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YACT: Backfiring

Toastedlightly

Toastedlightly

Diamond Member
So, as my mechanical work ends on a truck I've been working on ('74 Dodge D100), I have noticed that I tend to backfire quite often on starts (it may not be a backfire thought). The engine seems to run in reverse, shooting fuel out of the bowl vents and creating a lot of white smoke. Would having the engine too far advanced cause this hard-starting/backfiriing esc behavior? (15 degrees advanced to compensate for no vacuum advance on distributor)
 
I wouldn't be surprised, that sounds pretty high for idle. You can't find a distributor that has a vacuum advance for it?
 
Originally posted by: Linflas
I wouldn't be surprised, that sounds pretty high for idle. You can't find a distributor that has a vacuum advance for it?
Click to expand...

Yea, I switched carbs and it doesn't have a port for the vacuum advance. (Distributor has 15 degrees of mechanical advance, and draws (I think) 15-20 degrees advance from vacuum) W/o the 15 degree advance, the truck won't run over 50 mph. The idle is piss poor, but she does have some power. Just the hard starts driving me nuts. This is a temp solution until I can get to the junkyard and fidn a distributor for a 318 w/o the vacuum advance (all mechanical advance).
 
Hey, Kevin. You still messin' w/that dist.?
Here's a thought. Back that timing off about 10 or 12 degrees, you know, where it fires up and idles nice, and get yourself a vacuum pump ( $20/25) and some extra line. Run the line into the cab and pump your own vac.adv. Just till you find that mech. dist.
 
Originally posted by: Toastedlightly
Originally posted by: Linflas
I wouldn't be surprised, that sounds pretty high for idle. You can't find a distributor that has a vacuum advance for it?
Click to expand...

Yea, I switched carbs and it doesn't have a port for the vacuum advance. (Distributor has 15 degrees of mechanical advance, and draws (I think) 15-20 degrees advance from vacuum) W/o the 15 degree advance, the truck won't run over 50 mph. The idle is piss poor, but she does have some power. Just the hard starts driving me nuts. This is a temp solution until I can get to the junkyard and fidn a distributor for a 318 w/o the vacuum advance (all mechanical advance).
Click to expand...
All you need is ported vacuum on a mopar V8.

That carb must have a ported vacuum source somewhere. Maybe try the port that is used for the air cleaner flap.

And yes, that is too much advance for a 318.


 
Originally posted by: TwoBills
Hey, Kevin. You still messin' w/that dist.?
Here's a thought. Back that timing off about 10 or 12 degrees, you know, where it fires up and idles nice, and get yourself a vacuum pump ( $20/25) and some extra line. Run the line into the cab and pump your own vac.adv. Just till you find that mech. dist.
Click to expand...

I could try that, but since I am new to driving a manual, and this thing is a beast to drive (the clutch stiff, the throtle sensative). I could try that, I have holes in the firewall... hmm.
 
Originally posted by: Iron Woode
Originally posted by: Toastedlightly
Originally posted by: Linflas
I wouldn't be surprised, that sounds pretty high for idle. You can't find a distributor that has a vacuum advance for it?
Click to expand...

Yea, I switched carbs and it doesn't have a port for the vacuum advance. (Distributor has 15 degrees of mechanical advance, and draws (I think) 15-20 degrees advance from vacuum) W/o the 15 degree advance, the truck won't run over 50 mph. The idle is piss poor, but she does have some power. Just the hard starts driving me nuts. This is a temp solution until I can get to the junkyard and fidn a distributor for a 318 w/o the vacuum advance (all mechanical advance).
Click to expand...
All you need is ported vacuum on a mopar V8.

That carb must have a ported vacuum source somewhere. Maybe try the port that is used for the air cleaner flap.

And yes, that is too much advance for a 318.
Click to expand...


The engine needs ~30-40 degrees of advance at 4k RPM to generate power.
 
Originally posted by: Toastedlightly
Originally posted by: Iron Woode
Originally posted by: Toastedlightly
Originally posted by: Linflas
I wouldn't be surprised, that sounds pretty high for idle. You can't find a distributor that has a vacuum advance for it?
Click to expand...

Yea, I switched carbs and it doesn't have a port for the vacuum advance. (Distributor has 15 degrees of mechanical advance, and draws (I think) 15-20 degrees advance from vacuum) W/o the 15 degree advance, the truck won't run over 50 mph. The idle is piss poor, but she does have some power. Just the hard starts driving me nuts. This is a temp solution until I can get to the junkyard and fidn a distributor for a 318 w/o the vacuum advance (all mechanical advance).
Click to expand...
All you need is ported vacuum on a mopar V8.

That carb must have a ported vacuum source somewhere. Maybe try the port that is used for the air cleaner flap.

And yes, that is too much advance for a 318.
Click to expand...


The engine needs ~30-40 degrees of advance at 4k RPM to generate power.
Click to expand...
I know this.

At idle it requires no vacuum advance, just straight distributor advance.

This means a ported source. Once the engine revs up, the vacuum comes on line and viola proper advance for regular running.

Also consider getting the advance curve redone to bring full advance (mechanical) in by 2500-3000 rpm.

 
Originally posted by: Iron Woode
Originally posted by: Toastedlightly
Originally posted by: Iron Woode
Originally posted by: Toastedlightly
Originally posted by: Linflas
I wouldn't be surprised, that sounds pretty high for idle. You can't find a distributor that has a vacuum advance for it?
Click to expand...

Yea, I switched carbs and it doesn't have a port for the vacuum advance. (Distributor has 15 degrees of mechanical advance, and draws (I think) 15-20 degrees advance from vacuum) W/o the 15 degree advance, the truck won't run over 50 mph. The idle is piss poor, but she does have some power. Just the hard starts driving me nuts. This is a temp solution until I can get to the junkyard and fidn a distributor for a 318 w/o the vacuum advance (all mechanical advance).
Click to expand...
All you need is ported vacuum on a mopar V8.

That carb must have a ported vacuum source somewhere. Maybe try the port that is used for the air cleaner flap.

And yes, that is too much advance for a 318.
Click to expand...


The engine needs ~30-40 degrees of advance at 4k RPM to generate power.
Click to expand...
I know this.

At idle it requires no vacuum advance, just straight distributor advance.

This means a ported source. Once the engine revs up, the vacuum comes on line and viola proper advance for regular running.

Also consider getting the advance curve redone to bring full advance (mechanical) in by 2500-3000 rpm.
Click to expand...

I am thinking of getting a pure mechanical advance distrib. from a junkyard or ebay or something. Just have to look for it (should have one in the next week or so).
 
Originally posted by: Toastedlightly
Originally posted by: Iron Woode
Originally posted by: Toastedlightly
Originally posted by: Iron Woode
Originally posted by: Toastedlightly
Originally posted by: Linflas
I wouldn't be surprised, that sounds pretty high for idle. You can't find a distributor that has a vacuum advance for it?
Click to expand...

Yea, I switched carbs and it doesn't have a port for the vacuum advance. (Distributor has 15 degrees of mechanical advance, and draws (I think) 15-20 degrees advance from vacuum) W/o the 15 degree advance, the truck won't run over 50 mph. The idle is piss poor, but she does have some power. Just the hard starts driving me nuts. This is a temp solution until I can get to the junkyard and fidn a distributor for a 318 w/o the vacuum advance (all mechanical advance).
Click to expand...
All you need is ported vacuum on a mopar V8.

That carb must have a ported vacuum source somewhere. Maybe try the port that is used for the air cleaner flap.

And yes, that is too much advance for a 318.
Click to expand...


The engine needs ~30-40 degrees of advance at 4k RPM to generate power.
Click to expand...
I know this.

At idle it requires no vacuum advance, just straight distributor advance.

This means a ported source. Once the engine revs up, the vacuum comes on line and viola proper advance for regular running.

Also consider getting the advance curve redone to bring full advance (mechanical) in by 2500-3000 rpm.
Click to expand...

I am thinking of getting a pure mechanical advance distrib. from a junkyard or ebay or something. Just have to look for it (should have one in the next week or so).
Click to expand...
Better driveability and economy if you keep the vacuum advance.

If this is a non-modded 318 and using Mopar electronic ignition, then it should be relatively easy to get a normal dist. from the wreckers. That is what I did for my 318. But I had leanburn to deal with.

I recurved mine myself so all advance is in by 2500 rpm and set the initail advance using a vacuum gauge. Once the vacuum stops rising, you have found the required initial timing.
 
Originally posted by: Toastedlightly
Was looking at this distrib..

http://cgi.ebay.com/ebaymotors/ws/eBayI...7979600397&sspagename=STRK%3AMEWA%3AIT

but isn't for my year engine (1974) 🙁
Anyone know the differences between teh blocks/distribs?
Click to expand...
OMFG!!!!!!!!!

Stay away from that.

That is a LeanBurn Dist. It only works with LeanBurn. Way too much trouble to add weights and springs.

And you are asking about what distr. fit which blocks?

all 273/318LA/340/360LA use the same distr.
all 350/361/383LB/400 use the same distr.
all 383RB/413/426/440 use the same distr.

 
Originally posted by: Iron Woode
Originally posted by: Toastedlightly
Was looking at this distrib..

http://cgi.ebay.com/ebaymotors/ws/eBayI...7979600397&sspagename=STRK%3AMEWA%3AIT

but isn't for my year engine (1974) 🙁
Anyone know the differences between teh blocks/distribs?
Click to expand...
OMFG!!!!!!!!!

Stay away from that.

That is a LeanBurn Dist. It only works with LeanBurn. Way too much trouble to add weights and springs.
Click to expand...

Mmmmk. Know of any Mopars that came w/ a mechanical distrib (only)? I am off to work!!
 
Originally posted by: Toastedlightly
Originally posted by: Iron Woode
Originally posted by: Toastedlightly
Was looking at this distrib..

http://cgi.ebay.com/ebaymotors/ws/eBayI...7979600397&sspagename=STRK%3AMEWA%3AIT

but isn't for my year engine (1974) 🙁
Anyone know the differences between teh blocks/distribs?
Click to expand...
OMFG!!!!!!!!!

Stay away from that.

That is a LeanBurn Dist. It only works with LeanBurn. Way too much trouble to add weights and springs.
Click to expand...

Mmmmk. Know of any Mopars that came w/ a mechanical distrib (only)? I am off to work!!
Click to expand...
Only ones I know were the old single point racing ones.

Why not just buy the mopar electronic distr with recurved advance and maybe the orange control box. I use the chrome box myself.

 
Originally posted by: Iron Woode
Originally posted by: Toastedlightly
Originally posted by: Iron Woode
Originally posted by: Toastedlightly
Was looking at this distrib..

http://cgi.ebay.com/ebaymotors/ws/eBayI...7979600397&sspagename=STRK%3AMEWA%3AIT

but isn't for my year engine (1974) 🙁
Anyone know the differences between teh blocks/distribs?
Click to expand...
OMFG!!!!!!!!!

Stay away from that.

That is a LeanBurn Dist. It only works with LeanBurn. Way too much trouble to add weights and springs.
Click to expand...

Mmmmk. Know of any Mopars that came w/ a mechanical distrib (only)? I am off to work!!
Click to expand...
Only ones I know were the old single point racing ones.

Why not just buy the mopar electronic distr with recurved advance and maybe the orange control box. I use the chrome box myself.
Click to expand...

Tis already running electronic ignition... this is driving me nuts!! Isn't there something that pulls a certain amount of vacuum at different RPMS?!
 
Now I feel dumb. I think this carb has had the vacuum for advance all along. Lemmie take a pic of the port and see what you guys think.

That was it. Turns out I missed a gasket when I rebuilt it (a small circular one). Replaced it, now I have vacuum advance. Thanks for all the help 🙂
 
Originally posted by: Toastedlightly
Now I feel dumb. I think this carb has had the vacuum for advance all along. Lemmie take a pic of the port and see what you guys think.

That was it. Turns out I missed a gasket when I rebuilt it (a small circular one). Replaced it, now I have vacuum advance. Thanks for all the help 🙂
Click to expand...

Kool,so the 318 runs better now???

What carb you using?

 
Originally posted by: Toastedlightly
Now I feel dumb. I think this carb has had the vacuum for advance all along. Lemmie take a pic of the port and see what you guys think.

That was it. Turns out I missed a gasket when I rebuilt it (a small circular one). Replaced it, now I have vacuum advance. Thanks for all the help 🙂
Click to expand...
Yup, those gaskets can be a pain.

Don't you have a vacuum gauge?

In case this may help someone else out there:

Mopar put an electric vacuum switch on its 80's Mbodies, Fifth Ave, Diplomat,etc

Hook up your vaccum lines and then hook up the wires and with an off/on switch at the trottle you can have vacuum when you accelerate.
 
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