Back firing through Carberator

[annbonari]

We just purchased the American Clipper a 1978 with the 440 engine. First thing we did was to gas it up and put a bottle of lucas fuel treatment in it....Shortly after that we were getting a backfire though the carburetor and black smoke from the exhaust.....The first fuel filter we changed was black gas in color, with no change with the new fuel filter we changed it once more.  This time the filter had alot of rust in it.  My husband did adjust the carburetor and it is not blowing the black smoke like it was but the RV is still running bad..rough idle, backfiring and when i took it to the street with an incline it would only go ten miles an hour.  On a level street it was fine....Anyone with any suggestions on what we should check next for this problem would be greatly appreciated! I love my clipper but had to cancel my first trip planned in it....

[Rodney]

hello,
I would guess you have a couple things going on, changing the fuel filters is a good start. Also check the entire fuel line from the tank to the carburetor replacing as much of the rubber fuel line and  tightening all clamps. Popping from the carburetor is usually a lean condition so check the fuel pump pressure should be 5 to 8 pounds. The carb many need a rebuild depending on how gunked up it is, also check to see if it has a filter in it, it may be plugged. The top of the carb should come off to see how much rust made it up there.
got to run keep us posted.

[retrorob]

How long had the rig sat before you bought it? How many gallons where in the tank? I wonder if the old fuel had turned to varnish.
If you think the old gas was good I would hook up a vacuum gauge on the engine to check  for a burnt/sticky intake valve. A tune is also probably in order.
A flat camshaft could also be the problem. It's hard to see from here!

[Rodney]

Yes that's right old fuel can cause the engine to preform poorly and more than likely a contributing factor.
I let my home set for a couple of years with the some fuel in the tank, unfortunately I didn't fill the tank before parking it. since I have the 50 gallon steel tank {custom made from the looks of it} the tank condensed, probably been condensing since new, causing the tank to rust inside. I removed the tank and replaced the rubber fuel line from the gauge to the steel line and also the inline fuel filter along the frame {uni-body} up front. While doing this I flushed the lines the best I could, a lot of rust came out. Since I don't have the $$ right now to have an aluminum tank built I installed an electric fuel pump in front of the tank { I was experiencing a starting issue when the home sat for any length of time} with an inline filter before the pump
This fixed the hard start and when pulling a hill I now turn the electric pump on. I can tell when it needs the electric pump due to loss of power and it will pop through the carb.
I am running a fresh 440 with Doug Thorley headers RV cam, aluminum intake and an Edelbrock electric choke carb. Since the rebuild the Clipper ran ok but with the extra fuel pump it runs much better.
Another thing to take into consideration is in our area we now have 10% ethanol in out fuel, Bad deal since it destroys old rubber fuel line and brakes loose gunk from the tank, fuel lines and carb.
Fuel stabilizer is now a must when the home is parked for any length of time and run the engine and generator if so equipped for several minutes before parking.
I had to take apart the carburetor and clean and blow out the small orifices before the 440 would run like it should.  

[mccammonds]

TIMING?

[John Eversoll]

Sounds as though it is 180 out.....   " timing"  That would explain the back fire thru the carb...

Varnished gas would not have anything to do with that....

Sorry for that brick I droped.......

[Rodney]

If the timing were 180 out the engine wouldn't run.
Any 440 engine I've taken apart have steel timing gears which are pretty dependable, you can check the timing static by bringing number one piston to TDC on the compression stroke {I use a bore scope to see the top of the piston} and check the timing mark which on a Van would be on the top of the bell housing area of the transmission { the hole in the case}. If ok this rules out a cam timing issue {jumped timing chain}
While you are doing this you can also check the slop in the timing chain by observing the rotor while having someone turn the engine clockwise with a socket on the crank bolt {1 1/8 if I recall} and breaker bar, then turning the engine counter clockwise. You shouldn't see much lag ultimately no lag would be preferred but with a chain and gears I'd expect 5 degrees or maybe a little more. If you see a lot of slop time for a new chain and gears. 
of course when trying to solve an issue with any engine all of the obvious needs to be checked.
which would be to remove the dog house and check to see that all is ok from that view.
check:
fully charged battery and charging system working properly.
spark plug wires, vacuum and any fuel lines for damage, mice and other rodents can cause a lot of damage.
clean air filter.
choke working properly.
pull the spark plugs and inspect
do a leak down and compression test to see that the cylinders are sealing, preferably with the engine hot.
check timing
remove the distributor cap and inspect the inside of cap and rotor Chrysler EI is a good dependable ignition system IMO other than checking the air gap not much else to do.
While you have the top of the engine accessible I would tighten the valve covers and check the intake and carburetor bolts for torque.

my engine was popping plenty before I pulled the carb and cleaned. the biggest culprit was the accelerator pump squirters which were plugged solid from varnish. I had to take a small tip cleaner wire to get them clear.
good luck, keep us posted on your progress.

[retrorob]

Hey Rodney, did you notice a increase in milage when you installed the intake,headers and cam? My 78 is rock stock and have considered these upgrades. I think I will keep the thermoquad or change to a holley. I'm not a big fan of the carter AFB.

[Rodney]

To be honest I don't know if the mileage increased. I was getting 8-10 MPG when I was pulling my race car and trailer. about 3300 lb car and the trailer maybe total 4300 lbs? More like 8 with any head wind and hills. the new combo does pull much better and has more power {of course}
I use Holley's on our race cars but for the motor home I prefer either a Q jet or the edelbrock due to the float bowl configuration..

I rebuilt the engine and change rear end gears from 4.10's to 3.73.s and a little taller tire back about 8 years ago. I haven't put many miles on the new set up since, I was having some health issues which I am now getting taken care of {I hope}this put the Clipper on the back burner.
Now that I am retired and have a new knee and several other surgeries I am back together I'll be putting some more miles on the home soon.. I hope?
I am finishing the restore this summer and am to the point where I am able to take the home for a trip.
I am still not satisfied with how the home drives so have some more to do with that. Just was at the parts store to get new shocks and tail lights. I've already rebuilt the front end new ball joints, added a sway bar and an alignment. It drives ok but I feel it needs more caster and some work to the steering gear box.

[bulldog 1995]

mine is doing the same thing A mechanic I took it to said that if i rebuild or replace the carb it will fix the "spitting" problem and I need to service the trans (give it a fresh filter and flush the trans) to stop the improper shifting problem. until the trans warms up I have to manually shift it to have power to climb hills and pull away from stops. after it warms up it stops "spitting" and shifts fine it has to idle for about 10 to 15 mins and it only takes about 5 mins of driving for the trans. I had to drive it from Vancover WA near the Oregon border to about 35 miles north of Seattle WA where I live (between 300 and 400 miles). it's parked till I get the carb for it right now 

[Rodney]

FYI
Shifting the 727 torque flight manually is actually a real good idea. when you pull it in to first gear with the shifter lever the trans is using the forward - reverse band to lock in for first forward gear, much better than leaving the shift lever in drive which uses only the sprag to get first gear.
Don't go to long with the transmission working the way you described or you may be in for some major problems.
cold sputtering can also be caused by the choke not working or adjusted properly.

[bulldog 1995]

that's why i have parked mine for the time being, tranys are too pricey to take the chance of damageing it. I have only done it a couple of times once when I bought it. and once when i took it to the shop and back home. I already replaced the trans filter and am saving up for a new carb with automatic choke to get rid of the problematic OE choke

[Rodney]

with only 30K on your drive train I would find it hard to believe the trans needs anything to major unless it has been real hot and or ran low on fluid.
I'm sure you've checked the obvious:
does the fluid smell burnt
kick down linkage on the 727 is real important to have adjusted correctly, it not only works as a kick down but also adjusts line pressure and can cause trans damage if not working correctly
linkage moving smooth and free. also the linkage at the carb needs to have a return spring to pull the linkage forward.
the band adjustments should also be checked one is on the outside of the case the other once the pan is removed.
I've used the 1411 Edelbrock on several 440 engines I've built over the years with good results
link for the 1411
of course with any aftermarket parts everyone has there own preferences
Holley is my choice for drag racing, right now I'm running a 1250 cfm dominator on my 572 Cu in in my 63 Dodge
the ultimate goal for my home if money were now object would be to build a 500 cu in stroked 440 with around 500 hp but torque in the 600 + ft lb range.. oh that would be nice..
maybe some day!

[John Eversoll]

Hi Rod, I beleive that you are right on that one....

35, 000 on the drive train. probably just a mal ajusted trans..

The 727 is a good trans and I think the Best!!  The rebuild kit is only $80.00
and to have it rebuilt only cost me $125.00.  I put the trans back in myself
and everything is hunky and dory...
I am interested in your rig, and the front coils...
John

[Rodney]

I can take some images for you and measurement in a few days kind of sore from surgery.

rebuild kit prices vary a lot depending in whether getting a seal kit or master I quit building my trans. last year due to bad back and other disability's We use Clay's transmission in Sandy now
the trans in my 63 dodge I race with the upgraded drums planetary gears Kevlar clutches and the list goes on we are in to it about 8k plus another 1200 for the 8 inch converter   
I have a couple motor home trans for spares any way.