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Re: Where do you have your vacuum advance hooked up? [Re: hooziewhatsit] #2451938
02/15/18 12:34 AM
02/15/18 12:34 AM
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Bend,OR USA
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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?

Last edited by Cab_Burge; 02/15/18 12:35 AM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440] #2451957
02/15/18 01:08 AM
02/15/18 01:08 AM
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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.


Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440] #2452070
02/15/18 11:38 AM
02/15/18 11:38 AM
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Florida
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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.

Re: Where do you have your vacuum advance hooked up? [Re: scratchnfotraction] #2452235
02/15/18 05:43 PM
02/15/18 05:43 PM
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Dayton, WA
wesgtx440 Offline OP
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Thank you everyone for feedback it has been very informative. I have definitely learned a lot.


68 Charger R/T 440 auto
Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440] #2452385
02/16/18 12:27 AM
02/16/18 12:27 AM
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Bend,OR USA
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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


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Where do you have your vacuum advance hooked up? [Re: Cab_Burge] #2452396
02/16/18 12:50 AM
02/16/18 12:50 AM
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Florida
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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.

Re: Where do you have your vacuum advance hooked up? [Re: BDW] #2452401
02/16/18 01:08 AM
02/16/18 01:08 AM
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State of Jefferson
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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


If you ever find yourself in a fair fight, your tactics suck.
Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440] #2452511
02/16/18 12:57 PM
02/16/18 12:57 PM
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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?

Re: Where do you have your vacuum advance hooked up? [Re: dragon slayer] #2452828
02/16/18 11:04 PM
02/16/18 11:04 PM
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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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Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440] #2452951
02/17/18 06:22 AM
02/17/18 06:22 AM
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Balt. Md
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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

Last edited by 383man; 02/17/18 06:24 AM.
Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440] #2453427
02/18/18 12:53 PM
02/18/18 12:53 PM
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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.

Re: Where do you have your vacuum advance hooked up? [Re: NachoRT74] #2461602
03/05/18 06:23 PM
03/05/18 06:23 PM
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Dayton, WA
wesgtx440 Offline OP
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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.


68 Charger R/T 440 auto
Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440] #2462032
03/06/18 03:31 PM
03/06/18 03:31 PM
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Blairsden, CA
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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.

Re: Where do you have your vacuum advance hooked up? [Re: scratchnfotraction] #2462510
03/07/18 12:27 PM
03/07/18 12:27 PM
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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

Last edited by 383man; 03/07/18 12:28 PM.
Re: Where do you have your vacuum advance hooked up? [Re: fourgearsavoy] #2462515
03/07/18 12:38 PM
03/07/18 12:38 PM
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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

Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440] #2462796
03/07/18 09:29 PM
03/07/18 09:29 PM
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I always use ported.

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