vacuum advance - Moparts Forums

Register Log In Moparts Forums Moparts Question and Answer vacuum advance

Print Thread

vacuum advance #1679708 09/29/14 03:49 AM 09/29/14 03:49 AM
Joined: Feb 2007 Posts: 1,025 Las Vegas, NV dodgeboy11 OP super stock
dodgeboy11 OP super stock Joined: Feb 2007 Posts: 1,025 Las Vegas, NV	Anybody remember the size of the wrench and which way to turn it to give less advance at a given vacuum reading? Dual plane is giving more vacuum and it's rattling at cruise speeds.

Re: vacuum advance [Re: dodgeboy11] #1679709 09/29/14 08:50 AM 09/29/14 08:50 AM
Joined: Jun 2008 Posts: 3,916 usa L lewtot184 master
lewtot184 master L Joined: Jun 2008 Posts: 3,916 usa	3/32 allen wrench. turning the screw clockwise reduces the spring tension, counter clockwise increases tension. less tension means less vacuum to open the unit.

Re: vacuum advance [Re: dodgeboy11] #1679710 09/29/14 12:49 PM 09/29/14 12:49 PM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	Quote: Dual plane is giving more vacuum and it's rattling at cruise speeds. the DP might be packing the cyls more which is upping the cyl psi. Might need to go to a slightly stiffer spring combo as opposed to the can. For spot on (just me) I would (1) find the initial it wants with the vac gauge method (2) shorten the slots to get the appropriate total for your eng type (35-SB/31 if mag heads) & this total is initial+slots/can plugged. (3) spring combo- staying just under the pinging point at WOT up thru the gears on your hottest/driest (most likely to ping) day and the adv starts no less than 100 RPM above your hot in gear idle speed which is what you will be at at the stoplight (4) plug/adj the can. Anytime the cyl psi changes from a part/tuning change the dist needs changed from head to toe (for spot on). Easy/short version, for a cruiser (as said) the can adj may take care of this in minutes live every 24 hour block of time like it's your last day on earth

Re: vacuum advance [Re: lewtot184] #1679711 09/29/14 02:17 PM 09/29/14 02:17 PM
Joined: Jan 2003 Posts: 75,043 U.S.S.A. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,043 U.S.S.A.	Quote: 3/32 allen wrench. turning the screw clockwise reduces the spring tension, counter clockwise increases tension. less tension means less vacuum to open the unit. ^^^ this , you can't limit the amount of advance by turning the screw only the speed it comes in.

Re: vacuum advance [Re: RapidRobert] #1679712 09/29/14 03:08 PM 09/29/14 03:08 PM
Joined: Feb 2007 Posts: 1,025 Las Vegas, NV dodgeboy11 OP super stock
dodgeboy11 OP super stock Joined: Feb 2007 Posts: 1,025 Las Vegas, NV	Open chamber, 440. 38 degrees total with welded slots, heavy spring removed. Rattle goes away when throttle is pressed further or backed off. It might make more power with more timing, but I'm not going to check, runs exceptionally well with 38. Thanks for everyone's input, I appreciate it.

Re: vacuum advance [Re: dodgeboy11] #1679713 09/29/14 06:29 PM 09/29/14 06:29 PM
Joined: Jan 2003 Posts: 16,376 D dogdays I Live Here
dogdays I Live Here D Joined: Jan 2003 Posts: 16,376	38 is where it's supposed to be, vacuum advance off and plugged. That's the most referenced number for stock bigblocks. R.

Re: vacuum advance [Re: dodgeboy11] #1679714 09/29/14 10:04 PM 09/29/14 10:04 PM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	Quote: Rattle goes away when throttle is pressed further or backed off. It sounds like a prime candidate for 2 or 3 turns CCW & retest. just me I would T into the vac adv line (or manifold port) & run a vac gauge out taped to the windsheld & note the in hg (& RPM) that it starts/stops pinging at just for a baseline reference. live every 24 hour block of time like it's your last day on earth

Re: vacuum advance [Re: dodgeboy11] #1679715 09/29/14 10:31 PM 09/29/14 10:31 PM
Joined: Nov 2013 Posts: 97 Florida J johnmilner member
johnmilner member J Joined: Nov 2013 Posts: 97 Florida	Quote: Open chamber, 440. 38 degrees total with welded slots, heavy spring removed. Rattle goes away when throttle is pressed further or backed off. It might make more power with more timing, but I'm not going to check, runs exceptionally well with 38. Thanks for everyone's input, I appreciate it. put heavy spring back in there, that light throttle stumble will go away.

Re: vacuum advance [Re: johnmilner] #1679716 09/30/14 02:51 AM 09/30/14 02:51 AM
Joined: Feb 2007 Posts: 1,025 Las Vegas, NV dodgeboy11 OP super stock
dodgeboy11 OP super stock Joined: Feb 2007 Posts: 1,025 Las Vegas, NV	I appreciate all the input, I just couldn't remember which way to turn the allen wrench to require more vacuum to start things moving. Too lazy to do the trial and error method. Thanks for the info, couple turns out and retest it is.

Re: vacuum advance [Re: dogdays] #1679717 09/30/14 02:59 AM 09/30/14 02:59 AM
Joined: Feb 2007 Posts: 1,025 Las Vegas, NV dodgeboy11 OP super stock
dodgeboy11 OP super stock Joined: Feb 2007 Posts: 1,025 Las Vegas, NV	Quote: 38 is where it's supposed to be, vacuum advance off and plugged. That's the most referenced number for stock bigblocks. R. This one saw dyno time. KB flat tops, .007" out. Ported 452's, had a torker II, holley 750 hp'ish. 1.6 rockers and a tq50 erson cam. 485hp, 507 tq. 38 degrees timing was all I had time to test, had to pull off dyno due to a leaking rear main and no time to retest.

Re: vacuum advance [Re: johnmilner] #1679718 09/30/14 03:03 AM 09/30/14 03:03 AM
Joined: Feb 2007 Posts: 1,025 Las Vegas, NV dodgeboy11 OP super stock
dodgeboy11 OP super stock Joined: Feb 2007 Posts: 1,025 Las Vegas, NV	put heavy spring back in there, that light throttle stumble will go away. I disagree. If it had a light throttle stumble, pulling timing out of it would most likely make it worse.

Re: vacuum advance [Re: dodgeboy11] #1679719 09/30/14 10:16 AM 09/30/14 10:16 AM
Joined: Jun 2008 Posts: 3,916 usa L lewtot184 master
lewtot184 master L Joined: Jun 2008 Posts: 3,916 usa	Quote: Quote: 38 is where it's supposed to be, vacuum advance off and plugged. That's the most referenced number for stock bigblocks. R. This one saw dyno time. KB flat tops, .007" out. Ported 452's, had a torker II, holley 750 hp'ish. 1.6 rockers and a tq50 erson cam. 485hp, 507 tq. 38 degrees timing was all I had time to test, had to pull off dyno due to a leaking rear main and no time to retest. what i'm seeing here is no quench, and high cylinder pressure. I doubt juggling the timing is a cure if the intent is to run on pump gas. I don't agree that 38 degrees total is always the best. to many variables; such as combustion chamber design, plug location, quench vs no quench, rod ratio, etc.

Re: vacuum advance [Re: lewtot184] #1679720 09/30/14 03:10 PM 09/30/14 03:10 PM
Joined: Jan 2003 Posts: 16,376 D dogdays I Live Here
dogdays I Live Here D Joined: Jan 2003 Posts: 16,376	So what do we know about the engine? 440 stock (so we know the rod ratio) Stock open chamber heads (so we know the spark plug location and that there's no squish. I am interested in combustion chambers and ignition advance and their relationship. Over the last ten years or so, the vast majority of naturally aspirated non "quench dome" 440 dyno tests I have come across, using the open chamber stock iron heads, had the best max power at 38 degrees. If I had to pick one number that'd be it. If the OP wanted to do some testing, find a drag strip and use the advance that gives the highest MPH. But I'd still start at 38 degrees. It isn't rocket science. R.

Re: vacuum advance [Re: dogdays] #1679721 09/30/14 03:52 PM 09/30/14 03:52 PM
Joined: Jun 2008 Posts: 3,916 usa L lewtot184 master
lewtot184 master L Joined: Jun 2008 Posts: 3,916 usa	the more timing the worse the combustion efficiency; typical of open chambers and flat top pistons.

Moderated by Al_Alguire, Hotwheelsjr, moparts, not_a_charger, RangerDan440, tboomer

Hop To

Powered by UBB.threads™ PHP Forum Software 7.7.1