vacuum advance cold start experiment
Thread Starter
Race Director
Joined: Oct 2000
Posts: 15,055
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From: central FL, near the beach.
vacuum advance cold start experiment
coldest in 20years here. house gets so cold, i might as well dress warm and go in the garage in the AM. 
so after doing some research i dreamed up this experiment:
under dash "hold" valve for vac adv.
chrysler data says that cold, it needs more advance.
some cars like mine have weak vacuum on a cold start (no choke) so it gets less advance when it needs more. stalls.
.
if this cold was normal, i'd get a choke; but as a hobby idea, i'm going to try turning the valve "off" at 1500 when vac is high. then when i let up, it will maintain full vac adv even if vac goes real low.
the chrysler data also says it needs more adv even accelerating cold and will run soother and get more mpg advanced. so, what the heck, i'll try that too. Very crude test, but i'd like to see how it runs. Once it warms up, i'll open valve and vac adv will work normally.
EDIT: i'm just going to loop a long vacuum hose under the dash and clamp it on start up for the test.
so after doing some research i dreamed up this experiment:
under dash "hold" valve for vac adv.
chrysler data says that cold, it needs more advance.
some cars like mine have weak vacuum on a cold start (no choke) so it gets less advance when it needs more. stalls.
.
if this cold was normal, i'd get a choke; but as a hobby idea, i'm going to try turning the valve "off" at 1500 when vac is high. then when i let up, it will maintain full vac adv even if vac goes real low.
the chrysler data also says it needs more adv even accelerating cold and will run soother and get more mpg advanced.
so, what the heck, i'll try that too. Very crude test, but i'd like to see how it runs. Once it warms up, i'll open valve and vac adv will work normally. EDIT: i'm just going to loop a long vacuum hose under the dash and clamp it on start up for the test.
Last edited by Matt Gruber; Jan 12, 2010 at 07:09 AM.
Thread Starter
Race Director
Joined: Oct 2000
Posts: 15,055
Likes: 79
From: central FL, near the beach.
WORKS! Kudos to the Chrysler engineers!
Only took 1/2 hr to hook it up.
Started it, clamped hose w/18" vacuum, took 10 seconds to lock the advance on FULL. Drove out, no warmup.
It liked the extra advance lots! Ran like it does in the summer, despite the cold and no choke.
Too bad the 1976 "lean burn"(falsely named) was a failure, they used primitive electronics; i used some hose and a clamp
EDIT
this isn't all choke related. What happens when i pull out from a dead stop cold, it takes more throttle, and briefly, vac drops enough that the vac adv drops out, then it bogs, and i have to pump it or it will stall.
SO NOW,
advance does NOT drop out, it doesn't BOG, and it pulls out normally.
Started it, clamped hose w/18" vacuum, took 10 seconds to lock the advance on FULL. Drove out, no warmup.
It liked the extra advance lots! Ran like it does in the summer, despite the cold and no choke.
Too bad the 1976 "lean burn"(falsely named) was a failure, they used primitive electronics; i used some hose and a clamp
EDIT
this isn't all choke related. What happens when i pull out from a dead stop cold, it takes more throttle, and briefly, vac drops enough that the vac adv drops out, then it bogs, and i have to pump it or it will stall.
SO NOW,
advance does NOT drop out, it doesn't BOG, and it pulls out normally.
Last edited by Matt Gruber; Jan 12, 2010 at 03:15 PM.
Thread Starter
Race Director
Joined: Oct 2000
Posts: 15,055
Likes: 79
From: central FL, near the beach.
please read link
see Bill Jones posts:
.
29.9 mpg with carb!
uses TVS Trapped Vacuum Spark, similar to my test.
http://speedtalk.com/forum/viewtopic.php?t=2178
site loads FAST even w/dial up.
.
29.9 mpg with carb!
uses TVS Trapped Vacuum Spark, similar to my test.
http://speedtalk.com/forum/viewtopic.php?t=2178
site loads FAST even w/dial up.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
Model T Fords have a similar system: A lever on the steering column for the driver to adjust the timing as needed... Driving a Model T, you crank in more timing when cold and back it off when hot or under load.
Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
An adjustable timing control is what you need. These are no longer available from msd but come up once in a while on Ebay. They have one for an MSD box too.
http://cgi.ebay.com/ebaymotors/ws/eB...y=33691&ih=014
http://cgi.ebay.com/ebaymotors/ws/eB...y=33691&ih=014
Thread Starter
Race Director
Joined: Oct 2000
Posts: 15,055
Likes: 79
From: central FL, near the beach.
An adjustable timing control is what you need. These are no longer available from msd but come up once in a while on Ebay. They have one for an MSD box too.
http://cgi.ebay.com/ebaymotors/ws/eB...y=33691&ih=014
http://cgi.ebay.com/ebaymotors/ws/eB...y=33691&ih=014
crane made 1 too.
J&S has a knock retard system.
