum should drop to 0 at WOT. And maybe the ported port is high enough in the carb throat that it may pick up a little venturi vacuum which gets stronger with more throttle ?

Please let us know what your vacuum readings are if you get to take them as it has me curious of why it pings at part throttle on ported and not on manifold vacuum ? Thanks , Ron


Edited by 383man (03/07/18 09:28 AM)
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My car...63 Sport Fury Max Wedge wanna be street car..with new 493 pump gas full exh eng.......10.76 @ 124.49 ! ! ! My page on the cool 62-65 Mopar site ! http://www.1962to1965mopar.ornocar.com/mmo82008.html

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#2462515 - 03/07/18 09:38 AM Re: Where do you have your vacuum advance hooked up? [Re: fourgearsavoy]
383man Offline
Too Many Posts

Registered: 01/19/03
Posts: 26841
Loc: Balt. Md
Originally Posted By fourgearsavoy
I haven't seen many replies about compression ratio shruggy I run close to 11-1 compression on pump gas so I wouldn't want anything over 34 degrees timing EVER on my engine. I wouldn't recommend any type of advance until we get all the engine specs.
40-45 degrees of advance would cause some major detonation on a high compression street/strip engine. That's where the caps start walking and the cracks start opening up twocents

Gus beer




That's a good point about the comp ratio as I run on 92 pump with 10.6 comp. But I do know an engine will take much more timing at part throttle without the eng under much of a load like when cruising along on a level road. If the eng is at 1/2 or more throttle pulling a load it wont take as much timing and the vacuum will drop some when the eng is under a load to limit the vacuum advance as per when there is no load on the eng.

Myself I run a Mallory race dist that I got at a great price and it has no vacuum advance on it. I run a very fast mech advance as I idle at about 24 degrees and have my full 36 degrees by about 1800 rpm. It has no ping ever and runs great for me. Does not overheat and has great throttle response. That works very good in my eng combo that has good .045 quench I built in it and it has 10.6 comp with aluminum heads. Also my custom grind cam from Dwayne Porter has the intake closing point to also keep my cylinder pressure from being to high and it works great in my combo on 92 pump. Ron
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My car...63 Sport Fury Max Wedge wanna be street car..with new 493 pump gas full exh eng.......10.76 @ 124.49 ! ! ! My page on the cool 62-65 Mopar site ! http://www.1962to1965mopar.ornocar.com/mmo82008.html

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#2462796 - 03/07/18 06:29 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
lewtot184 Offline
master

Registered: 06/09/08
Posts: 2664
Loc: usa
I always use ported.

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