440 in the Imperial running weird - vacuum advance?
#1075569
09/15/11 03:44 PM
09/15/11 03:44 PM
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Joined: Jan 2007
Posts: 1,091 Czech Republic, Central Europe
BobAsh
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super stock
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OP
super stock
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Czech Republic, Central Europe
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A friend's Imperial with '69 440HP from a B-body is running a little rough, and it's MUCH slower in the top end than it should be - in a rolling start "drag race", it has been handed it's [Edited by Moparts - Family Friendly Site - Keep it clean] by a turbodiesel Renault Latitude... It seems to me that the problem can be in the vacuum advance regulation - the engine runs too rich, but get it any leaner and it starts to run rough. Maybe some problem in the vacuum lines? Guys who put the thing together have never seen a Mopar engine before, so they could just mismatch something, maybe? Here are some pictures - maybe someone can see something wrong there? https://picasaweb.google.com/115646732410106877156/20110915?authkey=Gv1sRgCMHO8LGtganhxwE
Gettin' old iron accross the pond...
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Re: 440 in the Imperial running weird - vacuum advance?
[Re: BobAsh]
#1075571
09/15/11 05:03 PM
09/15/11 05:03 PM
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Joined: Nov 2004
Posts: 2,825 Sk. Canada
RemCharger
master
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master
Joined: Nov 2004
Posts: 2,825
Sk. Canada
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Looks like you are on manifold vacuum adv. I would ditch that and put some light springs in the dist. Then time it up at high rpm for 38 degrees. That will eliminate ignition issues and leave you with just your carb problem( Carter )
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Re: 440 in the Imperial running weird - vacuum advance?
[Re: BobAsh]
#1075574
09/15/11 05:26 PM
09/15/11 05:26 PM
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Joined: Jan 2007
Posts: 1,091 Czech Republic, Central Europe
BobAsh
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OP
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By the way - is it possible that car starts running rough when the air cleaner is removed and installed back? It seems to me that the seal between the cleaner and the carb is not what it should be, but can it really make a difference?
Gettin' old iron accross the pond...
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Re: 440 in the Imperial running weird - vacuum advance?
[Re: greg_moreira]
#1075575
09/15/11 05:29 PM
09/15/11 05:29 PM
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Joined: Jan 2007
Posts: 1,091 Czech Republic, Central Europe
BobAsh
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super stock
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Quote:
is this a new problem that just developed?
Its not the vacuum advance. Simply put....the engine doesnt produce vacuum(or at least much more than maybe 1 inch) at full throttle. So any high rpm, full throttle issues wont be related to vac advance, because vac advance isnt in the mix or doing anything at all under full throttle.
Vac advance only works at idle/part throttle where the engine produces vacuum.
If its a new prob, Id be looking elsewhere
It's like this since the engine was put in the car - they really messed things up and didn't have much of an idea about what they were doing. It gets continually better and better, as the bugs are being fixed, but it still doesn't run even remotely how it should...
So, where we should look? Is it possible that advance is off?
Gettin' old iron accross the pond...
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Re: 440 in the Imperial running weird - vacuum advance?
[Re: BobAsh]
#1075576
09/15/11 05:46 PM
09/15/11 05:46 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
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Posts: 36,040
Lincoln Nebraska
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Start at the beginning. Want vac adv connected to the front pass nipple (carter) which'll b ported. pull the vac adv hose off & plug it w a golf tee & set the initial at 10BTDC (stock cam) 15 (wild cam) then run the rpm up until it will not adv any more & post what you have. If no dialback or timing tape 2&1/4" is 35.5 degrees. And if (10) or (15) makes it ping or if it pushe sit way past 38 total back that off. If it is not pinging you're good until you get it spot on & any pinging you can hear is way too much & you're racing it so not sure if you can hear it. take off the dist cap & see what springs you have, stock is a heavy spring with a long loop on one end and a light spring. may need to alter the dist slot length to get initial/total correct but start w initial & post what total you have now. Stock '69 carter AVS? What eng mods, what cam/what idle speed. rich at idle? smells like gas? The more info the better
live every 24 hour block of time like it's your last day on earth
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Re: 440 in the Imperial running weird - vacuum advance?
[Re: greg_moreira]
#1075578
09/15/11 06:00 PM
09/15/11 06:00 PM
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Joined: Sep 2011
Posts: 39 pittsburgh, pa
greg_moreira
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pittsburgh, pa
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Here is what you do to sort the timing.
First and foremost....unhook the vac advance completely and plug its port on the carb so that you dont have a vacuum leak.
Get a timing light and check initial timing at idle. For any performance engine, at least 10 degrees timing should be there at idle. Higher is not out of the question. Give the motor what it wants. Go up in 2 degree increments at a time just to see how she responds.
Then...I always put the absolute lightest advance springs in as possible and check total timing(that way your not under the hood with the engine spinning 4000 rpm or something....the quicker the timing comes in, the safer it "feels" checking total).
Anywhere from 34-40 degrees total is common depending on various factors. I always first find an initial value that it likes.
See where it idles best, and where it starts easiest and quickest(check after warmed up also to make sure it wont kick back on you or roll over or anytihng).
Then...find total timing. Start at 34 and go up 2 degrees at a time with some full throttle runs. Wherever it feels best, make note.
Say for example it likes 14 initial best, and 38 total best. With that in mind, you need 24 degrees of mechanical advance. This is where it gets fun, and recurving comes into play to adjust advance to 24 degrees mechanical so that you can have that 14/38. If you dont wanna play with it, compromise as best as possible.
Say your distributor only has 20 degrees as is. Set initial at 16 and you'll have 36 total. decent compromise.
Hook the vac advance back up to full manifold. If it adds too much adance and you experience pinging at part throttle...tweak the vac advance to limit how much advance it adds. Real real simple to add a stop plate to a non adjustable vac advance to limit how much timing it adds.
Some simple stuff.....check for full throttle! Dont assume your linkage is spot on. If your only opening the butterflies 80%....that would explain a loss in upper rpm power.
Then we get into carb tuning. The list goes on and on
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Re: 440 in the Imperial running weird - vacuum advance?
[Re: RemCharger]
#1075579
09/15/11 06:43 PM
09/15/11 06:43 PM
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Joined: Nov 2004
Posts: 2,825 Sk. Canada
RemCharger
master
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master
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Posts: 2,825
Sk. Canada
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Quote:
Looks like you are on manifold vacuum adv. I would ditch that and put some light springs in the dist. Then time it up at high rpm for 38 degrees. That will eliminate ignition issues and leave you with just your carb problem( Carter )
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Re: 440 in the Imperial running weird - vacuum advance?
[Re: RemCharger]
#1075580
09/15/11 06:52 PM
09/15/11 06:52 PM
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Joined: Jul 2008
Posts: 30,424 Florida STAYcation
dOrk !
The village idiot's idiot
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The village idiot's idiot
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Posts: 30,424
Florida STAYcation
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440 in the Imperial running weird .... DID you get a feets-guy tune-up ? THAT would 'splain it ! ...
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Re: 440 in the Imperial running weird - vacuum advance?
[Re: RemCharger]
#1075581
09/15/11 07:07 PM
09/15/11 07:07 PM
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Joined: Jan 2007
Posts: 1,091 Czech Republic, Central Europe
BobAsh
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super stock
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OP
super stock
Joined: Jan 2007
Posts: 1,091
Czech Republic, Central Europe
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And what about that air cleaner seal? It seems strange to me that after taking off and refitting the air cleaner, the car starts running better or worse, depending on how you put it in there... There's quite a high seal under the cleaner - maybe the problem is there? What about throwing the seal away? I had air cleaner without any seal on many cars and it worked just right...
Gettin' old iron accross the pond...
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